Modeling effects of nitrate from non-point sources on groundwater quality in an agricultural watershed in Prince Edward Island, Canada

Jiang, Yefang; Somers, George

Modeling effects of nitrate from non-point sources on groundwater quality in an agricultural watershed in Prince Edward Island, Canada | Modélisation des effets des apports nitratés diffus sur la qualité des eaux souterraines dans un bassin agricole de l’île du Prince Edouard, Canada Modelación de los efectos del nitrato de fuentes no puntuales en la calidad de las aguas subterráneas en una cuenca agrícola en Isla Prince Edward, Canadá 模拟非点源硝酸盐对加拿大爱德华王子岛某农业流域地下水水质的影响 Modelação da influência do nitrato de fontes não pontuais na qualidade da água subterrânea numa bacia hidrográfica de uso agrícola em Prince Edward Island, Canadá

2009

Jiang, Yefang | Somers, George

Intensification of potato farming has contaminated groundwater with nitrate in many cases in Prince Edward Island, Canada, which raises concerns for drinking water quality and associated ecosystem protection. Numerical models were developed to simulate nitrate-N transport in groundwater and enhance understanding of the impacts of farming on water quality in the Wilmot River watershed. Nitrate is assumed non-reactive based on δ¹⁵N and δ¹⁸O in nitrate and geochemical information. The source functions were reconstructed from tile drain measurements, N budget and historical land-use information. The transport model was calibrated to long-term nitrate-N observations in the Wilmot River and verified against nitrate-N measurements in two rivers from watersheds with similar physical conditions. Simulations show groundwater flow is stratified and vertical flux decreases exponentially with depth. While it would take several years to reduce the nitrate-N in the shallow portion of the aquifer, it would take several decades or even longer to restore water quality in the deeper portions of the aquifer. Elevated nitrate-N concentrations in base flow are positively correlated with potato cropping intensity and significant reductions in nitrate-N loading are required if the nitrate level of surface water is to recover to the standard in the Canadian Water Quality Guidelines.

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