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Effects of Groundwater‐Flow Paths On Nitrate Concentrations Across Two Riparian Forest Corridors 1
Author(s) -
Speiran Gary K.
Publication year - 2010
Publication title -
jawra journal of the american water resources association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.957
H-Index - 105
eISSN - 1752-1688
pISSN - 1093-474X
DOI - 10.1111/j.1752-1688.2010.00427.x
Subject(s) - water table , groundwater , riparian zone , hydrology (agriculture) , groundwater flow , nitrate , groundwater recharge , environmental science , aquifer , wetland , riparian buffer , groundwater discharge , surface water , riparian forest , geology , ecology , environmental engineering , habitat , geotechnical engineering , biology
Speiran, Gary K., 2010. Effects of Groundwater‐Flow Paths on Nitrate Concentrations Across Two Riparian Forest Corridors. Journal of the American Water Resources Association (JAWRA) 46(2):246‐260. DOI: 10.1111/j.1752‐1688.2010.00427.x Abstract: Groundwater levels, apparent age, and chemistry from field sites and groundwater‐flow modeling of hypothetical aquifers collectively indicate that groundwater‐flow paths contribute to differences in nitrate concentrations across riparian corridors. At sites in Virginia (one coastal and one Piedmont), lowland forested wetlands separate upland fields from nearby surface waters (an estuary and a stream). At the coastal site, nitrate concentrations near the water table decreased from more than 10 mg/l beneath fields to 2 mg/l beneath a riparian forest buffer because recharge through the buffer forced water with concentrations greater than 5 mg/l to flow deeper beneath the buffer. Diurnal changes in groundwater levels up to 0.25 meters at the coastal site reflect flow from the water table into unsaturated soil where roots remove water and nitrate dissolved in it. Decreases in aquifer thickness caused by declines in the water table and decreases in horizontal hydraulic gradients from the uplands to the wetlands indicate that more than 95% of the groundwater discharged to the wetlands. Such discharge through organic soil can reduce nitrate concentrations by denitrification. Model simulations are consistent with field results, showing downward flow approaching toe slopes and surface waters to which groundwater discharges. These effects show the importance of buffer placement over use of fixed‐width, streamside buffers to control nitrate concentrations.