Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Water Resources Management”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources
USGS2013

Dissolved methane in groundwater, Upper Delaware River Basin, Pennsylvania and New York, 2007-12

The prospect of natural gas development from the Marcellus and Utica Shales has raised concerns about freshwater aquifers being vulnerable to contamination. Well owners are asking questions about subsurface methane, such as, “Does my well water have methane and is it safe to drink the water?” and “Is my well system at risk of an explosion hazard associated with a combustible gas like methane in groundwater?” This newfound awareness of methane contamination of water wells by stray gas migration is based upon studies such as Molofsky and others (2011) who document the widespread natural occurrence of methane in drinking-water wells in Susquehanna County, Pennsylvania. In the same county, Osborn and others (2011) identified elevated methane concentrations in selected drinking-water wells in the vicinity of Marcellus Shale gas-development activities, although pre-development groundwater samples were not available for comparison. A compilation of dissolved methane concentrations in groundwater for New York State was published by Kappel and Nystrom (2012). Recent work documenting the occurrence and distribution of methane in groundwater was completed in southern Sullivan County, Pennsylvania (Sloto, 2013). Additional work is ongoing with respect to monitoring for stray gases in groundwater (Jackson and others, 2013). These studies and their results indicate the importance of collecting baseline or pre-development data. While such data are being collected in some areas, published data on methane in groundwater are sparse in the Upper Delaware River Basin of Pennsylvania, New York, and New Jersey. To manage drinking-water resources in areas of gas-well drilling and hydraulic fracturing in the Upper Delaware River Basin, the natural occurrence of methane in the tri-state aquifers needs to be documented. The purpose of this report is to present data on dissolved methane concentrations in the groundwater in the Upper Delaware River Basin. The scope is restricted to data for Pennsylvania and New York, no U.S. Geological Survey (USGS) methane analyses are presently available for northwestern New Jersey.

New York;Pennsylvania↗
USGS2013

Transient calibration of a groundwater-flow model of Chimacum Creek Basin and vicinity, Jefferson County, Washington: a supplement to Scientific Investigations Report 2013-5160

A steady-state groundwater-flow model described in Scientific Investigations Report 2013-5160, ”Numerical Simulation of the Groundwater-Flow System in Chimacum Creek Basin and Vicinity, Jefferson County, Washington” was developed to evaluate potential future impacts of growth and of water-management strategies on water resources in the Chimacum Creek Basin. This supplement to that report describes the unsuccessful attempt to perform a calibration to transient conditions on the model. The modeled area is about 64 square miles on the Olympic Peninsula in northeastern Jefferson County, Washington. The geologic setting for the model area is that of unconsolidated deposits of glacial and interglacial origin typical of the Puget Sound Lowlands. The hydrogeologic units representing aquifers are Upper Aquifer (UA, roughly corresponding to recessional outwash) and Lower Aquifer (LA, roughly corresponding to advance outwash). Recharge from precipitation is the dominant source of water to the aquifer system; discharge is primarily to marine waters below sea level and to Chimacum Creek and its tributaries. The model is comprised of a grid of 245 columns and 313 rows; cells are a uniform 200 feet per side. There are six model layers, each representing one hydrogeologic unit: (1) Upper Confining unit (UC); (2) Upper Aquifer unit (UA); (3) Middle Confining unit (MC); (4) Lower Aquifer unit (LA); (5) Lower Confining unit (LC); and (6) Bedrock unit (OE). The transient simulation period (October 1994–September 2009) was divided into 180 monthly stress periods to represent temporal variations in recharge, discharge, and storage. An attempt to calibrate the model to transient conditions was unsuccessful due to instabilities stemming from oscillations in groundwater discharge to and recharge from streamflow in Chimacum Creek. The model as calibrated to transient conditions has mean residuals and standard errors of 0.06 ft ±0.45 feet for groundwater levels and 0.48 ± 0.06 cubic feet per second for flows. Although the expected seasonal trends were observed in model results, the typical observed annual variation of groundwater levels of about 2 feet was not. Streamflow at the most downstream observation point was about three times larger than simulated streamflow. Because the transient version of the model proved inherently unstable, it was not used to simulate forecast conditions for alternate hydrologic or anthropogenic changes. Adaptation of alternate stream simulation packages, such as RIV, or newer versions of MODFLOW, such as MODFLOW-NWT, could possibly assist with achieving calibration to transient conditions.

Washington↗
USGS2014

Estuarine monitoring programs in the Albemarle Sound study area, North Carolina

Albemarle Sound was selected in 2012 as one of the two demonstration sites in the Nation to test and improve the design of the National Water Quality Monitoring Council’s National Monitoring Network (NMN) for U.S. Coastal Waters and their tributaries. The goal of the NMN for U.S. coastal waters and tributaries is to provide information about the health of our oceans and coastal ecosystems and inland influences on coastal waters for improved resource management. The NMN is an integrated, multidisciplinary, and multiorganizational program using multiple sources of data and information to augment current monitoring programs. The purpose of this report is to identify major natural resource management issues for the region, provide information on current monitoring activities occurring within the Albemarle Sound study area, determine how the current monitoring network fits into the design of the NMN, and determine what additional monitoring data are needed to address these issues. In order to address these questions, a shapefile and data table were created to document monitoring and research programs in the Albemarle Sound study area with an emphasis on current monitoring programs within the region. This database was queried to determine monitoring gaps that existed in the Albemarle Sound by comparing current monitoring programs with the design indicated by the NMN. The report uses this information to provide recommendations on how monitoring could be improved in the Albemarle Sound study area.

North Carolina↗
USGS2022

Microplastic particles in dust-on-snow, Upper Colorado River Basin, Colorado Rocky Mountains, 2013–16

Atmospheric dust deposited to snow cover (dust-on-snow) diminishes snow-surface albedo (SSA) to result in early onset and accelerated rate of melting, effects that challenge management of downstream water resources. During ongoing investigations to identify the light-energy absorbing dust particles most responsible for diminished SSA in the Upper Colorado River Basin of the Colorado Rocky Mountains, we found microplastic particles, which are defined as those less than 5 millimeters in any dimension. In each of the 38 samples that represented the last remaining dust layer during melt seasons of 2013–16, microplastics were identified by size, shape, and color, and their relative amounts were visually estimated using stereomicroscopy. Considering the remote, high-elevation settings of the sample sites, the microplastic particles must have been deposited from the atmosphere. The possible role of microplastics for diminishing SSA of snow cover in the Upper Colorado River Basin may be linked to the solar-energy absorptive properties of polymers and is the subject of ongoing investigation.

Colorado↗
USGS1979

Summary appraisals of the nation's ground-water resources – Lower Mississippi region

The Lower Mississippi Region comprises an area of 102,400 square miles (265,200 square kilometers). Almost all this area is in the physiographic province known as the Gulf Coastal Plain. Three small areas on the northwest boundary of the region are in the Interior Highlands. The Lower Mississippi Region has an abundance of ground water. The geologic structure in that part of the region within the Coastal Plain is an elongated trough which has been filled with permeable materials, resulting in vast subsurface reservoirs. Except in local areas where continued large withdrawals have caused significant water-level declines, these reservoirs are full. Recharge to the region's aquifers is primarily from rainfall. Annual rainfall in most of the region is well distributed throughout the year and is sufficient to satisfy evapotranspiration requirements and still provide recharge to the aquifers. An estimated 844 billion cubic feet (24 billion cubic meters) of fresh ground water is available for withdrawal annually in the region. Only about one-third of this quantity is being utilized. Therefore, on this basis alone, the region still has much potential for ground-water development. The Coastal Plain aquifers within the Lower Mississippi Region contain large reserves of saltwater in the downdip limits of the aquifers. The quantity of saltwater in the region is several times that of freshwater. As desalinization techniques are developed and as more uses are found for saltwater, this reserve could become an important source of water for the region. At present (1976), the most productive and potentially productive aquifers or aquifer systems in the region are the Mississippi River valley alluvial aquifer of Quaternary age and the Sparta Sand and the Memphis aquifer (Memphis Sand in Tennessee) of Tertiary age. The Sparta Sand and the Memphis aquifer are heavily utilized and have shown significant water-level declines. However, selected well hydrographs indicate that water levels may be stabilizing under present pumping conditions. The Mississippi River valley alluvial aquifer is the most extensive high-yielding aquifer in the region; yields of several thousand gallons per minute may be obtained at depths of less than 200 feet (61 meters). To obtain maximum benefit from the vast quantities of ground water in the region, adequate attention must be given to the effects of proposed development upon the ground-water regime. Knowledge of the geologic structure and hydraulic properties of the aquifer systems is essential to an evaluation of the effects of such development. Some studies have been made in sufficient detail to provide this knowledge, but additional studies are needed. Activities that could cause significant changes in the groundwater regime should be undertaken only after all available information has been considered. Failure to seek out and use such information may result in inefficient development of the groundwater resource and, in some instances, degradation of the quality of the resource. Some changes always result from ground-water development. The possible changes can be grouped into three categories: hydraulic, water quality, and those affecting the physical framework of the aquifers. Generally, they are small in magnitude and areal extent. Because these changes occur below the ground surface, they are unknown to the ground-water user unless they noticeably affect the quantity or quality of water produced or cause obvious physical effects, such as land subsidence. Great advances have been made in hydrologic technology in recent years. Predictive models have been developed that make it possible for the hydroiogist to simulate aquifer responses to proposed development or other stresses. These models would be invaluable tools in progressive water-resources planning and management.

Arkansas, Kentucky, Louisiana, Mississippi, Missou↗
USGS2005

Introduction to suspended-sediment sampling

Knowledge of the amount and timing of sediment transport in streams is important to those directly or indirectly responsible for developing and managing water and land resources. Such data are often used to judge the health of watershed and the success or failure of activities designed to mitigate adverse impacts of sediment on streams and stream habitats. This training class presents an introduction to methods currently used by the U.S. Geological Survey (USGS) to sample suspended-sediment concentrations in streams. The presentation is narrated, but you control the pace of the presentation. If the computer you are using can view 'MPEG' videos you will be able to take advantage of videos interspersed in the presentation. A test, found at the end of the presentation, can be taken to assess how well you understood the training material. The class, which is registered as class SW4416 with the National Training Center of the USGS, should take two or three hours to complete. In order to use the presentation provided via this Web page, you will need to download a large disc images (linked below) and 'burn' it to a blank CD-ROM using a CD-ROM recorder on your computer. The presentation will only run on a Windows-based personal computer (PC). The presentation was developed using Macromedia Director MX 20041 and is contained in the file 'SIR05-5077.exe' which should autolaunch. If it does not, the presentation can be started by double-clicking on the file name. A sound card and speakers are necessary to take advantage of narrations that accompany the presentation. Text of narrations is provided, if you are unable to listen to narrations. Instructions for installing and running the presentation are included in the file 'Tutorial.htm', which is on the CD. 1 Registered Trademark: Macromedia Incorporated

Scientific Investigations Report↗
USGS2011

Hydrogeology, chemical characteristics, and water sources and pathways in the zone of contribution of a public-supply well in San Antonio, Texas

In 2001, the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey initiated a series of studies on the transport of anthropogenic and natural contaminants (TANC) to public-supply wells (PSWs). The main goal of the TANC project was to better understand the source, transport, and receptor factors that control contaminant movement to PSWs in representative aquifers of the United States. Regional- and local-scale study areas were selected from within existing NAWQA study units, including the south-central Texas Edwards aquifer. The local-scale TANC study area, nested within the regional-scale NAWQA study area, is representative of the regional Edwards aquifer. The PSW selected for study is within a well field of six production wells. Although a single PSW was initially selected, because of constraints of well-field operation, samples were collected from different wells within the well field for different components of the study. Data collected from all of the well-field wells were considered comparable because of similar well construction, hydrogeology, and geochemistry. An additional 38 PSWs (mostly completed in the confined part of the aquifer) were sampled throughout the regional aquifer to characterize water quality. Two monitoring well clusters, with wells completed at different depths, were installed to the east and west of the well field (the Zarzamora and Timberhill monitoring well clusters, respectively). One of the monitoring wells was completed in the overburden to evaluate potential hydrologic connectivity with the Edwards aquifer. Geophysical and flowmeter logs were collected from one of the well-field PSWs to determine zones of contribution to the wellbore. These contributing zones, associated with different hydrogeologic units, were used to select monitoring well completion depths and groundwater sample collection depths for depth-dependent sampling. Depth-dependent samples were collected from the PSW from three different depths and under three different pumping conditions. Additionally, selected monitoring wells and one of the well-field PSWs were sampled several times in response to a rainfall and recharge event to assess short-term (event-scale) temporal variations in water quality. For comparison purposes, groundwater samples were categorized as being from regional aquifer PSWs, from the well field (wellhead samples), from the monitoring wells (excluding the overburden well), from the overburden well, from the PSW depth-dependent sampling, and from temporal sampling. Groundwater samples were analyzed for inorganic, organic, isotopic, and age-dating tracers to characterize geochemical conditions in the aquifer and provide understanding of the mechanisms of mobilization and movement of selected constituents from source areas to a PSW. Sources, tracers, and conditions used to assess water quality and processes affecting the PSW and the aquifer system included (1) carbonate host rock composition; (2) physicochemical constituents; (3) major and trace element concentrations; (4) saturation indices with respect to minerals in aquifer rocks; (5) elemental ratios, such as magnesium to calcium ratios, that are indicative of water-rock interaction processes; (6) oxidation-reduction conditions; (7) nutrient concentrations, in particular nitrate concentrations; (8) the isotopic composition of nitrate, which can point to specific nitrate sources; (9) strontium isotopes; (10) stable isotopes of hydrogen and oxygen; (11) organic contaminant concentrations, including pesticides and volatile organic compounds; (12) age tracers, apparent-age distribution, and dissolved gas data used in age interpretations; (13) depth-dependent water chemistry collected from the PSW under different pumping conditions to assess zones of contribution; and (14) temporal variability in groundwater composition from the PSW and selected monitoring wells in response to an aquifer recharge event. Geochemical results indicate that the well-field and monitoring well samples were largely representative of groundwater in the regional confined aquifer. Constituents of concern in the Edwards aquifer for the long-term sustainability of the groundwater resource include the nutrient nitrate and anthropogenic organic contaminants. Nitrate concentrations (as nitrogen) for regional aquifer PSWs had a median value of 1.9 milligrams per liter, which is similar to previously reported values for the regional aquifer. Nitrate-isotope compositions for groundwater samples collected from the well-field PSWs and monitoring wells had a narrow range, with values indicative of natural soil organic values. A comparison with historical nitrate-isotope values, however, suggests that a component of nitrate in groundwater from biogenic sources might have increased over the last 30 years. Several organic contaminants (the pesticide atrazine, its degradate deethylatrazine, trichloromethane (chloroform; a drinking-water disinfection byproduct), and the solvent tetrachloroethene (PCE)) were widely distributed throughout the regional aquifer and in the local-scale TANC study area at low concentrations (less than 1 microgram per liter). Higher concentrations of PCE were detected in samples from the well-field PSWs and Zarzamora monitoring wells relative to the regional aquifer PSWs. The urban environment is a likely source of contaminants to the aquifer, and these results indicate that one or more local urban sources might be supplying PCE to the Zarzamora monitoring wells and the well-field wells. Samples from the well field also had high concentrations of chloroform relative to the monitoring wells and regional aquifer PSWs. For samples from the regional aquifer PSWs, the most frequently detected organic contaminants generally decreased in concentration with increasing well depth. Deeper wells might intercept longer regional flow paths with higher fractions of older water or water recharged in rural recharge areas in the western part of the aquifer that have been less affected by anthropogenic contaminants. A scenario of hypothetical contaminant loading was evaluated by using results from groundwater-flow-model particle tracking to assess the response of the aquifer to potential contamination. Results indicate that the aquifer responds quickly (less than 1 year to several years) to contaminant loading; however, it takes a relatively long time (decades) for concentrations to reach peak values. The aquifer also responds quickly (less than 1 year to several years) to the removal of contaminant loading; however, it also takes a relatively long time (decades) to reach near background concentrations. Interpretation of geochemical age tracers in this well-mixed karst system was complicated by contamination of a majority of measured tracers and complexities of extensive mixing. Age-tracer results generally indicated that groundwater samples were composed of young, recently recharged water with piston-flow model ages ranging from less than 1 to 41 years, with a median of 17 years. Although a piston-flow model is typically not valid for karst aquifers, the model ages provide a basis for comparing relative ages of different samples and a reference point for more complex hydrogeologic models for apparent-age interpretations. Young groundwater ages are consistent with particle-tracking results from hydrogeologic modeling for the local-scale TANC study area. Age-tracer results compared poorly with other geochemical indicators of groundwater residence time and anthropogenic effects on water quality, indicating that hydrogeologic conceptual models used in groundwater age interpretations might not adequately account for mixing in this karst system. Groundwater samples collected from the well field under a variety of pumping conditions were relatively homogeneous and well mixed for numerous geochemical constituents (with the notable exception of age tracers). Groundwater contributions to the PSW were dominated by well-mixed, relatively homogeneous groundwater, typical of the regional confined aquifer. Zones of preferential flow were determined for the PSW, but groundwater samples from different stratigraphic units were not geochemically distinct. Variations in chemical constituents in response to a rainfall and aquifer recharge event occurred but were relatively minor in the PSW and monitoring wells. This observation is consistent with the hypothesis that the response to individual recharge events in the confined aquifer, unless intersecting conduit flow paths, might be attenuated by mixing processes along regional flow paths. Results of this study are consistent with the existing conceptual understanding of aquifer processes in this karst system and are useful for water-resource development and management practices.

Texas↗
USGS2011

Groundwater conditions and studies in the Augusta–Richmond County area, Georgia, 2008–2009

Groundwater studies and monitoring efforts conducted during 2008–2009, as part of the U.S. Geological Survey (USGS) Cooperative Water Program with the City of Augusta in Richmond County, Georgia, provided data for the effective management of local water resources. During 2008–2009 the USGS completed: (1) installation of three monitoring wells and the collection of lithologic and geophysical logging data to determine the extent of hydrogeologic units, (2) collection of continuous groundwater-level data from wells near Well Fields 2 and 3, (3) collection of synoptic groundwater-level measurements and construction of potentiometric-surface maps in Richmond County to establish flow gradients and groundwater-flow directions in the Dublin and Midville aquifer systems, (4) completion of a 24-hour aquifer test to determine hydraulic characteristics of the lower Dublin aquifer, and upper and lower Midville aquifers in Well Field 2, and (5) collection of groundwater samples from selected wells in Well Field 2 for laboratory analysis of volatile organic compounds and groundwater tracers to assess groundwater quality and estimate the time of groundwater recharge. Potentiometric-surface maps of the Dublin and Midville aquifer systems for 2008–2009 indicate that the general groundwater flow direction within Richmond County is eastward toward the Savannah River, with the exception of the area around Well Field 2, where pumping interrupts the eastward flow of water toward the Savannah River and causes flow lines to bend toward the center of pumping. Results from a 24-hour aquifer test conducted in 2009 within the upper and lower Midville aquifers at Well Field 2 indicated a transmissivity and storativity for the upper and lower Midville aquifers, combined, of 4,000 feet-squared per day and 2x10 -4 , respectively. The upper and lower Midville aquifers and the middle lower Midville confining unit, which is 85-feet thick in this area, yielded horizontal hydraulic conductivity and specific storage values of about 45 feet per day and 2x10 -6 ft -1 , respectively. Results from the 24-hour aquifer test also indicate a low horizontal hydraulic conductivity for the lower Dublin aquifer of less than 1 foot per day. Of the 35 volatile organic compounds (VOCs) analyzed in 23 groundwater samples during 2008–2009, only six were detected above laboratory reporting limits in samples from eight wells. No concentration in groundwater samples collected during 2008–2009 exceeded drinking water standards. Trichloroethene had the maximum VOC concentration (1.9 micrograms per liter) collected from a water sample during 2008–2009. Water-quality sampling of several wells near Well Field 2 indicate that, while in operation, the northernmost production well might have diverted groundwater, containing low levels of trichloroethene from at least two other production wells. Analysis of sulfur hexafluoride data indicate the average year of recharge ranges between 1981 and 1984 for water samples from five wells open to the upper and lower Midville aquifers, and 1991 for a water sample from one shallow well open to the lower Dublin aquifer. All of these ages suggest a short flow path and nearby source of contamination. The actual source of low levels of VOCs at Well Field 2 remains unknown. Three newly installed monitoring wells indicate that hydrogeologic units beneath Well Fields 2 and 3 are composed of sand and clay layers. Hydrogeologic units, encountered at Well Field 2, in order of increasing depth are the lower Dublin confining unit, lower Dublin aquifer, upper Midville confining unit, upper Midville aquifer, lower Midville confining unit, and lower Midville aquifer. West of Well Field 3, hydrogeologic units, in order of increasing depth are the Upper Three Runs aquifer, Gordon confining unit, Gordon aquifer, lower Dublin confining unit, lower Dublin aquifer, upper Midville confining unit, upper Midville aquifer, lower Midville confining unit, and lower Midville aquifer.

Georgia↗
USGS2013

Numerical simulation of the groundwater-flow system in Chimacum Creek Basin and vicinity, Jefferson County, Washington

A groundwater-flow model was developed to evaluate potential future effects of growth and of water-management strategies on water resources in the Chimacum Creek Basin. The model covers an area of about 64 square miles (mi 2 ) on the Olympic Peninsula in northeastern Jefferson County, Washington. The Chimacum Creek Basin drains an area of about 53 mi 2 and consists of Chimacum Creek and its tributary East Fork Chimacum Creek, which converge near the town of Chimacum and discharge to Port Townsend Bay near the town of Irondale. The topography of the model area consists of north-south oriented, narrow, regularly spaced parallel ridges and valleys that are characteristic of fluted glaciated surfaces. Thick accumulations of peat occur along the axis of East Fork Chimacum Creek and provide rich soils for agricultural use. The study area is underlain by a north-thickening sequence of unconsolidated glacial (till and outwash) and interglacial (fluvial and lacustrine) deposits, and sedimentary and igneous bedrock units that crop out along the margins and the western interior of the model area. Six hydrogeologic units in the model area form the basis of the groundwater-flow model. They are represented by model layers UC (upper confining), UA (upper aquifer), MC (middle confining), LA (lower aquifer), LC (lower confining), and OE (bedrock). Groundwater flow in the Chimacum Creek Basin and vicinity was simulated using the groundwater-flow model, MODFLOW-2005. The finite-difference model grid comprises 245 columns, 313 rows, and 6 layers. Each model cell has a horizontal dimension of 200 × 200 feet (ft). The thickness of model layers varies throughout the model area and ranges from 5 ft in the non-bedrock units to more than 2,400 ft in the bedrock. Groundwater flow was simulated for steady-state conditions, which were simulated for calibration of the model using average recharge, discharge, and water levels for the 180-month period October 1994–September 2009. The model as calibrated has a mean residual of 4.5 ft and a standard error on the mean of 2.1 ft for heads, and 0.64±0.42 cubic feet per second for streamflows. After the model was calibrated, a Current Conditions simulation was developed to reflect current (October 2008–September 2009) hydrologic conditions, with representative pumping, return flows, and “normal” recharge (based on National Weather Service average precipitation for 1981 to 2010). The Current Conditions simulation was used to estimate current flow quantities, and as a basis to compare other simulations.Simulated steady-state inflow to the model area from precipitation and secondary recharge, or “return flow,” was 16,347 acre-feet per year (acre-ft/yr); groundwater inflow from other basins to the north of the model boundary was 1,518 acre-ft/yr (net, 3,114 acre-ft/yr in and 1,596 acre-ft/yr out) and simulated inflow from lake leakage was 613 acre-ft/yr (net, 684 acre-ft/yr in and 71 acre-ft/yr out). Simulated outflow from the model primarily was through discharge to Puget Sound (10,022 acre-ft/yr), streams (5,424 acre-ft/yr ), springs and seeps (1,521 acre-ft/yr), and through withdrawals from wells (1,506 acre-ft/yr). Four simulations were formulated using the calibrated model—one to represent current conditions (2009, the end of the period used for calibration) and three to provide representative examples of how the model can be used to evaluate the relative effects of potential changes in groundwater withdrawals and consumptive use on groundwater levels and stream base flows: Probable Future Use, based on population projections; Full Beneficial Use, based on Jefferson County Public Utility District #1 water rights; Sanitary Sewer, based on eliminating septic return flows in the Urban Growth Area. Particle tracking was used to assess flowpaths from sources and to sinks, and the effects of the presence of irrigation wells and their depths was assessed.

Washington↗
USGS2014

Estimation of regional flow-duration curves for Indiana and Illinois

Flow-duration curves (FDCs) of daily streamflow are useful for many applications in water resources planning and management but must be estimated at ungaged sites. One common technique for estimating FDCs at ungaged sites in a given region is to use equations obtained by linear regression of FDC quantiles against multiple basin characteristics that can be computed by means of a geographic information system (GIS) computer program. In this study, such regional regression equations for estimating FDC quantiles were computed at the 0.1, 0.2, 0.5, 1, 2, 5, 10, 20, 25, 30, 40, 50, 60, 70, 75, 80, 90, 95, 98, 99, 99.5, 99.8, and 99.9-percent exceedance probabilities for rural, unregulated streams in Indiana and Illinois with temporally stationary records, using data through September 30, 2007. The approach used accounts for censored values below 0.01 cubic feet per second, which are observed at exceedance probabilities as low as 70 percent (that is, occurring at least 30 percent of the time). The basin characteristics used are suitable for computation by the USGS Web-based application, StreamStats, and are available for all U.S. Environmental Protection Agency (EPA) Region V states and the larger Great Lakes area, with some specific local exceptions. Indiana and Illinois were each divided into three regions, and a different set of equations for estimating FDC quantiles was computed for each region. The error of estimation of the FDC quantiles, measured as the mean square residual in log space converted to a percentage of the quantile, varies somewhat among regions and varies strongly with exceedance probability, with a minimum error of 10 to 20 percent at an exceedance probability of 5 or 10 percent, but rises to 17 to 38 percent at the high-flow end of the FDCs (the 0.1-percent quantile) and 100 to 745 percent at the low-flow end. For comparison, errors of estimation also were computed for FDC quantiles estimated by linear regression on drainage area alone and by using the drainage-area ratio (DAR) method. Three criteria, the nearest basin centroid and two others termed “strict” and “broad”, were used to select index stations for the DAR method. The “strict” and “broad” criteria put conditions on the basin centroid distance and the range of their drainage-area ratios, and the errors were averaged for all index station pairs satisfying each criterion. The use of the simpler DAR method usually resulted in higher errors of estimation compared to the linear regression equations with multiple basin characteristics, except occasionally in the case of the DAR method with the strict index station selection criterion, a criterion that is rarely possible to satisfy in practice. An example application of the estimated equations to one gaged and a few ungaged locations in a watershed in the study area is included to illustrate the steps required. These steps are the computation of the basin characteristics and, using those characteristics together with the estimated equations, the computation of the FDC quantiles and their uncertainties.

Illinois, Indiana↗
USGS2016

Methods for estimating peak-flow frequencies at ungaged sites in Montana based on data through water year 2011: Chapter F in Montana StreamStats

The U.S. Geological Survey (USGS), in cooperation with the Montana Department of Natural Resources and Conservation, completed a study to update methods for estimating peak-flow frequencies at ungaged sites in Montana based on peak-flow data at streamflow-gaging stations through water year 2011. The methods allow estimation of peak-flow frequencies (that is, peak-flow magnitudes, in cubic feet per second, associated with annual exceedance probabilities of 66.7, 50, 42.9, 20, 10, 4, 2, 1, 0.5, and 0.2 percent) at ungaged sites. The annual exceedance probabilities correspond to 1.5-, 2-, 2.33-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence intervals, respectively. Regional regression analysis is a primary focus of Chapter F of this Scientific Investigations Report, and regression equations for estimating peak-flow frequencies at ungaged sites in eight hydrologic regions in Montana are presented. The regression equations are based on analysis of peak-flow frequencies and basin characteristics at 537 streamflow-gaging stations in or near Montana and were developed using generalized least squares regression or weighted least squares regression. All of the data used in calculating basin characteristics that were included as explanatory variables in the regression equations were developed for and are available through the USGS StreamStats application (http://water.usgs.gov/osw/streamstats/) for Montana. StreamStats is a Web-based geographic information system application that was created by the USGS to provide users with access to an assortment of analytical tools that are useful for water-resource planning and management. The primary purpose of the Montana StreamStats application is to provide estimates of basin characteristics and streamflow characteristics for user-selected ungaged sites on Montana streams. The regional regression equations presented in this report chapter can be conveniently solved using the Montana StreamStats application. Selected results from this study were compared with results of previous studies. For most hydrologic regions, the regression equations reported for this study had lower mean standard errors of prediction (in percent) than the previously reported regression equations for Montana. The equations presented for this study are considered to be an improvement on the previously reported equations primarily because this study (1) included 13 more years of peak-flow data; (2) included 35 more streamflow-gaging stations than previous studies; (3) used a detailed geographic information system (GIS)-based definition of the regulation status of streamflow-gaging stations, which allowed better determination of the unregulated peak-flow records that are appropriate for use in the regional regression analysis; (4) included advancements in GIS and remote-sensing technologies, which allowed more convenient calculation of basin characteristics and investigation of many more candidate basin characteristics; and (5) included advancements in computational and analytical methods, which allowed more thorough and consistent data analysis. This report chapter also presents other methods for estimating peak-flow frequencies at ungaged sites. Two methods for estimating peak-flow frequencies at ungaged sites located on the same streams as streamflow-gaging stations are described. Additionally, envelope curves relating maximum recorded annual peak flows to contributing drainage area for each of the eight hydrologic regions in Montana are presented and compared to a national envelope curve. In addition to providing general information on characteristics of large peak flows, the regional envelope curves can be used to assess the reasonableness of peak-flow frequency estimates determined using the regression equations.

Montana↗
USGS2016

Selected low-flow frequency statistics for continuous-record streamgages in Georgia, 2013

This report presents the annual and monthly minimum 1- and 7-day average streamflows with the 10-year recurrence interval (1Q10 and 7Q10) for 197 continuous-record streamgages in Georgia. Streamgages used in the study included active and discontinued stations having a minimum of 10 complete climatic years of record as of September 30, 2013. The 1Q10 and 7Q10 flow statistics were computed for 85 streamgages on unregulated streams with minimal diversions upstream, 43 streamgages on regulated streams, and 69 streamgages known, or considered, to be affected by varying degrees of diversions upstream. Descriptive information for each of these streamgages, including the U.S. Geological Survey (USGS) station number, station name, latitude, longitude, county, drainage area, and period of record analyzed also is presented. Kendall’s tau nonparametric test was used to determine the statistical significance of trends in annual and monthly minimum 1-day and 7-day average flows for the 197 streamgages. Significant negative trends in the minimum annual 1-day and 7-day average streamflow were indicated for 77 of the 197 streamgages. Many of these significant negative trends are due to the period of record ending during one of the recent droughts in Georgia, particularly those streamgages with record through the 2013 water year. Long-term unregulated streamgages with 70 or more years of record indicate significant negative trends in the annual minimum 7-day average flow for central and southern Georgia. Watersheds for some of these streamgages have experienced minimal human impact, thus indicating that the significant negative trends observed in flows at the long-term streamgages may be influenced by changing climatological conditions. A Kendall-tau trend analysis of the annual air temperature and precipitation totals for Georgia indicated no significant trends. A comprehensive analysis of causes of the trends in annual and monthly minimum 1-day and 7-day average flows in central and southern Georgia is outside the scope of this study. Further study is needed to determine some of the causes, including both climatological and human impacts, of the significant negative trends in annual minimum 1-day and 7-day average flows in central and southern Georgia. To assess the changes in the annual 1Q10 and 7Q10 statistics over time for long-term continuous streamgages with significant trends in record, the annual 1Q10 and 7Q10 statistics were computed on a decadal accumulated basis for 39 streamgages having 40 or more years of record that indicated a significant trend. Records from most of the streamgages showed a decline in 7Q10 statistics for the decades of 1980–89, 1990–99, and 2000–09 because of the recent droughts in Georgia. Twenty four of the 39 streamgages had complete records from 1980 to 2010, and records from 23 of these gages exhibited a decline in the 7Q10 statistics during this period, ranging from –6.3 to –76.2 percent with a mean of –27.3 percent. No attempts were made during this study to adjust streamflow records or statistical analyses on the basis of trends. The monthly and annual 1Q10 and 7Q10 flow statistics for the entire period of record analyzed in the study are incorporated into the USGS StreamStatsDB, which is a database accessible to users through the recently released USGS StreamStats application for Georgia. StreamStats is a Web-based geographic information system that provides users with access to an assortment of analytical tools that are useful for water-resources planning and management, and for engineering design applications, such as the design of bridges. StreamStats allows users to easily obtain streamflow statistics, basin characteristics, and other information for user-selected streamgages.

Georgia↗
USGS2016

Suspended-sediment concentrations, bedload, particle sizes, surrogate measurements, and annual sediment loads for selected sites in the lower Minnesota River Basin, water years 2011 through 2016

Accurate measurements of fluvial sediment are important for assessing stream ecological health, calculating flood levels, computing sediment budgets, and managing and protecting water resources. Sediment-enriched rivers in Minnesota are a concern among Federal, State, and local governments because turbidity and sediment-laden waters are the leading impairments and affect more than 6,000 miles of rivers in Minnesota. The suspended sediment in the lower Minnesota River is deleterious, contributing about 75 to 90 percent of the suspended sediment being deposited into Lake Pepin. The Saint Paul District of the U.S. Army Corps of Engineers and the Lower Minnesota River Watershed District collaborate to maintain a navigation channel on the lower 14.7 miles of the Minnesota River through scheduled dredging operations. The Minnesota Pollution Control Agency has adopted a sediment-reduction strategy to reduce sediment in the Minnesota River by 90 percent by 2040. The U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, the Minnesota Pollution Control Agency, and the Lower Minnesota River Watershed District, collected suspended-sediment, bedload, and particle-size samples at five sites in the lower Minnesota River Basin during water years 2011 through 2014 and surrogate measurements of acoustic backscatter at one of these sites on the lower Minnesota River during water years 2012 through 2016 to quantify sediment loads and improve understanding of sediment-transport relations. Annual sediment loads were computed for calendar years 2011 through 2014. Data collected from water years 2011 through 2014 indicated that two tributaries, Le Sueur River and High Island Creek, had the highest sediment yield and concentrations of suspended sediment. These tributaries also had greater stream gradients than the sites on the Minnesota River. Suspended fines were greater than suspended sand at all sites in the study area. The range of median particle sizes matched the range for stream gradients from greatest to smallest. Bedload ranged from 3 to 20 percent of the total load at the Le Sueur River, Minnesota River at Mankato, and High Island Creek and was less than 1 percent of the total load at the Minnesota River near Jordan and at Fort Snelling State Park. The reach of the Minnesota River between Mankato and Jordan is a major source of sediment, with the sediment yield at Jordan being two and a half times greater than at Mankato. Between Jordan and Fort Snelling, the sediment yield decreases substantially, which indicates that the Minnesota River in this reach is a sink for sediment. Surrogate measurements (acoustic backscatter) collected with suspended-sediment concentration data from water years 2012 through 2016 from the Minnesota River at Fort Snelling State Park indicated strong relations between the acoustic backscatter and suspended-sediment concentrations. These results point to the dynamic nature of sediment aggradation, degradation, and transport in the Minnesota River Basin. The analyses described in this report will improve the understanding of sediment-transport relations and sediment budgets in the Minnesota River Basin.

Minnesota↗
USGS2017

Methods for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations on streams in North Georgia

The U.S. Geological Survey, in cooperation with the Georgia Department of Natural Resources, Environmental Protection Division, developed regional regression equations for estimating selected low-flow frequency and mean annual flow statistics for ungaged streams in north Georgia that are not substantially affected by regulation, diversions, or urbanization. Selected low-flow frequency statistics and basin characteristics for 56 streamgage locations within north Georgia and 75 miles beyond the State’s borders in Alabama, Tennessee, North Carolina, and South Carolina were combined to form the final dataset used in the regional regression analysis. Because some of the streamgages in the study recorded zero flow, the final regression equations were developed using weighted left-censored regression analysis to analyze the flow data in an unbiased manner, with weights based on the number of years of record. The set of equations includes the annual minimum 1- and 7-day average streamflow with the 10-year recurrence interval (referred to as 1Q10 and 7Q10), monthly 7Q10, and mean annual flow. The final regional regression equations are functions of drainage area, mean annual precipitation, and relief ratio for the selected low-flow frequency statistics and drainage area and mean annual precipitation for mean annual flow. The average standard error of estimate was 13.7 percent for the mean annual flow regression equation and ranged from 26.1 to 91.6 percent for the selected low-flow frequency equations. The equations, which are based on data from streams with little to no flow alterations, can be used to provide estimates of the natural flows for selected ungaged stream locations in the area of Georgia north of the Fall Line. The regression equations are not to be used to estimate flows for streams that have been altered by the effects of major dams, surface-water withdrawals, groundwater withdrawals (pumping wells), diversions, or wastewater discharges. The regression equations should be used only for ungaged sites with drainage areas between 1.67 and 576 square miles, mean annual precipitation between 47.6 and 81.6 inches, and relief ratios between 0.146 and 0.607; these are the ranges of the explanatory variables used to develop the equations. An attempt was made to develop regional regression equations for the area of Georgia south of the Fall Line by using the same approach used during this study for north Georgia; however, the equations resulted with high average standard errors of estimates and poorly predicted flows below 0.5 cubic foot per second, which may be attributed to the karst topography common in that area. The final regression equations developed from this study are planned to be incorporated into the U.S. Geological Survey StreamStats program. StreamStats is a Web-based geographic information system that provides users with access to an assortment of analytical tools useful for water-resources planning and management, and for engineering design applications, such as the design of bridges. The StreamStats program provides streamflow statistics and basin characteristics for U.S. Geological Survey streamgage locations and ungaged sites of interest. StreamStats also can compute basin characteristics and provide estimates of streamflow statistics for ungaged sites when users select the location of a site along any stream in Georgia.

Georgia↗
USGS2017

Streamflow characteristics and trends along Soldier Creek, Northeast Kansas

Historical data for six selected U.S. Geological Survey streamgages along Soldier Creek in northeast Kansas were used in an assessment of streamflow characteristics and trends. This information is required by the Prairie Band Potawatomi Nation for the effective management of tribal water resources, including drought contingency planning. Streamflow data for the period of record at each streamgage were used to assess annual mean streamflow, annual mean base flow, mean monthly flow, annual peak flow, and annual minimum flow. Annual mean streamflows along Soldier Creek were characterized by substantial year-to-year variability with no pronounced long-term trends. On average, annual mean base flow accounted for about 20 percent of annual mean streamflow. Mean monthly flows followed a general seasonal pattern that included peak values in spring and low values in winter. Annual peak flows, which were characterized by considerable year-to-year variability, were most likely to occur in May and June and least likely to occur during November through February. With the exception of a weak yet statistically significant increasing trend at the Soldier Creek near Topeka, Kansas, streamgage, there were no pronounced long-term trends in annual peak flows. Annual 1-day, 30-day, and 90-day mean minimum flows were characterized by considerable year-to-year variability with no pronounced long-term trend. During an extreme drought, as was the case in the mid-1950s, there may be zero flow in Soldier Creek continuously for a period of one to several months.

Kansas↗
USGS2018

Comparability of river suspended-sediment sampling and laboratory analysis methods

Accurate measurements of suspended sediment, a leading water-quality impairment in many Minnesota rivers, are important for managing and protecting water resources; however, water-quality standards for suspended sediment in Minnesota are based on grab field sampling and total suspended solids (TSS) laboratory analysis methods that have underrepresented concentrations of suspended sediment in rivers compared to U.S. Geological Survey equal-width-increment or equal-discharge-increment (EWDI) field sampling and suspended sediment concentration (SSC) laboratory analysis methods. Because of this underrepresentation, the U.S. Geological Survey, in collaboration with the Minnesota Pollution Control Agency, collected concurrent grab and EWDI samples at eight sites to compare results obtained using different combinations of field sampling and laboratory analysis methods. Study results determined that grab field sampling and TSS laboratory analysis results were biased substantially low compared to EWDI sampling and SSC laboratory analysis results, respectively. Differences in both field sampling and laboratory analysis methods caused grab and TSS methods to be biased substantially low. The difference in laboratory analysis methods was slightly greater than field sampling methods. Sand-sized particles had a strong effect on the comparability of the field sampling and laboratory analysis methods. These results indicated that grab field sampling and TSS laboratory analysis methods fail to capture most of the sand being transported by the stream. The results indicate there is less of a difference among samples collected with grab field sampling and analyzed for TSS and concentration of fines in SSC. Even though differences are present, the presence of strong correlations between SSC and TSS concentrations provides the opportunity to develop site specific relations to address transport processes not captured by grab field sampling and TSS laboratory analysis methods.

Minnesota↗
USGS2026

Simulation of the impacts of spring diversions on streamflow in the Strawberry Creek watershed, San Bernardino County, California, using an integrated hydrological model

The Strawberry Creek watershed, in the San Bernardino Mountains of southern California, features a group of natural springs known as Arrowhead Springs that have been augmented with diversions in the form of sub-horizontal borings and tunnels. Understanding the effects of these structures on streamflow through groundwater capture is crucial for managing surface-water resources in this watershed. In this study, we constructed the Strawberry Creek integrated hydrological model to increase this understanding. The Strawberry Creek integrated hydrological model is an integrated surface runoff and groundwater model, GSFLOW to simulate surface runoff and infiltration and groundwater flow. The model has 263 rows and 176 columns in each of its three layers. The model area includes the Strawberry Creek and four adjacent watersheds. The precipitation-runoff modeling system was calibrated using two streamflow gaging stations, and the groundwater and surface-water flow model was calibrated to the reported spring diversion discharge and a sparse number of groundwater-level measurements. The Strawberry Creek integrated hydrological model was run with and without diversions active, and simulated streamflow was compared, indicating that in the headwaters of Strawberry Creek, about 35 percent of the diversion flow was captured from base flow.

California↗
USGS2003

Geohydrologic Framework of Recharge and Seawater Intrusion in the Pajaro Valley, Santa Cruz and Monterey Counties, California

Pajaro Valley is a coastal watershed of 160 square miles located along Monterey Bay north of Elkhorn Slough and south of the city of Santa Cruz. The valley has been predominantly developed for agriculture since the late 1800s. In 1984 the Pajaro Valley Water Management Agency (PVWMA) was formed and was delegated with the responsibility of the management of the water resources within the Pajaro Valley by the State of California. About 84 percent of the water is used for agriculture and 16 percent is used for industrial and municipal water supply; almost all of the demand is supplied by ground water. Ground-water pumpage varies with seasonal and climatic periods. The alluvial aquifers are composed of Quaternary- and Tertiary-aged sediments that are layered marine and terrestrial coarse-grained deposits separated by extensive fine-grained deposits that potentially restrict vertical movement of ground water and seawater intrusion in the coastal subareas. The coarse-grained deposits, which persist over large areas, control pumpage and related seawater intrusion. The Aromas Sand crops out throughout the north and central parts of the PVWMA area and offshore on the continental shelf and in Monterey submarine canyon. Because many of the wells in the coastal and inland subregions are screened at depths of 200 to 400 feet below land surface, a direct avenue is provided for seawater intrusion through the coarse-grained deposits of the shallower alluvium and Aromas Sand. Geophysical logs from monitoring wells indicate discrete zones of saline water that are related to pumpage and seawater intrusion in the aquifers of the shallower alluvium and upper Aromas Sand in the upper-aquifer system and to deeper saline waters in the lower Aromas Sand within the lower-aquifer system. The precipitation data indicate that there were at least nine dry and nine wet periods that range from 2 to 19 years during the period of record, 1880?1997. The ground-water pumpage, runoff, streamflow and related water quality of streamflow also vary with seasonal and climatic periods. Recharge occurs from deep percolation of precipitation and from infiltration of streamflow. Streamflow originates from local runoff and from outside the valley as inflow from the Pajaro River. Although partly regulated, streamflow in the Pajaro River at Chittenden is less than 200 cubic feet per second 88 percent of the time and is less than 12 cubic feet per second 50 percent of the time. Streamflow water-quality data suggest that there may be several sources of poor-quality water that contribute to elevated chloride, sulfate, and nitrate concentrations in streamflow. The poor water quality occurring during lower streamflows indicates that low flows may be an additional source of salinity for ground-water recharge as streamflow infiltration along the Pajaro River. The geochemical data from this study indicate that the two main sources of recharge are deep percolation of local runoff and streamflow infiltration of Pajaro River water. The geophysical and geochemical data suggest that only the shallow alluvial aquifer and parts of the upper Aromas Sand that constitute the upper-aquifer system are being replenished by recent recharge in the coastal areas of Pajaro Valley and represent the renewable ground-water resources. These data also suggest that there is very little vertical flow through the layered aquifer systems in the coastal regions. The confining aquitards are laterally extensive but may be missing in places owing to fluvial erosion or offsetting by fault movement. Geochemical and geophysical data indicate that the ground water from some parts of the upper and lower Aromas Sand in the coastal regions was recharged thousands of years ago and may, in part, represent nonrenewable ground-water resources. The analysis of major-ion chemistry, in combination with isotope and trace-element/chloride ratios, indicates that the coastal ground-water and surface-water samples

Water-Resources Investigations Report↗