An integrated watershed and water quality modeling system to study lake water quality responses to agricultural management practices

Authors: CHAO, XIAOBO - University Of Mississippi; Witthaus, Lindsey; Bingner, Ronald - Ron; JIA, YAFEI - University Of Mississippi; Locke, Martin; Lizotte, Richard

Submitted to: Environmental Modelling & Software
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2023
Publication Date: 4/1/2023
Citation: Chao, X., Witthaus, L.M., Bingner, R.L., Jia, Y., Locke, M.A., Lizotte Jr, R.E. 2023. An integrated watershed and water quality modeling system to study lake water quality responses to agricultural management practices. Environmental Modelling & Software. 164. https://doi.org/10.1016/j.envsoft.2023.10569.

Interpretive Summary: The water quality entering a waterbody is significantly influenced by the upstream land use producing potentially large amounts of sediment, nutrients, and other pollutants. Linking information of upland watersheds with channel networks and receiving waterbodies is critical when developing an effective approach to identify causes for water quality issues and then target solutions to improve water resource management. This study evaluates the effects of land use/land cover, soil properties, climate, agriculture management, etc. on the water quality produced within agricultural watersheds to lakes using integrated watershed and lake modeling technology. The integrated modeling system was used to simulate flow, sediment and nutrient processes in both the landscape and waterbody system in Beasley Lake watershed in the Mississippi Delta as a study site. The water quality of Beasley Lake was monitored and used to calibrate and validate the models. The validated modeling system was then applied to the watershed to analyze the effects of alternative and targeted conservation practices, such reduced tillage and no tillage, on the water quality of Beasley Lake. This research provides a useful tool to analyze the impacts of nutrient and sediment loads from agricultural landscapes on the water quality of lakes.

Technical Abstract: This paper presents a technical approach to link a watershed model and surface water quality model to study the effects of agricultural conservation practices implemented in the upland watershed on the water quality of a receiving water body. The Annualized Agricultural Nonpoint Source Pollution (AnnAGNPS) watershed model was applied to simulate the runoff and loads of sediment and nutrients exported from upland watersheds. The effects of land use/land cover, soil properties, climate, agriculture management, etc. on the watershed loads were considered. The simulated results were used as boundary conditions for CCHE-WQ, a water quality model developed at the National Center for Computational Hydroscience and Engineering (NCCHE), to simulate the concentrations of water quality constituents in water bodies. In this model, the interactions between the sediment and water quality constituents were considered, and the distributions of nutrients, chlorophyll and dissolved oxygen in the water body can be obtained. The integrated modeling system can be used to simulate flow, sediment and nutrient processes in both the watershed and waterbody system. This proposed technical approach was tested using Beasley Lake watershed in the Mississippi Delta as a study site. The water quality of Beasley Lake watershed was monitored by USDA-ARS, and the measured data was used to calibrate and validate the AnnAGNPS and CCHE-WQ models. The validated modeling system was applied to analyze the effects of conservation practices (reduced tillage and no tillage) on the water quality of the receiving water body. This research provides useful tools to analyze the impacts of upland nutrient and sediment loads on the water quality of the receiving water bodies.