A Snapshot of Nitrate Contamination in 1994–2004

In 1994, the Division of Water completed a nonpoint source study of nitrate contamination in the Mad River Buried Valley Aquifer. The results of the study clearly show areas where nitrate contamination reaches and sometimes exceeds the safe drinking water standard of 10 Mg/L. The area defined by the box in the map is an area where there is a concentration of values at or near the safe drinking water standard.

The Division of Water has begun a new two and one-half year project to study nitrate levels in this small area in a detailed way. GIS will be used to model the Buried Valley Aquifer in the Kings Creek/Urbana area. All data sets are in a geodatabase. The three-dimensional numeric models for defining the flow system will be MODFLOW and MODPATH. MODFLOW will supplement and expand on the flow map data collected from water wells. MODPATH will yield time-of-travel values for important sites such as the Urbana well field and the Mad River. The models will be combined with the land use data to predict areas where nitrate contamination is likely to be small and identify areas where changes in land use patterns may result in reduced aquifer contamination.

To verify the results of the flow analysis, the project will sample groundwater for nitrate contamination along critical flow paths. Oxygen and nitrogen isotopes will be used to help identify the sources of the nitrate contamination along the groundwater flow path.