Forested riparian areas are believed to be important for reducing nonpoint source pollutants. These areas along streams, lakes, and wetlands have been reported to trap sediment and nutrients and enhance denitrification. Past research on the effectiveness of riparian areas has been based on existing forests rather than restored areas. An experiment using the paired-watershed design was established in northeastern Connecticut during 1992 to determine the water quality effects of reforestation on a riparian zone currently cropped in maize. Water quality fluxes in precipitation, overland flow, soil solution, groundwater, and streamflow were determined. Results indicate that this 35 m wide riparian zone had little attenuating influence on N concentrations in groundwater based on NO3−N concentrations and NO3−N:C1 ratios. The primary N flux to the stream was in the groundwater. Denitrification did not appear to be a major process operating in this system. Reforestation of this riparian buffer should result in improved surface and groundwater quality.

SummaryA bottom-contacting probe for measuring electrical conductivity at the sediment-water interface was used to scan the bed of the Columbia River adjacent to the Hanford Site in southeast Washington State during a 10-day investigation. Four river-sections, each about a kilometer in length, were scanned for variations in electrical conductivity. The probe was towed along the riverbed at a speed of 1 d s and its position was recorded using a Global Positioning System.The bottom tows revealed several areas of elevated electrical conductivity. Where these anomalies were relatively easy to access, piezometers were driven into the riverbed and porewater samples were taken. The upward flux of ground water at these locations was tested by measuring porewater electrical conductivity and, in selected ones, by measuring concentrations of contaminants. At these locations, porewater electrical conductivity ranged from 125 to 380 pS/cm and surface water electrical conductivity ranged from 11 1 to 150 pS/cm.The piezometers, placed in electrical conductivity "hotspots," yielded chemical or isotopic data consistent with previous analyses of water taken from monitoring wells and visible shoreline seeps. Tritium, nitrate, and chromium exceeded water quality standards in some porewaters. The highest tritium and nitrate levels were found near the Old Hanford Townsite at 120,000 pCi/L (& 8,850 p C f i total propagated analytical uncertainty) and 28,000 pg/L (i 5,880 pg/L), respectively. The maximum chromium (total and hexavalent) levels were found near 100-H reactor area where unfiltered porewater total chromium was 1,900 pg/L (2 798 p a ) and hexavalent chromium was 20 PI&-The electrical conductivity probe provided rapid, cost-effective reconnaissance for ground-water discharge areas when used in combination with conventional piezometers. It may be possible to obtain quantitative estimates of both natural and contaminated ground-water discharge in the Hanford Reach with more extensive surveys of the river bottom.iii RC-M-22 PNNL-11516

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