Groundwater is a critical resource for drinking water and food production, yet limited management... more Groundwater is a critical resource for drinking water and food production, yet limited management amid intensive use has led to aquifer depletion across the globe . Efforts to address this depletion have been stymied by an incomplete understanding of aquifer dynamics, data limitations, a mismatch between law and science, along with socio-economic, cultural, and political factors. The AGU Chapman Conference "The Quest for Sustainability of Heavily Stressed Aquifers at Regional to Global Scales" was held in October 2019 at the Universitat Politècnica de València in Spain to address these barriers to progress and explore promising paths forward. Presentations by researchers from the hydrology, law, economics, and social science communities provided the basis for discussions of the most critical data needs; the appropriate scale for aquifer analyses; assessments of supply and demand from local to global scales; and proposals for future directions that incorporate governance, the likely trajectory of anthropogenic stresses, the protection of ecosystems, and the evolution of modeling and analysis tools. The conference's presentations and discussions prompted the preparation of this special section focused on the prospects for a more sustainable future for the world's heavily stressed aquifers. The special section consists of 17 papers contributed by conference attendees and others with similar interests. Although these papers only present a partial picture of the topics covered in the conference's presentations and discussions, they aptly demonstrate the interest of the broader hydrological community in the future of the world's critically important groundwater resources.
The identification of spatial variations in hydraulic conductivity (K) on a scale of relevance fo... more The identification of spatial variations in hydraulic conductivity (K) on a scale of relevance for transport investigations has proven to be a considerable challenge. Recently, a new field method for the estimation of interwell variations in K has been proposed. This method, hydraulic tomography, essentially consists of a series of short‐term pumping tests performed in a tomographic‐like arrangement. In order to fully realize the potential of this approach, information about lateral and vertical variations in pumping‐induced head changes (drawdown) is required with detail that has previously been unobtainable in the field. Pumping tests performed in networks of multilevel sampling (MLS) wells can provide data of the needed density if drawdown can accurately and rapidly be measured in the small‐diameter tubing used in such wells. Field and laboratory experiments show that accurate transient drawdown data can be obtained in the small‐diameter MLS tubing either directly with miniature ...
Fine‐scale hydrostratigraphic features often play a critical role in controlling ground water flo... more Fine‐scale hydrostratigraphic features often play a critical role in controlling ground water flow and contaminant transport. Unfortunately, many conventional drilling‐ and geophysics‐based approaches are rarely capable of describing these features at the level of detail needed for contaminant predictions and remediation designs. Previous work has shown that direct‐push electrical conductivity (EC) logging can provide information about site hydrostratigraphy at a scale of relevance for contaminant transport investigations in many unconsolidated settings. In this study, we evaluate the resolution and quality of that information at a well‐studied research site that is underlain by highly stratified alluvial sediments. Geologic and hydrologic data, conventional geophysical logs, and particle‐size analyses are used to demonstrate the capability of direct‐push EC logging for the delineation of fine‐scale hydrostratigraphic features in saturated unconsolidated formations. When variations ...
Water level changes in wells provide a direct measure of the impact of groundwater development at... more Water level changes in wells provide a direct measure of the impact of groundwater development at a scale of relevance for management activities. Important information about aquifer dynamics and an aquifer's future is thus often embedded in hydrographs from continuously monitored wells. Interpretation of those hydrographs using methods developed for pumping-test analyses can provide insights that are difficult to obtain via other means. These insights are demonstrated at two sites in the High Plains aquifer in western Kansas. One site has thin unconfined and confined intervals separated by a thick aquitard. Pumping-induced responses in the unconfined interval indicate a closed (surrounded by units of relatively low permeability) system that is vulnerable to rapid depletion with continued development. Responses in the confined interval indicate that withdrawals are largely supported by leakage. Given the potential for rapid depletion of the unconfined interval, the probable source of that leakage, it is likely that large-scale irrigation withdrawals will not be sustainable in the confined interval beyond a decade. A second site has a relatively thick unconfined aquifer with responses that again indicate a closed system. However, unlike the first site, previously unrecognized vertical inflow can be discerned in data from the recovery periods. In years of relatively low withdrawals, this inflow can produce year-on-year increases in water levels, an unexpected occurrence in western Kansas. The prevalence of bounded-aquifer responses at both sites has important ramifications for modeling studies; transmissivity values from pumping tests, for example, must be used cautiously in regional models of such systems.
The only means of moderating alarming depletion rates in many of the world's major aquifers is to... more The only means of moderating alarming depletion rates in many of the world's major aquifers is to reduce pumping. We apply a new water-balance approach to assess the impact of pumping reductions in a portion of the High Plains aquifer in the United States. Although projected aquifer responses to pumping reductions vary, practically achievable reductions would have a large impact throughout the area. These findings demonstrate that modest pumping reductions could greatly enhance prospects for groundwater-supported irrigation in the High Plains aquifer and similar aquifers elsewhere.
Specific yield (Sy) is one of the most important aquifer parameters in groundwater models with la... more Specific yield (Sy) is one of the most important aquifer parameters in groundwater models with large storage changes. However, it has received limited attention from the modeling community and there are few, if any, approaches that can be widely applied for determination of Sy at the scale required for regional aquifer studies. Despite the limitations of parameter estimation methods and of direct measurements of aquifer storage properties in the field, the large uncertainty in model Sy values is typically ignored and Sy is incorrectly assumed to be a known quantity. These practices can introduce errors into model predictions of aquifer budget components, such as recharge and storage depletion. In turn, aquifer management and planning can be greatly impacted, as estimates of aquifer responses to pumping changes are highly dependent on those simulated budget components. In this work, we use a groundwater model of a portion of the High Plains aquifer in the central United States to illustrate the impacts of inappropriately large Sy values on model predictions and the related water management ramifications. Building on our recent work, we propose a data‐driven approach for determining specific yield for regional groundwater models. Results demonstrate that this new approach can improve model reliability and lead to more robust predictions of aquifer responses to management scenarios.
Aquifers supporting irrigated agriculture are a resource of global importance. Many of these syst... more Aquifers supporting irrigated agriculture are a resource of global importance. Many of these systems, however, are experiencing significant pumping‐induced stress that threatens their continued viability as a water source for irrigation. Reductions in pumping are often the only option to extend the lifespans of these aquifers and the agricultural production they support. The impact of reductions depends on a quantity known as “net inflow” or “capture.” We use data from a network of wells in the western Kansas portions of the High Plains aquifer in the central United States to demonstrate the importance of net inflow, how it can be estimated in the field, how it might vary in response to pumping reductions, and why use of “net inflow” may be preferred over “capture” in certain contexts. Net inflow has remained approximately constant over much of western Kansas for at least the last 15 to 25 years, thereby allowing it to serve as a target for sustainability efforts. The percent pumpin...
Groundwater is a critical resource for drinking water and food production, yet limited management... more Groundwater is a critical resource for drinking water and food production, yet limited management amid intensive use has led to aquifer depletion across the globe . Efforts to address this depletion have been stymied by an incomplete understanding of aquifer dynamics, data limitations, a mismatch between law and science, along with socio-economic, cultural, and political factors. The AGU Chapman Conference "The Quest for Sustainability of Heavily Stressed Aquifers at Regional to Global Scales" was held in October 2019 at the Universitat Politècnica de València in Spain to address these barriers to progress and explore promising paths forward. Presentations by researchers from the hydrology, law, economics, and social science communities provided the basis for discussions of the most critical data needs; the appropriate scale for aquifer analyses; assessments of supply and demand from local to global scales; and proposals for future directions that incorporate governance, the likely trajectory of anthropogenic stresses, the protection of ecosystems, and the evolution of modeling and analysis tools. The conference's presentations and discussions prompted the preparation of this special section focused on the prospects for a more sustainable future for the world's heavily stressed aquifers. The special section consists of 17 papers contributed by conference attendees and others with similar interests. Although these papers only present a partial picture of the topics covered in the conference's presentations and discussions, they aptly demonstrate the interest of the broader hydrological community in the future of the world's critically important groundwater resources.
The identification of spatial variations in hydraulic conductivity (K) on a scale of relevance fo... more The identification of spatial variations in hydraulic conductivity (K) on a scale of relevance for transport investigations has proven to be a considerable challenge. Recently, a new field method for the estimation of interwell variations in K has been proposed. This method, hydraulic tomography, essentially consists of a series of short‐term pumping tests performed in a tomographic‐like arrangement. In order to fully realize the potential of this approach, information about lateral and vertical variations in pumping‐induced head changes (drawdown) is required with detail that has previously been unobtainable in the field. Pumping tests performed in networks of multilevel sampling (MLS) wells can provide data of the needed density if drawdown can accurately and rapidly be measured in the small‐diameter tubing used in such wells. Field and laboratory experiments show that accurate transient drawdown data can be obtained in the small‐diameter MLS tubing either directly with miniature ...
Fine‐scale hydrostratigraphic features often play a critical role in controlling ground water flo... more Fine‐scale hydrostratigraphic features often play a critical role in controlling ground water flow and contaminant transport. Unfortunately, many conventional drilling‐ and geophysics‐based approaches are rarely capable of describing these features at the level of detail needed for contaminant predictions and remediation designs. Previous work has shown that direct‐push electrical conductivity (EC) logging can provide information about site hydrostratigraphy at a scale of relevance for contaminant transport investigations in many unconsolidated settings. In this study, we evaluate the resolution and quality of that information at a well‐studied research site that is underlain by highly stratified alluvial sediments. Geologic and hydrologic data, conventional geophysical logs, and particle‐size analyses are used to demonstrate the capability of direct‐push EC logging for the delineation of fine‐scale hydrostratigraphic features in saturated unconsolidated formations. When variations ...
Water level changes in wells provide a direct measure of the impact of groundwater development at... more Water level changes in wells provide a direct measure of the impact of groundwater development at a scale of relevance for management activities. Important information about aquifer dynamics and an aquifer's future is thus often embedded in hydrographs from continuously monitored wells. Interpretation of those hydrographs using methods developed for pumping-test analyses can provide insights that are difficult to obtain via other means. These insights are demonstrated at two sites in the High Plains aquifer in western Kansas. One site has thin unconfined and confined intervals separated by a thick aquitard. Pumping-induced responses in the unconfined interval indicate a closed (surrounded by units of relatively low permeability) system that is vulnerable to rapid depletion with continued development. Responses in the confined interval indicate that withdrawals are largely supported by leakage. Given the potential for rapid depletion of the unconfined interval, the probable source of that leakage, it is likely that large-scale irrigation withdrawals will not be sustainable in the confined interval beyond a decade. A second site has a relatively thick unconfined aquifer with responses that again indicate a closed system. However, unlike the first site, previously unrecognized vertical inflow can be discerned in data from the recovery periods. In years of relatively low withdrawals, this inflow can produce year-on-year increases in water levels, an unexpected occurrence in western Kansas. The prevalence of bounded-aquifer responses at both sites has important ramifications for modeling studies; transmissivity values from pumping tests, for example, must be used cautiously in regional models of such systems.
The only means of moderating alarming depletion rates in many of the world's major aquifers is to... more The only means of moderating alarming depletion rates in many of the world's major aquifers is to reduce pumping. We apply a new water-balance approach to assess the impact of pumping reductions in a portion of the High Plains aquifer in the United States. Although projected aquifer responses to pumping reductions vary, practically achievable reductions would have a large impact throughout the area. These findings demonstrate that modest pumping reductions could greatly enhance prospects for groundwater-supported irrigation in the High Plains aquifer and similar aquifers elsewhere.
Specific yield (Sy) is one of the most important aquifer parameters in groundwater models with la... more Specific yield (Sy) is one of the most important aquifer parameters in groundwater models with large storage changes. However, it has received limited attention from the modeling community and there are few, if any, approaches that can be widely applied for determination of Sy at the scale required for regional aquifer studies. Despite the limitations of parameter estimation methods and of direct measurements of aquifer storage properties in the field, the large uncertainty in model Sy values is typically ignored and Sy is incorrectly assumed to be a known quantity. These practices can introduce errors into model predictions of aquifer budget components, such as recharge and storage depletion. In turn, aquifer management and planning can be greatly impacted, as estimates of aquifer responses to pumping changes are highly dependent on those simulated budget components. In this work, we use a groundwater model of a portion of the High Plains aquifer in the central United States to illustrate the impacts of inappropriately large Sy values on model predictions and the related water management ramifications. Building on our recent work, we propose a data‐driven approach for determining specific yield for regional groundwater models. Results demonstrate that this new approach can improve model reliability and lead to more robust predictions of aquifer responses to management scenarios.
Aquifers supporting irrigated agriculture are a resource of global importance. Many of these syst... more Aquifers supporting irrigated agriculture are a resource of global importance. Many of these systems, however, are experiencing significant pumping‐induced stress that threatens their continued viability as a water source for irrigation. Reductions in pumping are often the only option to extend the lifespans of these aquifers and the agricultural production they support. The impact of reductions depends on a quantity known as “net inflow” or “capture.” We use data from a network of wells in the western Kansas portions of the High Plains aquifer in the central United States to demonstrate the importance of net inflow, how it can be estimated in the field, how it might vary in response to pumping reductions, and why use of “net inflow” may be preferred over “capture” in certain contexts. Net inflow has remained approximately constant over much of western Kansas for at least the last 15 to 25 years, thereby allowing it to serve as a target for sustainability efforts. The percent pumpin...
Uploads
Papers by James Butler