A process-based mesh-distributed watershed model for water runoff and soil erosion simulation

ABSTRACT

Runoff and sediment movement induced by storms have serious economic, environmental, and social impacts around the world. Hydrological models have become useful decision support tools for watershed management. The development of process-based distributed models is complex as it involves a range of disciplines and spans multiple spatial and temporal scales. In this study, a process-based and mesh-distributed model, suitable for both event-based and continuous simulations, is developed. The watershed is conceptualized in three distinct zones: a surface overland region, an unsaturated subsurface zone, and a groundwater zone. Overland flow is governed by the 2D diffusive wave equation with an optional 1D channel network solver; water in the unsaturated zone is modelled through mass conservation and vertical dominance of the processes; and saturated groundwater flow is governed by the 2D Dupuit equation. Soil erosion and transport are governed by the multi-size, non-equilibrium equations incorporating soil entrainment, transport, and deposition. The model is driven by meteorological input, land use and soil type properties. The numerical approach is a generalization of existing models to overcome some current modelling shortcomings. New contributions of the model are highlighted and model verification and validation are reported against benchmark cases. The model is then applied to the Cache Creek watershed in California, USA. Satisfactory agreement with the measured data is obtained with both the runoff flow rate and sediment load.

KEYWORDS:

• Hydrologic model
• process-based
• sediment delivery
• soil erosion
• watershed model
• gridded model

Acknowledgement

The research is jointly funded by the Science and Technology Program at the U.S. Bureau of Reclamation, USA, and the Water Resources Agency, Taiwan. Technical contribution and review by Blair Greimann, Technical Service Center, U.S. Bureau of Reclamation, are acknowledged. Jun Wang, at the Division of Planning, California Great Basin Region, U.S. Bureau of Reclamation, has shared the Cache Creek watershed data used for the model validation and application.

Disclosure statement

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

Additional information

Funding

This work was supported by Taiwan Water Resources Agency; Science and Technology Program at the U.S. Bureau of Reclamation: [Grant Number 1809].