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At least 523 records · Page 29Linked to original sources
USGS2005

Transport and fate of nitrate and pesticides: Hydrogeology and riparian zone processes

There is continuing concern over potential impacts of widespread application of nutrients and pesticides on ground- and surface-water quality. Transport and fate of nitrate and pesticides were investigated in a shallow aquifer and adjacent stream, Cow Castle Creek, in Orangeburg County, South Carolina. Pesticide and pesticide degradate concentrations were detected in ground water with greatest frequency and largest concentrations directly beneath and downgradient from the corn (Zea mays L.) field where they were applied. In almost all samples in which they were detected, concentrations of pesticide degradates greatly exceeded those of parent compounds, and were still present in ground waters that were recharged during the previous 18 yr. The absence of both parent and degradate compounds in samples collected from deeper in the aquifer suggests that this persistence is limited or that the ground water had recharged before use of the pesticide. Concentrations of NO3- in ground water decreased with increasing depth and age, but denitrification was not a dominant controlling factor. Hydrologic and chemical data indicated that ground water discharges to the creek and chemical exchange takes place within the upper 0.7 m of the streambed. Ground water had its greatest influence on surface-water chemistry during low-flow periods, causing a decrease in concentrations of Cl-, NO3-, pesticides, and pesticide degradates. Conversely, shallow subsurface drainage dominates stream chemistry during high-flow periods, increasing stream concentrations of Cl-, NO3-, pesticides, and pesticide degradates. These results point out the importance of understanding the hydrogeologic setting when investigating transport and fate of contaminants in ground water and surface water. ?? ASA, CSSA, SSSA.

Journal of Environmental Quality↗
USGS2001

Use of borehole and surface geophysics to investigate ground-water quality near a road-deicing salt-storage facility, Valparaiso, Indiana

Borehole and surface geophysics were used to investigate ground-water quality affected by a road-deicing salt-storage facility located near a public water-supply well field. From 1994 through 1998, borehole geophysical logs were made in an existing network of monitoring wells completed near the bottom of a thick sand aquifer. Logs of natural gamma activity indicated a uniform and negligible contribution of clay to the electromagnetic conductivity of the aquifer so that the logs of electromagnetic conductivity primarily measured the amount of dissolved solids in the ground water near the wells. Electromagnetic-conductivity data indicated the presence of a saltwater plume near the bottom of the aquifer. Increases in electromagnetic conductivity, observed from sequential logging of wells, indicated the saltwater plume had moved north about 60 to 100 feet per year between 1994 and 1998. These rates were consistent with estimates of horizontal ground-water flow based on velocity calculations made with hydrologic data from the study area. Ratios of chloride to bromide concentrations in water samples were used to distinguish sources of chloride in the ground water?whether from road-deicing salt, domestic wastewater, or natural occurrences. Water samples identified with the chloride/bromide ratios as being affected by road-deicing salt had concentrations of dissolved solids, chloride, and sodium many times the background levels for the study area. The largest concentrations were in water from wells near the salt-storage facility?12,400 to 12,800 milligrams per liter (mg/L) dissolved solids, 6,730 to 7,230 mg/L chloride, and 3,690 to 4,400 mg/L sodium. A conceptual, multi-layer model was developed to describe the vertical extent of the saltwater plume in the vicinity of the monitoring wells. A relation was derived between average borehole electromagnetic conductivity in the screened interval of the wells in the saltwater plume and concentrations of dissolved solids in water samples from those wells. This relation was used in the model to show borehole electromagnetic conductivity in transects of wells as a zone of saline water overlain by zones of brackish water and freshwater. The thickness and altitude of the zones of saline and brackish water decreased with increased distance from the salt-storage facility. Two surface surveys of terrain electromagnetic conductivity were used to map the horizontal extent of the saltwater plume in areas without monitoring wells. Background values of terrain conductivity were measured in an area where water-quality and borehole geophysical data did not indicate saline or brackish water. Based on a guideline from previous case studies, the boundaries of the saltwater plume were mapped where terrain conductivity was 1.5 times background. The extent of the saltwater plume, based on terrain conductivity, generally was consistent with the available water-quality and borehole electromagnetic-conductivity data and with directions of ground-water flow determined from water-level altitudes.

Indiana↗
USGS2021

Post-drought groundwater storage recovery in California’s Central Valley

Groundwater depletion is a major threat to agricultural and municipal water supply in California's Central Valley. Recent droughts during 2007–2009 and 2012–2016 exacerbated chronic groundwater depletion. However, it is unclear how much groundwater storage recovered from drought-related overdrafts during post-drought years, and how climatic conditions and water management affected recovery times. We estimated groundwater storage change in the Central Valley for April 2002 through September 2019 using four methods: GRACE satellite data, a water balance approach, a hydrologic simulation model, and monitoring wells. We also evaluated the sensitivity of drought recovery to different climate scenarios (recent climate ± droughts and future climate change scenarios: 20 GCMs and 2 RCPs) using water balance method and statistical sampling of historical climate data. Estimated Central Valley groundwater loss during the two droughts ranged from 19 km 3 (2007–2009) to 28 km 3 (2012–2016) (median of four methods). Median aquifer storage recovery was 34% and 19% of the overdraft during the 2010–2011 and 2017–2019 post-drought years, respectively. Numerical experiments show that recovery times are sensitive to climate forcing, with longer recovery times for a future climate scenario that replicate historical climatology relative to historical forcing with no droughts. Overdraft recovery times decrease by ∼2× with implementation of pumping restrictions (30th to 50th percentiles of historical groundwater depletion) to constrain groundwater depletion relative to no restrictions with a no-drought future climatology. This study highlights the importance of considering water management implications for future drought recoveries within the context of climate change scenarios.

California↗
USGS1979

Investigations by the U.S. Geological Survey of soil and moisture conservation on public domain lands, 1941-1964

The passage of the Taylor Grazing Act in 1934 marked the end of an era in the land policies in the United States in that disposal of the public lands by homesteading was terminated except under rigidly prescribed procedures, and the remaining public lands covering about 175 million acres in the western conterminous states were brought under regulatory authority for grazing use. In 1934 the lands were mostly in a severe state of deterioration as a result of overgrazing and drought. In addition to reducing numbers of livestock using the lands, successive programs of conservation practices were established of which the Soil and Moisture Conservation Program of the Department of the Interior is of particular interest here. The services of the Geological Survey, in an investigational and advisory capacity were enlisted in this program. The work of the Geological Survey has consisted of the collection of hydrologic data, investigations of range-water supplies to facilitate management and provide information for design of structures and land-treatment measures. Appraisal of the effects of treatment practices has also been an important activity. Conservation on the public domain involves mainly growing vegetation for forage and reducing erosion. The two elements are intimately related--accomplishment in one is usually reflected by an improvement in the other. Erosion is a serious problem on most of the public domain, but particularly in the Colorado River and Rio Grande basins where, despite low annual water yields, the public domain and similar lands on the Indian reservations contribute the major part of the sediment measured at the downstream gaging stations. In parts of the Missouri River basin also, erosion is obviously very active but the sediment yield contributed by the public domain cannot be as readily isolated. The reasons for the erosion are generally evident--the erodibility of the rock and soils and the sparsity of vegetation as a result of low precipitation, unfavorable soils, or past land use. How much is due to the land use is still controversial, resulting in many questions relative to planning corrective measures. The problem facing the early administrators of the Taylor Grazing Act to bring about proper use and conservation of the public domain was a difficult one because of the lack of records on actual grazing use in animal-unit months of the qualified allottees and the lack of data on treatment practices in an arid area. Reduction of grazing was imperative in some localities, but generally, it could not be brought about as rapidly as it should have been. Numbers of animal units in the grazing districts were reduced from about 3.6 million in 1941 to about 3.2 million in 1964, whereas the areas included in districts was increased about 3 percent. Reductions are still being made in certain areas where deterioration is evident. One of the earliest activities connected with management of the range was the development of water supplies to facilitate the distribution of grazing. The investigations needed for such development formed a large part of the early work in the Soil and Moisture program of the Geological Survey and has continued to be a major activity to the present time. Most of the work has involved investigations of sites for wells but has included also the investigation of proposed spring developments and collection of hydrologic data for use in reservoir design. Well-site investigations have been of two general types: (1) the investigation of a site selected by the land administration agency, and (2) an areal investigation covering entire grazing districts or units thereof. In each type of investigation, a study is made of the geology and the recharge conditions. Reports are prepared giving estimates of the depth of drilling required, the depth to water, the yield, and the quality of the water, together with other information on drilling conditions and developing. Springs are a significant so

Open-File Report↗
USGS1981

Hydrologic studies of the U.S. Geological Survey in major coal-resource areas of Utah through 1980

Increased interest in coal has created greater interest in water, both for environmental and water-supply reasons. This report summarizes hydrologic studies conducted in and near the major coal fields of Utah (fig. 1) by the U.S. Geological Survey through 1980. It is intended as a reference for those people dealing with coal-related hydrologic problems. Published reports and reports in preparation at the time of this compilation are summarized in an annotated bibliography. The 4? reports in the annotated bibliography deal with many components of the hydrologic system. Most of the reports are interpretive in nature, but some contain only hydrologic data. The reports deal with such varied subjects as the magnitude and frequency of floods, availability of ground water, and hydrologic impacts of coal mining. Seven hydrologic studies that are active in 1980 in Utah coal-resource areas are described. In addition to these seven, studies, that part of the Geological Survey statewide data-collection network in the vicinity of the major coal fields is described. The hydrologic studies are conducted and reports prepared, for the most part, by personnel of the Water Resources Division, Utah District. tost of the studies and data-collection programs are in cooperation with other Federal, State, and local agencies. Utah Power and Light Co. provides stream- flow data collected at one gaging station.

Utah↗
USGS2009

Spatially referenced statistical assessment of dissolved-solids load sources and transport in streams of the Upper Colorado River Basin

The Upper Colorado River Basin (UCRB) discharges more than 6 million tons of dissolved solids annually, about 40 to 45 percent of which are attributed to agricultural activities. The U.S. Department of the Interior estimates economic damages related to salinity in excess of $330 million annually in the Colorado River Basin. Salinity in the UCRB, as measured by dissolved-solids load and concentration, has been studied extensively during the past century. Over this period, a solid conceptual understanding of the sources and transport mechanisms of dissolved solids in the basin has been developed. This conceptual understanding was incorporated into the U.S. Geological Survey Spatially Referenced Regressions on Watershed Attributes (SPARROW) surface-water quality model to examine statistically the dissolved-solids supply and transport within the UCRB. Geologic and agricultural sources of dissolved solids in the UCRB were defined and represented in the model. On the basis of climatic and hydrologic conditions along with data availability, water year 1991 was selected for examination with SPARROW. Dissolved-solids loads for 218 monitoring sites were used to calibrate a dissolved-solids SPARROW model for the UCRB. The calibrated model generally captures the transport mechanisms that deliver dissolved solids to streams of the UCRB as evidenced by R2 and yield R2 values of 0.98 and 0.71, respectively. Model prediction error is approximated at 51 percent. Model results indicate that of the seven geologic source groups, the high-yield sedimentary Mesozoic rocks have the largest yield of dissolved solids, about 41.9 tons per square mile (tons/mi2). Irrigated sedimentary-clastic Mesozoic lands have an estimated yield of 1,180 tons/mi2, and irrigated sedimentary-clastic Tertiary lands have an estimated yield of 662 tons/mi2. Coefficients estimated for the seven landscape transport characteristics seem to agree well with the conceptual understanding of the role they play in the delivery of dissolved solids to streams in the UCRB. Predictions of dissolved-solids loads were generated for more than 10,000 stream reaches of the stream network defined in the UCRB. From these estimates, the downstream accumulation of dissolved solids, including natural and agricultural components, were examined in selected rivers. Contributions from each of the 11 dissolved-solids sources were also examined at select locations in the Grand, Green, and San Juan Divisions of the UCRB. At the downstream boundary of the UCRB, the Colorado River at Lees Ferry, Arizona, monitoring site, the dissolved-solids contribution of irrigated agricultural lands and natural sources were about 45 and 57 percent, respectively. Finally, model predictions, including the contributions of natural and agricultural sources for selected locations in the UCRB, were compared with results from two previous studies.

Arizona, Colorado, Idaho, New Mexico, Utah, Wyomin↗
USGS2010

Relation of carbon 14 concentrations to saline water contamination of coastal aquifers

Naturally occurring stable or radioactive isotopes may be used in some places to identify the origin of saline water that contaminates some coastal aquifers. In a recent study to determine the origin of saline water in the Ocala Limestone aquifer near Brunswick, Georgia, the following sources were analyzed for C 14 and deuterium concentrations: potable water from the Ocala Limestone, contaminated water from the Ocala Limestone, saune water from the underlying Claiborne Group, and nearby ocean water. The chloride concentration of the groundwater ranges from about 25 ppm in the potable water to more than 2000 ppm in the deeper part of the Claiborne Group. From an interpretation of piezometric maps and other hydrologic data, previous investigators had concluded that the source of the contaminating water was the Claiborne Group and not the nearby ocean. The essentially uniform range of low values of −965 to −987‰ of the modern standard (National Bureau Standard C 14 oxalic acid) for the C 14 activity of the groundwater samples (regardless of the degree of contamination) is in agreement with this conclusion. If recent ocean water, which had a C 14 value of +285‰, were the source of contamination, the contaminated water would have had a C 14 activity higher than the activity of the fresh water. Deuterium analyses are not inconsistent with the interpretation that water from the Claiborne Group, rather than recent ocean water, is the source of the contaminating water. The concurrence of the hydrologic and the isotopic data in this area where the hydrology is well known suggests that isotopic analysis may be used to identify the origin of water in different portions of a hydrologic environment.

Georgia↗
USGS2022

Hydrologic conditions in Kansas, water year 2021

The U.S. Geological Survey maintains a network of hydrologic monitoring stations across Kansas in cooperation with Federal, State, Tribal, and local agencies. During water year 2021, this network included 230 real-time surface water data collection sites, referred to as “streamgages.” A water year is the 12-month period from October 1 through September 30 and is designated by the calendar year in which it ends. These real-time data are routinely collected and calibrated by U.S. Geological Survey personnel via regular measurements of streamflow and water levels. Analyses of these data provide an understanding of hydrologic conditions in the State critical to the management of water resources, industrial and agricultural uses, protection of life and property during flooding, operation of reservoirs, recreation, and other activities.

Kansas↗
USGS2005

Baseline water-quality characteristics of the Alaska Army National Guard Stewart River Training Area near Nome, Alaska

The Alaska Army National Guard Stewart River Training Area is approximately 23 miles north of Nome on the Seward Peninsula in northwest Alaska. The Stewart River Training Area encompasses much of the Stewart River Basin and a small part of the Snake River Basin. Hydrologic, water-quality, and physical-habitat data were collected at seven surface-water sites within the Stewart River Training Area during the summer runoff months (late-May to early-September) in 2004. Two of the sampling sites selected for this study were on the main stem Stewart River, one at the upstream boundary and one at the downstream boundary of the training area. Continuous hydrologic, precipitation, and water temperature data were collected at these two sites throughout the summer of 2004. Three pond sites, along the upper, middle, and lower reaches of the Stewart River within the training area, were each sampled twice during the summer of 2004 for analysis of water-quality constituents. Two tributaries to the Snake River Basin, Goldbottom Creek and North Fork Snake River, within the Stewart River Training Area boundary, also were sampled twice during the summer of 2004. Water-quality data collected from the Stewart River at the upstream and downstream study sites indicate similar constituent concentrations. Concentrations of most water-quality constituents collected during the summer of 2004 did not exceed standards for drinking water or recreational contact. Analysis of trace-element concentrations in bed sediment samples indicate the threshold effect concentration (below which no adverse effects on organisms is expected) was exceeded for arsenic, chromium, and nickel concentrations at all sample sites within the Stewart River Training Area and cadmium, copper, zinc, and lead concentrations were found to exceed the threshold effect concentration in varying degrees at the sample sites. The probable effect concentration (above which toxic effects on organisms is likely) was exceeded by arsenic concentrations at all sites except the lower pond site. Chromium and nickel concentrations exceeded the probable effect concentration at the upstream Stewart River site and at the North Fork Snake River site.

Scientific Investigations Report↗
USGS2014

Africa-wide monitoring of small surface water bodies using multisource satellite data: A monitoring system for FEWS NET

Continental Africa has the highest volume of water stored in wetlands, large lakes, reservoirs, and rivers, yet it suffers from problems such as water availability and access. With climate change intensifying the hydrologic cycle and altering the distribution and frequency of rainfall, the problem of water availability and access will increase further. Famine Early Warning Systems Network (FEWS NET) funded by the United States Agency for International Development (USAID) has initiated a large-scale project to monitor small to medium surface water points in Africa. Under this project, multisource satellite data and hydrologic modeling techniques are integrated to monitor several hundreds of small to medium surface water points in Africa. This approach has been already tested to operationally monitor 41 water points in East Africa. The validation of modeled scaled depths with field-installed gauge data demonstrated the ability of the model to capture both the spatial patterns and seasonal variations. Modeled scaled estimates captured up to 60 % of the observed gauge variability with a mean root-mean-square error (RMSE) of 22 %. The data on relative water level, precipitation, and evapotranspiration (ETo) for water points in East and West Africa were modeled since 1998 and current information is being made available in near-real time. This chapter presents the approach, results from the East African study, and the first phase of expansion activities in the West Africa region. The water point monitoring network will be further expanded to cover much of sub-Saharan Africa. The goal of this study is to provide timely information on the water availability that would support already established FEWS NET activities in Africa. This chapter also presents the potential improvements in modeling approach to be implemented during future expansion in Africa.

Book chapter↗
USGS1989

Streamflow and water-quality data for Meadow Run basin, Fayette County, Pennsylvania, December 1987 - November 1988

Streamflow and water-quality data were collected throughout the Meadow Run basin, Fayette County, Pennsylvania, from December 7, 1987 through November 15, 1988, to determine the prevailing quality of surface water over a range of hydrologic conditions. This data will assist the Pennsylvania Department of Environmental Resources during its review of coal-mine permit applications. A water-quality station near the mouth of Meadow Run provided continuous-record of stream stage, pH, specific conductance, and water temperature. Monthly water-quality samples collected at this station were analyzed for total and dissolved metals, nutrients, major cations and anions, and suspended-sediment concentrations. Fourteen partial-record sites, located throughout the basin, were similarly sampled four times during the study. Streamflow and water-quality data obtained at these sites during a winter base flow, a spring rainfall event, a summer rainfall event, and a low summer base flow also are presented.

Open-File Report↗
USGS1968

Hydrologic and climatologic data, 1967, Salt Lake County, Utah

An investigation of the water resources of Salt Lake County, Utah, was undertaken by the Water Resources Division of the U.S. Geological Survey in July 1963. This investigation is a cooperative project financed chiefly by equal contributions of the State of Utah and the Federal Government in accordance with an agreement between the Division of Water Rights, Utah Department of Natural Resources, and the Geological Survey. The investigation was financed during the period covered by this report by the following organizations: Utah Division of Water Rights (formerly State Engineer), Utah Division of Water Resources (formerly Water and Power Board), Salt Lake County, Salt Lake County Water Conservancy District, Central Utah Water Conservancy District, Metropolitan Water District of Salt Lake City, City of Murray, Granger-Hunter Improvement District, Taylorsville-Bennion Improvement District, Holladay Water Company, Magna Water and Sewer District, U.S. Bureau of Reclamation, U.S. Geological Survey. The investigation encompasses the collection and interpretation of a large variety of climatologic, hydrologic, and geologic data in and near Salt Lake County. Utah Basic-Data Releases 11-13 contain data collected through 1966. This release contains climatologic and surfacewater data for the 1967 water year (October 1966 to September 1967) and ground-water data collected during the 1967 calendar year. A similar annual release will contain data collected during the remainder of the investigation, and interpretive reports will be prepared as the investigation proceeds. Organizations that furnished data are acknowledged in station descriptions and footnotes to tables.

Utah↗
USGS1969

Hydrologic and climatologic data, 1968, Salt Lake County, Utah

An investigation of the water resources of Salt Lake County, Utah, was undertaken by the Water Resources Division of the U.S. Geological Survey in July 1963. This investigation is a cooperative project financed chiefly by equal contributions of the State of Utah and the Federal Government in accordance with an agreement between the Division of Water Rights, Utah Department of Natural Resources, and the Geological Survey. The investigation was financed during the period covered by this report by the following organizations: Utah Division of Water Rights (formerly State Engineer), Utah Division of Water Resources (formerly Water and Power Board), Salt Lake County, Salt Lake County Water Conservancy District, Central Utah Water Conservancy District, Metropolitan Water District of Salt Lake City, City of Murray, Granger-Hunter Improvement District, Taylorsville-Bennion Improvement District, Holladay Water Company, Magna Water and Sewer District, U.S. Bureau of Reclamation, U.S. Geological Survey The investigation encompasses the collection and interpretation of a large variety of climatologic, hydrologic, and geologic data in and near Salt Lake County. Utah Basic-Data Releases 11-13 and 15 contain data collected through 1967. This release contains climatologic and surface-water data for the 1968 water year (October 1967 to September 1968) and ground-water data collected during the 1968 calendar year. This is the final annual release of basic data for this investigation. Interpretive reports summarizing the results are in preparation. Organizations that furnished data are acknowledged in station descriptions and footnotes to tables.

Utah↗
USGS1993

Water resources activities of the USGS, 1992

The Water Resources Division (WRD) of the U.S. Geological Survey has the principal responsibility within the Federal Government for providing hydrologic information and appraising the Nation's water resources. The USGS is unique among government organizations because it has neither regulatory nor developmental authority. Information that is made available equally to all interested parties is the sole product of the WRD. The mission, organization, source of funds, and major programs of the WRD are discussed in this report. Three types of programs are described: long-term programs, topical programs, and support programs. Emphasis is on programs that will contribute to identifying, mitigating, or solving nationwide water-resources problems in the remaining years of the 20th century. Completing the report are discussions of how the hydrologic data and information are disseminated and an index. The report describes the water-resources mission of the WRD and discusses the organization and principal sources of funds that support the activities conducted to meet this mission. Descriptions are given of the most significant water-resources activities, how the hydrologic data and information are disseminated is discussed. Each description of a significant water-resources activity has the following parts: 'Introduction', 'Activities', 'Recent Accomplishments' and 'Funding'. (USGS)

Open-File Report↗
USGS2011

U.S. Geological Survey Community for Data Integration-NWIS Web Services Snapshot Tool for ArcGIS

U.S. Geological Survey (USGS) data resources are so vast that many scientists are unaware of data holdings that may be directly relevant to their research. Data are also difficult to access and large corporate databases, such as the National Water Information System (NWIS) that houses hydrologic data for the Nation, are challenging to use without considerable expertise and investment of time. The USGS Community for Data Integration (CDI) was established in 2009 to address data and information management issues affecting the proficiency of earth science research. A CDI workshop convened in 2009 identified common data integration needs of USGS scientists and targeted high value opportunities that might address these needs by leveraging existing projects in USGS science centers, in-kind contributions, and supplemental funding. To implement this strategy, CDI sponsored a software development project in 2010 to facilitate access and use of NWIS data with ArcGIS, a widely used Geographic Information System. The resulting software product, the NWIS Web Services Snapshot Tool for ArcGIS, is presented here.

Fact Sheet↗
USGS1994

Water-resources activities of the U.S. Geological Survey in New Mexico, fiscal year 1992

Awareness of our environment in general, and water resources in particular, has brought increased interest in and support of hydrologic data collection and research. The quantity, quality, and distribution of water are extremely important to the future well-being of New Mexico. The State's surface-water resources are minimal and highly variable due to climate and to regulation and diversion; ground-water resources are subject to development that exceeds natural recharge and to potential contamination by land use. Issues related to global climate change, disposal of hazardous wastes, toxic substances in water, water rights, and ground-water contamination are evolving areas of greater public concern. At the same time there is a continuing need for a better understanding of various hydrologic systems and processes in order to manage these limited water resources for maximum benefit to present and future generations. The U.S. Geological Survey has collected and disseminated information on the water resources of New Mexico for more than a century. The Survey began to collect records of streamflow in New Mexico in December 1888 when the first discharge measurements were made on the Rio Grande near the present gaging station at Embudo. This site, called the "birthplace of systematic stream gaging," was chosen to be the training center for the first hydrographers of the Irrigation Survey, a bureau within the original Geological Survey. Since that time, in cooperation with Federal, State, local, and tribal agencies, we have monitored streams at hundreds of sites throughout the State and have a current network of more than 200 streamflow-gaging stations. Through the Cooperative Program, we also have established sites where ground-water levels are monitored to document changes in ground-water storage or where surface-water and groundwater samples are collected to determine water chemistry, and we have undertaken investigative studies to define the availability, quality, and distribution of water resources. Information from the data program and results of investigative studies are made available to water-resources managers, regulators, and the public to be used for the effective management of the State's water resources. This report provides a brief summary of the activities of the New Mexico District for FY (fiscal year) 1992, including our mission, organization, sources of funding, and descriptions of current projects. This report serves to document not only the content of the program, but also the diversity and complexity of that program. Cooperation among water-resources agencies will be essential in effectively dealing with water-related issues facing New Mexico. We look forward to the challenge of addressing these issues by continuing to provide factual hydrologic data and technically sound areal appraisals and interpretive studies.

New Mexico↗
USGS2014

Simulation of the effects of rainfall and groundwater use on historical lake water levels, groundwater levels, and spring flows in central Florida

The urbanization of central Florida has progressed substantially in recent decades, and the total population in Lake, Orange, Osceola, Polk, and Seminole Counties more than quadrupled from 1960 to 2010. The Floridan aquifer system is the primary source of water for potable, industrial, and agricultural purposes in central Florida. Despite increases in groundwater withdrawals to meet the demand of population growth, recharge derived by infiltration of rainfall in the well-drained karst terrain of central Florida is the largest component of the long-term water balance of the Floridan aquifer system. To complement existing physics-based groundwater flow models, artificial neural networks and other data-mining techniques were used to simulate historical lake water level, groundwater level, and spring flow at sites throughout the area. Historical data were examined using descriptive statistics, cluster analysis, and other exploratory analysis techniques to assess their suitability for more intensive data-mining analysis. Linear trend analyses of meteorological data collected by the National Oceanic and Atmospheric Administration at 21 sites indicate 67 percent of sites exhibited upward trends in air temperature over at least a 45-year period of record, whereas 76 percent exhibited downward trends in rainfall over at least a 95-year period of record. Likewise, linear trend analyses of hydrologic response data, which have varied periods of record ranging in length from 10 to 79 years, indicate that water levels in lakes (307 sites) were about evenly split between upward and downward trends, whereas water levels in 69 percent of wells (out of 455 sites) and flows in 68 percent of springs (out of 19 sites) exhibited downward trends. Total groundwater use in the study area increased from about 250 million gallons per day (Mgal/d) in 1958 to about 590 Mgal/d in 1980 and remained relatively stable from 1981 to 2008, with a minimum of 559 Mgal/d in 1994 and a maximum of 773 Mgal/d in 2000. The change in groundwater-use trend in the early 1980s and the following period of relatively slight trend is attributable to the concomitant effects of increasing public-supply withdrawals and decreasing use of water by the phosphate industry and agriculture. On the basis of available historical data and exploratory analyses, empirical lake water-level, groundwater-level, and spring-flow models were developed for 22 lakes, 23 wells, and 6 springs. Input time series consisting of various frequencies and frequency-band components of daily rainfall (1942 to 2008) and monthly total groundwater use (1957 to 2008) resulted in hybrid signal-decomposition artificial neural network models. The final models explained much of the variability in observed hydrologic data, with 43 of the 51 sites having coefficients of determination exceeding 0.6, and the models matched the magnitude of the observed data reasonably well, such that models for 32 of the 51 sites had root-mean-square errors less than 10 percent of the measured range of the data. The Central Florida Artificial Neural Network Decision Support System was developed to integrate historical databases and the 102 site-specific artificial neural network models, model controls, and model output into a spreadsheet application with a graphical user interface that allows the user to simulate scenarios of interest. Overall, the data-mining analyses indicate that the Floridan aquifer system in central Florida is a highly conductive, dynamic, open system that is strongly influenced by external forcing. The most important external forcing appears to be rainfall, which explains much of the multiyear cyclic variability and long-term downward trends observed in lake water levels, groundwater levels, and spring flows. For most sites, groundwater use explains less of the observed variability in water levels and flows than rainfall. Relative groundwater-use impacts are greater during droughts, however, and long-term trends in water levels and flows were identified that are consistent with historical groundwater-use patterns. The sensitivity of the hydrologic system to rainfall is expected, owing to the well-drained karst terrain and relatively thin confinement of the Floridan aquifer system in much of central Florida. These characteristics facilitate the relatively rapid transmission of infiltrating water from rainfall to the water table and contribute to downward leakage of water to the Floridan aquifer system. The areally distributed nature of rainfall, as opposed to the site-specific nature of groundwater use, and the generally high transmissivity and low storativity properties of the semiconfined Floridan aquifer system contribute to the prevalence of water-level and flow patterns that mimic rainfall patterns. In general, the data-mining analyses demonstrate that the hydrologic system in central Florida is affected by groundwater use differently during wet periods, when little or no system storage is available (high water levels), compared to dry periods, when there is excess system storage (low water levels). Thus, by driving the overall behavior of the system, rainfall indirectly influences the degree to which groundwater use will effect persistent trends in water levels and flows, with groundwater-use impacts more prevalent during periods of low water levels and spring flows caused by low rainfall and less prevalent during periods of high water levels and spring flows caused by high rainfall. Differences in the magnitudes of rainfall and groundwater use during wet and dry periods also are important determinants of hydrologic response. An important implication of the data-mining analyses is that rainfall variability at subannual to multidecadal timescales must be considered in combination with groundwater use to provide robust system-response predictions that enhance sustainable resource management in an open karst aquifer system. The data-driven approach was limited, however, by the confounding effects of correlation between rainfall and groundwater use, the quality and completeness of the historical databases, and the spatial variations in groundwater use. The data-mining analyses indicate that available historical data when used alone do not contain sufficient information to definitively quantify the related individual effects of rainfall and groundwater use on hydrologic response. The knowledge gained from data-driven modeling and the results from physics-based modeling, when compared and used in combination, can yield a more comprehensive assessment and a more robust understanding of the hydrologic system than either of the approaches used separately.

Florida↗