| Description |
As population and urban development increase along the Wasatch front, understanding the sources of groundwater in Salt Lake Valley (SLV) will remain critical in the creation of water management and contaminant mitigation plans. Currently, groundwater accounts for approximately one-third of SLV's public water supply, and most of these production wells are screened in the deeper, regional confined aquifer. However, the shallow unconfined aquifer is more impacted by contamination at the land surface and may contribute to the deeper aquifer in areas where there is a downward head gradient or where the confining layers are absent. In this study, the noble-gas recharge temperatures and apparent ages of groundwater from valley springs, shallow monitoring wells, and deeper monitoring and production wells in northeast SLV, as well as mountain-front springs and springs at the headwaters of Red Butte Creek in Red Butte Canyon, were determined in order to better understand the sources of this shallow groundwater. Stable isotope values and major ion chemistries of these groundwaters were also utilized in determining a potential source. Groundwater from the valley springs and shallow monitoring wells is observed to have warmer recharge temperatures and younger apparent ages than expected from mountain block recharge. These springs and shallow monitoring wells also display an urban-chemistry signature, having high concentrations of chloride and nitrate. This suggests that groundwater in the northeast SLV shallow groundwater system is not sourced primarily from mountain block recharge that flows in one continuous, saturated flow-path from recharge to discharge; instead, recharge originating in the valley comprises a significant portion of this groundwater. In addition, production wells in northeast SLV have warmer recharge temperatures, younger apparent ages, and higher nitrate concentrations than expected for wells entirely sourced from mountain-block recharge, suggesting that they may also receive a portion of valley recharge. These findings have important implications for northeast SLV, where there is an ongoing Superfund investigation into the movement of a groundwater contaminant plume. |
