Controlling the Brantas river: construction and impact of Japan-supported irrigation infrastructure on the agricultural economy and the environment in East Java

Abstract

This article examines the crucial role played by Japan in the development of irrigation infrastructure in Indonesia from the 1960s to the 1990s. While the assistance provided by Japan in irrigation infrastructure significantly enhanced the prominence of the Brantas river valleys as a major rice granary during the green revolution, it has been largely overlooked in Indonesian historiography. Despite the historical influence of the Dutch, this article aims to elucidate the reasons behind Japan’s involvement in the modernization of irrigation systems along the Brantas river in East Java, as well as the resultant effects on food production and the environment. Employing a historical approach and drawing on both primary and secondary sources, this study argues that Japan’s role in Indonesia’s irrigation development during the independence period originated from the war compensation fund paid by the Japanese government. This fund subsequently paved the way for greater involvement of Japanese agencies in mutual cooperation in developing irrigation infrastructure. The expansion of irrigated lands and increased rice productivity, facilitated by Japan-supported irrigation infrastructure, mitigated the risks of harvest failure due to droughts and floods. The infrastructure has also played a significant role in flood control during rainy seasons and in securing irrigation water, especially during dry seasons. Additionally, while acknowledging sacrifices incurred during the construction process and the environmental consequences of their operations, it is evident that the Japan-supported irrigation infrastructure effectively tamed the ferocity of the river and optimized its benefits, significantly improving the livelihoods of many people. To ensure the long-term sustainability of Japanese-funded infrastructure along the Brantas River, comprehensive strategies encompassing regular maintenance, technological updates, community engagement, integrated water resource management, agriculture diversification, and climate change adaptation are essential.

Keywords:

• Irrigation infrastructure
• Japan’s aid
• Brantas river
• rice production
• flood control
• environmental impacts

REVIEWING EDITOR:

• Samuel Adu-Gyamfi, History and Political Studies, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

SUBJECTS:

• Landscape
• Landscape History
• Building and Construction
• Rural Development
• Environment and the Developing World
• Human Geography
• History

1. Introduction

The effects of irrigation infrastructure on agriculture and the environment have been thoroughly investigated, revealing a spectrum of advantages and drawbacks linked to its deployment. Extensive research demonstrates that irrigation infrastructure significantly boosts crop yields and agricultural output. Notably, examinations of the impacts of the Green Revolution underscore remarkable production increases directly linked to large-scale irrigation projects (Evenson & Gollin, 2003; Pinstrup-Andersen & Hazell, 1985). Irrigation infrastructure significantly enhances land productivity and cropping intensity (Dhawan, 1988; Karunakaran & Palanisami, 1998; Saith & Tankha, 1992). A study by Hussain and Hanjra (2004) found that cropping intensity nearly doubled in irrigated areas of Asia. Studies by Bravo-Ureta et al. (2020) and Yao (2005) showcased substantial enhancements in crop yield and productivity in the Philippines owing to well-developed irrigation systems. Additionally, Gebregzaiabher et al. (2011) highlight how irrigation boosts the productivity of complementary inputs like seeds and fertilizer. Meanwhile, Huang et al. (2005) demonstrated positive net returns on investments in irrigation systems developed in China.

However, the expansion and intensification of irrigation infrastructure also entail significant environmental repercussions. By its very nature, irrigation disrupts the natural environment by altering river flows and modifying water pathways across landscapes. Particularly, the infrastructure associated with irrigation, such as large dams, can profoundly impact flow patterns and other variables critical to ecosystem health. The construction of the High Aswan Dam drastically reduced sediment transport, causing wetland erosion in the Nile Delta 800 kilometers downstream (Penvenne, 1996). Similarly, the damming of the Indus River in Pakistan led to reduced sediment transport, resulting in the decline of mangrove forests in the downstream delta (Meynell & Qureshi, 1995). Additionally, irrigation introduces new risks related to crop diseases and diversity as demand for traditional varieties diminishes (Hazell, 1982; Mehra, 1981; Pinstrup-Andersen & Hazell, 1985). Moreover, irrigation infrastructure is associated with decreased sediment transport, increased soil erosion, chemical contamination, and loss of biodiversity (Boelee, 2013; Falkenmark et al., 2007). Furthermore, studies like Gammelsrød (1996) highlight how reduced water flow due to dam constructions in Mozambique led to declines in marine prawn populations and fish diversity.

Scholars have extensively examined the historical trajectory of irrigation systems in Indonesia, shedding light on their evolution, impact, and governance structures. Several studies offer a comprehensive overview of irrigation projects from pre-colonial times to the modern era (Angoedi, 1984). van der Meulen (1939/1940) underlines the weaknesses of native irrigation and the need for modern irrigation infrastructure to meet the needs of the western export oriented agriculture. Boeke (1953) elaborates on the economic implications of irrigation development, particularly in delineating the dualistic nature of Indonesian society and its impact on agricultural systems. This framework remains instrumental in understanding the disparities in access to and benefits derived from irrigation infrastructure. Geertz’s seminal work (1963) offers a foundational analysis of how irrigation practices shaped agrarian systems in Java. Geertz reveals the intricate socio-cultural dimensions intertwined with irrigation, highlighting its role in shaping power dynamics and social hierarchies.

Studies by Booth (1977a, 1977b) examined the institutional aspects and organizational problems that inhibited the irrigation rehabilitation and expansion. Booth outlines the complex problems existing in the water management such as the incompatibility of the existing management organizations with the new irrigation schemes, the overlapping tasks of administrative and irrigation authorities, and complex technical issues of water distribution and water charges. Booth’s study (1998) provides crucial insights into the historical context and economic implications of irrigation development. Booth elucidates how colonial policies, land tenure systems, and agrarian structures shaped the evolution of irrigation networks, influencing agricultural productivity and rural livelihoods. Meanwhile, van der Eng’s work (2003) traces the technological advancements, state interventions, and socio-economic factors that have influenced the management and effectiveness of irrigation systems in Indonesia. Their research not only deepens our understanding of Indonesia’s agricultural history but also offers valuable insights for contemporary policy-making and sustainable water management practices.

Recent studies by Dutch scholars have emphasized the important role of the Dutch agency in the development of irrigation infrastructure in Indonesia. An estimate by Geertz (1963) suggests that from 1880 to 1940 the Dutch spent about 250 million guldens on irrigation works in Java. Ravestein (2005) elaborates on the irrigation development in the Solo valley of Java during the Dutch colonial era. Ertsen (2005) examines the emergence of engineering irrigation design during the Dutch colonial era and its legacy in the context of independent Indonesia. From the studies, much has been known about the Dutch influences on Indonesia’s irrigation works, irrigation organization, and management system. A study by Kop et al. (2015) voices the Dutch’s role in the rehabilitation of irrigation infrastructure in Indonesia during the independence era from 1965 to 2014. Ravestein (2018) portrays the role of Dutch engineers in developing irrigation buildings and public works in Indonesia both during the colonial and independence Indonesia. These studies suggest that the Dutch have shaped the face of Indonesian irrigation infrastructure and played a key role in the promotion of agricultural productivity in colonial and post-colonial Indonesia.

Despite their valuable contributions, the existing studies practically make no mention of the role of non-Dutch agency, particularly Japan. In general, books on the economic historiography of Indonesia and the representation of Japan’s role in the historical episode of Indonesia’s green revolution are absent (Dick et al., 2002; Leirissa et al., 1996). Surprisingly, the absence of a narrative is also found in Indonesian agricultural history books, which pay much attention to irrigation infrastructure, organization, and management (Booth, 1988). The only frequently mentioned international agency in Indonesian historiography is the Los Banos-based International Rice Research Institute (IRRI) of the Philippines. This institute has been recognized as contributing significantly to Indonesian success in promoting rice production by supplying highly-yielding rice varieties widely adopted under the green revolution. The lack of historical accounts on the issue could easily lead to misunderstandings. Only the Dutch have shaped the irrigation system in Indonesia. Japan and other countries did not contribute to Indonesia’s irrigation infrastructure and its success story in promoting food production.

The lack of Japanese representation in the grand narrative of Indonesia’s success story of the green revolution has been very contrastive to the rich historical source materials available on the issue. Part of these materials is kept and accessible in the Library and Archival Office of East Java Province in Surabaya under the Department of Public Works Collection (BAPERSIP, 2002). There are also extensive historical materials in the National Archive of the Republic of Indonesia in Jakarta under the Jasa Tirta Archival Collection (ANRI, 2020). Unfortunately, the rich historical sources are rarely interrogated by scholars to draw academic accounts of the region’s historical episodes of the New Order’s green revolution from outside/international perspectives, more specifically from Japan’s perspective. The poor historical representation of Japan’s role in Indonesian irrigation is strikingly different from the robust scholarly works on Japan’s investment in Indonesia (Toshihika, 1986; Wie, 1984). Much scholarly attention has also been paid to discuss knowledge and technological transfers from Japan to Indonesia (Harris, 1995; Purwanto & Suryo, 2002; Wie, 1994).

However, Japan’s influences were much broader than merely a capital investment automotive and manufacturing industry. Japan has also contributed remarkably to Indonesia’s agricultural sector, especially infrastructure vital for producing life-supporting foodstuffs. Japan’s profound impact on Indonesia’s irrigation systems exemplifies its expertise in this realm, particularly evident in dam construction. A study by Itsukushima (2023) delves into the historical trajectory of dam development in Japan, highlighting its dynamic role as a catalyst for economic progress, adapting to evolving socio-economic contexts. The necessity for dams in Japan became apparent as early as the 1870s, leading to a sustained effort in constructing numerous dams aimed at enhancing food production, securing water resources, generating hydroelectric power, and mitigating flood risks. The 1950s marked the onset of a significant surge in dam construction activity in Japan (Takahashi, 2004). In Japan, the importance of dams in flood control cannot be overstated, given that nearly half of the country’s population resides in low-lying areas prone to flooding, resulting in substantial devastation (Itsukushima et al., 2021; Yoshimura et al., 2005). Despite the undeniable benefits offered by these structures, an increasing body of research has raised concerns regarding the environmental consequences associated with dam construction in Japan. Issues such as biodiversity degradation (Fukushima et al., 2007; Hatano et al., 2005) and alterations in fish species composition (Mori, 1999; Nagasawa et al., 2009) have garnered attention, prompting a closer examination of the trade-offs involved in such development initiatives.

This present study holds significant importance in enhancing our comprehension of Japan’s role in the agricultural development of Indonesia, particularly within East Java. Notably, Japan’s involvement in irrigation infrastructure stands as a critical factor in the successful promotion of rice production. Contrary to common perception, Japan’s impact extends beyond the realms of manufacturing and automotive industry. Furthermore, from a theoretical standpoint, this study offers a fresh perspective on Indonesia’s agricultural development success story. It transcends previous seminal works such as Geertz’s ‘Agricultural Involution’ (1963) and Booth’s ‘Agricultural Development’ (1988). Geertz’s analysis sought to elucidate the stark differences between Japan and Indonesia in terms of agricultural productivity, while Booth’s study underscored the similarities between late 19th and early 20th century Japan and Indonesia in the 1960s–1980s. However, rather than merely scrutinizing why these two nations differ or resemble each other, this study delves into the intricate connections between Japan and Indonesia from the 1970s onward. It examines how Japan’s influence on Indonesia’s agriculture and environmental landscape burgeoned through collaborative efforts in irrigation infrastructure.

To address a critical gap in our understanding, this study will spotlight Japan-funded irrigation infrastructure. Its primary objectives are to elucidate the development of Japan-funded irrigation infrastructure along the Brantas River in East Java, delineate the construction processes involved, and scrutinize the infrastructure’s impact on the agricultural productivity and the environment. The study contends that Japan played an integral role in the agricultural development within the Brantas River watershed during the New Order period. By focusing on this specific region, the research aims to unravel the reasons behind Japanese agencies’ involvement in irrigation infrastructure construction, delineate the construction process, and assess the resultant impact on agricultural production and environmental conditions. Through this investigation, we anticipate addressing key questions surrounding the motivations, methods, and outcomes of Japan’s engagement in irrigation infrastructure development in East Java.

The implementation of irrigation infrastructure, encompassing dams, weirs, lakes, and irrigation networks, along the Brantas River basin, epitomized a river development paradigm. Central to this paradigm were strategies such as river correction involving straightening, cutting, narrowing, simplifying, and various river engineering techniques such as damming, wiring, and diverting (Maryono, 2003). The ethos behind this approach was to harness scientific and technological advancements to harness the river’s potential in service of human needs. This ideology found expression in President Soeharto’s address commemorating the completion of the Karangkates dam on 2 May 1972, a significant milestone in the Brantas river development initiative. The overarching objectives of this endeavor were articulated as follows: ‘to regulate the Brantas river’s course, thereby preventing flooding in the surrounding areas… [and] to utilize the abundant water resources to enhance livelihoods… through irrigation for increased food production and augmented inland fishery output’ (Soeharto, 1972). President Soeharto underscored the notion that development entails harnessing the forces of nature to advance human welfare. Aligned with this ethos, the Brantas river’s flow was meticulously regulated and managed to facilitate improved living standards for the local populace.

This article will address two principal issues. Firstly, it will delve into the factors driving the construction of irrigation infrastructure along the Brantas River basin, deemed imperative for the inhabitants of this region during the New Order era. To elucidate this matter, an exploration of the agricultural sector in Indonesia, particularly in East Java province, is necessary, alongside an examination of the challenges stemming from inadequate irrigation infrastructure. Secondly, the article will scrutinize the motives behind Japan’s engagement in the region’s irrigation infrastructure development. This aspect warrants attention due to Indonesia’s array of potential collaborators, including the Netherlands, renowned for its expertise and technology in irrigation infrastructure. Additionally, Indonesia shares historical ties with the Netherlands, with remnants of Dutch colonial irrigation systems still prevalent in post-colonial Indonesia, notably on Java Island (Ertsen, 2005). The intriguing shift towards Japan, rather than the Netherlands, in spearheading irrigation infrastructure development in East Java merits further exploration. It is posited that a confluence of factors, including the economic and environmental challenges in the Brantas River area, governmental decisions, and Japanese agency support, drove the development of irrigation and flood control infrastructure along the river. Japan’s substantial contribution to this endeavor can be traced back to its historical involvement during the Japanese occupation era and subsequent post-war negotiations with the Indonesian government concerning war compensation issues.

2. Methods

The present study constitutes a historical investigation, making the utilization of a historical methodology imperative for comprehensively addressing the subject matter. This approach is deemed optimal due to the study’s focus on historical events and processes, necessitating reliance on historical documents as the sole means to probe realities that have since vanished. Employing both primary and secondary historical sources, the study’s source materials primarily comprise corporations’ reports. The acquisition of primary sources has been significantly facilitated by the ANRI publication based in Jakarta, which catalogues the extensive archival materials within the Malang based Perum Jasa Tirta’s collection (Santoso, 2020). Notable among these primary sources are various reports from Nippon Koei Co Ltd, such as the ‘Study on the Wlingi Project’, ‘Wlingi Multipurpose Project Report on Groundwater’, ‘Feasibility Report on the Tulungagung Drainage Project’, and ‘Additional Investigation Report for Detailed Design Work of the Irrigation Project in Tulungagung’. Additionally, reports pertaining to irrigation projects along the Brantas River in Malang, Blitar, and Nganjuk regencies have been collected from the Directorate General of Irrigation and the Indonesian Minister of Public Works.

A significant portion of the collected materials originates from institutions such as the Provincial Library and Archival Office of East Java Province (Bapersip Jatim) in Surabaya, the Brantas River Resources Office in Surabaya, and the Jasa Tirta Company in Malang. Furthermore, materials were gathered from various locations within East Java, including archival and library resources in Blitar, Tulungagung, Kediri, Nganjuk, and Mojokerto. Official publications by the Provincial Office of Statistics of East Java (BPS Jawa Timur) regarding irrigation networks, food crop cultivation, and agricultural production figures have also been instrumental. Additional materials were sourced from various institutions in Jakarta, notably the National Archives of the Republic of Indonesia (ANRI) and the National Library of the Republic of Indonesia (PNRI). Secondary sources encompass articles, books, and unpublished research reports collected from diverse locales, with particular emphasis on sources from Surabaya, Yogyakarta, and Jakarta.

2.1. The war reparations fund and Japan’s expanding engagement

The involvement of Japan in irrigation infrastructure development in Indonesia has been a longstanding phenomenon, representing a resurgence of historical interest within a contemporary political context. During the period of occupation, Japan undertook several irrigation projects in Java, notably including the construction of the Yoshiro Canal (now known as the Mataram Canal or Selokan Mataram) in Yogyakarta, the Neyama Tunnel in Kediri (Kurasawa, 1993; Sato, 1994), and the New Sampean Irrigation Project in the easternmost region of Java (Nawiyanto, 2007). However, some of these projects remained incomplete. Following a hiatus during the revolution and the early years of independence, initiatives commenced during the occupation were revived. Japan’s increasing involvement in the development of irrigation infrastructure in East Java and other parts of Indonesia during the post-independence period was closely linked to war reparations payments. Initially undertaken as a duty, Japan’s participation in the construction of irrigation systems funded by war reparations not only fulfilled an obligation but also provided opportunities for Japan to extend its influence in shaping Indonesia’s irrigation infrastructure.

The surrender of Japan to the Allies on 14 August 1945, marked the conclusion of the Japanese military occupation of Indonesia and triggered the imposition of consequences on Japan as the defeated party in the war. Japan was compelled to bear the full costs and losses incurred during the conflict. This obligation was enshrined in the San Francisco Peace Treaty, which Japan signed on 8 September 1951 (Kurasawa, 2019). Article 14 (a) of the Treaty stipulates that

‘It is recognized that Japan should pay reparations to the Allied Powers for the damage and suffering caused by it during the war. Nevertheless, it is also recognized that the resources of Japan are not presently sufficient if it is to maintain a viable economy, to make complete reparation for all such damage and suffering, and at the same time meet its other obligations.’ (United Nations Treaty Series No 1832, 1952).

The payment of war reparations was intended for the benefit of the Allied Powers and the territories they occupied, including Indonesia. The years of Japanese occupation inflicted extensive damage and suffering upon the Indonesian people.

The emergence of Japanese military rule ushered in a new authority aiming to reshape the Indonesian economy to align with Japan’s strategic objectives. Among the foremost goals of the Japanese occupation government was the realization of the ‘New Java Construction’ initiative. This initiative designated Java as the primary source of food supplies for the Japanese army in Southeast Asia and sought to achieve self-sufficiency in food production within the occupied territories (Sato, 1994). To fulfill these objectives, the Japanese military administration launched vigorous campaigns to mobilize farmers and boost rice production, as evidenced by numerous publications and eyewitness accounts (Kurasawa, 1993). The Japanese authorities held a strong belief in the agricultural potential of Java and envisioned that by implementing agricultural techniques developed in Japan, Java could become a significant contributor to Japan’s interests in Southeast Asia. They were confident that with modifications to rice cultivation technology and techniques, Java could generate a surplus of rice substantial enough to support Japan’s export ambitions, estimated at between 150,000 and 200,000 tons in 1943 (Margana, 2010). Bolstered by this optimism, Japanese agricultural experts, including figures like Mori Hideo, were dispatched to Java in 1942. Tasked with assessing current practices and offering practical recommendations, these experts played a pivotal role in the efforts to enhance rice cultivation on the island (Reid & Akira, 1986).

The Japanese pursued two main strategies to promote rice production in Java. Firstly, they expanded the acreage dedicated to rice cultivation by repurposing land, including converting estate lands deemed of lesser strategic importance to Japan’s interests. One report suggests that ∼46,000 hectares of estates and 20,000 hectares of coffee plantations were repurposed for food crop cultivation. In Priangan, seven tea estates covering 4078 hectares were transformed into rice fields, where workers from the estates, as well as members of Seinendan and Keibodan from nearby villages, were engaged in cultivation efforts (Kurasawa, 1993). Similarly, in Besuki residency, significant portions of tobacco estates in the Jember regency were transitioned to rice cultivation. Areas previously used for sugarcane cultivation were repurposed for rice farming (Nawiyanto, 2005). Additionally, the Japanese authorities undertook efforts to expand agricultural land by converting forested areas. According to a NEFIS report, ∼15,000 hectares of forest land were transformed into agricultural fields. Notable among these conversions was the former Yamada village, now known as Jatireja village, located in the Subang regency. Furthermore, new agricultural lands were created in Bogor residency, with reports indicating the establishment of 850 hectares of such lands in 1943, ready for cultivation (Kurasawa, 1993). Similar initiatives to reclaim agricultural lands from forests were also undertaken in the remote regions of East Java (Nawiyanto, 2005).

To bolster rice production, Japan embarked on the development of irrigation infrastructure. In the Besuki residency, for instance, Japanese authorities launched the ‘Sampean Baru Irrigation Project’. The government earmarked ƒ 700,000 for its financing, with construction commencing on 14 August 1944, with a target completion within one year (Soeara Asia, 1945). Meanwhile, in the Yogyakarta Sultanate, construction began on the Yoshiro Canal in 1943, linking the Progo and Opak rivers. This project, which mobilized numerous romusha workers, was perceived as part of the sultan’s strategy to prevent his people from being conscripted for Japan’s endeavors elsewhere (Suharman, 2018). In Kediri Residency, the Japanese authorities undertook the construction of the Neyama or Niyama tunnel to mitigate the recurrent threat of floods to the Tulungagung regency. This undertaking required JP¥ 750,000 and the labor of 20,000 romusha workers under Resident Kihara Enji. Construction commenced in February 1943 and concluded in July 1944. Upon completion, ∼16,000 acres of land along the banks of the Brantas River were reclaimed and converted into agricultural plots.

However, reality diverged significantly from expectations. The Japanese endeavor to boost rice production fell short of its objectives. Instead of yielding higher outputs, rice production in Java plummeted during the years of Japanese occupation. From 8,302,000 tons in 1942, rice production declined sharply to 6,470,000 tons in 1945. Similarly, there were declines in the production of other food crops during the same period; maize production dropped from 2,165,000 to 1,399,000 tons (Van der Eng, 1996, p. 299). Anne Booth’s estimate suggests that rice production in Java declined by 4.8% and food crop production in general by 5.1% during the Japanese occupation period (Booth, 1988). The decline in rice and food crop production exacerbated the impact of Japanese occupation on the local economy and the lives of the population. Instead of prosperity, the Japanese occupation brought immense suffering, widespread starvation, and chronic poverty to the Indonesians (Abdullah et al., 1978; Saleh, 2000).

The occupation by the Japanese and the subsequent independence revolution left Indonesia’s infrastructure severely damaged. Numerous offices, factory buildings, machine tools, infrastructure facilities, and transportation equipment lay in ruins, with debris strewn across the landscape. Economic losses resulting from this destruction were estimated at ∼2.3 trillion guilders. The rehabilitation efforts encompassed various sectors, with 814 million guilders allocated for the mining industry, another 814 million for agriculture, 140 million for manufacturing, 172 million for rail and tram networks, 150 million for marine vessels, 80 million for ports, and 85 million for vehicle replacement. Notably, repairing the rail transportation sector alone necessitated 300 passenger carriages, 3000 freight cars, 150 locomotives, and 55,000 tons of rail. The total cost required to rehabilitate the economic infrastructure was roughly estimated to be half of the total GDP in 1941 (Van Zanden & Marks, 2012).

For the newly independent Indonesian government, the imperative of post-war economic reconstruction was compounded by a host of simultaneous challenges. Under the KMB agreement between the Indonesian government and the Netherlands in 1949, Indonesia assumed the responsibility of servicing the debts accrued by the former Dutch East Indies colonial government, amounting to ∼4.3 billion guilders (Ricklefs, 2008). This debt burden was monumental for a fledgling nation, particularly one ravaged by war and possessing limited revenue streams. The establishment of an effective tax system was still in progress, and efforts to augment income from alternative sources were underway. Moreover, enhancing access to alternative financing from foreign countries and international agencies remained a priority (Leirissa et al., 1996). The severity of these financial challenges led Higgins (1957) to characterize Indonesia as confronting a first-class financial crisis.

The Indonesian government faced urgent financial needs to address budget deficits and had to explore all possible avenues to fund its programs. Among the limited sources of revenue available at the time, war reparations emerged as one of the most crucial, albeit challenging, options to pursue. According to the Djuanda Mission, the losses incurred from Japan’s wartime campaigns and military occupation amounted to US$ 17.5 million. However, Japan viewed Indonesia’s demand for war reparations as excessive. The requested amount far exceeded Japan’s annual gross national income of US$ 15.2 million in 1951 (Nishihara, 1993). Consequently, Japan rejected Indonesia’s claim, deeming it inconsistent with the provisions of the San Francisco Treaty. Japan insisted that the reparations payment be reduced to a more manageable level that would not unduly burden its economy.

The issue of war reparations became a contentious point in negotiations between Indonesian delegates and their Japanese counterparts, yet it was not the sole concern. Other critical matters revolved around the scope of compensation and the method of payment for war reparations. Indonesia insisted that the compensation should be extended to include restitution for the hardships endured by romusha workers and women coerced into serving as sex workers for Japanese soldiers during the occupation. However, Japan rejected this demand, arguing that Article 14 of the San Francisco Treaty did not include provisions for individual compensation to comfort women. Additionally, Japan opposed Indonesia’s request for cash payments, citing the treaty’s stipulation that war reparations should be provided in the form of services rendered by the Japanese people (Kurasawa, 2019).

In Japan, two perspectives emerged regarding the issue of war reparations to Indonesia. Firstly, some advocated for minimal payments, citing concerns over the potential strain on the Japanese economy. They argued that payments should be kept as small as possible to alleviate burdens on the Japanese populace. Additionally, there were those who deemed war reparations to Indonesia unnecessary, asserting that Japan was not directly involved in conflicts against Indonesia. Instead, it was believed that Japan aided Indonesia in achieving independence from Dutch colonial rule. During the occupation, Japan supported preparations for Indonesian independence, contributed to the drafting of the Indonesian constitution, and even provided weaponry to Indonesian defense forces. Secondly, another faction viewed war reparations as an opportunity to enhance economic relations. In a speech to Japanese business leaders in Osaka in 1954, Okazaki emphasized that war reparations should not be perceived merely as an obligation but rather as a chance to engage in Southeast Asia’s development and reap benefits from it. It was believed that investing in war reparations could yield long-term advantages for Japan, fostering trade and investment opportunities in the region (Kurasawa, 2019).

Following extensive negotiations spanning from September 1951 to December 1957, Indonesia and Japan eventually reached an agreement. The treaty was formally signed on 20 January 1958, by the Indonesian Minister of Foreign Affairs, Mr. Subandrio, and his Japanese counterpart, Mr. Aiichiro Fujiyama. As outlined in Article 4 of the Treaty, the war compensation amounted to US$ 223,080,000 (JP¥ 80,308,800,000) over a duration of 12 years. The compensation was to be provided in the form of capital goods and services. Annually, an average of US$ 20,000,000 (equivalent to JP¥ 7,200,000) was to be disbursed for eleven years, with the remaining amount settled in the twelfth year. The treaty received approval under Law No. 13 on 27 March 1958 and was subsequently ratified by President Sukarno on 10 April 1958 (Nawiyanto, 2022). To further bolster cooperation between the two nations, Indonesia and Japan officially re-established diplomatic ties in April 1958 (Dick et al., 2002).

Concurrently, alongside the finalization of the peace and war reparations treaty, an economic cooperation agreement was also forged between Indonesia and Japan. This collaboration was deemed crucial as it entailed significant Japanese capital investments and loans, exerting substantial and long-term influence on Indonesian economic development (Nishihara, 1993). Despite the completion of war reparations compensation payments, Japan’s investment and economic assistance continued to pour into Indonesia across various sectors, thanks to the existing economic agreement between the two nations In conjunction with capital and technical aid from socialist countries such as the Soviet Union, Eastern European countries, and The People’s Republic of China, Japan’s assistance in the form of war reparations compensation and loans played a pivotal role in supporting the implementation of Indonesian development programs (Feith, 1995). Even after the aid from socialist countries ceased in the late 1960s, Japan’s capital and technical assistance persisted. This support further expanded during the New Order period.

In East Java Province, the key projects covered by war reparations compensation contracts included the Neyama Tunnel in Tulungagung, the Karangkates Dam, and the Konto River Dam. These projects were valued at $US 1,972,000, $US 19,237,000, and $US 3,441,000, respectively. Nippon Koei and Kajima Construction were entrusted with the implementation of these three projects. Their objective was to mitigate floods along the Brantas River and exploit its irrigation potential. Additionally, there were projects such as the Banyuwangi-based paper company valued at $US 8,500,000 and the Lawang (Malang)-based textile company valued at $US 4,906,000. Tomen Company was responsible for managing both endeavors (Nishihara, 1993). The completion of projects funded by war reparations compensation was followed by additional initiatives along the Brantas River and its tributaries, supported by significant Japanese aid and agencies.

Two Japanese corporations played pivotal roles in the development of irrigation infrastructure along the Brantas River: Nippon Koei and Kajima. Nippon Koei, established in 1946 by Yutaka Kubota, had a distinguished history in dam and hydropower plant development spanning nearly two decades. Kubota’s career included notable projects in Japan and Japan’s occupied Korea, such as the Pujon River Dam (1929), Changjin River Dam (1938), and Sup’ung Dam (1942). He held significant positions, serving as the chief engineer for Chochitsu hydropower construction and later assuming roles as managing director and director of the Chosen Power Transmission Company. Kubota had visited Indonesia before and during Japan’s occupation years, fostering a keen interest in dam and hydropower facility development in the region. His pre-war and wartime experiences significantly contributed to the accumulation of technical expertise, shaping Nippon Koei’s paradigm of ‘comprehensive development’. This approach emphasized the construction of multipurpose dams and other infrastructure to foster national development (Moore, 2020).

In 1953, Kubota visited Indonesia and met with Djuanda, the chairman of the National Planning Board (Dewan Perancang Nasional). During the meeting, Kubota proposed the Asahan Development Project to Djuanda, who pledged to present the proposal at a cabinet meeting. Upon returning to Japan, Kubota promptly met with Prime Minister Yoshida and urged the Japanese government to take on the Asahan Project. Additionally, Kubota explored the possibility of using war compensation funds to finance the project (Nishihara, 1993). Despite his efforts, Kubota was unsuccessful in securing the Asahan project, which was ultimately awarded to the Soviet Union for political reasons. However, Kubota’s company managed to secure nearly exclusive rights to handle infrastructure projects financed by war compensation funds in East Java. This success was attributed in part to Kubota’s adept lobbying skills, which garnered support from Indonesian officials within the Department of Public Works and even President Sukarno himself. During President Sukarno’s visit to Japan in 1963, he invited Kubota to dinner and sought his assistance in arranging a meeting with President Nkrumah of Ghana. At times, Indonesian ministers sought Kubota’s help in persuading President Sukarno and Minister Djuanda to approve specific projects and allocate state budget funds accordingly (Nishihara, 1993).

Kajima, established in 1840, is a renowned Japanese construction company that has evolved into one of the oldest and largest in the industry. Its headquarters is located in Motoakasaka, Minato, Tokyo. In the early 1960s, Morinosuke Kajima served as the chief director of the company and also held a prominent position in the Indonesia-Japan Association, comprising over a hundred members engaged in business relations with Indonesia. Kajima, through this association, vigorously advocated for the Japanese government’s involvement in mediating the Indonesia-Malaysia dispute in the 1960s. Concerned about the escalating influence of communism and Sukarno’s perceived neglect of Indonesia’s economic management, Kajima passionately urged for Japan’s active role in resolving the Indonesia-Malaysia conflict. It is worth noting that Kajima’s advocacy for mediation was closely linked to the company’s business interests. Kajima’s company was entrusted with significant dam projects in East Java, funded by Japan’s war compensation payments to Indonesia. Beyond his business endeavors, Morinosuke Kajima was widely recognized as a politician, diplomat, and intellectual who espoused Pan-Asian ideas. As a member of the ruling party and the Foreign Affairs Commission, Kajima played a pivotal role in shaping Japan’s Asia policy (Hirakawa, 2011; Nishihara, 1993).

The disbursement of war compensation funds to Indonesia significantly elevated Japan’s position in Indonesian development. Before the signing of the war compensation agreement in December 1957, Japanese business corporations had a limited presence in Indonesia and played a comparatively minor role in the country’s affairs (Wie, 2005). However, by spearheading projects funded through war compensation payments, certain Japanese corporations gained unprecedented access to operate businesses in Indonesia. They enjoyed privileges that were largely inaccessible to many Western corporations during the Sukarno era, and they demonstrated an anti-Western stance against capitalism (Kurasawa, 2015). The burgeoning presence of Japanese corporations in Indonesia represented a substantial advantage for Japan, especially in the decades following the disappearance of most Western enterprises, notably the longstanding Dutch concerns. This shift has facilitated Japan’s increased involvement and influence in Indonesian developmental endeavors.

2.2. Japan agencies and Brantas irrigation infrastructure

The influential presence of Japanese agencies in East Java is particularly notable in the realm of irrigation infrastructure development projects, particularly along the Brantas River Basin. As one of East Java’s three primary irrigation zones, alongside the Bengawan Solo Irrigation Area and the Pekalen-Sampean Irrigation Area (Fox, 1997), the Brantas River Basin harbors the largest expanse of rice fields in the region, its irrigation infrastructure distinctly shaped by Japanese influences. The development of the Brantas River underwent three interconnected master plans. Master Plan I was formulated in 1959 with technical support from the Japanese government through Kabushiki Kaisha. Subsequently, Master Plan II, initiated in 1973, entailed comprehensive surveys, investigations, and feasibility studies conducted by the Brantas River Basin Development Project, benefiting from technical assistance from Japan’s Overseas Technical Cooperation Agency (OTCA). Concurrently, Master Plan III, crafted in 1985, also received technical guidance from the Japanese government (Direktorat Jenderal Sumber Daya Air Wilayah Tengah, 2002).

The development of the Brantas River area unfolded in two distinct stages. The initial stage encompassed the construction of both upstream and downstream Brantas projects aimed at mitigating water loads. Upstream initiatives comprised the Karangkates Dam, Lahor Dam, Selorejo Dam, Widas Dam, Kesamben Dam, Amprong River Dam, and Lesti River. Downstream endeavors included the New Lengkong Weir and Porong River Improvement (Projek Induk Serbaguna Kali Brantas, 1972). The subsequent stage prioritized the middle Brantas project, emphasizing the reduction of sand loads in this section. Noteworthy projects in this phase included South Tulungagung, Wlingi Dam, sand channels, Lodoyo irrigation, sand capture along Kali Badak and Kali Putih, and sand control in Central Brantas. Five principal projects were identified along the Brantas River basin: Karangkates Dam, Wlingi Dam, Lengkong Weir, Selorejo Dam, and Porong River Rehabilitation, with supplementary initiatives such as the Widas irrigation network (Sutami, 1972).

The inaugural and most extensive irrigation infrastructure project supported by Japan was the Karangkates Dam in Malang. Planning for the dam concluded in 1961, drawing upon research conducted by the Nippon Koei Corporation. Construction commenced on 1 December 1962, with all equipment entrusted to the Kajima Construction Corporation. Initially, during the project’s first two years, there was minimal involvement of Indonesian technicians. However, following the Indonesian government’s request for increased participation of local personnel and subsequent specialized training, Indonesians gradually became more engaged in the project (Projek Induk Serbaguna Kali Brantas, 1972). By 1966, there were 22 Japanese staff members employed in the Karangkates Project. This figure grew to 44 personnel in 1968 and further to 59 by 1970. Concurrently, the number of Indonesian workers in the project also saw significant growth, from 413 in 1966 to 1466 by 1970 (Suharyono, 1992).

The construction of the Karangkates Dam incurred a total cost exceeding USD 28.7 million, with funding sourced from two channels provided by Japan. The first stream of funding derived from the war compensation fund, while the second originated from foreign loans repayable by the Indonesian government. Specifically, the war compensation fund allocated for the construction amounted to IDR 5,081,374,728 (equivalent to USD 17,103,000), while funds from the Japanese Loan Project totaled IDR 3,228,499,500 (equivalent to USD 11,135,000). Overall, Japanese funding for the Karangkates project constituted 58.33% of the total cost, comprising 35.45% from the war compensation fund and 22.88% from the project loan (Projek Induk Serbaguna Kali Brantas, 1972). The dam was officially inaugurated by President Soeharto on 2 May 1972 (Dwipayana & Samsudin, 1991). Tragically, fatalities occurred during the construction process, including some Japanese workers among the victims (Sutami, 1972).

One pivotal task necessitated by the dam project was the relocation of residents whose settlements were impacted. Numerous meetings were convened to underscore the significance of the Karangkates Dam, with assurances of compensation in the form of permanent or temporary housing, building materials, or financial remuneration for those affected. The provision of compensation elicited varied reactions. Some residents found it satisfactory, noting that the land value in Bandung Hamlet, where relocation occurred, surpassed that of Karangkates Village. Bandung Hamlet’s proximity to the Malang-Blitar highway facilitated transportation. Conversely, those feeling disadvantaged argued that the replacement land was smaller than their Karangkates Village plots. They also highlighted the permanence of their former homes and their convenient proximity to workplaces. Consequently, the relocation from Karangkates Village to Bandung Hamlet encountered challenges. Intensive persuasion and pledges of mosque facilities, markets, sports fields, and assembly halls were necessary to convince initially reluctant residents. Others yielded to relocation under the threat of forced demolition. By the end of 1972, the relocation of 85 affected families to Bandung Hamlet, renamed Karangkates Baru, was successfully executed (Suharyono, 1992).

Another noteworthy project assisted by Japan was the Wlingi dam located in Blitar. This dam, a composite structure comprising concrete and earth fill, boasts impressive dimensions: with a height reaching 46 meters from the bottom of the deepest excavation and a peak elevation of 167 meters. Its length spans 735 meters, with a width of 8 meters, featuring an upstream slope of 1:3.50 and a downstream slope of 1:2.50 (Direktorat Jenderal Sumber Daya Air Satker Direktorat Bina Operasi dan Pemeliharaan, 2012). Although conceived in the early 1960s, the project’s materialization was delayed for approximately a decade. The Directorate General of Irrigation convened a meeting in Tretes, East Java, on 29–30 June 1970, to deliberate on the Wlingi Project. During this session, several key points were agreed upon, including the exploration of alternatives to the initial plan proposed by Nippon Koei and the consideration of additional ideas to ensure sound technical and economic feasibility. Subsequently, the outcomes of the Tretes meeting led to the establishment of the Wlingi Team in 1970, chaired by Ir. Soetojo and with Ir. Srimoerni Doelhomid serving as Deputy Chair (Direktorat Djenderal Pengairan Departemen Pekerdjaan Umum dan Tenaga Listrik, 1970).

On 30 August 1970, the Wlingi Team embarked on a journey from Jakarta to Tokyo. The delegation comprised Ir. Soetojo, Ir. Srimoerni Doelhamid, Ir. Soerjono, Ir. Soebadi Koesno, Ir. Mardjono Notodihardjo, and Achmad Ashari Bie (ANRI, Jasa Tirta, No. 69). The team had a specific agenda for discussion during their visit to Japan, which included the following key points:

1. Determining the schedule and formulating the discussion outcomes for Wlingi Project I (31 August–September 2 1970)

2. Observing the Tone River Basin Development and engaging in field discussions (3–5 September 1970).

3. Reviewing sand control projects around Mount Fuji and participating in field discussions (8–9 September 1970).

4. Convening discussions on the Wlingi Project II (10 September 1970).

5. Upon their return from Tokyo (12 September 1970), the Wlingi Team submitted a comprehensive report on their mission to the Minister of Public Works and Manpower and the Director General of Irrigation (Badan Pelaksana Proyek Induk Pengembangan Wilayah Sungai Kali Brantas, 1987).

Following numerous talks and deliberations, a meeting held in Werdhapura, Sanur, Bali, on 2–3 November 1970, concluded that the Wlingi dam could proceed with the site design proposed by Nippon Koei and endorsed by the Wlingi Team (Nippon Koei Co. Ltd., 1976). The findings of the Nippon Koei study were subsequently presented to the Government of Indonesia, while the Wlingi Team also submitted recommendations to the Minister of Public Works and the Directorate General of Irrigation regarding the planning of the Wlingi Project (PT Anggun Tridaya, 1970).

The construction costs of the Wlingi dam amounted to US$ 38.33 million, with project funding sourced in rupiah, yen, and dollars. Rupiah funding was provided by the Government of Indonesia, while yen or USD funding came from overseas sources. Specifically, the Japan Overseas Economic Cooperation Fund (OECF) facilitated the provision of foreign funds in the form of loans to support the project (Department of Public Works & Energy, 1975). Nippon Koei Ltd served as the consultant for the Wlingi Project, with a team of six Japanese consultants dedicated to the project: Y. Marusugi (Resident engineer), Y. Miura (Mechanical engineer), N. Ebisawa (Electrical engineer), N. Tok (Administrative staff), K. Honmo (Procurement Expert), and T. Ohkanda (Guidance engineer) (Roejito, 1980). Additionally, several Japanese corporations, including Nichiment, Co., Ltd and Sumitomo Shoji Kaisha, were involved in the project (Nippon Koei Co. Ltd., 1982; Perusahaan Umum Listrik Negara, 1976). The construction of the Wlingi dam spanned four years. President Suharto officially inaugurated the dam on 12 November 1977, although its completion required an additional year.

In the downstream area of Brantas, Japan participated in the construction of the New Lengkong Weir, replacing the outdated Dutch-built structure. Situated 150 meters downstream from the Old Lengkong Weir, construction commenced in 1970 and concluded in 1973. The project incurred a total cost of IDR 1,422,568,567 and JPY 478,839,544. Rupiah funds were secured from Indonesia’s state budget, while yen funds were obtained through loans from the Japanese government. Noteworthy Japanese corporations vied for the project tender, including Sumitomo Shoji Kaisha Ltd., C. Itoh & Co. Ltd., Mitsubishi Shoji Kaisha Ltd., Toyota Menka Kaisha Ltd., Mitsui & Co. Ltd., Nichimen Co. Ltd., Marubeni Co. Ltd., and Nomura (Badan Pelaksanaan Proyek Induk Pengembangan Wilayah Sungai Kali Brantas, 1980a, 1980b). Additionally, other Japanese companies competing for the project included Tomen-Takada Kiko, Sumitomo-Marushima Gate, Nichimen-Hitachi Ship Building, Marubeni-Nippon Kokan, and Sakai Iron Works. Ultimately, the project tender was awarded to Tomen-Takada Kiko. Meanwhile, Nippon Koei Co. Ltd. assumed the role of supervisor and technical guide (Badan Pelaksanaan Proyek, 1979). The New Lengkong Weir was officially inaugurated on 16 November 1973, with the Minister of PTUL, Sutami, symbolically activating the floodgate button (Album Foto 4, 1980).

Japan’s involvement extended to the Widas irrigation project, which received technical assistance in 1973 from Japan’s Overseas Technical Cooperation Agency (OTCA). The construction project was overseen by the Executive Board of the Brantas Multi-purpose Project. Feasibility studies for the project commenced in October 1975 (Direktorat Jenderal Pengairan, 1976a, 1976b). Consultants from Nippon Koei Co. were engaged for the project, with a team of seven personnel assigned to various roles: H. Sonoda (team leader), K. Furudate (foundation engineer), T. Kagayama (mechanical engineer), T. Nakano (soil engineer), K. Ohnuma (civil engineer), O. Takahashi (graphic engineer), and Matsuura (irrigation engineer) (Staf Proyek Brantas, 1980).

The realignment of the Widas River was undertaken in conjunction with the development of the Widas Irrigation network to address the recurring 25-year flood cycle of the Widas River. This endeavor encompassed the straightening of 81.8 km of the river course, comprising various segments including the lower Widas River (21 km), the upstream Widas River and the Ulo River (15.1 km), the Sudetan channel and the upstream Ulo River (7.9 km), the Kedungsoko River (9.8 km), the Kuncir River (10.3 km), and its tributaries (17.7 km). Integral to the project was the establishment of retardation areas along the Ulo River, Kedungsoko River, and the mouth of the Widas River. The feasibility study for the project received support from the Japan International Cooperation Agency (JICA) and was finalized in March 1986. This study included comprehensive surveys and soil investigations conducted throughout the Widas watershed, with a particular focus on downstream river regions (Direktorat Jenderal Pengairan, 1987; Prabowo & Nawiyanto, 2020).

Japan played a significant role in the construction of the Wonorejo dam in Tulungagung, which spanned ∼7 years for completion. The total expenditure for the Wonorejo Reservoir construction project amounted to JP¥ 25.282 billion (Lembaga Pengabdian Kepada Masyarakat, 2003). Project financing comprised foreign currency from Japan (JP¥ 15.932 billion yen) and local currency (IDR 143.01 billion) (Mardiyah, 2016). In addition to Indonesia’s state budget, funding for the project was sourced from loan assistance provided by Japan’s Overseas Economic Cooperation Fund (OECF). The initial loan agreement contracts were prepared by the Directorate General of Irrigation for phases I in March 1993 and II in January 1996. The Director General of Irrigation acted as the employer, while OECF, serving as the financial agent, and the Brantas Agency, played crucial roles in managing and supervising construction activities. Nippon Koei Co Ltd served as the consultant service for the project over a period of 65 months, from 1 June 1994 to 31 October 1999. Y. Marusugi acted as the project director, with Mr. M. Kiyoura serving as the team leader and Mr. A. Shiroya as the construction planner. A total of 1617 consultants and contractors were involved in the project, comprising 370 foreign experts and 1247 Indonesian experts (Lembaga Pengabdian Kepada Masyarakat, 2003). Additionally, manual laborers recruited from Wonorejo and its surrounding villages contributed to the project’s workforce.

2.3. Impact of the Japan-supported irrigation infrastructure

The construction of Japan-supported irrigation infrastructure along the Brantas River has yielded significant ramifications for both the agricultural economy and the environment. Notably, the construction of the Karangkates Dam has facilitated irrigation across an expansive area of ∼30,000 hectares of rice fields (Projek Induk Serbaguna Kali Brantas, 1972). This expansion has resulted in an augmented rice cultivation area of nearly 3000 hectares. Throughout the 1970s and into the early 1980s, despite annual fluctuations, the rice cultivation area consistently surpassed pre-dam levels. This augmentation was primarily enabled by the incorporation of additional rice cultivation zones across various locales. Before the dam’s operation, these areas typically served as sites for secondary crop cultivation during periods of limited irrigation availability, particularly in the dry season. However, with the Karangkates Dam ensuring a reliable water supply, the constraints of water scarcity were alleviated, thereby facilitating uninterrupted rice cultivation. Notably, the cultivation of lowland rice experienced a marked increase as farmers capitalized on the opportunity to engage in secondary and tertiary rice plantings, particularly following the introduction of short-duration rice varieties (Fox, 1997).

In tandem with the expansion of the harvested area, rice production has demonstrated a notable upward trajectory since 1972. In 1971, production stood at ∼187,000 tons; however, by 1972, it had surged to over 233,000 tons, marking an increase of 46,000 tons. Since 1974, rice production in Malang Regency has consistently surpassed the 300,000-ton mark. Between 1974 and 1983, production levels ranged from 302,000 to 423,000 tons, with the lowest recorded output in 1974 and the highest achieved in 1981. Fluctuations in production during the post-operational phase of the Karangkates Dam were primarily attributed to rice pest infestations. The substantial expansion of irrigated areas facilitated by the Karangkates Dam significantly contributed to the escalating trend in harvested area and rice production in Malang Regency. For instance, in Kepanjen District, rice production doubled from 19,900 tons in 1970 to 40,700 tons in 1982. Similarly, in Sumberpucung District, production increased by ∼50%, rising from 20,700 tons to nearly 31,300 tons (Santoso, 1986; Santoso, 1997).

In Blitar Regency, the provision of irrigation from the Wlingi Dam has facilitated the conversion of arid lands into fertile, irrigated fields. This transformation is not limited solely to Blitar Regency, where the Wlingi Reservoir was constructed, but also extends to Tulungagung Regency. The outcomes of this conversion process are outlined in Table 1. It is evident from the data that the conversion to irrigated lands in Blitar between 1980 and 1983 exceeded that of Tulungagung. The southern region of Blitar was predominantly characterized by arid lands, bisected from east to west by the Brantas River, and northern Blitar was similarly arid before the establishment of the reservoir. Before this development, only a small portion of agricultural lands in South Blitar benefitted from existing irrigation from the Brantas River. The creation of irrigated lands in South Blitar primarily occurred within narrow valleys nestled between hills, formed through sedimentation and erosion of the surrounding terrain (Mustopo, 1969; Setiyono, 2002).

Table 1. Conversion of drylands into irrigated fields (1980–1986).

Year	Blitar	Tulungagung	Total
1980	3069	324	3393
1981	3520	875	4395
1982	4045	2386	6431
1983	4095	3679	7784
1984	4095	4510	8605
1985	4110	5048	9158
1986	4115	5575	9690

Source: Shiamah (2019, p. 104).

The agricultural zones proximate to the dam were the initial recipients of irrigation water from the Wlingi Reservoir. Subsequently, as the distribution channels were completed, the benefits stemming from the Wlingi Reservoir gradually extended to areas situated farther from the river. Notably, between 1984 and 1986, the conversion of arid fields in Tulungagung surpassed that of converted agricultural fields in Blitar Regency. The aggregate conversion of arid lands in 1986 amounted to nearly 10,000 hectares across both regencies, constituting ∼79% of the targeted conversion of 12,600 hectares (Nippon Koei Co. Ltd., 1985). With the transition to irrigated lands, two contrasting agricultural practices emerged. From 1978 to 1990, the area under irrigation in Blitar doubled from 20,982 hectares to 40,331 hectares, while the extent of arid lands decreased by ∼10,000 hectares, declining from 55,244 hectares to 46,537 hectares (BPS Kabupaten Blitar, 1979, 1991).

The expansion of irrigated lands went hand in hand with the increased cultivation of food crops, particularly rice. In 1980, the harvested area of lowland rice in Blitar encompassed ∼56,400 hectares, a figure that rose to 57,700 hectares by 1990, marking an increase of about 1300 hectares. Concurrently, the harvested area of rice in Tulungagung experienced a significant surge during the same period, escalating by ∼6500 hectares, from 29,700 hectares in 1980 to nearly 36,200 hectares in 1990. Notably, the decrease in harvested area was observed solely for gaga rice, cultivated in rainfed areas. This demonstrated the success of the conversion of arid land into paddy fields, facilitated by the improved irrigation infrastructure comprising dams and distribution channels. Moreover, there was a notable shift in cropping patterns. Before the construction of the Wlingi Dam, land utilization was primarily limited to crop cultivation during the rainy season from October to February. Rice was cultivated in both irrigated and rainfed areas, while secondary crops were planted in arid lands. During the dry season from March to September, a substantial portion of the land was allocated for secondary crops, with only a limited area available for rice cultivation. Particularly during the peak of the dry season between July and September, a significant portion of agricultural land lay fallow, while paddy fields were utilized for secondary crop cultivation (JICA, 1986).

Information pertaining to the South Blitar area indicates that in the late 1960s, only irrigated lands situated close to the Brantas River could sustain rice cultivation, with a maximum of two planting cycles per year. However, there was a pressing need to expand the planting area. Dry rice cultivation was also practiced, with some villages allocating up to 80% of their land due to inadequate irrigation, leaving only 20% suitable for irrigated rice (Mustopo, 1969; Setiyono, 2002). During the dry season, a considerable portion of agricultural land was utilized for cultivating beans, cassava, or corn. In areas such as Wates and several other villages, agricultural lands remained fallow during the dry season due to water scarcity. This scarcity is further corroborated by historical accounts from a witness named Rewang, a resident of the South Blitar area in the latter half of the 1960s, who recalled only one planting cycle per year owing to the arid and infertile soil conditions (Hearman, 2015). Cassava emerged as the primary crop cultivated, serving as a staple food, although maize and dry rice were also cultivated during the growing season.

With the introduction of irrigation water from the Wlingi Reservoir and its distribution channels, a significant alteration in cropping patterns occurred. In numerous locations, the traditional cropping sequence shifted to (1) Rice → rice → rice, (2) Rice → rice → legumes/corn, and (3) Rice → legumes/corn → fallow. The irrigation supply from the Wlingi Dam led to an expansion of ∼2300 hectares in the area of irrigated lands suitable for year-round rice cultivation. Furthermore, the cultivation of rice twice a year and secondary crops on irrigated lands increased by over 5000 hectares. Specifically, the area of irrigated lands devoted to rice cultivation witnessed an increment of about 2000 hectares (Shiamah, 2019). Thanks to the fulfillment of irrigation requirements facilitated by the Wlingi Dam, rice cultivation has become more prevalent and is increasingly practiced on irrigated lands (Figure 1).

Figure 1. Wlingi Dam and Ricefields (Source: Photo Collection of Perum Jasa Tirta I).

Similar outcomes were evident with the Wonorejo Dam. The primary impact of enhanced irrigation distribution was the substantial expansion of irrigated lands. In the district, the area of irrigated lands increased from 21,161 hectares in 2000 to 24,005 hectares in 2009, representing an augmentation of ∼3000 hectares. This reservoir’s influence in expanding rice fields has also prompted crucial shifts in local farmers’ cropping patterns. Rice has historically been the predominant crop cultivated in irrigated lands. The assurance of irrigation needs has provided farmers with increased opportunities to intensify rice cultivation. The surge in harvested area, production, and productivity of irrigated rice between 2000 and 2009 can be attributed to farmers exploiting the expanded opportunities for rice cultivation, facilitated by the adequate irrigation guaranteed by the presence of the Wonorejo Reservoir.

Additionally, the reconstruction of the Lengkong Weir, which enhances irrigation distribution, has contributed to heightened rice yields in Sidoarjo Regency. In 1970, the harvested area of lowland rice amounted to ∼35,600 hectares. By 1980, this area had increased by over 3000 hectares. By the time Indonesia achieved rice self-sufficiency in 1985, the harvested area of lowland rice in Sidoarjo remained relatively consistent. The increase in harvested area was accompanied by a rise in rice production from around 177,000 tons in 1970 to over 203,000 tons in 1985. However, there was a noticeable decline in rice-harvested areas during the latter half of the 1980s, a trend that persisted into the 1990s and beyond. This decline was primarily attributed to the extensive conversion of irrigated lands for non-agricultural purposes, such as industrial complexes and settlements, in line with the industrialization process unfolding in the Sidoarjo area (Wasista, 2013). In 1971, the area of irrigated lands in Sidoarjo spanned 32,360 hectares (Bupati Sidoarjo, 2019). By 1980, it had increased to 32,809 hectares, marking a rise of almost 450 hectares. However, by 1996, the area of irrigated lands in Sidoarjo had dwindled to only 26,758 hectares (Kantor Statistik, 1983, 1997), representing a decrease of 6051 hectares.

The decline in irrigated lands and rice harvested areas was somewhat offset by an increase in productivity during the period from 1980 to 1996. In contrast to the trend of crop expansion observed from 1970 to 1985 followed by a decline in the subsequent period, the productivity of irrigated rice in Sidoarjo exhibited an upward trajectory from 47.86 quintals/ha to 57.39 quintals/ha during the period of 1980 to 1996. Rice productivity in Sidoarjo Regency ranked among the highest in East Java. For instance, in 1970, rice productivity in Sidoarjo Regency stood at 49 quintals/ha, marking the highest figure within the Brantas watershed. By comparison, the productivity of lowland rice in Mojokerto Regency during the same year was only 40.74 quintals/ha, in Jombang it was 39.56 quintals/ha, in Kediri it was 39.01 quintals/ha, in Blitar it was 37.15 quintals/ha, in Tulungagung it was 38.93 quintals/ha, and in Nganjuk it was 32.58 quintals/ha. Sidoarjo’s rice productivity was second only to Banyuwangi, which reached 53.71 quintals/ha (Kantor Sensus dan Statistik, 1972). For instance, in 1980, with a productivity of 47.86 quintals/ha, Sidoarjo’s irrigated rice productivity was approximately on par with other areas within the Brantas watershed such as Mojokerto (47.53 quintals/ha), Jombang (48.22 quintals/ha), and Nganjuk (49.69 quintal/ha). The productivity of irrigated rice within the Brantas watershed area, in general, was only exceeded by Banyuwangi Regency, known as the rice granary of Indonesia, with a productivity of 50.41 quintals/ha (BPS Jawa Timur, 1983).

There is no denying that the adoption of high-yielding seeds and chemical inputs constitutes a crucial aspect of the green revolution. However, it is imperative to underscore that within the rice farming sector, the adoption of such practices would have a limited impact without the presence of improved irrigation infrastructure ensuring adequate water supply. It is only through the provision of secure irrigation that the adoption of superior seeds and the application of chemical fertilizers can yield optimal results. The enhancement of irrigation infrastructure emerges as a pivotal supporting element facilitating a revolution in the rice farming sector. Indeed, irrigation improvements represent one of the four key factors elucidating what Australian economist Hal Hill describes as ‘Indonesia’s dramatic rice success’ during the New Order period (Hill, 2000).

The transformation of the watershed area into a freshwater ecosystem has led to the creation of diverse habitats and ecosystems. This newly formed ecosystem offers an environment conducive to the development of various animal populations and microorganisms. Among the species thriving in this habitat are freshwater fish. Before the construction of the Karangkates Dam, the Brantas River and its tributaries were inhabited by a wide array of fish species. In 1962, for instance, there were recorded to be at least 120 species of fish residing in the waters of the Brantas River (Kompas.com, 2011). With the construction of the Karangkates Reservoir, which impounds a section of the Brantas River, these fish populations have persisted, and in some cases, even proliferated at a faster rate. The Karangkates freshwater Reservoir harbors various fish species, including wader (Puntius Brevis), catfish (Clarias sp), and mujair (Oreochromis mossambiccus). Some of these species have been intentionally introduced to augment the fish population in the reservoir waters. Periodically, the Malang District Fisheries Service undertakes the stocking of the Karangkates Reservoir with different types of fish. For instance, a report from 1980 mentions the cultivation of the Karangkates reservoir waters with tombro, tawes, and tilapia (Projek Induk Serbaguna Kali Brantas, 1980).

Between 1974 and 1977, there was an observable upward trend in the quantities of fish caught. This increase paralleled the rise in fish population, facilitated by the establishment of the freshwater reservoir (Projek Induk Serbaguna Kali Brantas, 1980). Among the various types of fish caught, wader fish were particularly abundant, owing to their longstanding presence in the Brantas River. Additionally, tilapia fish constituted a significant portion of the catch. However, fish species intentionally introduced by the Fisheries Service, such as tombro, tilapia, and tawes, had not yet become the dominant fish population in the Karangkates Reservoir. Fishing in the Karangkates Reservoir served as a vital source of income, with earnings fluctuating depending on the catch and prevailing selling prices. It was estimated that fishers earned an average daily income of IDR 233.99 from the sale of fish, equivalent to the price of ∼3.5 kg of rice, which was sold for Rp. 68.5/kg in 1974 (Suharyono, 1992).

While the reservoir’s aquatic ecosystem serves as a habitat for fish, concerns have arisen regarding the declining diversity of fish species in both the Karangkates Reservoir and the Brantas River. Factors contributing to this decline include overexploitation, pollution, and the introduction of invasive species. A study has identified several fish species inhabiting the Karangkates Reservoir, including the red devil (Amphilopus labiatus), mujair (Oreochromis mossambiccus), nilem (Ostheochillus vittatus), wader (Puntius Brevis), brek fish (Puntius bramoides), and tawes fish (Barbonymus gonionotus) (Kholidulazhhar, 2019). Notably, the red devil fish in the Karangkates Reservoir is classified as an invasive species (Amin et al., 2019). Initially introduced as an ornamental fish, the red devil has rapidly proliferated, posing a threat to the diversity of endemic fish populations. Economically valuable fish species such as tilapia, tombro, tawes, and wader struggle to compete with the red devil fish, which are omnivorous and highly aggressive. Consequently, the red devil fish now dominate the fish population in the reservoir, despite being unsuitable for consumption (Sutedjo, 2006).

Another anticipated benefit of the dam and weir constructed along the Brantas River is flood control. Before the construction of the dam, the Brantas River frequently experienced flooding, causing significant damage and disrupting the lives of local residents. Instances of flooding along the Brantas River were recorded in consecutive years, including 1964, 1965, 1966, 1967, and 1968 (Projek Induk Serbaguna Kali Brantas, 1972). The phrase ‘Blitar turned into a yard, Tulungagung turned into a lake, and Kediri turned into a river’ vividly illustrates how the flood disaster altered the landscape of these three regions due to the Brantas River overflowing its banks. The recurrent floods were exacerbated by the accumulation of sand and mud sediments at the riverbed, a consequence of Mount Kelud’s eruptions. Following the eruptions of Mount Kelud in 1951 and 1966, for instance, river deposits along a stretch of 175 km between Kaulon and Jabon increased by 33 million tons during the period from 1951 to 1970 (Soekistijono, 2008). The silting of the riverbed diminished the Brantas River’s capacity to contain water.

Following the construction of the dams, the recurring threats of catastrophic flooding and the potential for extensive damage have been mitigated. The presence of the Wlingi dam has reduced water flow rates from 2824 to 2370 m³/second. Functioning as a reservoir, the dam serves to retain water and stabilize downstream water levels. Moreover, it plays a crucial role in controlling the flow of sediment, such as sand and mud, which contributes to riverbed siltation. This, in turn, enhances the river’s capacity to contain water, reducing the risk of overflow into surrounding areas. Both the Wlingi dam and upstream dams along the Brantas River, particularly the Karangkates dam, have effectively diminished the occurrence of flood disasters in Blitar, Tulungagung, and Kediri. Meanwhile, the newly constructed Lengkong weir has safeguarded 7000 hectares of rice fields in Sidoarjo from annual flooding (Restanti, 2021). This weir is designed to regulate the flow of the Brantas River into the Porong River (Sinarno et al., 2007). By diverting water towards the Porong River, the Lengkong Weir forms an integral part of essential infrastructure aimed at protecting Surabaya, the economic hub and capital city of East Java Province, from frequent flooding. Other flood control measures for the Surabaya area include the construction of the Gunungsari weir and the rehabilitation of the Surabaya River, Mas River, and Marmoyo River (Husain, 2020; Team Penyusun, 1985). With these improved infrastructural interventions, the threat of flooding posed by the Brantas River, which was prevalent before the construction of the dam, has significantly diminished (Parwanto, 2008).

3. Conclusion

This study underscores the pivotal role of foreign entities, particularly Japan, in the development of irrigation infrastructure along the Brantas River. Japan’s involvement is traced back to its defeat in the Greater East Asia War and the subsequent obligations it incurred, particularly in the form of war reparations to Indonesia. This marked a significant turning point in the post-colonial era, solidifying Japanese influence in East Java. With the allocation of war reparations funds, Japanese entities, including the government and various companies and institutions, emerged as key players driving infrastructure development along the Brantas River. The initiation of projects such as the Karangkates Dam Project (Sutami Dam), financed through war reparations funds from the Japanese government, marked the beginning of Japan’s significant contributions. Subsequently, various irrigation infrastructure projects were undertaken along the Brantas River and its tributaries, with Japan providing both financial assistance and technical expertise. Notable projects include the Wlingi Dam, Wonorejo Dam, the Widas Irrigation Network, and the New Lengkong Weir in Mojokerto.

Several Japanese agencies collaborated in the implementation of Japan-supported projects aimed at managing the Brantas River through the construction of dams, weirs, irrigation networks, and river straightening initiatives. The design preparation received technical assistance from the Japanese government, facilitated by the Overseas Technical Cooperation Agency (OTCA). Furthermore, funding assistance from the Japanese government, in the form of grants and project loans, was administered through the Overseas Economic Cooperation Fund (OECF). Several Japanese corporations played significant roles in the infrastructure development along the Brantas River. Notably, Nippon Koei Co., Ltd. and Kajima Construction Corporation emerged as prominent contributors. Nippon Koei’s involvement in Brantas River infrastructure construction was closely tied to Kubota’s relationships with Indonesian political elites, facilitating access to infrastructure projects in Indonesia with Japanese funding and assistance. Meanwhile, Kajima Construction Corporation’s pivotal role in the projects was attributed to its chief director, Kajima Morinosuke, a prominent figure in the Indonesia-Japan Association, fostering strong business ties with Indonesia. In addition, several other companies also supported the implementation of infrastructure development along the Brantas River. These include Nichiment Co., Ltd., Sumitomo Shoji Kaisha, Tomen, and Takada Kiko.

The existence of Japanese-funded irrigation infrastructure significantly contributed to the success of the New Order in enhancing rice production. It was the Japanese factor that bolstered the Brantas valley’s status as a food granary. The outcomes of this study affirm that the landscape of irrigation infrastructure in East Java, and Indonesia as a whole, was not solely shaped and inherited from the era of the Dutch East Indies. Rather, it was also profoundly influenced by Japanese agencies, which manifested in various forms including ideas, designs, and financial support. Post-colonial Indonesia’s trajectory is intricately intertwined with Japan through collaboration in the development of river infrastructure.

The Japan-supported irrigation infrastructure along the Brantas River has significantly impacted the agricultural sector in the Brantas River basin. The expansion of rice fields has been notable, as irrigation distribution transforms previously dry agricultural land into highly productive rice fields. Areas that were previously unsuitable for rice cultivation during the dry season can now support rice crops two or even three times a year, thanks to guaranteed irrigation distribution. The availability of irrigation is a pivotal factor driving changes in cropping patterns adopted by farmers, with rice emerging as the primary crop. With irrigation in place, rice cultivation has expanded, allowing for more frequent planting cycles. Consequently, the presence of irrigation infrastructure has reinforced the Brantas River basin’s role as a crucial food source in Indonesia. Furthermore, the establishment of artificial lakes and water ecosystems has led to a notable increase in freshwater fish production from open waters along the Brantas River. This trend reflects the broader ecological benefits resulting from the development of irrigation infrastructure in the region.

Another significant environmental impact anticipated from the construction of irrigation infrastructure funded by Japan is its role in flood control. The recurring flood disasters along the Brantas River have been a perennial challenge for communities residing along its watershed, spanning from upstream to downstream. Controlling the devastating floods has been an enduring struggle, embodying the complex relationship between blessings and curses that has persisted between the Brantas River and the local communities for centuries. The introduction of Japanese-funded river infrastructure has acted as a crucial tool for taming the untamed nature of the Brantas River, mitigating its destructive potential, and safeguarding the surrounding communities. Through technological interventions supported by Japan, flood risks in the Brantas River basin have been significantly reduced, although the issue has not been entirely eradicated.

The achievement is undoubtedly commendable, yet it remains transient due to the perpetual evolution of the Brantas River and its surrounding environmental elements. Likewise, the inhabitants residing in the Brantas River watershed, whose lives are intricately intertwined with the river, undergo continual changes, whether directly or indirectly. The dynamic interplay between the natural ecosystem and the cultural milieu will inevitably exert an influence on the infrastructure erected to regulate the river’s ferocity and optimize its potential, bearing in mind that such infrastructure has a finite operational lifespan. As changes occur within both the natural and cultural realms, disrupting the environmental equilibrium, the efficacy of the regulatory and optimizing functions may diminish with the aging of the infrastructure. In such instances, the Brantas River may unleash its full force, exacerbating its destructive capabilities. Furthermore, the capacity of the Brantas River and its tributaries to sustain life could deteriorate. Only through diligent maintenance of the infrastructure and adept management of its supporting physical and social environments can such disasters be averted, or at the very least, their adverse impacts mitigated.

Given the pivotal role of Japanese-funded infrastructure in managing the Brantas River, it is crucial to ensure regular maintenance and upkeep of these structures. Establishing a comprehensive maintenance schedule and allocating resources for repairs and upgrades will help extend the lifespan of the infrastructure and maintain its effectiveness in flood control and irrigation management. Building local capacity in river management and infrastructure maintenance is vital for long-term sustainability. Collaborative programs between Japanese technical experts and local stakeholders can facilitate knowledge transfer and skill development, ensuring its proper management. Involving local communities in decision-making processes related to river management and infrastructure development is essential for ensuring social acceptance and support. Community engagement initiatives, such as public consultations, awareness campaigns, and participatory planning workshops, can foster a sense of ownership and responsibility among local residents. Adopting an integrated approach to water resource management is crucial for balancing competing demands for water resources while ensuring environmental sustainability. This involves coordinating various stakeholders, including government agencies, private sector entities, and civil society organizations, to develop holistic solutions that address the needs of both humans and the environment. While irrigation infrastructure has significantly boosted rice production in the Brantas River basin, promoting crop diversification can enhance resilience to climate change and market fluctuations. Encouraging the cultivation of alternative crops that require less water or have higher market value can help optimize agricultural productivity while reducing pressure on water resources.

Acknowledgments

The research activities were carried out between April 2021 and September 2022. The authors extend their sincere gratitude to the President of the Sumitomo Foundation and its staff for their generous support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The research for this article was financially supported by the Sumitomo Foundation, Tokyo, Japan, through its Japan-related research project for fiscal year 2020.

Notes on contributors

Nawiyanto

Nawiyanto is a professor in the Faculty of Humanities, Department of History at Universitas Jember, Indonesia. He specializes in the economic and environmental history of Indonesia. His research interests include environmental change, nature conservation, environmental movements, and river historiography, particularly in Indonesia’s island of Java from the Dutch colonial to the early independence periods.

Sarkawi B. Husain

Sarkawi B. Husain is an associate professor in the Faculty of Humanities at Airlangga University in Indonesia. He obtained PhD degree from Gadjah Mada University with research interest, particularly in urban floods and socio-economic issues in Indonesia’s border areas.

Wisnu

Wisnu is an associate professor in the Faculty of Social Sciences Education, at the Universitas Negeri Surabaya, Indonesia. His research focus is on the social-economic history of Indonesian towns, especially in East Java.

Mohamad Nai’m

Mohamad Nai’m is an associate professor in the Faculty of Education and Teacher Training, at Universitas Jember. His research interests include agricultural history and various aspects of history education, particularly its methods and contents.