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...
The purpose of this study was to; (1) determine the extent of well water contamination with nitrate and pesticides, and to understand the relationships among nitrate, pesticide, dissolved chloride, dissolved sulfate, well age, and well depth in the southern Willamette Valley, Oregon; and, (2) to investigate local residents' perceptions and...
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 region’s high winter rainfall provides aquifers
that are often within 50 feet of the land surface. In
many parts of the United States and in other countries
where groundwater is this close to the surface, pesticide
contamination has been observed. Thus, with our
high population, significant applications of pesticides,...
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...
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...