Guest Editorial/
Focus Issue on Public Supply Well Vulnerability by Kristine Uhlman PG
The vulnerability of groundwater-based public water systems to anthropogenic contaminants was first addressed in the 1986 amendment to the Safe Drinking Water Act. Wellhead protection programs across the United States delineated recharge areas and often zoned land-use options around a wellhead based on groundwater time of travel and/or calculated drawdown. Similar community wellhead protection programs are common around the world. Tools available to the Hydrologist have evolved since the last century, with advanced numerical simulations, new laboratory techniques, and enhanced subsurface exploration methods allowing for a fuller understanding of aquifer systems. As our science has become more sophisticated, so has the capacity of the public to demand more. Management of public water supply has become more aggressive to meet the public’s growing awareness of water quality—and quantity—issues. As aquifers are being depleted, the impact on drinking water supplies by naturally occurring constituents, recharge source, capture, and storage depletion is pertinent to water supply sustainability. This special Focus Issue on the Vulnerability of Public Water Well Systems expands beyond wellhead protection to the spatial and temporal considerations necessary to assess the full vulnerability of public water supply. The collection of papers in this Focus Issue focus on a wide range of monitoring and management options related to public well vulnerability and protection of the public from the risk of contaminant exposure. Much of the work is being reported by the U.S. Geological Survey, with an introduction by Dr. Sandra Eberts’ Technical Commentary, “If groundwater is contaminated, will water from the well be contaminated?” Water supply wells in the sands of New Jersey, Basin and Range alluvium of New Mexico and Utah, valley sediment of California, and the karst of Florida and central Texas are investigated. Chlorinated hydrocarbons, nitrate, arsenic, and uranium are mobilized and transported, with flowpaths predicted Bureau of Economic Geology, University of Texas at Austin, Austin 78720, TX; [email protected] © 2014, National Ground Water Association. doi: 10.1111/gwat.12259
NGWA.org
and travel times calculated by the Survey scientists. Residence time and recharge age are found to be important to water quality, with vertical head gradients and mixing of stratified aquifer water quality contributing to the vulnerability of the pumping well to quality degradation. The influence of seasonality is somewhat unexpected, finding that changes to seasonal pumping patterns and/or well depth contributes to reduced vulnerability to selected natural or anthropogenic contaminants. Other papers with examples from the Nagaoka Plain of Japan and the Indus Basin address aquifer characterization and pumping-induced flow regime change. The hydrodynamics of aquifer systems responding to land-use change, pumping, and air temperature warming suggests that urbanization and intensive groundwater extraction can be responsible for geochemical change in aquifers. In another paper, examination of 33 aquifers with published data from both the United States and abroad found drawdown and aquifer depletion is a function of recharge and extraction rate, as to be expected. However, examination of these real water systems found that long-term pumping is derived from capture, making streamflow and fragile ecosystems reliant on surface water vulnerable to groundwater extraction. Risk of water supply well contamination is investigated from the perspective of wellhead protection delineation options in Germany, with options to reduce the risk of contaminant exposure by management of groundwater recharge. The vulnerability of unregulated, domestic groundwater systems to bacteria in rural Georgia is also presented in this Issue, using a risk screening strategy based on watershed characteristics. In addition, a survey of 83 pesticide compounds and the trends in concentration in groundwater over the past 20 years in the United States are also reported, identifying aquifers at risk. Tested across a multiyear field sampling campaign in California, a new sampling and monitoring protocol is presented to assist in the identification of potential sources of groundwater contamination by enteric pathogens in agricultural settings. Finally, from California, nitrogen isotope fractionation following groundwater recharge by treated municipal waste water is also reported as a case study. Groundwater
1
The series of Methods Notes and Issue Paper brings our focus around to the actual performance of water wells, with works addressing pumping tests, well construction, sustainable yield, and aquifer productivity. The interactive web-based tool developed by the USGS allows for ready conceptualization of flow pathlines to
2
Groundwater
a well and provides an excellent outreach tool for the public. This special Focus Issue documents how our science has grown from the wellhead protection programs of the 1980s to the future of aquifer management and water system risk reduction.
NGWA.org
Focus Issue on Public Supply Well Vulnerability by Kristine Uhlman PG
The vulnerability of groundwater-based public water systems to anthropogenic contaminants was first addressed in the 1986 amendment to the Safe Drinking Water Act. Wellhead protection programs across the United States delineated recharge areas and often zoned land-use options around a wellhead based on groundwater time of travel and/or calculated drawdown. Similar community wellhead protection programs are common around the world. Tools available to the Hydrologist have evolved since the last century, with advanced numerical simulations, new laboratory techniques, and enhanced subsurface exploration methods allowing for a fuller understanding of aquifer systems. As our science has become more sophisticated, so has the capacity of the public to demand more. Management of public water supply has become more aggressive to meet the public’s growing awareness of water quality—and quantity—issues. As aquifers are being depleted, the impact on drinking water supplies by naturally occurring constituents, recharge source, capture, and storage depletion is pertinent to water supply sustainability. This special Focus Issue on the Vulnerability of Public Water Well Systems expands beyond wellhead protection to the spatial and temporal considerations necessary to assess the full vulnerability of public water supply. The collection of papers in this Focus Issue focus on a wide range of monitoring and management options related to public well vulnerability and protection of the public from the risk of contaminant exposure. Much of the work is being reported by the U.S. Geological Survey, with an introduction by Dr. Sandra Eberts’ Technical Commentary, “If groundwater is contaminated, will water from the well be contaminated?” Water supply wells in the sands of New Jersey, Basin and Range alluvium of New Mexico and Utah, valley sediment of California, and the karst of Florida and central Texas are investigated. Chlorinated hydrocarbons, nitrate, arsenic, and uranium are mobilized and transported, with flowpaths predicted Bureau of Economic Geology, University of Texas at Austin, Austin 78720, TX; [email protected] © 2014, National Ground Water Association. doi: 10.1111/gwat.12259
NGWA.org
and travel times calculated by the Survey scientists. Residence time and recharge age are found to be important to water quality, with vertical head gradients and mixing of stratified aquifer water quality contributing to the vulnerability of the pumping well to quality degradation. The influence of seasonality is somewhat unexpected, finding that changes to seasonal pumping patterns and/or well depth contributes to reduced vulnerability to selected natural or anthropogenic contaminants. Other papers with examples from the Nagaoka Plain of Japan and the Indus Basin address aquifer characterization and pumping-induced flow regime change. The hydrodynamics of aquifer systems responding to land-use change, pumping, and air temperature warming suggests that urbanization and intensive groundwater extraction can be responsible for geochemical change in aquifers. In another paper, examination of 33 aquifers with published data from both the United States and abroad found drawdown and aquifer depletion is a function of recharge and extraction rate, as to be expected. However, examination of these real water systems found that long-term pumping is derived from capture, making streamflow and fragile ecosystems reliant on surface water vulnerable to groundwater extraction. Risk of water supply well contamination is investigated from the perspective of wellhead protection delineation options in Germany, with options to reduce the risk of contaminant exposure by management of groundwater recharge. The vulnerability of unregulated, domestic groundwater systems to bacteria in rural Georgia is also presented in this Issue, using a risk screening strategy based on watershed characteristics. In addition, a survey of 83 pesticide compounds and the trends in concentration in groundwater over the past 20 years in the United States are also reported, identifying aquifers at risk. Tested across a multiyear field sampling campaign in California, a new sampling and monitoring protocol is presented to assist in the identification of potential sources of groundwater contamination by enteric pathogens in agricultural settings. Finally, from California, nitrogen isotope fractionation following groundwater recharge by treated municipal waste water is also reported as a case study. Groundwater
1
The series of Methods Notes and Issue Paper brings our focus around to the actual performance of water wells, with works addressing pumping tests, well construction, sustainable yield, and aquifer productivity. The interactive web-based tool developed by the USGS allows for ready conceptualization of flow pathlines to
2
Groundwater
a well and provides an excellent outreach tool for the public. This special Focus Issue documents how our science has grown from the wellhead protection programs of the 1980s to the future of aquifer management and water system risk reduction.
NGWA.org
