GROUND WATER AS A SOURCE OF NUTRIENTS AND ATRAZINE TO STREAMS IN THE SOUTH PLATTE RIVER BASIN¹

Abstract

Concentrations of nitrite plus nitrate, ammonia, orthophosphate, and atrazine were measured in streams and ground water beneath the streams at 23 sites in the South Platte River basin of Colorado, Nebraska, and Wyoming to assess: (1) the role of ground water as a source of nutrients and atrazine to streams in the basin, and (2) the effect of land‐use setting on this process. Concentrations of nitrite plus nitrate, ammonia, orthophosphate, and atrazine were higher in ground water than in the overlying streams at 2, 12, 12, and 3 of 19 sites, respectively, where there was not a measurable hydraulic gradient directed from the stream to the ground water. Orthophosphate was the only constituent that had a significantly higher (p ≤ 0.05) concentration in ground water than in surface water for a given land‐use setting (range land). Redox conditions in ground water were more important than land‐use setting in influencing whether ground water was a source of elevated nitrite plus nitrate concentrations to streams in the basin. The ratios of nitrite plus nitrate in ground water/surface were were significantly lower (p ≤ 0.05) at sites having concentrations of dissolved oxygen in ground water ≤ 0.5 mg/L than at sites having dissolved oxygen concentrations ≥ 0.5 mg/L. Elevated concentrations of ammonia or atrazine in ground water occurred at sites in close proximity to likely sources of ammonia or atrazine, regardless of land‐use setting. These results indicate that land‐use setting is not the only factor that influences whether ground water is a source of elevated nutrient and atrazine concentrations to streams in the South Platte River Basin.

The Molecular Pathway to ZIF‐7 Microrods Revealed by In Situ Time‐Resolved Small‐ and Wide‐Angle X‐Ray Scattering, Quick‐Scanning Extended X‐Ray Absorption Spectroscopy, and DFT Calculations

“…Groundwater as a source of P to streams has been identified in several other studies (e.g. McMahon et al , 1994; Taniguchi et al , 1997; Sonoda and Yeakley, 2007; Holman et al , 2008). Mayer and Jarrell (1995) found that groundwater contributions to stream water quality were especially important under low flow conditions.…”

The ordination of benthic invertebrate communities in the South Platte River Basin in relation to environmental factors

“…Samples of surface and hyporheic (8-64 cm below the stream channel) water were collected and analysed for ammonia-N, nitrate + nitrite-N, nitrite-N, organic nitrogen + ammonia, and total phosphorus (McMahon etal, 1994). Hyporheic water samples were collected to determine whether groundwater was a source of nutrients to surface water (McMahon et al, 1994). Analyses of nutrient concentrations followed methods described in Fishman (1993) and Patton & Truitt (1992).…”

Identifying and linking source areas of flow and P transport in dairy‐grazed headwater catchments, North Island, New Zealand

“…Groundwater as a source of P to streams has been identified in several other studies (e.g. McMahon et al, 1994;Taniguchi et al, 1997;Sonoda and Yeakley, 2007;Holman et al, 2008). Mayer and Jarrell (1995) found that groundwater contributions to stream water quality were especially important under low flow conditions.…”