An ArcGIS Extension for Estimating Nitrate Fate and Transport

2010 ESRI Southeast Regional User Group Conference

Fernando Rios, Ming Ye, Raoul Fernandes, Tingting Zhao,and Paul Lee

“Estimating groundwater nitrate fate and transport is an important task in water resources and environmental management because excess nitrate loads may have negative impacts on human and environmental health. A project has been initiated and funded by the Florida Department of Environmental Protection to develop an ArcGIS tool for estimating nitrate loads to surface water bodies from onsite wastewater treatment systems (OWTS). A key feature of this project is the reduced data demands and simplicity of use compared to traditional groundwater contamination transport modeling. This arises from the use of a simplified conceptual model of groundwater flow in the surficial aquifer and an analytical solution to the advectiondispersion equation and denitrification reaction. Denitrification is modeled using physico-statistical methods based on literature and site-specific data. Another key feature of the software is that it leverages the power of ArcGIS to take into account the spatial location of the OWTS. In the first stage of the project the groundwater flow model was developed and implemented. By using a digital elevation model (DEM) as the starting point, an approximation to the hydraulic gradient is derived which is then calibrated with very limited number of field water table data and combined with information on the physical properties of the surficial aquifer to determine the magnitude and direction of flow. The flow model keeps data requirements to a minimum by only requiring a DEM, aquifer conductivity and porosity, and information on the location of target water bodies.”