2023 CSDMS meeting-030


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A Linked Hydrologic, Hydraulic, and Water Quality Model for Simulation of Freshwater Inflow to Estuaries in Coastal Watersheds

Shimelis Setegn, SFWMD/FIU West Palm Beach Florida, United States. ssetegn@sfwmd.gov

Freshwater inflow plays a substantial role in the water quality of coastal and estuarine watersheds and ecosystems. The salinity of an estuary can vary depending on the amount of freshwater received. In highly managed systems, such as St. Lucie and Caloosahatchee estuaries in south Florida, USA, understanding total freshwater inflow and the sources of inflow is very important for management decision-making. There is very little information on the quantity of freshwater inflow to St. Lucie and Caloosahatchee estuaries from their ungauged tidal basins. This study examines a linked hydrologic, hydraulic, and watershed water quality model (WaSh) for simulating freshwater inflow to these two systems. The WaSh model is a time-dependent simulation model that represents basic surface hydrology, groundwater flow, surface water flow, and water quality fate and transport. The WaSh model consists of four basic components; a cell-based representation of the watershed basin land surface, a groundwater component, a surface-water drainage system, and a water management component that can consider the effects of reservoirs, stormwater treatment areas, irrigation supply and demand, and land-use changes. The model is capable of simulating hydrology in watersheds with high groundwater tables and dense drainage canal networks, which is typical in South Florida.

The model was developed using long-time series of rainfall, temperature, evapotranspiration, basin boundaries, hydrography including streams and canals features, soils, land use, and land surface elevations. The results indicate that the model accurately simulates the distribution of freshwater over the coastal watersheds and the transport of freshwater through the estuary and that it is a valuable tool for understanding the dynamics of freshwater inflow to estuaries in coastal watersheds.

Keywords: Coastal Hydrology, Ungauged basin, WaSh model, estuary, Salinity, hydrologic and hydraulic model, water quality