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Impact of artificial groundwater recharge at two Nebraska sites
Abstract
The dissertation research focuses on two ground water recharge projects. Herbicide behavior is interpreted in a watershed system with data collected from runoff, Recharge Lake and ground water at the York Ground Water Recharge Project. Maximum atrazine inputs to Recharge Lake occurred in spring runoff events and resulted in atrazine concentrations of 36 and 17 $\mu$g L$\sp{-1}$ in 1993 and 1994, respectively. Only about 0.28% and 0.19% of total applied atrazine was lost to runoff in 1993 and 1994. Atrazine concentrations in Recharge Lake decreased exponentially with degradation half-lives of 237 d in 1993 and 209 d in 1994. Adjusted DEA concentrations in Recharge Lake remained relatively constant, indicating little evidence for biotic degradation, and suggesting that abiotic degradation of atrazine to hydroxyatrazine was the most likely major degradative pathway in Recharge Lake. Maximum bromide concentrations obtained in the nearby aquifer represented only 27% of the initial concentration in Recharge Lake. The low detected concentrations might be due to the low infiltration rates and dilutions. Effects of artificial recharge on ground water quality and quantity was studied at the Wood River Ground Water Recharge Project. A total of 1.10 million m$\sp3$ of Platte River water recharged the aquifer near Wood River through 5016 m$\sp2$ of the recharge basins during 1992, 1993 and 1994. This is equivalent to the quantity needed to completely displace the ground water beneath 33.75 ha of the local primary aquifer. The water table rose rapidly in response to recharge during the early stage then leveled off as infiltration rates declined. The NO$\sb3$-N contamination improved from concentrations exceeding the maximum contaminant levels to those of drinking water quality. Infiltration rates decreased with time presumably because of clogging. Management practices such as scraping the basin floor, using a pulsed recharge strategy and maintaining low standing water heads in the basins appeared to reduce clogging, therefore enhanced infiltration. Stable isotopes, anion concentrations and hydraulic gradients were used to delineate streamlines and mixing in ground water impacted by artificial recharge. The surface water fraction estimated from D/H ratios indicated that the recharged surface water completely displaced the ground water beneath the recharge basins from the regional water table at 7.60 m to 12.16 m below the land surface. Mixing occurred beneath the recharge structures in the lower portions of the aquifer ($>$12.16 m). At the end of the third recharge season, recharged surface water represented $\sim$50% of the water in the deeper zone of the primary aquifer $\sim$1000 m downgradient from the recharge basin.
Subject Area
Soil sciences|Geochemistry|Hydrology
Recommended Citation
Ma, Li, "Impact of artificial groundwater recharge at two Nebraska sites" (1996). ETD collection for University of Nebraska-Lincoln. AAI9628242.
https://digitalcommons.unl.edu/dissertations/AAI9628242