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At least 595 records · Page 33Linked to original sources
USGS2010

Potentiometric Surface of the Upper Floridan Aquifer, West-central Florida, May 2010

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2010. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when groundwater levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 55.21 inches for west-central Florida (from June 2009 through May 2010) was 2.55 inches above the historical cumulative average of 52.66 inches (Southwest Florida Water Management District, 2010). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 17-21, 2010. Supplemental water-level data were collected by other agencies and companies. Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

Scientific Investigations Map↗
USGS2019

Basin, climatic, and irrigation factors associated with median summer water yields for streams in Southwestern Michigan, 1945-2015

Median summer water yields and resultant flows for streams are used in Michigan to regulate large water withdrawals to help prevent negative effects on characteristic fish populations. Large water withdrawals commonly are associated with irrigation in rural areas. In an earlier statewide report, an index-flow statistic for the period of record, defined as the median flow during the summer month of lowest flow, was used to characterize median summer flows and associated water yields. In this report, the annual series of median summer water yields for the period July 1 through September 30 within the period of record is used to characterize median summer water yields. For 27 streamgages included in both reports, the average index water yield was at the 37th percentile of the distribution of median summer water yields. In contrast to an index statistic, an annual time series provides a basis for detecting trends in median summer water yields and for determining basin, climatic, and irrigation factors affecting spatial and temporal variations in summer water yields. Daily flow data from 40 selected U.S. Geological Survey streamgages in southwestern Michigan were used in this analysis. Two mixed models were identified to estimate median summer water yields based on fixed basin characteristics and temporally varying climatic factors for 1945–2015. No irrigation data were available prior to 1970, so no irrigation variables were included in the mixed models for 1945–2015. Then, two mixed models were developed for 1970–2015, a period in which a partial annual series of county-level irrigation data also were available. One of the 1970–2015 mixed models provides a basis for estimating median summer water yields at sites in southwestern Michigan using an estimated trend component, and selected basin, climatic, and irrigation factors. Re-estimation of model parameters in this mixed model with more spatially precise information on irrigation withdrawals may improve model accuracy.

Michigan↗
USGS2014

Estimated 2012 groundwater potentiometric surface and drawdown from predevelopment to 2012 in the Santa Fe Group aquifer system in the Albuquerque metropolitan area, central New Mexico

Historically, the water-supply requirements of the Albuquerque metropolitan area of central New Mexico were met almost exclusively by groundwater withdrawal from the Santa Fe Group aquifer system. In response to water-level declines, the Albuquerque Bernalillo County Water Utility Authority (ABCWUA) began diverting water from the San Juan-Chama Drinking Water Project in December 2008 to reduce the use of groundwater to meet municipal demand. Modifications in the demand for water and the source of the supply of water for the Albuquerque metropolitan area have resulted in a variable response in the potentiometric surface of the production zone (the interval of the aquifer, from within about 200 feet below the water table to 900 feet or more, in which supply wells generally are screened) of the Santa Fe Group aquifer system. Analysis of the magnitude and spatial distribution of water-level change can help improve the understanding of how the groundwater system responds to withdrawals and variations in the management of the water supply and can support water-management agencies’ efforts to minimize future water-level declines and improve sustainability. The U.S. Geological Survey (USGS), in cooperation with the ABCWUA, has developed an estimate of the 2012 potentiometric surface of the production zone of the Santa Fe Group aquifer system in the Albuquerque metropolitan area. This potentiometric surface is the latest in a series of reports depicting the potentiometric surface of the area. This report presents the estimated potentiometric surface during winter (from December to March) of water year 2012 and the estimated changes in potentiometric surface between predevelopment (pre-1961) and water year 2012 for the production zone of the Santa Fe Group aquifer system in the Albuquerque metropolitan area. Hydrographs from selected piezometers are included to provide details of historical water-level changes. In general, water-level measurements used for this report were collected in small-diameter observation wells screened over short intervals near the middle of the production zone and were considered to best represent the potentiometric head in the production zone. The water-level measurements were collected by various local and Federal agencies. The water year 2012 potentiometric surface map was created in a geographic information system, and the change in water-level altitude from predevelopment to water year 2012 was calculated. The 2012 potentiometric surface indicates that the general direction of groundwater flow is from the Rio Grande towards clusters of supply wells in the east, north, and west. Water-level changes from predevelopment to 2012 were variable across the Albuquerque metropolitan area. Estimated drawdown from 2008 was spatially variable across the Albuquerque metropolitan area. Hydrographs from piezometers on the east side of the river indicate an increase in the annual highest water-level measurement from 2008 to 2012. Hydrographs from piezometers in the northwest part of the study area indicate either steady decline of the water-level altitude over the period of record or recently variable trends in which water-level altitudes increased for a number of years but have declined since water year 2012.

New Mexico↗
USGS2005

Base flow in the Great Lakes Basin

Hydrograph separations were performed using the PART, HYSEP 1, 2, and 3, BFLOW and UKIH methods on 104,293 years of daily streamflow records from 3,936 streamflow-gaging stations in Ontario, Canada and the eight Great Lakes States of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, and Wisconsin to estimate base-flow index (BFI) and base flow. BFI ranged an average of 0.24 BFI depending on which hydrograph-separation method was used. BFI data from 959 selected streamflow-gaging stations with a combined 28,784 years of daily streamflow data were used to relate BFI to surficial geology and the proportion of surface water within the gaged watersheds. This relation was then used to derive estimates of BFI throughout the Great Lakes, Ottawa River, and upper St. Lawrence River Basins at a scale of 8-digit hydrologic unit code (HUC) watersheds for the U.S. and tertiary watersheds in Canada. This process was repeated for each of the six hydrograph-separation methods used. When applied to gaged watersheds, model results predicted observed base flow within 0.2 BFI up to 94 percent of the time. Estimates of long-term (length of streamflow record) average annual streamflow in each HUC and tertiary watershed were calculated and used to determine average annual base flow from BFI estimates. Possibilities for future study based on results from this study include long-term trend analysis of base flow and improving the scale at which base-flow estimates can be made.

Great Lakes Basin↗
USGS2006

Ground-water hydrology and water quality of the Southern High Plains Aquifer, Cannon Air Force Base, Curry County, New Mexico, 1994-2005

In cooperation with the U.S. Air Force, the U.S. Geological Survey has collected hydrologic data about the Southern High Plains aquifer at Cannon Air Force Base in east-central New Mexico since 1994. Under the guidance of the State of New Mexico, ground-water quality of the aquifer has been analyzed as part of annual monitoring at regulated sites at the base. This report provides a summary and interpretation of all available hydrologic data collected by the U.S. Geological Survey for Cannon Air Force Base environmental managers for the regulated sites of Landfill 5 and the Sewage Lagoons between 1994 and 2005.

New Mexico↗
USGS2009

Detection of conveyance changes in St. Clair River using historical water-level and flow data with inverse one-dimensional hydrodynamic modeling

St. Clair River is a connecting channel that transports water from Lake Huron to the St. Clair River Delta and Lake St. Clair. A negative trend has been detected in differences between water levels on Lake Huron and Lake St. Clair. This trend may indicate a combination of flow and conveyance changes within St. Clair River. To identify where conveyance change may be taking place, eight water-level gaging stations along St. Clair River were selected to delimit seven reaches. Positive trends in water-level fall were detected in two reaches, and negative trends were detected in two other reaches. The presence of both positive and negative trends in water-level fall indicates that changes in conveyance are likely occurring among some reaches because all reaches transmit essentially the same flow. Annual water-level fall in reaches and reach lengths was used to compute conveyance ratios for all pairs of reaches by use of water-level data from 1962 to 2007. Positive and negative trends in conveyance ratios indicate that relative conveyance is changing among some reaches. Inverse one-dimensional (1-D) hydrodynamic modeling was used to estimate a partial annual series of effective channel-roughness parameters in reaches forming the St. Clair River for 21 years when flow measurements were sufficient to support parameter estimation. Monotonic, persistent but non-monotonic, and irregular changes in estimated effective channel roughness with time were interpreted as systematic changes in conveyances in five reaches. Time-varying parameter estimates were used to simulate flow throughout the St. Clair River and compute changes in conveyance with time. Based on the partial annual series of parameters, conveyance in the St. Clair River increased about 10 percent from 1962 to 2002. Conveyance decreased, however, about 4.1 percent from 2003 to 2007, so that conveyance was about 5.9 percent higher in 2007 than in 1962.

St. Clair River↗
USGS1978

Fluvial sediment study of Fishtrap and Dewey Lakes drainage basins, Kentucky-Virginia

Fourteen drainage basins above Fishtrap and Dewey Lakes in the Levisa Fork and Johns Creek drainage basins of eastern Kentucky and southwestern Virginia were studied to determine sedimentation rates and origin of sediment entering the two lakes. The basins ranged in size from 1.68 to 297 square miles. Sediment yields ranged from 2,890 to 21,000 tons per square mile where surface-mining techniques predominated, and from 732 to 3 ,470 tons per square mile where underground mining methods predominated. Yields, in terms of tons per acre-foot of runoff, ranged from 2.2 to 15 for surface-mined areas, and from 0.5 to 2.7 for underground-mined areas. Water and sediment discharges from direct runoff during storms were compared for selected surface-mined and underground-mined areas. Data points of two extensively surface-mined areas, one from the current project and one from a previous project in Beaver Creek basin, McCreary County, Kentucky, grouped similarly in magnitude and by season. Disturbed areas from mining activities determined from aerial photographs reached 17 percent in one study area where extensive surface mining was being practiced. For most areas where underground mining was practiced, percentage disturbed area was almost negligible. Trap efficiency of Fishtrap Lake was 89 percent, and was 62 percent for Dewey Lake. Average annual deposition rates were 464 and 146 acre-feet for Fishtrap and Dewey Lakes, respectively. The chemical quality of water in the Levisa Fork basin has been altered by man 's activities.

Kentucky, Virginia↗
USGS1984

Simulated effects of an artificial-recharge experiment near Proctor, Logan County, Colorado

An artificial-recharge experiment was conducted near Proctor, Colorado in which a computed 620 acre-feet were pumped from a well during a 4-month period. A computed 420 acre-feet were delivered at the potential reservoir site, and the remaining 200 acre-feet leaked from the pipeline. No pond was created due to the high rates of infiltration. Water levels in the nearest well (about 0.1 mile from the recharge site) rose almost 25 feet. Computer simulations indicate that this 4-month pumping-recharge experiment would cause stream depletions from the nearby South Platte River for the first 16 months, thereafter, stream accretions due to the recharge would exceed stream depletions due to pumpage. If the experiment was conducted annually, the simulations indicate that stream depletions would occur for 6 months of each year and stream acretions for the remaining 6 months once the system reached an equilibrium condition. To reach the cyclic equilibrium condition would take at least 7 years. (USGS)

Water-Resources Investigations Report↗
USGS1986

Hydrogeology of the surficial and intermediate aquifers of central Sarasota County, Florida

The geohydrologic units underlying a 300 sq mi area in central Sarasota County, Florida, consist of the surficial aquifer, intermediate aquifers (Tamiami-upper Hawthorn and lower Hawthorn-upper Tampa aquifers) and confining units, the Floridan aquifer system, and the sub-Floridan confining unit. The saturated thickness of the surficial aquifer ranges from about 40 to 75 ft and the water table is generally within 5 ft of land surface. The Tamiami-upper Hawthorn is the uppermost intermediate aquifer. The top of the aquifer ranges from about 50 ft to about 75 below sea level and has an average thickness of about 100 ft. The lower Hawthorne-upper Tampa aquifer is the lowermost intermediate aquifer. The top of the aquifer ranges from about 190 to about 220 ft below sea level and its thickness ranges from about 200 to 250 ft. The quality of water in the surficial and the two intermediate aquifers is acceptable for potable use except near the coast. Water from the Floridan aquifer system is used primarily for agricultural purposes because it is too mineralized for most other uses; therefore, the surficial and intermediate aquifers are developed for water supply. The artesian pressure of the various aquifers generally increases with depth. A more detailed geohydrologic description is presented for the Ringling-MacArthur Reserve, a 51 sq mi area in the central part of the county that may be used by Sarasota County as a future water supply. Average annual rainfall is 56 inches and evapotranspiration is about 42 in at the Reserve. The area has a high water table, many sloughs and swamps, and undeveloped land, making it an attractive site as a potential source of water.

Florida↗
USGS1996

Low-flow characteristics of Florida streams

Knowledge of the low-flow characteristics of Florida streams and rivers is essential in planning for the availability of adequate quantities of water for commercial- and public-water supply, agricultural irrigation, artificial recharge, and the dilution of waste discharge. This report provides low-flow characteristics for 216 continuous-record gaging stations using frequency analysis techniques. Included are low-flow frequency characteristics for 143 unregulated, gaging stations; and sample percentiles for 32 stations that were subject to regulation or diversion, and sample percentiles for 41 stations, regulated and unregulated, that exhibited significant trends in the annual low-flow time series. Estimates of low-flow frequency characteristics are provided for 242 partial-record stations and miscellaneous sites based on correlations with daily mean discharges at continuous-record stations. Low-flow measurement data are available at approximately 1,300 continuous-record gaging stations, partial- record stations and miscellaneous sites. Historic low-flow measurement data are accessible through the U.S. Geological Survey Automatic Data Processing System.

Florida↗
USGS2025

Fisheries research and monitoring activities of the Lake Erie Biological Station, 2024

A comprehensive understanding of fish populations and their interactions is the cornerstone of modern fishery management and the basis for Lake Erie’s Fish Community Objectives (FCOs) developed in 2020 (Francis et al. 2020). The 2024 U.S. Geological Survey (USGS) Lake Erie Biological Station Annual Report is responsive to these FCOs and the USGS obligations via a Memorandum of Understanding (MOU 2017) with the Great Lakes Fishery Commission (GLFC) Council of Lake Committees (CLC) to provide scientific information in support of fishery management. Goals for the USGS Great Lakes Deepwater Fish Assessment and Ecological Studies were to monitor long-term changes in the fish community and track population dynamics of key fishes of interest to management agencies. Specific to Lake Erie, expectations were sustained investigations of native percids, prey fish populations, and Lake Trout. All work was conducted as part of the Deepwater Science Program under the authority of the Great Lakes Fishery Research Authorization Act of 2019 (16 USC §941h). The USGS 2024 Deepwater Science Program fieldwork began in Lake Erie in March and concluded in December, using trawl, gill net, hydroacoustic, lower trophic sampling devices, and telemetry methods. This work resulted in 44 bottom trawls covering 41 ha of lake bottom and catching 48,936 fish totaling 995 kg in the West Basin of Lake Erie, with detailed results described below. Overnight gill net sets (n=25) for coldwater species were performed in the East Basin of Lake Erie. A total of 8 km of gillnet was deployed during these surveys, which caught 106 fish, 92 of which were native coldwater species: Lake Trout, Burbot, and Lake Whitefish. Results from coldwater species assessments will be reported in the Coldwater Task Group report to the GLFC and the CLC (CTG 2025). These reports are used to inform Lake Trout stocking decisions and direct lamprey control measures (16 USC §939a). USGS hydroacoustic sampling included twenty-six 5-km transects (130 km total) in the Central Basin as part of a collaborative lake-wide survey with details and results reported by the Forage Task Group (FTG 2025). Lower trophic sampling provided data from zooplankton samples (n=12) and water quality profiles (n=12) to populate a database maintained by the Michigan Department of Natural Resources (MDNR), Ontario Ministry of Natural Resources (OMNR), Ohio Department of Natural Resources (ODNR), Pennsylvania Fish and Boat Commission (PFBC), and New York State Department of Environmental Conservation (NYSDEC). USGS also assisted CLC member agencies with deployment and maintenance of Great Lakes Acoustic Telemetry Observation System (GLATOS) infrastructure throughout all three Lake Erie basins and tributaries, supporting multiple coordinated telemetry investigations. This report presents biomass-based summaries of fish communities in western Lake Erie derived from USGS bottom trawl surveys conducted from 2013 to 2024 during June and September. The survey design compliments the August ODNR- OMNRF effort by reinforcing stock assessments with more robust data. Analyses herein evaluated trends in total biomass, abundance of dominant predator and forage species, non-native species composition, biodiversity, and community structure. Data from this effort are accessible for download (Keretz et al. 2025)

Lake Erie↗
USGS1982

Magnitude and frequency of floods from selected drainage basins in South Dakota

The 2-, 5-, 10-, 25-, 50-, and 100-year floods are determined for gaged sites on 120 selected, small drainage basins in South Dakota. These estimates are from the frequency curves defined from the streamflow records. Short-term records for 66 sites were extended on the basis of long-term climatic records and a rainfall-runoff model. These frequency curves may provide the best estimates of floods at these gaged sites. Analyses of flood-frequency information from these gaged sites have been the basis for techniques (published previously) used in estimating flood magnitude and frequency at ungaged sites in South Dakota. This report supplements flood-frequency information published earlier. It presents: Annual peak discharges colected during a 25-year period at 124 crest-stage partial-record stations; maximum observed and unit discharges determined for 124 crest-stage and 120 continuous-record gaging stations; updated flood-frequency curves for 120 crest-stage gages; a documentation of analytical procedures used; and a summary of the small-streams flood-peak data collection program in the State from 1955 to 1981. Maximum flood peaks determined at 244 partial- and continuous-record gaging stations and at 52 miscellaneous sites are compared with regional flood relationships.

South Dakota↗
USGS2025

Summer snow determines the depth to ice-cemented ground under dry permafrost in Antarctica

Dry permafrost underlain by ice-cemented permafrost has been reported in several locations in Antarctica. Initially thought to be relic ice, it is now understood that this subsurface ice is in equilibrium with the surface conditions, although it is not in equilibrium with the atmosphere. We use year-round data from University Valley in the Dry Valleys and Elephant Head in the Ellsworth Mountains to investigate the seasonal variations in water vapour flux that control the depth to the ice table under dry permafrost. Our analysis shows that the mean annual water vapour density of the soil surface exceeds the atmospheric value by a factor of up to ~2 due to summer snow. The attenuation and phase shift of the annual temperature cycle with depth result in colder temperatures at the ice table than at the surface of the soil in summer. We conclude that this temperature gradient, combined with the summer snow, provides the flux of water to the ice table necessary to maintain the ice. In University Valley, reducing the snow days by 40% moves the stability depth of the ice table from 42 to 66 cm. Increasing the snow days by 60% shifts the ice table to 17 cm. These variations can explain the observed gradient in the depth to the ice table in University Valley.

Antarctic Science↗
USGS1964

Hydrology and hydrogeology of Navajo Lake, Kane County, Utah

Navajo Lake, whose entire outflow disappears underground, is on the high Markagurit Plateau where the average annual precipitation is more than 30 inches. It nestles among the headwaters of several streams that flow into arid regions where competition for municipal, industrial, and irrigation water sup- plies is very keen. Several proposals for additional development and use of the water of Navajo Lake have led to controversies and raised questions in regard to the total water supply and its disposition, and to the effect of the proposed projects on existing water rights. This report summarizes the results of an investigation of the water supply of Navajo Lake and the present disposition of that supply.

Utah↗
USGS2011

Potentiometric surface of the upper Floridan aquifer, west-central Florida, May 2011

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2011. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when groundwater levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 45.74 inches for west-central Florida (from June 2010 through May 2011) was 6.85 inches below the historical cumulative average of 52.59 inches (Southwest Florida Water Management District, 2011). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September from 1975 through 2010. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 23-27, 2011. Supplemental water-level data were collected by other agencies and companies. Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a "snapshot" of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

Florida↗
USGS2016

United States copper metal and scrap use and trade patterns, 1995‒2014

In 1995, China accounted for 10 percent of world copper consumption. By 2014, China accounted for about 49 percent of world copper consumption. This change has affected global copper and copper scrap prices, the sources of copper supply, and U.S. trade of copper-containing materials. This report considers changes to the copper and copper scrap industries of the United States. For the study period, 1995 through 2014, U.S. refined copper production from all sources (primary and secondary materials) decreased from 2.28 million metric tons (Mt) of copper to 1.05 Mt (a 54 percent decrease). During the same period, U.S. copper scrap net exports increased from 0.203 Mt to 0.737 Mt (a 263 percent increase and a compound annual growth rate of about 7.0 percent per year). Copper and copper scrap prices (in constant 2014 dollars) rose such that 2014 prices were about 48 percent greater than 1995 prices. From 1995 through 2014, Chinese imports of copper scrap from the United States grew from 0.061 Mt to 0.569 Mt (an increase of about 830 percent and a compound annual growth rate of about 12.5 percent per year). In 2011, Chinese imports of U.S. copper scrap peaked at 0.745 Mt of contained copper. In 1995, Chinese imports of U.S. copper scrap accounted for 17 percent of U.S. copper scrap exports. By 2014, Chinese imports accounted for 69 percent of U.S. copper scrap exports (by weight), and Chinese imports of U.S. copper scrap were valued at $1.45 billion.

Scientific Investigations Report↗
USGS1979

Hydrology and water quality in the Nederlo Creek Basin, Wisconsin, before construction of two water-retention structures

The Nederlo Creek basin, in the "Driftless Area" of southwest Wisconsin, is geographically and hydrologically similar to other small basins in the area. Topography is rugged, with approximately 400 feet of relief between the boundary ridge tops and the valley floor. The water-retention structures (a dry floodwater- retention structure and a 43-acre reservoir) are to provide recreation and flood protection for the basin. Streamflow, springflow, precipitation, and groundwater levels were monitored at several sites to describe the hydrologic system. Streamflow is fairly constant at base flow, but rapid changes in discharge occur during periods of snowmelt or heavy rain; recession to base-flow discharge following these events is rapid. Surface runoff is a significant contributor to Streamflow only 10 percent of the time. The mean annual hydrologic budget for water years 1968-72 shows that of the 32.5 inches of precipitation on the basin, 6.4 inches left as runoff and 25.9 inches as evapotranspiration; ground-water storage increased an average of 0.2 inches per year. The water is a hard calcium magnesium bicarbonate type. Concentrations of major constituents in ground water and streams at base flow are similar, but concentrations in the stream generally decrease during periods when surface runoff contributes to Streamflow. Dissolved-oxygen concentrations in the stream are generally lowest during the summer; nighttime lows are generally between 7 and 8 milligrams per liter and daily maximums between 11 and 12.5 milligrams per liter. Diurnal water-temperature fluctuations of several degrees are common in streams during summer; daily maximum water temperatures as high as 26°C have been measured in some areas, but temperatures this high seldom persist for more than 2 hours. Estimates of mean annual total phosphorus and total nitrogen loads during 1967-74 fall within the ranges of 0.02 to 0.07 and 0.4 to 0.8 tons per square mile, respectively; 70 to 80 percent of the total phosphorus and 35 to 55 percent of the total nitrogen are transported during periods when surface runoff contributes to Streamflow. Mean annual suspended-sediment loads during 1968-74 range from 13 to 60 tons per square mile, with 74 to 86 percent of the total transported during periods when surface water contributes to streamflow. These sediment loads are at the low end of the range previously reported for streams in the "Driftless Area".

Wisconsin↗
USGS2012

Groundwater flow and water budget in the surficial and Floridan aquifer systems in east-central Florida

A numerical transient model of the surficial and Floridan aquifer systems in east-central Florida was developed to (1) increase the understanding of water exchanges between the surficial and the Floridan aquifer systems, (2) assess the recharge rates to the surficial aquifer system from infiltration through the unsaturated zone and (3) obtain a simulation tool that could be used by water-resource managers to assess the impact of changes in groundwater withdrawals on spring flows and on the potentiometric surfaces of the hydrogeologic units composing the Floridan aquifer system. The hydrogeology of east-central Florida was evaluated and used to develop and calibrate the groundwater flow model, which simulates the regional fresh groundwater flow system. The U.S. Geological Survey three-dimensional groundwater flow model, MODFLOW-2005, was used to simulate transient groundwater flow in the surficial, intermediate, and Floridan aquifer systems from 1995 to 2006. The East-Central Florida Transient model encompasses an actively simulated area of about 9,000 square miles. Although the model includes surficial processes-rainfall, irrigation, evapotranspiration (ET), runoff, infiltration, lake water levels, and stream water levels and flows-its primary purpose is to characterize and refine the understanding of groundwater flow in the Floridan aquifer system. Model-independent estimates of the partitioning of rainfall into ET, streamflow, and aquifer recharge are provided from a water-budget analysis of the surficial aquifer system. The interaction of the groundwater flow system with the surface environment was simulated using the Green-Ampt infiltration method and the MODFLOW-2005 Unsaturated-Zone Flow, Lake, and Streamflow-Routing Packages. The model is intended to simulate the part of the groundwater system that contains freshwater. The bottom and lateral boundaries of the model were established at the estimated depths where the chloride concentration is 5,000 milligrams per liter in the Floridan aquifer system. Potential flow across the interface represented by this chloride concentration is simulated by the General Head Boundary Package. During 1995 through 2006, there were no major groundwater withdrawals near the freshwater and saline-water interface, making the general head boundary a suitable feature to estimate flow through the interface. The east-central Florida transient model was calibrated using the inverse parameter estimation code, PEST. Steady-state models for 1999 and 2003 were developed to estimate hydraulic conductivity (K) using average annual heads and spring flows as observations. The spatial variation of K was represented using zones of constant values in some layers, and pilot points in other layers. Estimated K values were within one order of magnitude of aquifer performance test data. A simulation of the final two years (2005-2006) of the 12-year model, with the K estimates from the steady-state calibration, was used to guide the estimation of specific yield and specific storage values. The final model yielded head and spring-flow residuals that met the calibration criteria for the 12-year transient simulation. The overall mean residual for heads, defining residual as simulated minus measured value, was -0.04 foot. The overall root-mean square residual for heads was less than 3.6 feet for each year in the 1995 to 2006 simulation period. The overall mean residual for spring flows was -0.3 cubic foot per second. The spatial distribution of head residuals was generally random, with some minor indications of bias. Simulated average ET over the 1995 to 2006 period was 34.47 inches per year, compared to the calculated average ET rate of 36.39 inches per year from the model-independent water-budget analysis. Simulated average net recharge to the surficial aquifer system was 3.58 inches per year, compared with the calculated average of 3.39 inches per year from the model-independent water-budget analysis. Groundwater withdrawals from the Floridan aquifer system averaged about 920 million gallons per day, which is equivalent to about 2 inches per year over the model area and slightly more than half of the simulated average net recharge to the surficial aquifer system over the same period. Annual net simulated recharge rates to the surficial aquifer system were less than the total groundwater withdrawals from the Floridan aquifer system only during the below-average rainfall years of 2000 and 2006.

Florida↗