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Statistical Evaluation of Effects of Riparian Buffers on Nitrate and Ground-Water Quality

Journal of Environmental Quality Volume 29 Number 5: p. 1523-1538
By Timothy B. Spruill

Full Journal Article (16 pages, 2.8M)

Abstract

A study was conducted to statistically evaluate the effectiveness of riparian buffers for decreasing nitrate concentrations in ground water and for affecting other chemical constituents. Values for pH, specific conductance, alkalinity, dissolved organic carbon (DOC), silica, ammonium, phosphorus, iron and manganese at 28 sites in the Contentnea Creek basin were significantly higher (p < 0.10) in old (>20 years) discharging ground water draining areas with riparian buffers compared to areas without riparian buffers. No differences in chloride, nitrate-nitrogen, calcium, sodium and dissolved oxygen concentrations in old ground water between buffer and non-buffer areas were detected. Comparison of samples of young (<20years) discharging ground-water samples from buffer and non-buffer areas indicated significantly higher specific conductance, calcium, chloride, and nitrate-nitrogen in non-buffer areas. Riparian buffers along streams can affect the composition of the hyporheic zone by providing a source of organic carbon to the streambed, which creates reducing geochemical conditions that consequently can affect the chemical quality of old ground water discharging through it. Buffer zones between agricultural fields and streams facilitate dilution of conservative chemical constituents in young ground water that originate from fertilizer applications and also allow denitrification in ground water by providing an adequate source of organic carbon generated by vegetation in the buffer zone. Based on the median chloride and nitrate data of young ground water in the Contentnea Creek Basin, nitrate was 95% lower in buffer areas compared with non-buffer areas, with 30-35% reduction estimated to be due to dilution and 65-70% due to reduction and/or denitrification.

Spruill, T.B., 2000, Statistical evaluation of effects of riparian buffers on nitrate and ground-water quality: Journal of Environmental Quality, v. 29, no. 5, p. 1523-1538.