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At least 685 records · Page 38Linked to original sources
USGS2005

Geochemistry and characteristics of nitrogen transport at a confined animal feeding operation in a coastal plain agricultural watershed, and implications for nutrient loading in the Neuse River basin, North Carolina, 1999-2002

Chemical, geologic, hydrologic, and age-dating information collected between 1999 and 2002 were used to examine the transport of contaminants, primarily nitrogen, in ground water and the pathways to surface water in a coastal plain setting in North Carolina. Data were collected from more than 35 wells and 4 surface-water sampling sites located in a 0.59 square-mile basin to examine detailed hydrogeology and geochemical processes affecting nutrient fate and transport. Two additional surface-water sampling sites were located downstream from the primary study site to evaluate basin-scale effects. Chemical and flow data also were collected at an additional 10 sites in the Coastal Plain portion of the Neuse River basin located between Kinston and New Bern, North Carolina, to evaluate loads transported in the Neuse River and primary tributary basins. At the Lizzie Research Station study site in North Carolina, horizontal flow is induced by the presence of a confining unit at shallow depth. Age-dating, chemical, and piezometric data indicate that horizontal flow from the surficial aquifer is the dominant source of ground water to streamflow. Nitrogen applied on cultivated fields at the Lizzie Research Station is substantially reduced as it moves from recharge to discharge areas. Denitrification in deeper parts of the aquifer and in riparian zones is indicated by a characterization of redox conditions in the aquifer and by the presence of excess nitrogen gas. Direct ground-water discharge of nitrate to surface water during base-flow conditions is unlikely to be significant because of strongly reducing conditions that occur in the riparian zones of these streams. Nitrate loads from a drainage tile at the study site may account for much of the nitrate load in the receiving stream, indicating that a major source of nutrients from ground water to this stream is artificial drainage. During base-flow conditions when the streams are not flowing, it is hypothesized that the mineralization of organic matter on the streambed is the source of nitrate and(or) ammonium in the stream. Base flow is a small contributor to nitrogen loads, because both flows and inorganic nitrogen concentrations are low during summer months. Effects of a confined hog operation on ground-water quality also were evaluated. The use of sprayed swine wastes to fertilize crops at the Lizzie Research Station study site since 1995 resulted in increased concentrations of nitrate and other chemical constituents in ground water beneath spray fields when compared to ground water beneath fields treated with commercial fertilizer. The nitrate concentration in ground water from the spray field well increased by a factor of 3.5 after 4 years of spray applications. Nitrate concentrations ranged from 10 to 35 milligrams per liter, and one concentration as high as 56 milligrams per liter was observed in water from this well in spring 2002. This finding is in agreement with findings of other studies conducted in the Coastal Plain of North Carolina that nitrate concentrations were significantly higher in ground water from cultivated fields sprayed with swine wastes than from fields treated with commercial fertilizer. Loads and yields of nitrogen and phosphorus in 14 streams in the Neuse River basin were evaluated for calendar years 2000 and 2001. Data indicate that anthropogenic effects on nitrogen yields were greatest in the first-order stream studied (yields were greater than 2 tons per square mile [ton/mi2] and 1 ton/mi2 or less in second- and higher-order streams) in the Little Contentnea Creek subbasin. Nitrogen yields in streams in the Contentnea Creek subbasin ranged from 0.59 to 2 ton/mi2 with typical yields of approximately 1 ton/mi2. Contentnea Creek near Evansdale had the highest yield (2 ton/mi2), indicating that a major source of nitrogen is upstream from this station. Nitrogen yields were lower at Contentnea Creek at Hookerton in 2000 and 2001 compared to previous yi

Scientific Investigations Report↗
USGS2013

Potential depletion of surface water in the Colorado River and agricultural drains by groundwater pumping in the Parker-Palo Verde-Cibola area, Arizona and California

Water use along the lower Colorado River is allocated as “consumptive use,” which is defined to be the amount of water diverted from the river minus the amount that returns to the river. Diversions of water from the river include surface water in canals and water removed from the river by pumping wells in the aquifer connected to the river. A complication in accounting for water pumped by wells occurs if the pumping depletes water in drains and reduces measured return flow in those drains. In that case, consumptive use of water pumped by the wells is accounted for in the reduction of measured return flow. A method is needed to understand where groundwater pumping will deplete water in the river and where it will deplete water in drains. To provide a basis for future accounting for pumped groundwater in the Parker-Palo Verde-Cibola area, a superposition model was constructed. The model consists of three layers of finite-difference cells that cover most of the aquifer in the study area. The model was run repeatedly with each run having a pumping well in a different model cell. The source of pumped water that is depletion of the river, expressed as a fraction of the pumping rate, was computed for all active cells in model layer 1, and maps were constructed to understand where groundwater pumping depletes the river and where it depletes drains. The model results indicate that if one or more drains exist between a pumping well location and the river, nearly all of the depletion will be from drains, and little or no depletion will come from the Colorado River. Results also show that if a well pumps on a side of the river with no drains in the immediate area, depletion will come from the Colorado River. Finally, if a well pumps between the river and drains that parallel the river, a fraction of the pumping will come from the river and the rest will come from the drains. Model results presented in this report may be considered in development or refinement of strategies for accounting for groundwater pumping in the river aquifer connected to the Colorado River in the study area.

Arizona;California↗
USGS2026

Variability of discharge, nutrients, and Escherichia coli from tile drains in a small agricultural stream, a synoptic study in the School Branch watershed, Hendricks County, Indiana

The U.S. Geological Survey, in cooperation with the Indiana Department of Environmental Management, sampled a 1-mile stream reach of School Branch in Hendricks County, Indiana. Sampling consisted of 24 tile drain sites and surface-water sites both upstream and downstream from the tile drains. This study intended to (1) assess the variability of discharge, nutrients, and Escherichia coli ( E. coli ) among tiles within a stream reach in variable conditions; (2) define how the tiles affect the stream hydrology and water quality; and (3) determine potential management implications. Samples were collected on three dates—round 1 on June 12, 2018, after fertilizer was applied; round 2 on September 11, 2018, in fall harvest conditions; and round 3 on April 16, 2019, before fertilizer was applied—to encompass differing precipitation events, multiple seasons, and field conditions. Sites were sampled for water-quality parameters, dissolved and total nutrients (ammonia, nitrate plus nitrite, total nitrogen, orthophosphate, and total phosphorus), E. coli , and instantaneous discharge. Instantaneous nutrient loads were calculated from tiles and at the upstream and downstream surface-water sites. Nutrient concentrations and instantaneous loads varied depending on the tile and the sampling date. Tiles contributed between 26.5 and 66.0 percent of increased discharge between the surface-water sites. Tiles contributed between 34.7 and 87.4 percent and between 19.7 and 65.9 percent of the increased total nitrogen and phosphorus loads, respectively, for the downstream site relative to the upstream site. Most of the total nitrogen and total phosphorus from the tiles was in the dissolved forms (nitrate plus nitrite and orthophosphate). Surface-water samples had a nitrate plus nitrite to total nitrogen ratio of 71 to 93 percent, with an average of 82 percent; tile samples ranged from 44 to nearly 100 percent, with an average of 91 percent dissolved nitrogen. Surface-water samples had an orthophosphate to total phosphorus ratio of 30 to 65 percent, with an average of 53 percent; tile samples ranged from 32 to nearly 100 percent, with an average of 85 percent dissolved phosphorus. E. coli was detected in all but 5.79 percent of tile and surface-water samples. The E. coli results indicated the possibility of human or animal fecal contamination by way of septic systems leaking or directly linked to the tiles draining into the study area. Consequently, five microbial source tracking samples were collected from the upstream and downstream surface-water sites between August 3, 2021, and May 18, 2022. Human, canine, ruminant, and avian sources of fecal contamination were evaluated. The microbial source tracking samples indicated that human-specific sources are likely consistently contributing to elevated fecal contamination. Differences in discharge, nutrient concentrations, nutrient loads, and E. coli concentrations show that many factors affect how tiles alter the hydrology and water quality of receiving waters. The timing and severity of precipitation events, season, and the antecedent conditions of the field or watershed before sampling can affect the results. Tiles with the largest discharge rate had the most potential effect on the water quality and quantity of the stream. Targeting high-flowing tiles may affect efforts to improve overall water quality.

Indiana↗