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At least 613 records · Page 34Linked to original sources
USGS2014

Integrated hydrologic model of Pajaro Valley, Santa Cruz and Monterey Counties, California

Increasing population, agricultural development (including shifts to more water-intensive crops), and climate variability are placing increasingly larger demands on available groundwater resources in the Pajaro Valley, one of the most productive agricultural regions in the world. This study provided a refined conceptual model, geohydrologic framework, and integrated hydrologic model of the Pajaro Valley. The goal of this study was to produce a model capable of being accurate at scales relevant to water management decisions that are being considered in the revision and updates to the Basin Management Plan (BMP). The Pajaro Valley Hydrologic Model (PVHM) was designed to reproduce the most important natural and human components of the hydrologic system and related climatic factors, permitting an accurate assessment of groundwater conditions and processes that can inform the new BMP and help to improve planning for long-term sustainability of water resources. Model development included a revision of the conceptual model of the flow system, reevaluation of the previous model transformed into MODFLOW, implementation of the new geohydrologic model and conceptual model, and calibration of the transient hydrologic model. The PVHM model, using MODFLOW with the Farm Process (MF-FMP2), is capable of being accurate at seasonal to interannual time frames and subregional to valley-wide spatial scales for the assessment of the groundwater hydrologic budget for water years 1964–2009, as well as potential assessment of the BMP components and sustainability analysis of conjunctive use. The model provides a good representation of the regional flow system and the use and movement of water throughout the valley. Simulated changes in storage over time show that, prior to the 1984–92 dry period, significant withdrawals from storage occurred only during drought years. Since about 1993, growers in the Pajaro Valley have shifted to more water intensive crops, such as strawberries, bushberries, and vegetable row crops, as well as making additional rotational plantings, which have increased demand on limited groundwater resources. Simulated groundwater flow indicates that vertical hydraulic gradients between horizontal layers fluctuate and even reverse in several parts of the basin as recharge and pumpage rates change seasonally and annually. The majority of recharge predominantly enters the Alluvial aquifer system, and along with pumpage and the largest fractions of storage depletion, occurs in the inland regions. Coastal inflow as seawater intrusion replaces much of the potential storage depletion in the coastal regions. The simulated long-term imbalance between inflows and outflows indicates overdraft of the groundwater basin averaging about 12,950 acre-feet per year (acre-ft/yr) over the 46-year period of water years (1964–2009). Annual overdraft varies considerably from year to year, depending on land use, pumpage, and climate conditions. Climatically driven factors can affect inflows, outflows, and water use by as much as a factor of two between wet and dry years. Coastal inflows and outflows vary by year and by aquifer; the net coastal inflow, or seawater intrusion, ranges from about 1,000 to more than 6,000 acre-ft/yr. Maps of simulated and measured water-level elevations indicate regions with water levels below sea level in the alluvium and Aromas layers. Ongoing expansion of local hydrologic monitoring networks indicates the importance of these networks to the understanding of changes in groundwater flow, streamflow, and streamflow infiltration. In particular, the monitoring of streamflow, groundwater pumpage, and groundwater levels throughout the valley not only indicates the state of the resources, but also provides valuable information for model calibration and for model-based evaluation of management actions. The HS-ASR was simulated for the years 2002–09, and replaced about about 1,290 acre-ft of coastal pumpage. This was combined with the simulation of additional 6,200 acre-ft of deliveries from supplemental wells, recycled water, and city connection deliveries through the CDS that also supplanted some coastal pumpage. Total simulated deliveries were 7,350 acre-ft of the 7,500 acre-ft of reported deliveries for the period 2002-09. The completed CDS should be capable of delivering about 8.8 million cubic meters (7,150 acre-ft) of water per year to coastal farms within the Pajaro Valley, if all the local supply components were fully available for this purpose. This would represent about 15 percent of the 48,300 acre-ft (59.6 million cubic meters) average agricultural pumpage for the period 2005 to 2009. Combined with the potential capture and reuse of some of the return flows and tile-drain flows, this could represent an almost 70 percent reduction of average overdraft for the entire valley and a large part of the coastal pumpage that induces seawater intrusion.

California↗
USGS2015

The source, discharge, and chemical characteristics of selected springs, and the abundance and health of associated endemic anuran species in the Mojave network parks

Hydrological and biological investigations were done during 2005 and 2006 in cooperation with the U.S. National Park Service to investigate the source, discharge, and chemical characteristics of selected springs and the abundance and health of endemic anuran (frog and toad) species at Darwin Falls in Death Valley National Park, Piute Spring in Mojave National Preserve, and Fortynine Palms Oasis in Joshua Tree National Park. Discharge from the springs at these sites sustains isolated riparian habitats in the normally dry Mojave Desert. Data were collected on water quantity (discharge) and quality, air and water temperature, and abundance and health of endemic anuran species. In addition, a single survey of the abundance and health of endemic anuran species was completed at Rattlesnake Canyon in Joshua Tree National Park. Results from this study were compared to limited historical data, where they exist, and can provide a baseline for future hydrological and biological investigations to evaluate the health and sustainability of the resource and its response to changing climate and increasing human use. Radiocarbon dating of the water yielded estimated ages of about 7,000 years at Piute Spring and about 3,000 years at Darwin Spring, and tritium-helium-3 dating indicated an age of less than 2 years at Fortynine Palms Oasis. Stable hydrogen-isotope ratios were used to interpret an average altitude of recharge of 2,348 meters for Darwin Spring (about 1,415 meters higher than the altitude of Darwin Spring), 1,668 meters for Piute Spring (about 766 meters higher than the altitude of Piute Spring), and 1,400 meters for the Upper Pool at Fortynine Palms Oasis (about 543 meters higher than the altitude of the Upper Pool). Water-quality data collected for this study did not appear to be sensitive to trends in precipitation or seasonality in the Darwin Falls and Piute Spring study areas; however, it was sensitive to trends in Fortynine Palms Oasis where salinity increased by more than 10 percent during the 2 years of this study. Such a rapid response is consistent with the comparatively short travel time of less than 2 years from recharge to discharge at Fortynine Palms Oasis. Of the 14 trace elements analyzed, only concentrations of uranium at Fortynine Palms Oasis and arsenic at Darwin Spring were above drinking water standards; both constituents are derived from natural sources in the drainage basin and, therefore, are likely to have accumulated as a result of natural processes. Endemic anuran species were surveyed at Darwin Falls for the western toad ( Anaxyrus boreas ) and the red-spotted toad ( Anaxyrus punctatus ), at Piute Spring for the red-spotted toad, and at Fortynine Palms Oasis for the red-spotted toad and California treefrog ( Pseudacris cadaverina ). Historically, red-spotted toads were at the edge of their range at Darwin Falls, but they were not detected during this study and have not been detected since the early 1980s. The 2006 western toad population at Darwin Falls was estimated at 381 adults (95-percent confidence interval [CI] of 314–482). The population of red-spotted toads at Piute Spring was estimated at 1,153 adults (95-percent CI of 935–1,503). However, an elevated rate of abnormalities (approximately 5 percent) was recorded in red-spotted toads as well as the presence of the chytrid fungus, Bactrochochytrium dendrobatidis , at Piute Spring. In Joshua Tree National Park, the California treefrog now occupies only three of the seven historically occupied drainages. Populations of California treefrogs at Fortynine Palms Oasis have declined more than 50 percent from 288 in 1969–71 to 109 in 2006. A similar decline was observed in the populations of red-spotted toads at Fortynine Palms Oasis from 300 adults in 1969–71 to 155 adults (95-percent CI of 90–139) in 2006. The red-spotted toads at Fortynine Palms Oasis also exhibited the presence of Bactrochochytrium dendrobatidis .

California↗
USGS2015

Geohydrology and water quality of the stratified-drift aquifers in Upper Buttermilk Creek and Danby Creek Valleys, Town of Danby, Tompkins County, New York

In 2006, the U.S. Geological Survey, in cooperation with the Town of Danby and the Tompkins County Planning Department, began a study of the stratified-drift aquifers in the upper Buttermilk Creek and Danby Creek valleys in the Town of Danby, Tompkins County, New York. In the northern part of the north-draining upper Buttermilk Creek valley, there is only one sand and gravel aquifer, a confined basal unit that overlies bedrock. In the southern part of upper Buttermilk Creek valley, there are as many as four sand and gravel aquifers, two are unconfined and two are confined. In the south-draining Danby Creek valley, there is an unconfined aquifer consisting of outwash and kame sand and gravel (deposited by glacial meltwaters during the late Pleistocene Epoch) and alluvial silt, sand, and gravel (deposited by streams during the Holocene Epoch). In addition, throughout the study area, there are several small local unconfined aquifers where large tributaries deposited alluvial fans in the valley. The principal sources of recharge to the unconfined aquifers in the study area include direct infiltration of precipitation (rain and snowmelt) at land surface, unchanneled surface runoff from adjacent hillsides that seeps into the aquifer along the edges of the valley, groundwater inflow from adjacent till and bedrock that enters the aquifer along the sides of the valley, and seepage loss from upland-tributary streams where they flow over their alluvial fans in the valley. The percentages of all sources of recharge to the contiguous unconfined aquifer in Danby Creek valley include 16 percent from precipitation that falls directly over the aquifer, 55 percent from unchanneled surface runoff and groundwater inflow from hillsides, and 29 percent from losing tributary streams that cross the aquifer. The total annual recharge to the contiguous unconfined aquifer is 2.56 cubic feet per second (604 million gallons per year). The principal sources of recharge to the confined aquifers include precipitation that falls directly on the surficial confining unit, which then slowly flows vertically downward through the fine-grained sediments and enters the confined aquifer, and groundwater inflow from till and bedrock that borders the aquifer along adjacent hillsides and at the bottom of the valley. In addition, there is substantial amounts of recharge to the confined aquifers where the confining units are locally absent (forming windows) and where parts of the confining units consist of sediments of low to moderate permeability (forming a semiconfining layer). In the northern part of the study area (upper Buttermilk Creek valley), groundwater in the stratified-drift aquifers discharges to (1) domestic and commercial wells; (2) Buttermilk Creek in the area near the northern town border, and (3) and a small unnamed stream in a ravine in Buttermilk State Park just north of the town border. In the southern part of the study area (Danby Creek valley), groundwater discharges (1) to domestic, commercial, and farm wells; (2) to Danby Creek; (3) to a large wetland in the central parts of Danby Creek valley; and (4) as losses because of plant uptake and evaporation. About 300 people depend on groundwater from the upper Buttermilk Creek and Danby Creek stratified-drift aquifer system. An unconfined surficial aquifer about 8,000 feet (ft) long and as much as 800 ft wide, with a saturated thickness of about 20 ft, occupies the lower (southeastern most) 8,000 ft of Danby Creek valley within the Town of Danby. However, because the aquifer is thin, the volume of water stored in the aquifer is small and the potential for induced recharge from Danby Creek during summer periods of low flow is also small, an array of wells would probably be needed to provide sustainable continuous amount of water to large water users such as municipalities and industries. Additional data and a groundwater flow model would be required to estimate sustainable withdrawal from the confined aquifers in upper Buttermilk Creek valley. Well data from water-well drillers through 2012 indicate that the confined aquifers in upper Buttermilk Creek valley are thin (typically about 10 feet thick) and the reported well-yield data suggest these aquifers may not be capable of supplying sufficient water to meet the needs of municipalities and industries. However, additional geohydrologic data leading to calibration of a groundwater flow model would be needed to properly evaluate the long-term (multiple years) potential yield of the confined aquifer system in upper Buttermilk Creek valley and of the unconfined aquifer in Danby Creek valley. During 2007–10, groundwater samples were collected from 13 wells including 7 wells that are completed in the confined sand and gravel aquifers, 1 well that is completed in the unconfined aquifer, and 5 wells that are completed in the bedrock aquifers. Calcium dominates the cation composition and bicarbonate dominates the anion composition in most groundwater. Water quality in the study area generally meets state and Federal drinking-water standards but concentrations of some constituents exceeded the standards. The standards that were exceeded include sodium (3 samples), dissolved solids (1 sample), iron (3 samples), manganese (8 samples), and arsenic (1 sample).

New York↗
USGS2016

Streamflow and estimated loads of phosphorus and dissolved and suspended solids from selected tributaries to Lake Ontario, New York, water years 2012–14

This report presents results of the evaluation and interpretation of hydrologic and water-quality data collected as part of a cooperative program between the U.S. Geological Survey and the U.S. Environmental Protection Agency. Streamflow, phosphorus, and solids dissolved and suspended in stream water were the focus of monitoring by the U.S. Geological Survey at 10 sites on 9 selected tributaries to Lake Ontario during the period from October 2011 through September 2014. Streamflow yields (flow per unit area) were the highest from the Salmon River Basin due to sustained yields from the Tug Hill aquifer. The Eighteenmile Creek streamflow yields also were high as a result of sustained base flow contributions from a dam just upstream of the U.S. Geological Survey monitoring station at Burt. The lowest streamflow yields were measured in the Honeoye Creek Basin, which reflects a decrease in flow because of withdrawals from Canadice and Hemlock Lakes for the water supply of the City of Rochester. The Eighteenmile Creek and Oak Orchard Creek Basins had relatively high yields due in part to groundwater contributions from the Niagara Escarpment and seasonal releases from the New York State Barge Canal. Annual constituent yields (load per unit area) of suspended solids, phosphorus, orthophosphate, and dissolved solids were computed to assess the relative contributions and allow direct comparison of loads among the monitored basins. High yields of total suspended solids were attributed to agricultural land use in highly erodible soils at all sites. The Genesee River, Irondequoit Creek, and Honeoye Creek had the highest concentrations and largest mean yields of total suspended solids (165 short tons per square mile [t/mi 2 ], 184 t/mi 2 , and 89.7 t/mi 2 , respectively) of the study sites. Samples from Eighteenmile Creek, Oak Orchard Creek at Kenyonville, and Irondequoit Creek had the highest concentrations and largest mean yields of phosphorus (0.27 t/mi 2 , 0.26 t/mi 2 , and 0.20 t/mi 2 , respectively) and orthophosphate (0.17 t/mi 2 , 0.13 t/mi 2 , and 0.04 t/mi 2 , respectively) of the study sites. These results were attributed to a combination of sources, including discharges from wastewater treatment plants, diversions from the New York State Barge Canal, and manure and fertilizers applied to agricultural land. Yields of phosphorus also were high in the Genesee River Basin (0.17 t/mi 2 ) and were presumably associated with nutrient and sediment transport from agricultural land and from streambank erosion. The Salmon and Black Rivers, which drain a substantial amount of forested land and are influenced by large groundwater discharges, had the lowest concentrations and yields of phosphorus and orthophosphate of the study sites. Mean annual yields of dissolved solids were the highest in Irondequoit Creek due to a high percentage of urbanized area in the basin and in Oak Orchard Creek at Kenyonville and in Eighteenmile Creek due to groundwater contributions from the Niagara Escarpment. High yields of dissolved solids of 840 t/mi 2 , 829 t/mi 2 , and 715 t/mi 2 , respectively, from these basins can be attributed to seasonal chloride yields associated with use of road deicing salts. The Niagara Escarpment can produce large amounts of dissolved solids from the dissolution of minerals (a continual process reflected in base flow samples). Groundwater inflows in the Salmon River have very low concentrations of dissolved solids due to minimal bedrock interaction along the Tug Hill Plateau and discharge from the Tug Hill sand and gravel aquifer, which has minimal mineralization.

New York↗
USGS2016

Hydrogeologic framework and characterization of the Truxton Aquifer on the Hualapai Reservation, Mohave County, Arizona

The U.S. Geological Survey, in cooperation with the Bureau of Reclamation, developed this study to determine an estimate of groundwater in storage in the Truxton aquifer on the Hualapai Reservation in northwestern Arizona. For this study, the Truxton aquifer is defined as the unconfined, saturated groundwater in the unconsolidated to semiconsolidated older and younger basin-fill deposits of the Truxton basin overlying bedrock. The physical characteristics of the Truxton aquifer have not been well characterized in the past. In particular, the depth to impermeable granite bedrock and thickness of the basin are known in only a few locations where water wells have penetrated into the granite. Increasing water demands on the Truxton aquifer by both tribal and nontribal water users have led to concern about the long-term sustainability of this water resource. The Hualapai Tribe currently projects an increase of their water needs from about 300 acre-feet (acre-ft) per year to about 780 acre-ft per year by 2050 to support the community of Peach Springs, Arizona, and the southern part of the reservation. This study aimed to quantitatively develop better knowledge of aquifer characteristics, including aquifer storage and capacity, using (1) surface resistivity data collected along transects and (2) analysis of existing geologic, borehole, precipitation, water use, and water-level data. The surface resistivity surveys indicated that the depth to granite along the survey lines varied from less than 100 feet (ft) to more than 1,300 ft below land surface on the Hualapai Reservation. The top of the granite bedrock is consistent with the erosional character of the Truxton basin and exhibits deep paleochannels filled with basin-fill deposits consistent with the results of surface resistivity surveys and borehole logs from wells. The estimated average saturated thickness of the Truxton aquifer on the Hualapai Reservation is about 330 ft (with an estimated range of 260 to 390 ft), based on both resistivity results and the depth to water in wells. The saturated thickness might be greater in parts of the Truxton aquifer where paleochannels are incised into the granite underlying the basin-fill sediments. The estimated groundwater storage of the Truxton aquifer on the Hualapai Reservation ranges from 420,000 to 940,000 acre-ft and does not include groundwater storage in the aquifer outside the Hualapai Reservation boundary. In addition, the calculation of total storage in the Truxton aquifer does not determine nor indicate the availability and sustainability of that groundwater as a long-term resource. These results compared well with studies done on alluvial-basin aquifers in areas adjacent to this study. The part of the Truxton aquifer on the Hualapai Reservation represents about 20 percent of the entire aquifer.

Arizona↗
USGS2018

Water budget of the upper Chehalis River Basin, southwestern Washington

Groundwater and surface water collectively supply the domestic, agricultural, and industrial needs of the 895-square mile upper Chehalis River Basin upstream of Grand Mound, Washington, while providing streamflow for fish and other aquatic species in the Chehalis River and its tributaries. To support sustainable water management decision-making, a water budget (including precipitation, interception, groundwater recharge, surface runoff, and groundwater pumping) was developed for the upper Chehalis River Basin during October 2001–September 2015. Water-budget components were estimated from the U.S. Geological Survey Soil-Water-Balance (SWB) model except for groundwater pumping, which was estimated from public water purveyor records, annual system data from the Washington State Department of Health, census population data, and water-use estimates. Groundwater recharge estimated from the SWB model was compared to base flow, a proxy for groundwater recharge, independently estimated from separation of the hydrograph recorded by the U.S. Geological Survey streamgage at the outlet of the basin. Mean annual precipitation for the basin was estimated at 72.6 inches, of which 35 percent was lost to evapotranspiration, 30 percent was recharged to groundwater, 30 percent was surface runoff, and 5 percent was lost to interception. SWB model estimates of groundwater recharge were 17 percent less than estimates of base flow from hydrograph separation. Groundwater pumpage in the basin was estimated at 1 percent of groundwater recharge estimated by SWB and 0.8 percent of base flow estimated by hydrograph separation. These estimates form a baseline for understanding future changes to components of water use and may be used to inform numerical groundwater models to support sustainable management of water resources in the upper Chehalis River Basin.

Washington↗
USGS2018

Simulation of groundwater flow and analysis of projected water use for the Rush Springs aquifer, western Oklahoma

The U.S. Geological Survey, in cooperation with the Bureau of Reclamation and the Oklahoma Water Resources Board, (1) quantified the groundwater resources of the Rush Springs aquifer in western Oklahoma by developing a numerical groundwater-flow model, (2) evaluated the effects of estimated equal-proportionate-share (EPS) pumping rates on aquifer storage and streamflow for time periods of 20, 40, and 50 years into the future, (3) assessed the uncertainty in the EPS scenario results, and (4) evaluated the effects of (a) projected groundwater-use rates extended 50 years into the future and (b) sustained hypothetical drought conditions over a 10-year period on stream base flow and groundwater in storage. The Rush Springs aquifer is an important source of water for municipal and irrigation use by many communities and agricultural users in the study area. The study area is composed of about 4,970 square miles (3,181,003 acres) of Rush Springs aquifer bedrock deposits located in 14 counties. The study area also includes the alluvium and terrace deposits of the Canadian and Washita Rivers, as well as alluvium along the Little Washita River, Deer Creek, and a number of smaller tributaries of the Washita River that overlie the bedrock. A numerical groundwater-flow model of the Rush Springs aquifer was constructed by using MODFLOW with the Newton solver. Groundwater flow was simulated for January 1979–December 2015 by using monthly stress periods, and an initial steady-state stress period was configured to represent mean annual inflows and outflows. The model was calibrated to groundwater-level observations at selected wells, monthly base flow at nine streamgages, stream seepage as estimated for the conceptual water budget, and Fort Cobb Reservoir stage. The EPS scenarios for the Rush Springs aquifer were run for periods of 20, 40, and 50 years. The 20-, 40-, and 50-year EPS pumping rates under normal recharge conditions were 0.82, 0.49, and 0.43 acre-foot per acre per year, respectively. Given the 2,954,545-acre aquifer area used for the EPS scenarios, the 20-year rate corresponds to an annual yield of about 2,422,727 acre-feet per year. Groundwater storage at the end of the 20-year EPS scenario was about 13,321,000 acre-feet, or about 31,516,437 acre-feet (70 percent) less than the starting EPS scenario storage. This decrease in storage was equivalent to a mean groundwater-level decline of about 152 feet. Water availability under the EPS pumping rate was primarily from the western area of the model. Saturation was sustained though the entire EPS scenario where the aquifer was sufficiently thick or a shallow hydraulic gradient was present. Fort Cobb Reservoir stage was below the dead-pool stage after about 5 years of 20-year EPS pumping. An uncertainty analysis was conducted to assess the uncertainty in the EPS scenario results. An ensemble of 400 random sets of possible parameter values was performed for the uncertainty analysis by using a multivariate normal distribution centered on the calibrated parameter values. The parameter bounds for the uncertainty analysis were determined by using the posterior covariance matrix, which allows for the incorporation of knowledge gained during the calibration process as well as observation uncertainty and the correlation between estimated parameters. The uncertainty results indicate a 95-percent confidence interval for the 20-year EPS pumping rate between 0.73 and 0.95 acre-foot per acre per year. Projected 50-year pumping scenarios were used to simulate the effects of selected well withdrawal rates on groundwater storage of the Rush Springs aquifer. The effects of well withdrawals were evaluated by comparing changes in groundwater storage between four 50-year scenarios using (1) no groundwater use, (2) mean groundwater use for the study period (1979–2015), (3) increasing groundwater use, and (4) groundwater use at the 2015 rate. The increasing-use scenario assumed a 38-percent increase in pumping over 50 years on the basis of 2010–60 demand projections for western Oklahoma. Simulated groundwater storage changes ranged between an increase of 6.3 percent for the scenario with no groundwater use, and 0.9 percent for the scenario with 2015 groundwater-use rates. For the Fort Cobb Reservoir surface watershed, simulated groundwater storage changes ranged between an increase of 23.6 percent for the scenario with no groundwater use and a decrease of 4.0 percent for the increasing groundwater-use scenario. Groundwater-level changes were generally greater in areas with a large concentration of groundwater wells and groundwater use such as the Fort Cobb Reservoir surface watershed. A hypothetical 10-year drought scenario was used to simulate the effects of a prolonged period of reduced recharge on the Rush Springs aquifer groundwater storage and Fort Cobb Reservoir stage and storage. Drought effects were quantified by comparing the results of the drought scenario to those of the calibrated numerical model. To simulate the hypothetical drought, recharge in the calibrated numerical model was reduced by 50 percent during the simulated drought period (1983–1992), and upstream inflows to the Canadian and Washita Rivers and associated tributaries were reduced by 37 percent. Groundwater storage at the end of the hypothetical drought period in December 1992 was about 42,983,000 acre-feet, or about 3,525,000 acre-feet (7.6 percent) less than the groundwater storage of the calibrated numerical model. This change in groundwater storage is equivalent to a mean groundwater-level decline of 15.8 feet. Simulated mean base-flow declines at the Canadian and Washita River streamgages were between 39 and 59 percent during the drought period. The minimum stage in Fort Cobb Reservoir at the end of the hypothetical drought period was 1,311 feet, indicating a storage capacity of only 10 percent of active conservation pool storage. The Fort Cobb Reservoir storage declines mostly resulted from reduced base flows in Cobb, Lake, and Willow Creeks upstream from the reservoir.

Oklahoma↗
USGS2018

Revised groundwater-flow model of the glacial aquifer system north of Aberdeen, South Dakota, through water year 2015

The city of Aberdeen, in northeastern South Dakota, requires an expanded and sustainable supply of water to meet current and future demands. Conceptual and numerical models of the glacial aquifer system in the area north of Aberdeen were developed by the U.S. Geological Survey in cooperation with the City of Aberdeen in 2012. The U.S. Geological Survey, in cooperation with the City of Aberdeen, completed a study to revise the original numerical groundwater-flow model using data through water year (WY) 2015 to aid the City of Aberdeen in their development of plans and strategies for a sustainable water supply and to increase understanding of the glacial aquifer system and groundwater-flow system near Aberdeen. The original model was revised to improve the fit between model-simulated values and observed (measured or estimated) data, provide greater insight into surface-water interactions, and improve the usefulness of the model for water-supply planning. The revised groundwater-flow model (hereafter referred to as the “revised model”) presented in this report supersedes the original model. The purpose of this report is to describe a revised groundwater-flow model including data collection, model calibration, and model results for the glacial aquifer system including the Elm, Middle James, and Deep James aquifers north of Aberdeen, South Dakota, using updated hydrologic data through WY 2015. The original numerical model was revised in several ways. The model was modified by adding four new layers, which included a surficial layer, two intervening confining layers, and a shale bedrock layer. The revised model provides an improved understanding of the groundwater-flow system in comparison to the original model. The principal aquifers of the model area include portions of the Elm, Middle James, and Deep James aquifers. The lithologic information used to define and describe the aquifers in the model area was unaltered; however, aquifer properties and boundary conditions were reviewed and updated using geological information reported by the South Dakota Department of Environmental and Natural Resources and information obtained from geophysical investigations for this study. The horizontal extent of the Elm, Middle James, and Deep James aquifers was unaltered from the original model. The thickness of the Deep James aquifer was modified based on interpretations from the geophysical investigations. In general, groundwater in the Elm aquifer flowed from northwest to southeast and locally towards rivers and streams. Similarly, in the Middle James and Deep James aquifers, groundwater also typically flowed southeast. The revisions made to the original model include use of the following MODFLOW stress packages: Recharge, Evapotranspiration, Time-Variant Specified Head, Wells, Drains, and Stream Flow Routing, all of which were updated from the original model except for the Stream Flow Routing Package, which replaced the River Package used in the original model. Model calibration is the process of estimating model parameters to minimize the differences, or residuals, between observed data and simulated values; therefore, Parameter ESTimation (PEST) software was used to optimize model input parameters by matching model-simulated values to observed data. Calibration parameters included horizontal hydraulic conductivity, vertical hydraulic conductivity, specific yield, specific storage, and vertical streambed conductance for stream and drain cells. Multipliers were used to calibrate the recharge and evapotranspiration stresses. Evapotranspiration extinction depth also was adjusted during model calibration. Comparisons to the original model are described to highlight the changes made in the revised model. In general, the revised model adequately simulates the natural system and compares favorably with observed hydrologic data. Simulated water levels were evaluated by comparing them to single water-level observations at selected well locations. The selected wells were the same wells used in the original model. The coefficient of determination value between simulated and observed water levels for the revised model was 0.89 and included simulated and observed values from October 1, 1974 (WY 1975), through September 30, 2015 (WY 2015). The coefficient of determination value for the original model was 0.94 and included simulated and observed values from October 1, 1974, through September 30, 2009. The difference may indicate that the original model could have been overfit to hydraulic head observations because base flow was not simulated. The additional data used in the revised model included some climatically wetter, more extreme periods, such as 2011, in which annual precipitation was 30.9 inches. Average annual precipitation for the original model timeframe, which included data from WYs 1975–2009, was 20.26 inches. Additional precipitation data for WYs 2010–15, included in the revised model timeframe, resulted in an average annual precipitation for WYs 1975–2015 in the model area of 20.6 inches. The larger variability in climate data coupled with the additional water-level data could explain the lower coefficient of determination for water levels in the revised model. The revised model was used to calculate various groundwater-budget components for steady-state and transient conditions for WYs 1975–2015. The time-variant specified-head cells in the revised model had the largest change when compared to the original steady-state model for inflows and outflows. Comparing the transient budget components between the original and the revised models indicated that inflow from recharge and time-variant specified-head cells had the greatest effect on groundwater inflows, and outflow from storage had the greatest effect on groundwater outflows. The simulated potentiometric contours from the revised model were compared with (1) the observed (interpreted) potentiometric surface (layer 2) and the hydraulic head values (layers 4 and 6) and (2) the simulated contours from the original model. The simulated hydraulic gradients and general direction of groundwater flow in the Elm aquifer in the revised model generally matched the observed potentiometric contours, the simulated potentiometric contours from the original model, and general flow directions interpreted to be perpendicular to the contours. Minor discrepancies between simulated potentiometric contours from the revised model and the observed potentiometric contours may be due to the lack of observed data in the model area. The revised model was designed to reduce the limitations of the original model. The revisions were validated by comparing the results of the original model with the revised model. A primary benefit of the revised model is the inclusion of the surficial deposits and the confining units as explicit layers in the model. The addition of the surficial layer was beneficial for three primary reasons: (1) more accurate representation of recharge from precipitation, (2) more accurate representation of groundwater evapotranspiration, and (3) more accurate representation of groundwater and surface-water interactions. The groundwater model is a numeric approximation of a complex physical hydrologic system, and the revised model data were interpolated in regions with sparse data. Additionally, model discretization included averaged and interpolated values for water use, withdrawal rates, and hydraulic conductivity. The revised model provides a useful estimate for hydraulic gradients, groundwater-flow directions, and aquifer response to groundwater withdrawals.

South Dakota↗
USGS2020

Hydrology and geomorphology of the Taiya River near the West Creek Tributary, southeast Alaska

The Taiya River flows through the Chilkoot Trail Unit of Klondike Gold Rush National Historical Park in southeast Alaska, which was founded to preserve cultural and historical resources and further understanding of natural processes active in the surrounding coastal-to-subarctic basin. Riverine processes exert an important influence on ecologically important boreal toad ( Anaxryus boreas boreas ), salmon [chum salmon ( Oncorhynchus keta ), pink salmon ( O. gorbushca ), and coho salmon ( O. kisutch )], and eulachon ( Thaleichthys pacificus ) habitats, erosion of the historic ghost town of Dyea and other cultural and historical artifacts, and recreational opportunities in the lower 7.5 kilometers (km) of the Taiya River valley bottom. Recurrent consideration of hydroelectric development in West Creek upstream of the park since the 1980s has included proposals for damming and diverting West Creek, which could alter the delivery of water and sediment to this section of the Taiya River. To improve understanding of the hydrologic dependence of park resources for the purposes of guiding effective monitoring and conservation, this study, conducted by the U.S. Geological Survey in cooperation with the National Park Service, used a review of hydrologic data, collection of discrete suspended sediment data, geomorphic mapping, and analysis of historical aerial and ground photographs in a reconnaissance of formative geomorphic processes and hydrologic conditions in the lower 7.5 km of the Taiya River valley bottom. Streamflow and suspended sediment data collected at the U.S. Geological Survey streamgages on the Taiya River and West Creek, combined with historical data, document conditions consistent with streams draining strongly glacierized basins in Alaska. Suspended sediment concentrations from samples collected concurrently over six varying flow levels during 2017–18 ranged from 6 to 284 milligrams per liter (mg/L) for the Taiya River and 13 to 162 mg/L for West Creek, which are similar to or slightly higher than historical values. For the common period of record (1970–77), correlation of daily mean discharge between the two streams was strongest (Pearson’s r = 0.97) during the prolonged May–October high-flow season and weakest ( r = 0.90) during the November–April low-flow season, when West Creek daily mean discharge was proportionally higher. For the Taiya River, streamflow data compared between the available periods of record (1970–77 and 2004–17) showed no decadal-scale patterns in mean annual discharge but did show a shift toward an earlier spring snowmelt pulse. Notable flooding in the Taiya River Basin includes glacial lake outburst floods from the Nourse River valley prior to and during the 1897–98 Gold Rush, a 2002 glacial lake outburst flood from the West Creek valley, and a 1967 rainfall-generated flood. Geomorphic mapping identified four categories of surfaces in the valley bottom—active main stem, abandoned main stem, alluvial fans, and emergent tidal surfaces. Using the maps, main-stem surfaces were subdivided into age categories to identify channel migration patterns from prior to 1940s to 2018. The valley bottom is dominated by active or abandoned channels of the Taiya River except at the extensive low-angle West Creek fan. The active main stem presently supports a mostly single-thread channel with bars and a few sloughs, but the channel actively moved and sometimes was braided within multiple, wider unvegetated corridors in 1894 and earlier. An inventory of 29 off-main-stem channels identified for the study indicates that abandoned main stem channels provide local topographic lows that can intercept groundwater or sustain tributary flow, facilitating the formation of most nonestuarine wetlands in the valley and sustaining important boreal toad breeding habitat. Within the active main stem corridor, the channel has episodically built and reworked meanders and bars, eroding more than one-half of the historic Dyea townsite, in response to glacially controlled delivery of water and sediment, flooding, inputs from West Creek, local features including large woody debris and beaver dams, and rapid uplift from isostatic rebound. West Creek has constructed a large, persistent fan, provoked kilometer-scale Taiya River channel change near the confluence, constructively added to high-season streamflow that affects Taiya River channel migration capacity, disproportionately contributed early-season streamflow, and possibly contributed to groundwater levels in the valley bottom. The progressive narrowing and stability of the main stem corridor, possibly a result of reduction in the magnitude or frequency of glacial lake outburst floods or glacial sediment delivery to streams, indicates less active future reworking of abandoned main-stem surfaces or regeneration of wetland features. The fluvial history of the Taiya River valley bottom collectively indicates continued channel change within a limited corridor, relative stability in wetland locations but uncertainty in stability of groundwater supply to them, and channel incision and extension in response to uplift.

Alaska↗
USGS2021

Aquaculture and Irrigation Water-Use Model (AIWUM) version 1.0—An agricultural water-use model developed for the Mississippi Alluvial Plain, 1999–2017

Water use is a critical and often uncertain component of quantifying any water budget and securing reliable and sustainable water supplies. Recent water-level declines in the Mississippi Alluvial Plain (MAP), especially in the central part of the Mississippi Delta, pose a threat to water sustainability. Aquaculture and Irrigation Water-Use Model (AIWUM) 1.0, one of the first national agricultural water-use models that provides water use at the scale of most groundwater models, was developed and compared to other reported and estimated aquaculture and irrigation water-use values within the MAP study area for 1999 through 2017 to improve water-use estimates needed as input to a hydrologic decision-support system in the MAP. Results indicate annual total water-use estimates from 1999 through 2017 ranged from about 5 to 13 billion gallons per day and, on average, a majority of the water use was applied to rice (about 51 percent), followed by soybeans (about 26 percent), and less than (<) 10 percent each was applied to aquaculture, corn, cotton, and other crops. Comparisons indicated that annual total water-use estimates from AIWUM 1.0 were smaller than or comparable to all other sources of water-use data. Although there is disagreement at the monthly timescale in estimates in the Mississippi Delta within each part of the growing season, the annual total water use is comparable between AIWUM 1.0 and the Mississippi Embayment Regional Aquifer Study groundwater model 2.1. Estimates from AIWUM 1.0 could be used in models at all scales (for example, local, regional, national) and could provide a nationally consistent methodology in estimating water use driven by regional crop-specific withdrawal rates.

Arkansas, Illinois, Kentucky, Louisiana, Mississip↗
USGS2021

Borehole analysis, single-well aquifer testing, and water quality for the Burnpit well, Mount Rushmore National Memorial, South Dakota

Mount Rushmore National Memorial (hereafter referred to as “the memorial”), in western South Dakota, is maintained by the National Park Service (NPS) and includes 1,278 acres of land in the east-central part of the Black Hills. An ongoing challenge for NPS managers at the memorial is providing water from sustainable and reliable sources for operations, staff, and the increasing number of visitors. In 2020, the U.S. Geological Survey (USGS) and NPS completed a hydrological study of the Burnpit well (well 5), a 580-foot-deep open hole groundwater well completed in metamorphic (crystalline) rock at the memorial. The purpose of this study was to estimate the geological and hydraulic properties of the aquifer supplying the well and to determine the water quality of the groundwater from the well. The study provides NPS staff and managers background information for assessing future uses for the well. Methods for data collection and analysis for the study included borehole and video camera analysis in 2020, aquifer testing by the NPS in 2009 and the USGS in 2020, and water-quality sampling in 2020. Borehole camera video generally matched the lithology recorded in the well log. Fractures recorded in the well log and observed with the borehole camera, including more than 20 less prominent fractures and rough sidewall areas, indicated a fractured aquifer. The fractures are the primary conduits for groundwater flow through the rock and into the well. Transmissivity was estimated for the upper and lower water-level drawdown zones at the Burnpit well with data from the NPS and USGS using the Theis and Cooper-Jacob methods. Transmissivity for the NPS test using the Theis method was 9.0 and 11 feet squared per day (ft 2 /d) for the upper and lower drawdown zones, respectively. Using the Cooper-Jacob method, the transmissivity was 22 and 14 ft 2 /d for the upper and lower drawdown zones of the aquifer, respectively. Transmissivity estimates from data from the USGS test were similar. The Theis method, applied to the upper and lower drawdown zones of the aquifer, produced transmissivity estimates of 7.7 and 10 ft 2 /d, and the Cooper-Jacob method produced estimates of 9.7 and 12 ft 2 /d, respectively. Storativity (specific yield) estimated using the Theis method for the NPS aquifer-test data was 0.85 and 0.92 for the upper and lower drawdown zones of the aquifer, respectively. The Cooper-Jacob method applied to the NPS aquifer-test data produced storativity estimates of 0.11 and 0.50 for the upper and lower drawdown zones, respectively. The Theis method applied to the USGS aquifer-test data estimated storativity values of 0.77 and 1.0 for the upper and lower drawdown zones, respectively. The Cooper-Jacob method estimated storativity of 0.50 and 0.60 for the upper and lower drawdown zones of the USGS aquifer test, respectively. The estimated storativity values from the NPS and USGS aquifer tests for the upper and lower drawdown zones were higher than expected for limestones and schists. The hypothetical equilibrium drawdown for the Burnpit well was estimated after the NPS test in 2009 at no more, and possibly less, than 35 gallons per minute. The NPS noted that the sustainable yield likely was overestimated because the water level did not stabilize during the NPS aquifer test. The specific capacity for the NPS aquifer test in 2009 was 0.16 gallon per minute per foot ([gal/min]/ft) of drawdown at 3 hours, and the specific capacity for the USGS aquifer test in 2020 was 0.13 (gal/min)/ft of drawdown at 3 hours. The rate of water-level recovery after pumping ceased was 0.017 and 0.013 (gal/min)/ft for the NPS and USGS aquifer tests, respectively. The water-level recovery rate was nearly an order of magnitude less than the specific capacity estimated during pumping, indicating that water levels in the Burnpit well may not recover quickly enough during pumping to provide for a continuous source of water. Water-quality samples were collected at the Burnpit well on June 24 and July 23, 2020, and analyzed for field-measured properties, major ions, metals, nutrients, and perchlorate. Iron, zinc, and lithium concentrations for unfiltered samples in the well were at least three times greater than the mean filtered sample concentrations reported for crystalline aquifers in the Black Hills. Manganese concentrations were less than the mean concentration for crystalline aquifers but exceeded the U.S. Environmental Protection Agency (EPA) secondary drinking-water standards. The iron concentration from the June 24 sample was about 11 times greater than the EPA secondary drinking-water standards and mean concentrations from crystalline aquifers in the Black Hills. Arsenic concentrations in Burnpit well samples collected in 2020 were greater than the EPA primary drinking-water standard and the mean concentration for crystalline aquifers in the Black Hills. Arsenic occurs naturally in the rock of crystalline aquifers, and concentrations from samples in the Black Hills commonly exceed the EPA primary drinking-water standard of 10 micrograms per liter. High concentrations of arsenic, iron, and manganese metals in the Burnpit well make groundwater from the well in its natural state unusable as a drinking-water source, and water treatment would be necessary to reduce the trace element concentrations to less than the EPA primary and secondary drinking-water standards. However, if the memorial has immediate nonpotable water requirements, such as for construction and fire suppression, groundwater from the Burnpit well could provide water without causing additional stress to current (2021) drinking-water sources.

South Dakota↗
USGS2022

Assessment of well yield, dominant fractures, and groundwater recharge in Wake County, North Carolina

A cooperative study led by the U.S. Geological Survey and Wake County Environmental Services was initiated to characterize the fractured-rock aquifer system and assess the sustainability of groundwater resources in and around Wake County. This report contributes to the development of a comprehensive groundwater budget for the study area, thereby helping to enable resource managers to make sound and sustainable water-supply and water-use decisions. Construction information was used to analyze the well depth, casing depth, and reported well yield of more than 7,500 inventoried wells. The median well depth and casing depth were 265 feet (ft) below land surface (bls) and 68 ft bls, respectively, and the median well yield was 10 gallons per minute. Generally, well yield increased with depth to around 200 ft bls and then began to decrease with depth within the fractured-rock aquifer. Borehole geophysical logging methods were used to characterize the fractured-rock aquifer by mapping the orientation of geologic structures within the subsurface. Structure measurements were made on resulting log data and mapped to observed general spatial trends within the regional groundwater system and more distinct hydrogeologic units. Many of the fractures observed within the borehole logs are steeply dipping across Wake County, although open fractures with shallow dip angles were also observed in most rock classes. Regional geologic structural trends were observed in proximity to the Jonesboro Fault. Potential groundwater recharge in the study area was estimated using a Soil-Water-Balance (SWB) model, as well as using base flow hydrograph separation. The SWB model calculated net infiltration below the root zone for 1981 through 2019 for a 5,402-square-mile area that extends to the counties surrounding Wake County. The mean annual net infiltration rate for the 39-year period was about 8.6 inches per year for the study area. The mean annual net infiltration results from the SWB model were comparable to annual base flow estimates using the PART hydrograph-separation method at six U.S. Geological Survey streamgages within the study area. Mean annual base flow for all six drainage basins was near 7.5 inches per year and estimates ranged from 2.9 to 8.9 inches. Comparisons of mean annual potential recharge from the SWB model and base flow estimates were generally within 2 inches, except during high flows for most of the drainage basins in the study area.

North Carolina↗
USGS2022

Updated annual and semimonthly streamflow statistics for Wild and Scenic Rivers, Owyhee Canyonlands Wilderness, southwestern Idaho, 2021

The U.S. Geological Survey, in cooperation with the Bureau of Land Management (BLM), continued streamflow data collection in water years 2013–21 to update daily streamflow regressions and annual and semimonthly streamflow statistics initially developed in 2012 for streams designated as “wild,” “scenic,” or “recreational” under the National Wild and Scenic Rivers System in the Owyhee Canyonlands Wilderness in southwestern Idaho. To sustain “outstanding remarkable values” in the Owyhee Canyonlands Wilderness, BLM determined that maintaining specific streamflow conditions in rivers was important for sustaining ecological health, recreational opportunities, and water demands for stock water and irrigation in a region with increased pressure from upstream land development. Streamflow statistics previously developed using regional regressions based on limited number of streamgages and generalized basin characteristics were determined to inaccurately represent hydrologic characteristics in the Owyhee Canyonlands Wilderness. In this study, updated streamflow regressions and statistics are provided for 11 partial-record sites in the Owyhee Canyonlands Wilderness using 311 additional streamflow measurements. A partial-record Maintenance of Variance Extension, Type 1 (MOVE.1) streamflow regression method was used to relate discrete streamflow measurements collected at partial-record sites with daily mean streamflow at nearby index sites. The updated regressions were used to estimate a synthetic daily mean streamflow record at each partial-record site for the period of record of the selected index site. The computed synthetic streamflow record was then used to determine annual and semimonthly streamflow statistics at each partial-record site. Annual bankfull streamflow statistics were calculated at each partial-record site using the computed bankfull streamflow at the selected index site and the updated streamflow regression. Additional streamflow measurements representing a larger range of hydrologic conditions since 2012, reevaluation of index site selection, and updated regression techniques improved streamflow statistic estimates in the Owyhee Canyonlands Wilderness. Regression performance was evaluated based on the coefficient of determination (R 2 ) between the partial-record and index sites, percent bias, and similarity of basin characteristics between the selected index site and the partial-record site. Generally, the updated regressions performed well for partial-record sites with an index site located upstream or downstream on the same stream. Regression performance was degraded and less robust for index sites located farther away from the corresponding partial-record site. Additional streamflow measurements at partial-record sites with few measurements over a small range in hydrologic conditions could improve regression performance and reduce prediction intervals. Furthermore, additional index sites in the Owyhee Canyonlands Wilderness could improve the updated streamflow regressions and statistics.

Idaho↗
USGS2023

Evaluation of potential stresses and hydrologic conditions driving water-level fluctuations in well ER-5-3-2, Frenchman Flat, southern Nevada

Well ER-5-3-2 is part of a well network designed to monitor long-term water levels and radionuclide concentrations downgradient from underground nuclear tests that occurred in Frenchman Flat, an area of the U.S. Department of Energy Nevada National Security Site in southern Nevada. Interpretation of monitoring records for well ER-5-3-2 was confounded by previously unexplained water-level fluctuations in the well hydrograph. This study integrated geologic, hydrologic, and water-chemistry data to evaluate potential stresses and hydrologic conditions that likely affected the well ER-5-3-2 hydrograph. Numerical groundwater models were applied to evaluate four model scenarios: (1) wellbore leakage without recharge, (2) wellbore leakage with recharge, (3) equilibration to vertical heterogeneities between shallow (low transmissivity) and deep (higher transmissivity) carbonate zones, and (4) equilibration to lateral heterogeneities in carbonate rocks. Meteoric recharge was not the cause of the 21-foot (ft) water-level rise in well ER-5-3-2 from 2001 to 2011 or the 4-ft decline from 2012 to 2016. Based on observed water-level fluctuations in nearby wells, the water-level rise and decline from recharge for these periods was less than 3 and 1 ft, respectively. The lateral-heterogeneity scenario is based on the assumption that the 21-ft water-level rise from 2001 to 2011 was a natural water-level reequilibration following the pumping-induced depressurization of a large volume of high transmissivity and low-storage carbonate rock that is surrounded by low transmissivity and high-storage carbonate rock. The lateral-heterogeneity scenario was discounted because simulated water levels cannot match the well ER-5-3-2 hydrograph. Underground nuclear testing and temperature effects were discounted based on hydraulic connections and water-temperature data. Wellbore-leakage scenarios are based on the assumption that the water-level rise was sustained from leakage rates required to cause a localized mounding in the carbonate system near well ER-5-3-2, where the carbonate transmissivity is 530 square feet per day. Even though simulated and measured water levels compare favorably for scenarios of wellbore leakage with and without recharge, large volumes (178–184 million gallons) of groundwater from volcanic rocks would be required to leak into the carbonate system, which is not supported by water-chemistry data. An alternative conceptualization of wellbore leakage is based on the assumption that the 21-ft water-level rise from 2001 to 2011 was sustained by the hydraulic disconnection of well ER-5-3-2 from the carbonate system. The disconnection occurred several months after a constant-rate test in well ER-5-3-2 when carbonate rocks were hydraulically disconnected from the well by either (1) the shifting of sloughed fill in the open hole or (2) the encrusting of carbonate precipitate in the well screen. The hydraulic disconnection effectively sealed the well and caused a 21-ft water-level rise from wellbore leakage during 2001–11. In this case, total wellbore leakage from 2001 to 2011 was about 50 gallons. The 4-ft water-level decline from 2012 to 2016 was conceptualized to have occurred from the slow breaking of the seal and reconnection of the well to the carbonate system. This alternative conceptualization of wellbore leakage was consistent with water-chemistry analyses because the computed wellbore leakage (50 gallons) was small relative to purged volumes (30,000–40,000 gallons) for sampling, and the water chemistry would not be expected to change. The shallow-deep carbonate scenario provided another explanation for the well ER-5-3-2 hydrograph. This scenario is based on the assumption that well-construction effects and vertical heterogeneity of the carbonate system explain the ER-5-3-2 water-level trend. Well-construction effects are attributed to a temporary clogging of the open interval below the well screen that was opened during pumping events, which affected the hydraulic connection of deep transmissive carbonate rocks to the wellbore. The 21-ft water-level rise from 2001 to 2011 was a natural equilibration to shallow, low-transmissivity carbonate rocks during a period when the lower open interval was clogged. The 4-ft decline from 2012 to 2016 represents equilibration between the shallow and deep intervals, because of a partial unclogging of the connection between the two intervals. The low water levels from 2016 to 2021 resulted from pumping for sampling and an unclogging of the open interval so that the low head in the deep carbonate dominated the water level. Despite potential well-construction effects, from either a wellbore leakage or shallow-deep carbonate scenario, samples collected from well ER-5-3-2 are representative of the carbonate system.

Nevada↗
USGS2025

Completion summary for monitor wells NRF-17 and NRF-18 at the Naval Reactors Facility, Idaho National Laboratory, Idaho

The U.S. Geological Survey (USGS)—in cooperation with the U.S. Department of Energy (DOE) for the Naval Reactors Laboratory Field Office that supports operations for the Naval Reactors Facility (NRF) located at the Idaho National Laboratory (INL)—drilled and constructed well NRF-17 (formerly borehole USGS 151) and well NRF-18 (formerly borehole USGS 152) for stratigraphic framework analyses and water-quality monitoring at the Idaho National Laboratory (INL) near the NRF, in southeastern Idaho. Borehole USGS 151 was continuously cored from about 48 to 1,070 feet (ft) below land surface (BLS); rotary drilled from approximately 1,070 to 1,720 ft BLS; and re-drilled to complete construction as a monitor well NRF-17, completed to 461 ft BLS. Borehole USGS 152 was continuously cored from approximately 19 to 1,259 ft BLS; rotary drilled from approximately 1,259 to 1,630 ft BLS; and re-drilled to complete construction as a monitor well NRF-18, completed to 450 ft BLS. Geophysical data were examined with photographed core material to record lithologic descriptions and to suggest zones where groundwater flow was anticipated. Basalt flows varied from highly fractured to dense, with high-to-low vesiculation. Well NRF-17 generally was constructed in mostly dense basalt (greater than 75 percent), and well NRF-18 was constructed in primarily fractured and (or) vesicular basalt. In well NRF-17, the well capacity is directly affected by the limited amount of fractured basalt, which serves as the primary pathway for groundwater. This effect was observed during the pumping test conducted after the well's final construction. Single-well aquifer tests were done at wells NRF-17 and NRF-18 to provide estimates of transmissivity and hydraulic conductivity after final well construction and initial well development. Estimated values of transmissivity and hydraulic conductivity for well NRF-17 were 8.81 feet squared per day (ft 2 /d) and 1.04×10 -2 feet per day (ft/d), respectively. Estimated values of transmissivity and hydraulic conductivity for well NRF-18 were 4.77×10 3 ft 2 /d and 5.61 ft/d, respectively. The NRF-17 pump test resulted in 19.41 ft of measured drawdown at a sustained average pumping rate of 3.3 gallons per minute (gal/min). The NRF-18 pump test resulted in 0.55 ft of measured drawdown at a sustained average pumping rate of 31.0 gal/min. Water-quality samples collected from the two wells were analyzed for cations, anions, metals, nutrients, volatile organic compounds, stable isotopes, and radionuclides. Water samples for select inorganic constituents showed concentrations consistent with signatures from tributary valley groundwater with influences from ephemeral surface-water recharge from the Big Lost River. Water-quality samples analyzed for stable isotopes of oxygen and hydrogen are consistent with signatures from tributary valley groundwater and surface-water recharge inputs to the aquifer. No measured water-quality results were greater than their respective maximum contaminant levels for public drinking-water supplies. Inorganic and nutrient water-quality results for well NRF-17 and well NRF-18 suggest the groundwater in this area is potentially affected by industrial wastewater disposal.

Idaho↗
USGS2025

An inset groundwater-flow model to evaluate the effects of layering configuration on model calibration and assess managed aquifer recharge near Shellmound, Mississippi

The U.S. Geological Survey has developed a high-resolution inset groundwater-flow model in the Mississippi Delta as part of an interdisciplinary collaboration coordinated by the Mississippi Alluvial Plain project to provide a tool that stakeholders can use to support water-resource management decisions. Groundwater withdrawals from the Mississippi River Valley alluvial (MRVA) aquifer have been vital to support agricultural production in the region, but substantial groundwater-level declines near Shellmound, Mississippi, have caused concerns for long-term sustainability of the aquifer. To better understand the subsurface and try to mitigate the long-term groundwater-level declines, stakeholders have undertaken actions including a Groundwater Transfer and Injection Pilot (GTIP) project using a riverbank filtration-based managed aquifer recharge approach. The pilot project consisted of extracting groundwater near the Tallahatchie River and reinjecting it into the aquifer 3 kilometers west where water levels have substantially declined. A high-resolution airborne electromagnetic (AEM) survey was also completed to collect electrical resistivity data to support the GTIP project and the development of the groundwater model. The inset groundwater-flow model was developed to (1) integrate the AEM data into the optimal layering configuration of the MRVA aquifer that the available observation data can support through calibration, and (2) assess the potential effect of the GTIP project on the groundwater levels. The AEM data were processed into three different layering configurations leading to the development of model A (18 layers), model B (16 layers), and model C (8 layers), all at a 100- x 100-meter cell spatial resolution using the U.S. Geological Survey modular finite-difference flow model 6 code with Newton-Raphson formulation. The model development process integrated recent advances in modeling, such as the incorporation of AEM data, the use of outputs from the soil-water-balance (SWB) model, and the Aquaculture and Irrigation Water-Use Model, and was facilitated by robust automation using the open-source python packages Modflow-setup and SFRmaker. Using Parameter Estimation ++ Iterative Ensemble Smoother, the three numerical groundwater-flow models (models A, B, and C) were calibrated against a set of observations, which included aquifer groundwater levels, streamflows, stream stage, and aquifer transmissivity. Results indicate that the detailed representation of MRVA aquifer layers in model A produced the best calibrated model by history matching, and the integration of data representing surficial connectivity played a key role in improving groundwater recharge and enhancing the ability of the model to match groundwater levels in the cone of depression. A forecast model simulated the managed aquifer recharge approach, and the results indicated that, given average irrigation and recharge conditions (2010–15), the GTIP project has the potential to induce groundwater-level increases of as much as 3 meters around the injection site, but a sustained increase would require repetition in subsequent years of water transfer at 2022 rates or above.

Mississippi↗
USGS2026

Water-withdrawal and groundwater-level fluctuations, physical and infiltration characteristics of Ohio River sediment, and isotope-based estimates of water sources relative to a riverbank filtration system in an alluvial aquifer, Louisville, Kentucky, 2000–20

The U.S. Geological Survey and the Louisville Water Company, from 2000 to 2020, cooperatively investigated physical and hydrologic conditions in the Ohio River alluvial aquifer and adjacent riverbed sediments in the northeast part of Louisville, Kentucky, to increase knowledge of processes affecting water sources to collector wells during operation of a riverbank filtration system (RBF). The RBF, in 2020, included an initial collector well (CW1) completed in 1999 and a tunnel and collector well system (TCWS) composed of four collector wells (CW2–CW5) completed in late 2010 that were connected by a tunnel that routed water to a pumping station and a treatment plant. Daily mean water-withdrawal rates typically ranged from about 10.4 to 20.7 million gallons per day (Mgal/d) from 2005 to 2007, then were cyclic from 2008 to 2010 and ranged from as low as about 9 to 13 Mgal/d in winter-spring months up to about 19 to 20 Mgal/d in summer-autumn months. From 2011 through 2017, peak daily mean water-withdrawal rates from CW2–CW5 fluctuated between winter-spring lows of about 20–30 Mgal/d to summer-autumn peak rates of about 41.6 Mgal/d in 2013 to about 48.2 Mgal/d in 2012. From 2017 to 2020, TCWS peak daily mean water-withdrawal rates decreased from about 45.7 Mgal/d in 2017 to about 37.5 Mgal/d in 2020 and peak daily mean rates from CW1 ranged from about 20.7 Mgal/d in 2020 to about 21.6 Mgal/d in 2018. Periods in 2019–20 with tunnel pumping station daily mean water-withdrawal rates smaller than about 30 Mgal/d had generally stable water levels in CW2 and indicated the sustainable yield of the TCWS collector wells under the prevailing hydrologic conditions. Drawdown during July–August of 2008 and 2009 was associated with CW1, the sole operating collector well. Groundwater-flow directions outside the CW1 cone of depression during July–August of 2008 and 2009 were from areas near the alluvial valley margin toward the Ohio River and in 2009 toward Harrods Creek. Collector wells CW2 through CW5 derived water during 2011–19 surveys from surface-water infiltration, as indicated by drawdown that extended beneath the Ohio River and Harrods Creek. Increases in drawdown toward the alluvial valley margins in July–August of 2013 and 2015, compared with July 2011, indicated less available recharge from those flow directions and decreased yield of groundwater from the aquifer after progressively longer TCWS water withdrawals. Drawdown at CW2–CW5 and at observation wells between them lessened in October 2019 and indicated that onshore groundwater levels can recover when collector well withdrawals decrease. Overlapping cones of depression in 2011–15 potentiometric surfaces centered around CW2, CW3, CW4, and CW5, and drawdown along divides between those wells indicated well interference between collector wells. Well-interference effects increased during 2013 and 2015 survey periods, despite decreased water-withdrawal rates compared with July 2011, and expanded to include CW1 when its use resumed. Groundwater-level fluctuations in observation wells near the Ohio River were consistent with gradual depletion of groundwater yield during tunnel pumping station operation at river elevations of about 420 feet above the National Geodetic Vertical Datum of 1929 (NGVD 29) and enhanced recharge of the aquifer when river elevations were above flood stage of about 430 feet above NGVD 29. Groundwater-level declines in observation wells near the Ohio River were most apparent in summer and some autumn months between 2012 and 2017 during periods when tunnel pumping station mean daily water-withdrawal rates were about 35 Mgal/d or more. Periods of relatively stable groundwater levels during 2019–20 in observation wells between CW2–CW5, when tunnel pumping station water-withdrawal rates were about 30–33 Mgal/d or less, also indicated that the prevailing sustainable yield was about 30 Mgal/d or less. Wells associated with CW3 and CW4 had the largest increases in slopes of best-fit lines relating water-level difference to water-withdrawal rate between 2012 and 2020, an indication of decreased efficiencies of those wells to supply water or of changes in groundwater yield around the well. Increased slopes of best-fit lines relating water-level difference to water-withdrawal rate from 2019 to 2020, when groundwater levels were otherwise relatively stable, also indicated that the specific capacity of one or more TCWS collector wells may have declined during that period. Riverbed surface elevation, roughness, and hardness changes between hydroacoustic surveys indicated active accretion and erosion of bed sediment offshore from the riverbank filtration system in 2002–4. Riverbed hydraulic conductivity computed from 2013 to 2015 in tests at 11 sites ranged from 0.2 to 230 feet per day. Ten temporary piezometer sites with adjacent operating collector wells had drawdowns that ranged from about 4 to 11.7 feet and hammer blows greater than or equal to 49 counts, which indicated a relatively great density of alluvial sediments and the potential for diminished riverbed infiltration rates. Contributions of Ohio River infiltration to collector wells estimated from deuterium and oxygen-18 isotopic ratios in representative Ohio River and groundwater samples were considerably larger in warmer months than cooler months and ranged from 80–90 percent in CW1–CW5 in May 2020 to 100 percent in May 2019 at CW2, CW4, and CW5. Groundwater contributions to water withdrawals by collector wells increased in cooler autumn months and ranged from 40 percent at CW3 and CW5 in November 2020 to 70 percent at CW2, CW4, and CW5 in November–December 2019. November 2019 and November 2020 isotopic compositions of water from the collector wells had enriched deuterium and oxygen-18 isotopic ratios consistent with mixtures of evaporation-modified water from the Ohio River and meteoric-origin groundwater.

Indiana, Kentucky↗
USGS2001

Historical water-quality data for the High Plains Regional Ground-Water Study Area in Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming, 1930-98

The High Plains aquifer underlies 174,000 square miles in parts of eight States and includes eight primary hydrogeologic units, including the well-known Ogallala Formation. The High Plains aquifer is an important resource, providing water for 27 percent of the Nation?s irrigated agricultural lands in an otherwise dry landscape. Since the 1980?s there has been concern over the sustainability of the aquifer due to water-level declines caused by substantial pumping. Water quality of the aquifer is a more recent concern. As part of the U.S. Geological Survey?s National Water-Quality Assessment Program, historical water-quality data have been gathered for the High Plains Regional Ground-Water Study Area into a retrospective data base, which can be used to evaluate the occurrence and distribution of water-quality constituents of concern.Data from the retrospective data base verify that nitrate, pesticides, and dissolved solids (salinity) are important water-quality concerns in the High Plains study area. Sixteen percent of all measured nitrate concentrations were larger than the U.S. Environmental Protection Agency drinking-water standard of 10 milligrams per liter. In about 70 percent of the counties within the High Plains study area, nitrate concentrations for 1980-98 were significantly larger than for 1930-69. While nitrate concentrations are largest where depth to water is shallow, concentrations also have increased in the Ogallala Formation where depth to water is large. Pesticide data primarily are available only in the northern half of the study area. About 50 pesticides were detected in the High Plains study area, but only four pesticides (atrazine, alachlor, cyanazine, and simazine) had concentrations exceeding a drinking-water standard. The occasional detection of pesticides in deeper parts of the Ogallala Formation indicates that contamination pathways exist. Dissolved solids, which are a direct measure of salinity, had 29 percent of measured concentrations in excess of the secondary drinking-water standard of 500 milligrams per liter. Comparison of dissolved-solids concentrations prior to 1980 to concentrations after 1980 indicates dissolved-solids concentrations have increased in the alluvial valleys of the Platte, the Republican, and the Arkansas Rivers, as well as in the Ogallala Formation?South hydrogeologic unit.Water-quality results indicate that human activities are affecting the water of the High Plains aquifer. Because there is a potential for water quality to become impaired relative to the historical uses of the aquifer, water quality needs to be considered when evaluating the sustainability of the High Plains aquifer. Data collected as part of the High Plains Regional Ground-Water Study will help to fill in gaps in water-quality information and provide additional information for understanding the factors that govern ambient water quality.

Colorado, Kansas, Nebraska, New Mexico, Oklahoma, ↗