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At least 1,657 records · Page 92Linked to original sources
USGS2006

Water-management studies of a stream-aquifer system, Arkansas River Valley, Colorado

A mathematical model was developed and used to simulate the stream-aquifer system in the Arkansas River valley in southeastern Colorado, from Pueblo to the Colorado-Kansas State line. The model simulates the interrelations among ground water and surface water including reservoirs, losses, and transmountain diversions, utilizing various water-distribution rules. The model was used to analyze 24 water-management plans designed to reduce shortages in the irrigation supply. One management plan simulated salvage of water from phreatophyte evapotranspiration, different reservoir operation regulations, use of imported ground and surface water, a new reservoir, additional ground-water use, and application of excess streamflow. The resulting annual dependable supply was increased from 610,000 acre-feet to 870,000 acre-feet in relation to an annual demand of 1,100,000 acre-feet. The model can be used as a tool to analyze other water-management plans.

Colorado↗
USGS2022

River channel response to invasive plant treatment across the American Southwest

Invasive riparian plants were introduced to the American Southwest in the early 19th century and contributed to regional trends of decreasing river channel width and migration rate in the 20th century. More recently, efforts to remove invasive riparian vegetation (IRV) have been widespread, especially since 1990. To what extent has IRV treatment reversed the earlier trend of channel narrowing and reduced dynamism? In this study, paired treated and untreated reaches at 15 sites along 13 rivers were compared before and after IRV treatment using repeat aerial imagery to assess long-term (~10-year) channel change due to treatment on a regional scale across the Southwest USA. We found that IRV treatment significantly increased channel width and floodplain destruction. Treated reaches had higher floodplain destruction than untreated reaches at 14 of 15 sites, and IRV treatment increased the rate of floodplain destruction by a median factor of 1.9. The effect of treatment increased with the stream power of the largest flow over the study period. Resolving observations of channel change into separate measures of floodplain destruction and formation provided more information on underlying processes than simple measurements of channel width and centerline migration rate. Restoration practitioners who perform IRV treatment projects often focus on wildlife or vegetation response; however, geomorphic processes should be considered in restoration planning because they drive aquatic habitat and vegetation dynamics, and because of the potential for damage to downstream infrastructure. Depending on the restoration goal, management practices can be used to enhance or minimize the increase in channel dynamism caused by IRV treatment.

Arizona, California, Colorado, New Mexico, Texas, ↗
USGS2018

Rivers are social–ecological systems: Time to integrate human dimensions into riverscape ecology and management

Incorporation of concepts from landscape ecology into understanding and managing riverine ecosystems has become widely known as riverscape ecology. Riverscape ecology emphasizes interactions among processes at different scales and their consequences for valued ecosystem components, such as riverine fishes. Past studies have focused strongly on understanding the ecological processes in riverscapes and how human actions modify those processes. It is increasingly clear, however, that an understanding of the drivers behind actions that lead to human modification also merit consideration, especially regarding how those drivers influence management efficacy. These indirect drivers of riverscape outcomes can be understood in the context of a diverse array of social processes, which we collectively refer to as human dimensions. Like ecological phenomena, social processes also exhibit complex interactions across spatiotemporal scales. Greater emphasis on feedbacks between social and ecological processes will lead scientists and managers to more completely understand riverscapes as complex, dynamic, interacting social–ecological systems. Emerging applications in riverscapes, as well as studies of other ecosystems, provide examples that can lead to stronger integration of social and ecological science. We argue that conservation successes within riverscapes may not come from better ecological science, improved ecosystem service analyses, or even economic incentives if the fundamental drivers of human behaviors are not understood and addressed in conservation planning and implementation.

WIREs Water↗
USGS2004

Scientific objectives and selection of targets for the SMART-1 Infrared Spectrometer (SIR)

The European SMART-1 mission to the Moon, primarily a testbed for innovative technologies, was launched in September 2003 and will reach the Moon in 2005. On board are several scientific instruments, including the point-spectrometer SMART-1 Infrared Spectrometer (SIR). Taking into account the capabilities of the SMART-1 mission and the SIR instrument in particular, as well as the open questions in lunar science, a selection of targets for SIR observations has been compiled. SIR can address at least five topics: (1) Surface/regolith processes; (2) Lunar volcanism; (3) Lunar crust structure; (4) Search for spectral signatures of ices at the lunar poles; and (5) Ground truth and study of geometric effects on the spectral shape. For each topic we will discuss specific observation modes, necessary to achieve our scientific goals. The majority of SIR targets will be observed in the nadir-tracking mode. More than 100 targets, which require off-nadir pointing and off-nadir tracking, are planned. It is expected that results of SIR observations will significantly increase our understanding of the Moon. Since the exact arrival date and the orbital parameters of the SMART-1 spacecraft are not known yet, a more detailed planning of the scientific observations will follow in the near future. ?? 2004 Elsevier Ltd. All rights reserved.

Planetary and Space Science↗
USGS2000

Chapter 4. Predicting post-fire erosion and sedimentation risk on a landscape scale

Historic fire suppression efforts have increased the likelihood of large wildfires in much of the western U.S. Post-fire soil erosion and sedimentation risks are important concerns to resource managers. In this paper we develop and apply procedures to predict post-fire erosion and sedimentation risks on a pixel-, catchment-, and landscape-scale in central and western Colorado. Our model for predicting post-fire surface erosion risk is conceptually similar to the Revised Universal Soil Loss Equation (RUSLE). One key addition is the incorporation of a hydrophobicity risk index (HY-RISK) based on vegetation type, predicted fire severity, and soil texture. Post-fire surface erosion risk was assessed for each 90-m pixel by combining HYRISK, slope, soil erodibility, and a factor representing the likely increase in soil wetness due to removal of the vegetation. Sedimentation risk was a simple function of stream gradient. Composite surface erosion and sedimentation risk indices were calculated and compared across the 72 catchments in the study area. When evaluated on a catchment scale, two-thirds of the catchments had relatively little post-fire erosion risk. Steeper catchments with higher fuel loadings typically had the highest post-fire surface erosion risk. These were generally located along the major north-south mountain chains and, to a lesser extent, in west-central Colorado. Sedimentation risks were usually highest in the eastern part of the study area where a higher proportion of streams had lower gradients. While data to validate the predicted erosion and sedimentation risks are lacking, the results appear reasonable and are consistent with our limited field observations. The models and analytic procedures can be readily adapted to other locations and should provide useful tools for planning and management at both the catchment and landscape scale.

Journal of Sustainable Forestry↗
USGS2025

Living with wildfire in Estes Valley Fire Protection District, Larimer County, Colorado: 2023 Data report

Homeowner wildfire risk mitigation and preparedness are critical components of community wildfire readiness. This report describes the data collected through two efforts conducted in the Estes Valley Fire Protection District of Larimer County, Colorado, study area: (1) parcel-level rapid wildfire risk assessments performed by trained assessors and (2) homeowner surveys in which respondents provided self-assessments of their parcel-level wildfire risk. This project was undertaken to support Estes Valley Fire Protection District’s desire to enhance resident wildfire risk mitigation and evacuation planning. The household surveys also explored the social dimensions of wildfire, including understanding of wildfire risk, outreach or communication preferences, mitigation and evacuation preparedness activities, and perceptions of community risk reduction strategies. The results provide evidence that despite high levels of wildfire awareness and experience, respondents underestimate the risk on their properties as compared to a trained professional and have not completed important steps in the evacuation preparedness process. However, respondents would like more information on wildfire risk reduction via newsletters (mailed or emailed), community meetings, and in-person interactions.

Colorado↗
USGS1905

Economic geology of the Bingham mining district, Utah

The field work of which this report represents the final results was first undertaken in the summer of the year 1900. This district had long been selected by the writer as worthy of special economic investigation, as well on account of the importance of its products as because of its geological structure and the peculiar relations of its ore deposits. It was not, however, until the summer mentioned above that the means at the disposal of the Survey, both pecuniary and scientific, justified its undertaking. As originally planned, the areal or surface geology was to have been worked out by Mr. Keith, who had already spent many years in unraveling the complicated geological structure of the Appalachian province, while Mr. Boutwell, who had more recently become attached to the Survey, was to have charge of the underground geology, or a study of the ore deposits, under the immediate supervision of the writer. When the time came for actually taking the field, it was found that the pressure of other work would not permit Mr. Keith to carry out fully the part allotted to him, and in consequence a part of his field work has fallen to Mr. Boutwell. Field work was commenced by the writer and Mr. Boutwell early in July, 1900. Mr. Keith joined the party on August 10, but was obliged to leave for other duties early in September. Mr. Boutwell carried on his field work continuously from July until December, taking up underground work after the snowfall had rendered work on the surface geology impracticable. The geological structure had proved to be unexpectedly intricate and complicated, so that, on the opening of the field season of 1901, it was found necessary to make further study in the light of results already worked out, and Mr. Boutwell spent some weeks in the district in the early summer of 1901. His field work that year, partly in California and partly in Arizona, as assistant to Mr. Waldemar Lindgren, lasted through the summer and winter and well into the spring of 1902, so that but little time , was left before he was obliged to take the field again in his study of the Park City district of Utah. Mr. Keith had been too closely occupied with his Appalachian work to complete his part,' and thus the publication of this report has been unusually delayed. While the delay is a cause for regret, this regret is much tempered by the consideration that had the report been published earlier many facts brought to light during the vigorous development of the region in late years, which have an important bearing upon the structure and genesis of the ore deposits, could not have been used in its preparation.

Utah↗
USGS2006

Evaluation of baseline ground-water conditions in the Mosteiros, Ribeira Paul, and Ribeira Fajã Basins, Republic of Cape Verde, West Africa, 2005-06

This report documents current (2005-06) baseline ground-water conditions in three basins within the West African Republic of Cape Verde (Mosteiros on Fogo, Ribeira Paul on Santo Antão, and Ribeira Fajã on São Nicolau) based on existing data and additional data collected during this study. Ground-water conditions (indicators) include ground-water levels, ground-water recharge altitude, ground-water discharge amounts, ground-water age (residence time), and ground-water quality. These indicators are needed to evaluate (1) long-term changes in ground-water resources or water quality caused by planned ground-water development associated with agricultural projects in these basins, and (2) the feasibility of artificial recharge as a mitigation strategy to offset the potentially declining water levels associated with increased ground-water development. Ground-water levels in all three basins vary from less than a few meters to more than 170 meters below land surface. Continuous recorder and electric tape measurements at three monitoring wells (one per basin) showed variations between August 2005 and June 2006 of as much as 1.8 meters. Few historical water-level data were available for the Mosteiros or Ribeira Paul Basins. Historical records from Ribeira Fajã indicate very large ground-water declines during the 1980s and early 1990s, associated with dewatering of the Galleria Fajã tunnel. More-recent data indicate that ground-water levels in Ribeira Fajã have reached a new equilibrium, remaining fairly constant since the late 1990s. Because of the scarcity of observation wells within each basin, water-level data were combined with other techniques to evaluate ground-water conditions. These techniques include the quantification of ground-water discharge (well withdrawals, spring discharge, seepage to springs, and gallery drainage), field water-quality measurements, and the use of environmental tracers to evaluate sources of aquifer recharge, flow paths, and ground-water residence times. In the Mosteiros Basin, measured well and spring discharge is about 220,000 cubic meters per year. For the Ribeira Paul Basin, measured well discharge, spring discharge, and ground-water seepage to springs is about 1,600,000 cubic meters per year. Ribeira Fajã Basin is the driest of the three basins with a precipitation rate of about half that of the other two basins. The only measurable ground-water discharge from this basin is from Galleria Fajã, estimated to be about 150,000 cubic meters per year. Measured discharge for all three basins does not include submarine outflow or agricultural/phreatophyte consumptive use (Paul Basin, only) and is assumed to be less than total ground-water discharge. Ground-water ages indicate that recharge to wells and springs occurred from more than 50 years ago at some locations to within the past decade at other sites. Ground water in Paul is younger than that in the other two basins, indicating that recharge generally occurred within the past 50 years. Ground water at all the dateable sites using tritium/helium in both the Mosteiros and Ribeira Fajã Basins show that recharge occurred more than 50 years before the sampling dates. Ground-water tritium/helium age dating was not possible at some sites in Mosteiros and Ribeira Fajã Basins because of the presence of helium in the aquifer derived from the mantle or aquifer matrix. However, this helium was useful for accurate age dating of the unaffected ground-water sites. Dissolved gases indicate that most ground-water recharge occurs at mid and high altitudes within all three basins; calculated recharge altitudes ranged from 700 to more than 2,000 meters. In the Mosteiros and Ribeira Fajã Basins, recharge altitudes are much higher than the wells and springs. This suggests that it may take many years for artificial recharge to result in a beneficial impact on the aquifer in areas where the agricultural projects are implemented. Recharge altitudes in Paul Basin also were generally higher than their respective ground-water discharge sampling sites except for one spring, Seladinha. This spring, in combination with generally younger ground-water ages in Paul, indicates the existence of some short flow paths where artificial recharge may possibly enhance available water resources within a few years. The salinity of wells and springs is generally low in the Ribeira Paul and Ribeira Fajã Basins, but somewhat higher in Mosteiros Basin. Specific-conductance measurements of wells and springs in Ribeira Paul and Ribeira Fajã ranged from about 200 to 700 microsiemens per centimeter at 25 degrees Celsius. Although the Monte Vermelho spring in Mosteiros Basin also has very low salinity (200 microsiemens per centimeter at 25 degrees Celsius), water from the wells along the coastal plain has specific-conductance measurements of as much as 16,000 microsiemens per centimeter at 25 degrees Celsius. These higher values indicate some brackish water intrusion. Additional ground-water development of the Mosteiros coastal plain may exacerbate this situation.

Mosteiros basin, Ribeira Fajã basin, Ribeira Paul ↗
USGS1982

A plan for hydrologic investigations of in situ, oil-shale retorting near Rock Springs, Wyoming

The recovery of shale oil by the in-situ retort process may cause hydrologic impacts, the most significant being ground-water contamination and possible transport of contaminants into surrounding areas. Although these impacts are site-specific, many of the techniques used to investigate each retort operation commonly will be the same. The U.S. Geological Survey has begun a study of hydrologic impacts in the area of an in-situ retort near Rock Springs, Wyoming, as a means of refining and demonstrating these techniques. Geological investigations include determining the areal extent and thickness of aquifers. Emphasis will be placed on determining lithologic variations from geophysical logging. Hydrologic investigations include mapping of potentiometric surfaces, determining rates of ground-water discharge, and estimating aquifer properties by analytical techniques. Water-quality investigations include monitoring solute migration from the retort site and evaluating sampling techniques by standard statistical procedures. A ground-water-flow and solute-transport model will be developed to predict future movement of the water plume away from the retort. (USGS)

Open-File Report↗
USGS1994

Relations of changes in wastewater-treatment practices to changes in stream-water quality during 1978-88 in the Chicago area, Illinois, and implications for regional and national water-quality assessments

A study in the upper Illinois River Basin defined relations between changes in wastewater-treatment practices and changes in stream-water quality on the basis of available information. These relations were examined for five large wastewater-treatment plants in the Chicago area, Illinois. At the three largest treatment plants, two major changes in wastewater-treatment practices were identified--the cessation of chlorination and the implementation of Chicago's Tunnel and Reservoir Plan (TARP). Other changes, such as improved aeration and expansion of the facilities, also were made at some of the treatment plants. At the Calumet Water Reclamation Plant, median densities of fecal coliform bacteria in the effluent increased from 3,100 to 1,200,000 colonies per 100 milliliters after the cessation of chlorination. Median densities at the nearest downstream monitoring site increased from 9,500 to 250,000 colonies per 100 milliliters. Similar changes in bacteria densities were indicated for other treatment plants and stream-monitoring sites, but increases in densities of fecal coliform bacteria were not indicated at distances greater than 7 miles downstream. Substantial changes in effluent and stream-water quality, primarily improvements, were identified after the implemen- of TARP and improvements in aeration. Decreases in some of the largest concentrations of ammonia were particularly notable and were likely results of the cape and treatment of combined sewer overflows by TARP. Improvements in water quality were commonly related to climatic season, with greater changes taking place during warm periods. Substantial decreases in concentrations were identified for many constituents, including oxygen demand, ammonia, bacteria, and cyanide. The water-quality data available for this study were considered to be more accurate and were more comprehensive than data from most other monitoring programs. The results of this study, however, identified some needed enhancements to increase the usefulness of the data for additional purposes and analyses.

Water-Resources Investigations Report↗
USGS2024

A conceptual framework to assess post-wildfire water quality: State of the science and knowledge gaps

Wildfire substantially alters aquatic ecosystems by inducing moderate to catastrophic physical and chemical changes. However, the relations of environmental and watershed variables that drive those effects are complex. We present a Driver-Factor-Stressor-Effect (DFSE) conceptual framework to assess the current state of the science related to post-wildfire water-quality. We reviewed 64 peer-reviewed papers using the DFSE framework to identify drivers, factors, stressors, and effects associated with each study. A total of five drivers were identified and ranked according to their frequency of occurrence in the literature: atmospheric processes > fire characteristics > ecologic processes and characteristics > land surface characteristics > soil characteristics. Commonly reported stressors include increased nutrients, runoff, and sediment transport. Furthermore, although several different factors have been used at least once to explain water-quality effects, relatively few factors outside of precipitation and fire characteristics are frequently studied. We identified several gaps indicating the need for long-term monitoring, multi-factor studies, consideration of organic contaminants, consideration of groundwater, and inclusion of soil characteristics. This assessment expands on other reviews and meta-analyses by exploring causal linkages between influential variables and overall effects in post-wildfire watersheds. Information gathered from our assessment and the framework itself can be used to inform future monitoring plans and as a guide for modeling efforts focused on better understanding specific processes or to mitigate potential risks of post-wildfire water quality.

Water Resources Research↗
USGS2003

Cruise report for A1-02-SC southern California CABRILLO project, Earthquake Hazards Task

A two-week marine geophysical survey obtained sidescan-sonar images and multiple sets of high-resolution seismic-reflection profiles in the southern California offshore area between Point Arguello and Point Dume. The data were obtained to support two project activities of the United States Geological Survey (USGS) Coastal and Marine Geology (CMG) Program: (1) the evaluation of the geologic hazards posed by earthquake faults and landslides in the offshore areas of Santa Barbara Channel and western Santa Monica Basin and (2) determine the location of active hydrocarbon seeps in the vicinity of Point Conception as part of a collaborative study with the Minerals Management Service (MMS). The 2002 cruise, A1-02- SC, is the fourth major data-collection effort in support of the first objective (Normark et al., 1999a, b; Gutmacher et al., 2000). A cruise to obtain sediment cores to constrain the timing of deformation interpreted from the geophysical records is planned for the summer of 2003.

California↗
USGS2013

Residential and service-population exposure to multiple natural hazards in the Mount Hood region of Clackamas County, Oregon

The objective of this research is to document residential and service-population exposure to natural hazards in the rural communities of Clackamas County, Oregon, near Mount Hood. The Mount Hood region of Clackamas County has a long history of natural events that have impacted its small, tourism-based communities. To support preparedness and emergency-management planning in the region, a geospatial analysis of population exposure was used to determine the number and type of residents and service populations in flood-, wildfire-, and volcano-related hazard zones. Service populations are a mix of residents and tourists temporarily benefitting from local services, such as retail, education, or recreation. In this study, service population includes day-use visitors at recreational sites, overnight visitors at hotels and resorts, children at schools, and community-center visitors. Although the heavily-forested, rural landscape suggests few people are in the area, there are seasonal peaks of thousands of visitors to the region. “Intelligent” dasymetric mapping efforts using 30-meter resolution land-cover imagery and U.S. Census Bureau data proved ineffective at adequately capturing either the spatial distribution or magnitude of population at risk. Consequently, an address-point-based hybrid dasymetric methodology of assigning population to the physical location of buildings mapped with a global positioning system was employed. The resulting maps of the population (1) provide more precise spatial distributions for hazard-vulnerability assessments, (2) depict appropriate clustering due to higher density structures, such as apartment complexes and multi-unit commercial buildings, and (3) provide new information on the spatial distribution and temporal variation of people utilizing services within the study area. Estimates of population exposure to flooding, wildfire, and volcanic hazards were determined by using overlay analysis in a geographic information system. Population exposure to flood hazards is low (less than 10 percent of residents) and does not vary substantially between 100-year and 500-year flood-hazard scenarios. Moderate, moderate-to-high, and high wildfire-risk areas within the study region account for 72 percent of residents, 62 percent of employees, and 60 percent of daytime visitors to recreation sites. Fifteen percent of businesses in the study area are in moderate-to-high or high wildfire-risk areas but these businesses represent 51 percent of the local workforce. A volcanic event at Mount Hood could directly impact up to 60 percent of residents in their homes and 87 percent of employees at their workplaces. The proximal volcanic-hazard zone alone includes 65 percent of employees, 80 percent of schools and community facilities, more than 60 percent of overnight visitors in peak seasons, and 82–100 percent of daytime visitors to recreation sites during the summer and winter months, respectively. The number of day-use visitors to recreation sites in the region is greatest during winter months (averaging 129,300 people per month), whereas overnight visitors are greatest during summer months (averaging 34,000 per month). This analysis of residential and service-population exposure to natural hazards supports the development of targeted risk-reduction efforts in the region, while also expanding the discourse on characterizing and assessing population dynamics in tourist-frequented areas.

Oregon↗
USGS2014

Waterbird egg mercury concentrations in response to wetland restoration in south San Francisco Bay, California

The conversion of 50–90 percent of 15,100 acres of former salt evaporation ponds to tidal marsh habitat in the south San Francisco Bay, California, is planned as part of the South Bay Salt Pond Restoration Project. This large-scale habitat restoration may change the bioavailability of methylmercury. The South Bay already is known to have high methylmercury concentrations, with methylmercury concentrations in several waterbirds species more than known toxicity thresholds where avian reproduction is impaired. In this 2013 study, we continued monitoring bird egg mercury concentrations in response to the restoration of the Pond A8/A7/A5 Complex to a potential tidal marsh in the future. The restoration of the Pond A8/A7/A5 Complex began in autumn 2010, and the Pond A8 Notch was opened 5 feet (one of eight gates) to muted tidal action on June 1, 2011, and then closed in the winter. In autumn 2010, internal levees between Ponds A8, A7, and A5 were breached and water depths were substantially increased by flooding the Pond A8/A7/A5 Complex in February 2011. In June 2012, 15 feet (three of eight gates) of the Pond A8 Notch was opened, and then closed in December 2012. In June 2013, 15 feet of the Pond A8 Notch again was opened, and the Pond A8/A7/A5 Complex was a relatively deep and large pond with muted tidal action in the summer. This report synthesizes waterbird data from the 2013 breeding season, and combines it with our prior study’s data from 2010 and 2011.

California↗
USGS1977

National coal resource investigations of the United States Geological Survey

The objective of this report is to provide a record of some of the goals and accomplishments of the coal resource investigations of the U. S. Geological Survey for 1977. Successful completion of these goals will aid the Nation in the years ahead because proper usage of coal resource data may lessen economic displacements resulting from the energy shortage. This report is concerned only with one mineral fuel -- coal -- and only with coal resource investigations in the Geologic Division of the U. S. Geological Survey. Other divisions involved with coal or coal-related work are the Conservation, Water Resources, and Topographic Divisions. It is one of a series of reports on the energy resource studies conducted by the Geological Survey that provide a public record of the objectives, activities, and accomplishments of these programs. Similar reports have been prepared on oil and gas, oil shale, uranium, thorium, and energy-related industrial minerals. This report includes descriptions of the program, each sub-element of the program, individual projects, and a selected list of program publications from 1970-76. It also describes how the program is responsive to Presidential pronouncements and Congressional mandates. The program is cooperative with several Federal bureaus, many state agencies, universities, and industry. This coordination assures that the program supplements the work of these interested groups and is not duplicative. A scientific program such as the coal resource investigations is difficult for the non-involved person to understand solely from the existing reports on various studies made in the program. This report provides an explanation that the scientist, decision maker, personnel of other government agencies, and the layman can use to relate various activities and to gain a better understanding of the relation of coal to the Nation's requirements for energy and of the importance of a carefully planned program on this energy resource.

Open-File Report↗
USGS2007

Hydrogeology and Potentiometric Surface of the Dublin and Midville Aquifer Systems in Richmond County, Georgia, January 2007

INTRODUCTION The Dublin and Midville aquifer systems are part of the Cretaceous aquifer system that underlies most of Richmond County, Georgia (Gorday, 1985; Falls and others, 1997). The Cretaceous aquifer system is the second most productive aquifer in Georgia and is a major source of water in the region. About 220 million gallons per day (Mgal/d) of water was withdrawn from the Cretaceous aquifer system during 2000 in Georgia (Fanning, 2003). The Augusta-Richmond County Water System is the largest public water supplier in the county and withdrew 13 Mgal/d of ground water during 2000; withdrawals decreased from 2001 to 2005. The towns of Hephzibah and Blythe withdrew 0.4 and 0.03 Mgal/d, respectively. Industrial ground-water withdrawals are concentrated along the Savannah River and totaled 2.89 Mgal/d. To monitor seasonal and long-term water-level fluctuations and trends in the aquifers, the U.S. Geological Survey (USGS) - in cooperation with Augusta Utilities - maintains a countywide network of about 100 water-level monitoring wells in various aquifers, including a new continuous monitoring site (well 30AA33) and two existing USGS-Georgia Environmental Protection Division network sites (wells 29AA09 and 30AA04). Data compiled during this study were used to better define the hydrogeologic units and to construct an updated potentiometric-surface map for the area, which is used to better understand ground-water movement in the Cretaceous aquifer system. In addition, the potentiometric surface and related water-level data can be used for water-resource planning and to update ground-water flow models for the region (Clarke and West, 1997; Cherry, 2006).

Georgia↗
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↗
USGS2015

Data Collection and Simulation of Ecological Habitat and Recreational Habitat in the Shenandoah River, Virginia

This report presents updates to methods, describes additional data collected, documents modeling results, and discusses implications from an updated habitat-flow model that can be used to predict ecological habitat for fish and recreational habitat for canoeing on the main stem Shenandoah River in Virginia. Given a 76-percent increase in population predictions for 2040 over 1995 records, increased water-withdrawal scenarios were evaluated to determine the effects on habitat and recreation in the Shenandoah River. Projected water demands for 2040 vary by watershed: the North Fork Shenandoah River shows a 55.9-percent increase, the South Fork Shenandoah River shows a 46.5-percent increase, and the main stem Shenandoah River shows a 52-percent increase; most localities are projected to approach the total permitted surface-water and groundwater withdrawals values by 2040, and a few localities are projected to exceed these values. The habitat model used for this study evaluates the suitability of ecological habitat, represented by fish, and recreational habitat, represented by canoeing, based on depth, velocity, and substrate conditions, which are weighted for the physical habitat types (riffles, runs, or pools) present within a stretch of river. Weighted usable-habitat area in the Lockes Mill reach was maximized for adult smallmouth bass and sub-adult smallmouth bass ( Micropterus dolomieu ) and river chub ( Nocomis micropogon ) when streamflows were equal to median flow (900 cubic feet per second) for summer months. Ecological maximum weighted usable-habitat areas for smaller fish, such as spotfin or satinfin shiner ( Cyprinella spp.), margined madtom ( Noturus insignis ), and juvenile redbreast sunfish ( Lepomis auritus ) occurred with 10 th percentile flows (482 cubic feet per second) and lower. Recreational weighted usable-habitat areas for canoeing were maximized when streamflows were above the 75 th percentile (1,410 cubic feet per second). During historic droughts, streamflows were less than the 10 th percentile, and adult smallmouth bass and sub-adult smallmouth bass habitat was below normal for the majority of days during at least 2 months of the summer. When streamflows were less than the lowest 7-day average in a 10-year period, or 7Q10 flow (357 cubic feet per second), margined madtom, river chub, and sub-adult redbreast sunfish habitat areas were below normal as well. Streamflows that limit most fish species habit availability range from 300 to 500 cubic feet per second. For the drought years simulated, flows that were equal to or less than the 10 th percentile for summer months did not provide adequate depth for canoe passage through riffle habitats. A modeling limitation for higher flows than those studied during development of the habitat-suitability criteria is that modeled habitat availability will decrease as flows increase. Time-series analyses were used to investigate changes in habitat availability with increased water withdrawals of 10, 20, and almost 50 percent (48.6 percent) up to the 2040 amounts projected by local water supply plans. Adult and sub-adult smallmouth bass frequently had habitat availability outside the normal range for habitat conditions during drought years, yet 10- or 20-percent increases in withdrawals did not contribute to a large reduction in habitat. When withdrawals were increased by 50 percent, there was an additional decrease in habitat. During 2002 drought scenarios, reduced habitat availability for sub-adult redbreast sunfish or river chub was only slightly evident with 50-percent increased withdrawal scenarios. Recreational habitat represented by canoeing decreased lower than normal during the 2002 drought. For a recent normal year, like 2012, increased water-withdrawal scenarios did not affect habitat availability for fish such as adult and sub-adult smallmouth bass, sub-adult redbreast sunfish, or river chub. Canoeing habitat availability was within the normal range most of 2012, and increased water-withdrawal scenarios showed almost no affect. For both ecological fish habitat and recreational canoeing habitat, the antecedent conditions (habitat within normal range of habitat or below normal) appear to govern whether additional water withdrawals will affect habitat availability. As human populations and water demands increase, many of the ecological or recreational stresses may be lessened by managing the timing of water withdrawals from the system.

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