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摘要
The total maximum daily load (TMDL) study for Pineview Reservoir in Ogden Valley, Utah, called for reductions in phosphorus loads from irrigated agriculture and on-site wastewater treatment systems, but historical groundwater flow estimates and associated phosphorus loads were highly variable and based on little data. The objective of the present study was to quantify the spatial variability of groundwater flow, groundwater nutrient concentrations, and nutrient transport toward Pineview Reservoir and improve the groundwater flow and nutrient loading estimates for the reservoir using this information. ArcGIS kriging techniques were employed in analyzing high-frequency groundwater flow and grab-sample nutrient concentration data. Results from the study showed large spatial variations in groundwater flows and nutrient loadings. Spatial variation in flows was attributed to variations in hydraulic gradients and saturated thickness, while nutrient loading variations were attributed to source variations and nutrient flushing to groundwater due to snow-melt and irrigation water. Both agricultural and domestic nonpoint sources appeared to influence the nutrient loadings. The median total dissolved phosphorus concentration (32 mu g P L-1) for five of the nine wells monitored was more than three-fold lower than the median (10(4) mu g P L-1) for all nine wells, signifying large spatial variations. Spatial variation in flow rate had confidence intervals ranging from 1,518 to 5,077 m(3) d(-1) on 6 May 2011 to 447 to 1,814 m(3) d(-1) on 27 June 2011. Knowledge of the spatial distribution of nutrient concentrations and loading would help decision makers in determining specific management practices that would help abate groundwater nutrient loading and its subsequent impact on surface water bodies.
- 出版日期2014
