Groundwater nitrate contamination is a well-documented issue in the Southern Willamette Valley (SWV) of Oregon, as a Groundwater Management Area (GWMA) has recently been declared. As a GWMA, groundwater nitrate monitoring must occur until regional concentrations are below 7 mg/L NO3-N. However, the presence of temporal variability can make it...
Low-permeability geologic units may offer significant chemical and hydraulic protection of adjacent aquifers, and are important for managing groundwater quality, especially in areas with significant non-point source contamination. Nitrate in the Willamette Valley is attenuated across the Willamette Silt, a semi-confining unit overlying a regionally important aquifer. To quantify the...
The Willamette Valley of Oregon has high rates of winter precipitation that cause leaching losses of residual fertilizer nitrogen (N) as nitrate (NO₃). Cover crops may have potential to mitigate N loss. Shallow groundwater was sampled for 11 years from plots planted in summer vegetables with and without winter cover...
A relatively stable, persistent and historical problem with elevated NO₃⁻ concentrations in rural drinking wells in the southern Willamette Valley, Oregon is evident. What is the origin of NO₃⁻ in rural drinking water wells in this area? The answer to the question is not simple. Many non-point sources contribute to...