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Groundwater budgets for the Big Lost River Basin, south-central Idaho, 2000–19

The Big Lost River Basin, located in parts of Butte and Custer Counties in south-central Idaho, supports the communities surrounding the cities of Arco, Leslie, Mackay, and Moore and provides for agricultural resources that depend on a sustainable supply of surface water from the Big Lost River and its tributaries and groundwater from an unconfined aquifer. The aquifer, situated in a structurally controlled intermontane valley, is composed of unconsolidated alluvium, consolidated sedimentary and volcanic rocks, and younger interbedded volcanic rocks. This report presents two separate groundwater budgets for the aquifer, one above and one below Mackay Dam, as well as a combined groundwater budget for the aquifer within the entire Big Lost River Basin. The budgets span a 20-year period (2000–19), characterizing average conditions, a dry year (2014), and a wet year (2017). The groundwater budgets will help address questions regarding the availability of groundwater supply in the Big Lost River Basin and inform future groundwater modeling. The Idaho Geological Survey has prepared the groundwater budgets as part of a larger hydrogeologic investigation completed by the U.S. Geological Survey and the Idaho Geological Survey in cooperation with the Idaho Department of Water Resources during 2018–21. Other reports describe the hydrogeologic framework and several streamflow-measurement events to evaluate gains and losses on the Big Lost River. Collectively, these reports provide an updated characterization of groundwater resources in the Big Lost River Basin which will help address water resources challenges. A groundwater budget is a conceptual and numerical accounting of inflow (recharge) to groundwater and outflow (discharge) from groundwater. The predominant sources of recharge to the aquifer include losing river reaches (33 percent), areal recharge (as precipitation less evapotranspiration and surface runoff, comprising about 23 percent of the total inflow), tributary canyon underflow from higher altitudes (20 percent), canal seepage (13 percent), recharge through applied irrigation on fields below the root zone and other minor sources (11 percent), and Mackay Reservoir seepage (less than 1 percent). The primary sources of discharge from the aquifer are groundwater pumpage to meet irrigation demand, domestic supply, and municipal supply (76 percent) and gaining river reaches (24 percent). The positive or negative difference between the sum of all inflows and outflows is regarded as the residual, representing the change in groundwater storage, groundwater outflow from the basin or subbasins, and uncertainty and errors in the budget. In the Big Lost River Basin, groundwater outflow is at the mouth of the basin below Arco into the eastern Snake River Plain aquifer. The total mean annual estimated recharge to the Big Lost River Basin was 439,100 acre-feet per year (acre-ft/yr; 607 cubic feet per second [ft 3 /s]) for 2000–19, 373,900 acre-ft/yr (516 ft 3 /s) in 2014, and 762,100 acre-ft/yr (1,053 ft 3 /s) in 2017. The mean annual estimated groundwater discharge from the aquifer was about 112,300 acre-ft/yr (155 ft 3 /s) for 2000–19, 153,500 acre-ft/yr (212 ft 3 /s) in 2014, and 53,400 acre-ft/yr (74 ft 3 /s) in 2017. The estimated mean annual groundwater residual was 326,800 acre-ft/yr (451 ft 3 /s) for 2000–19, 220,400 acre-ft/yr (304 ft 3 /s) in 2014, and 708,700 acre-ft/yr (979 ft 3 /s) in 2017. The mean annual residual above Mackay Dam was 100,400 acre-ft/yr (2000-19), 96,700 acre-ft (2014), and 248,300 acre-ft (2017). The mean annual residual contribution below Mackay Dam, minus any groundwater-flow above Mackay Dam, was 226,400 acre-ft/yr (2000-19), 123,700 acre-ft (2014), and 460,400 acre-ft (2017). These results are highly sensitive to assumptions about certain budget inflow parameters. In particular, the magnitude of the budget residuals during especially dry and wet periods is amplified by the groundwater-budget terms tributary streamflow and tributary underflow that contribute appreciable recharge but also have high uncertainty. The results of the groundwater-budget evaluation describe an interconnected and complex hydrologic response throughout the basin to various climatic and water-use trends. The part of the basin above Mackay Dam typically has a positive groundwater residual derived from snowmelt recharge to tributary canyons and areal recharge in excess of groundwater pumpage for irrigation demand. This supply is used to meet irrigation demand above Mackay Dam and to provide for water supply below Mackay Dam. On average, groundwater inflow from above Mackay Dam to below Mackay Dam, assuming negligible reservoir storage effects, accounts for about 25 percent of the total groundwater recharge below Mackay Dam. Considerable recharge to groundwater below Mackay Dam occurs through seepage from the Big Lost River and canals and ditches. Most groundwater discharge from the aquifer is through irrigation pumping. The water supply below Mackay Dam is highly dependent on available upstream surface-water flows, the magnitude of the groundwater residual from above Mackay Dam, and annual variability in local groundwater conditions.

Idaho

Occurrence and distribution of methyl tert-butyl ether and other volatile organic compounds in drinking water in the Northeast and Mid-Atlantic regions of the United States, 1993-98

Data on volatile organic compounds (VOCs) in drinking water supplied by 2,110 randomly selected community water systems (CWSs) in 12 Northeast and Mid-Atlantic States indicate 64 VOC analytes were detected at least once during 1993-98. Selection of the 2,110 CWSs inventoried for this study targeted 20 percent of the 10,479 active CWSs in the region and represented a random subset of the total distribution by State, source of water, and size of system. The data include 21,635 analyses of drinking water collected for compliance monitoring under the Safe Drinking Water Act; the data mostly represent finished drinking water collected at the pointof- entry to, or at more distal locations within, each CWS?s distribution system following any watertreatment processes. VOC detections were more common in drinking water supplied by large systems (serving more than 3,300 people) that tap surface-water sources or both surface- and groundwater sources than in small systems supplied exclusively by ground-water sources. Trihalomethane (THM) compounds, which are potentially formed during the process of disinfecting drinking water with chlorine, were detected in 45 percent of the randomly selected CWSs. Chloroform was the most frequently detected THM, reported in 39 percent of the CWSs. The gasoline additive methyl tert-butyl ether (MTBE) was the most frequently detected VOC in drinking water after the THMs. MTBE was detected in 8.9 percent of the 1,194 randomly selected CWSs that analyzed samples for MTBE at any reporting level, and it was detected in 7.8 percent of the 1,074 CWSs that provided MTBE data at the 1.0-?g/L (microgram per liter) reporting level. As with other VOCs reported in drinking water, most MTBE concentrations were less than 5.0 ?g/L, and less than 1 percent of CWSs reported MTBE concentrations at or above the 20.0-?g/L lower limit recommended by the U.S. Environmental Protection Agency?s Drinking-Water Advisory. The frequency of MTBE detections in drinking water is significantly related to high- MTBE-use patterns. Detections are five times more likely in areas where MTBE is or has been used in gasoline at greater than 5 percent by volume as part of the oxygenated or reformulated (OXY/RFG) fuels program. Detection frequencies of the individual gasoline compounds (benzene, toluene, ethylbenzene, and xylenes (BTEX)) were mostly less than 3 percent of the randomly selected CWSs, but collectively, BTEX compounds were detected in 8.4 percent of CWSs. BTEX concentrations also were low and just three drinkingwater samples contained BTEX at concentrations exceeding 20 ?g/L. Co-occurrence of MTBE and BTEX was rare, and only 0.8 percent of CWSs reported simultaneous detections of MTBE and BTEX compounds. Low concentrations and cooccurrence of MTBE and BTEX indicate most gasoline contaminants in drinking water probably represent nonpoint sources. Solvents were frequently detected in drinking water in the 12-State area. One or more of 27 individual solvent VOCs were detected at any reporting level in 3,080 drinking-water samples from 304 randomly selected CWSs (14 percent) and in 206 CWSs (9.8 percent) at concentrations at or above 1.0 ?g/L. High co-occurrence among solvents probably reflects common sources and the presence of transformation by-products. Other VOCs were relatively rarely detected in drinking water in the 12-State area. Six percent (127) of the 2,110 randomly selected CWSs reported concentrations of 16 VOCs at or above drinking-water criteria. The 127 CWSs collectively serve 2.6 million people. The occurrence of VOCs in drinking water was significantly associated (p<0.0001) with high population- density urban areas. New Jersey, Massachusetts, and Rhode Island, States with substantial urbanization and high population density, had the highest frequency of VOC detections among the 12 States. More than two-thirds of the randomly selected CWSs in New Jersey reported detecting VOC concentrations in drinking water at or above 1

Water-Resources Investigations Report

Hydrogeologic and water-quality reconnaissance of the artesian aquifer under the Shoalwater Bay Indian Reservation and Tokeland Peninsula, Pacific County, Washington, 1998-99

The U.S. Geological Survey (USGS) collected and compiled hydrogeologic and water quality data from September 1998 through September 1999 to describe the hydrogeologic setting and to assess the quality of the water in the artesian aquifer under the Shoalwater Bay Indian Reservation and the adjacent Tokeland Peninsula area of Pacific County, Washington. Hydrogeologic data include descriptions of 38 wells, lithologic data for 27 wells, and water-level data for 17 wells and 1 tidal station. Water-quality data include field measurements for temperature, specific conductance, pH, alkalinity, bicarbonate, carbonate, dissolved oxygen, and laboratory analyses for major inorganic ions, metals, nutrients, methylene blue-active substances, and pesticides. None of the 93 field measurements or chemicals analyzed for exceeded the U.S. Environmental Protection Agency (USEPA) primary standards for drinking water and only 2 constituents (iron and manganese) exceeded the USEPA secondary standards. Sixty-six of the constituents (including all 53 pesticides) were at or below the reporting or detection levels established by the USGS National Water Quality Laboratory.

Water-Resources Investigations Report

Reconnaissance of ground-water resources in a part of the Yampa River basin between Craig and Steamboat Springs, Moffat and Routt counties, Colorado

This report presents the results of an investigation of ground-water resources in that part of the Yampa River basin between the towns of Craig and Steamboat Springs. The location of the study area is shown on the index map. The investigation was begun in 1975 by the U.S. Geological Survey in cooperation with the Colorado Department of Natural Resources, Division of Water Resources, Office of the State Engineer.

Colorado

Hydrogeologic data for the southwestern coastal river basins, Connecticut

This report presents hydrologic and geologic data collected by the U.S. Geological Survey during an investigation of water resources in the southwestern coastal river basins of Connecticut in cooperation with the Connecticut Water Resources Commission. These basins occupy about 394 square miles in Connecticut and 46 square miles in New York, including the towns of Greenwich, Stamford, Darien, New Canaan, Norwalk, Wilton, Westport, Weston, Fairfield, Easton, and Bridgeport and parts of Danbury, Ridgefield, Redding, Bethel, Newtown, Trumbull, Monroe, Shelton, and Stratford. A companion interpretive report evaluating the water resources of the basins will be published as Connecticut Water Resources Bulletin No. 17. The data on the following pages serve to document and supplement that report and should be especially useful in planning the development of water resources at specific localities. Data were collected as part of this investigation during the period July 1963 through November 1966. Streamflow records from continuous-record gaging stations in the basins have been published annually along with data from other parts of the State in a series of U.S. Geological Survey reports entitled "Surface Water Records of Connecticut." Water-level measurements in wells throughout the State from 1960 through 1966, including most of those made as part of this investigation, are published in Connecticut Water Resources Bulletins No. 7 and No. 13. Most other data collected during this investigation are tabulated on the following pages. Included are some well records and chemical analyses of water samples collected prior to July 1963 and not previously published. The locations of sites at which data were collected are shown on plate A in the pocket at the back of the report. Data presented, unless otherwise noted, were collected by U.S. Geological Survey personnel.

Connecticut

Northern part, Ten Mile and Taunton River basins

The northern part of the Ten Mile and Taunton River basins is an area of about 195 square miles within Norfolk, Plymouth, and Bristol Counties in southeastern Massachusetts. The northern boundary of the area (plate 1) is the drainage divide separating these basins from that of the Charles, Neponset, and Weymouth River basins. The western boundary is, for the most part, the divide separating the basins from the Blackstone River basin. The eastern boundary is at the edge of the Brockton-Pembroke area (Petersen, 1962; Petersen and Shaw, 1961). The southern boundary in Seekonk is the northern limit of the East Providence quadrangle, for which a ground-water map was prepared by Allen and Gorman (1959); eastward, the southern boundaries of the city of Attleboro and the towns of Norton, Easton, and West Bridgewater form the southern boundary of the area. This report is one of two prepared by the Geological Survey for the Water Resources Commission. The principal purpose of this report is to make available the basic data on which the other, a map showing availability of ground water, is based. This basic-data report also can be used by engineers, planners, and others interested in or responsible for water-resources planning to determine the materials to be encountered (tables 3 and 4) and the yields which may be obtained from wells and test holes (tables 1 and 2) in the stratified sand and gravel that are the principal source of ground water and in bedrock. Partial and complete chemical analyses (tables 7 and 8) of these test holes and of some privately-owned wells provide information on the general quality of the water for domestic and other uses. A tabulation of existing municipal supplies, their capacity, production (table 5), and chemical quality of the water (table 6) may be used for regional planning purposes. Water-level measurements (figure 1) can be used to determine the annual fluctuations of the water table in certain types of materials. Seismic work (table 9) in the Canoe River valley, Norton, and test drilling with a power augur (tables 2 and 4) were done for the Geological Survey as part of the investigation.

Massachusetts

Water-resources of western Douglas County, Oregon

In western Douglas County, Quaternary coastal dune sands and marine terrace deposits may have the best potential for ground-water development. Yields of 200 gallons per minute have been reported from wells completed in Quaternary fluvial deposits along the lower Umpqua River. The entire area is underlain by Tertiary marine sediments that yield quantities of water barely adequate for domestic use. On the basis of wells sampled and the constituents analyzed, ground-water quality was generally good, but the recommended criteria level of 300 micrograms per liter for iron was exceeded in about one-third of the samples. Average annual runoff from eight streams in western Douglas County was estimated to range from 2.4 cubic feet per second per square mile for Elk Creek to 6.8 cubic feet per second per square mile for Scholfield Creek. The estimated 7-day , 20-year low flow ranges from 0.01 cubic foot per second per square mile for Weatherly Creek to 3.6 cubic feet per second per square mile for the Smith River. The dissolved-solids of the Umpqua River is small and stable, with little seasonal and yearly variation. Likewise, the eight small streams in the project area have small dissolved-solids but have noticeably higher nitrite plus nitrate nitrogen concentrations than those of the Umpqua River. All the lakes in the project area have dissolved-solids concentrations of less than 100 milligrams per liter and, except for Loon Lake, have limited phosphorus available for algal production. Tahkenitch and Elbow Lakes are considered to be the most active in terms of biological productivity.

Oregon

Effects of agricultural best-management practices on the Brush Run Creek headwaters, Adams County, Pennsylvania, prior to and during nutrient management

The U.S. Geological Survey, in cooperation with the Susquehanna River Basin Commission and the Pennsylvania Department of Environmental Resources, investigated the effects of agricultural best-management practices on surface-water quality as part of the U.S. Environmental Protection Agency's Chesapeake Bay Program. This report characterizes a 0.63-square- mile agricultural watershed underlain by shale, mudstone, and red arkosic sandstone in the Lower Susquehanna River Basin. The water quality of the Brush Run Creek site was studied from October 1985 through September 1991, prior to and during the implementation of nutrient management designed to reduce sediment and nutrient discharges into Conewago Creek, a tributary to the Chesapeake Bay. The original study area was 0.38 square mile and included an area immediately upstream from a manure lagoon. The study area was increased to 0.63 square mile in the fall of 1987 after an extensive tile-drain network was discovered upstream and downstream from the established streamflow gage, and the farm owner made plans to spray irrigate manure to the downstream fields. Land use for about 64 percent of the 0.63 square mile watershed is cropland, 14 percent is pasture, 7 percent is forest, and the remaining 15 percent is yards, buildings, water, or gardens. About 73 percent of the cropland was used to produce corn during the study. The average annual animal population consisted of 57,000 chickens, 1,530 hogs, and 15 sheep during the study. About 59,340 pounds of nitrogen and 13,710 pounds of phosphorus were applied as manure and commercial fertilizer to fields within the subbasin during the 3-year period prior to implementation of nutrient management. During nutrient management, about 14 percent less nitrogen and 57 percent less phosphorus were applied as commercial and manure fertilizer. Precipitation totaled 209 inches, or 13 percent less than the long-term normal, during the 6-year study. Concentrations of total ammonia in precipitation were as high as 2.7 mg/L (milligrams per liter); in dry deposition the concentrations were as high as 5.4 mg/L, probably because of the ammonia that had volatilized from the manure-storage lagoon. Nitrate nitrogen in the upper 4 feet of the soil ranged from 17 to 452 pounds per acre and soluble phosphorus content ranged from 0.29 to 65 pounds per acre. The maximum concentration of total nitrogen was 2,400 mg/L on September 10, 1986, in discharge from the tile drain near the streamflow gage. Median concentrations of total nitrogen and dissolved nitrite plus nitrate in base flow at the water-quality gage were 14 mg/L and 4.4 mg/L, respectively; prior to nutrient management and during nutrient management, median concentrations were 14 mg/L and 6.2 mg/L, respectively. Significant reductions in total phosphorus and suspended-sediment concentrations occurred at the water-quality gage. The maximum concentrations of total phosphorus (160 mg/L) and suspended sediment (3,530 mg/L) were measured at a tile line above the water-quality gage. Concentrations of total nitrogen, dissolved ammonia, and total phosphorus in base flow increased during dry periods when discharges from the tile drain were not diluted. During nutrient management, only base-flow loads of suspended sediment increased. Total streamflow was about 121.8 inches. About 81 percent was storm runoff. Loads of total nitrogen, total phosphorus in stormflow, and suspended sediment increased 14, 44, and 41 percent during nutrient management, respectively. A load of about 787,780 pounds of sediment, 22,418 pounds of nitrogen, and 5,479 pounds of phosphorus was measured during 214 sampled stormflow days that represented 84 percent of the stormflow. About 812,924 pounds of sediment, 38,421 pounds of nitrogen, and 6,377 pounds of phosphorus were discharged during the 6-year study.

Pennsylvania

Water resources of the Port Madison Indian Reservation, Washington

The study summarized in this report was made to provide Suquamish Tribal leaders with information on the reservation's surface- and ground-water resources. The Tribal leaders need this information to help them manage and protect their water resources against overdevelopment. The quantity of ground water that is estimated to be available for withdrawal on a long-term basis is about 600 million gallons per year in the western part of the reservation and 400 million gallons per year in the eastern part of the reservation. It should be possible, economically and practically, to capture at least 40 percent of this ground water with properly constructed and located wells before it is discharged into the sea. This is enough water to supply at least 5,000 and 3,500 people with domestic water in these respective areas—about four times the present population. Of nine stream sites that were studied on and near the reservation, the lowest average streamflows for a 7-day period estimated to occur an average of once in 2 years were 1.3 cubic feet per second or less. Streams at three of the sites have been observed dry at least once. The short period of data collection during this study limits the accuracy of statistical estimates of low flows. Both surface and ground water were found to be of good quality with no unusual or harmful constituents; there was no evidence of major pollution in 1977. In the future, seawater intrusion into the ground-water system and pollution of the surface water by improperly treated sewage waste water could become problems.

Washington

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory-Determination of organophosphate pesticides in filtered water by gas chromatography with flame photometric detection

A method for the isolation of 20 parent organophosphate pesticides and 5 pesticide degradates from filtered natural-water samples is described. Seven of these compounds are reported permanently with an estimated concentration because of performance issues. Water samples are filtered to remove suspended particulate matter, and then 1 liter of filtrate is pumped through disposable solid-phase extraction columns that contain octadecyl-bonded porous silica to extract the compounds. The C-18 columns are dried with nitrogen gas, and method compounds are eluted from the columns with ethyl acetate. The extract is analyzed by dual capillary-column gas chromatography with flame photometric detection. Single-operator method detection limits in all three water-matrix samples ranged from 0.004 to 0.012 microgram per liter. Method performance was validated by spiking all compounds into three different matrices at three different concentrations. Eight replicates were analyzed at each concentration level in each matrix. Mean recoveries of method compounds spiked in surface-water samples ranged from 39 to 149 percent and those in ground-water samples ranged from 40 to 124 percent for all pesticides except dimethoate. Mean recoveries of method compounds spiked in reagent-water samples ranged from 41 to 119 percent for all pesticides except dimethoate. Dimethoate exhibited reduced recoveries (mean of 43 percent in low- and medium-concentration level spiked samples and 20 percent in high-concentration level spiked samples) in all matrices because of incomplete collection on the C-18 column. As a result, concen-trations of dimethoate and six other compounds (based on performance issues) in samples are reported in this method with an estimated remark code.

Water-Resources Investigations Report

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory-Arsenic speciation in natural-water samples using laboratory and field methods

Analytical methods for the determination of arsenite [As(III)], arsenate [As(V)], dimethylarsinate (DMA), monomethylarsonate (MMA), and roxarsone in filtered natural-water samples are described. Various analytical methods can be used for the determination, depending on the arsenic species being determined. Arsenic concentration is determined by using inductively coupled plasma-mass spectrometry (ICP-MS) as an arsenic-specific detector for all methods. Laboratory-speciation methods are described that use an ion chromatographic column to separate the arsenic species; the column length, column packing, and mobile phase are dependent on the species of interest. Regardless of the separation technique, the arsenic species are introduced into plasma by eithe rpneumatic nebulization or arsine generation. Analysis times range from 2 to 8 minutes and method detection limits range from 0.1 to 0.6 microgram-arsenic per liter (ug-As/L), 10 to 60 picograms absolute (for a 100-microliter injection), depending on the arsenic species determined and the analytical method used. A field-generation specciation method also is described that uses a strong anion exchange cartridge to separate As(III) from As(V) in the field. As(III) in the eluate and the As(V) in the cartridge extract are determined by direct nebulization ICP-MS. Methylated arsenic species that also are retained on the cartridge will positively bias As(V) results without further laboratory separations. The method detection limit for field speciation is 0.3 ug-As/L. The distribution of arsenic species must be preserved in the field to eliminate changes caused by photochemical oxidation or metal oxyhydroxide precipitation. Preservation techniques, such as refrigeration, the addition of acides, or the additoin of ethylene-diaminetetraacetic acid (EDTA) and the effects of ambient light were tested. Of the preservatives evaluated, EDTA was found to work best with the laboratory- and field-speciation methods for all sample matrices tested. Storing the samples in opaque polytethylene bottles eliminated the effects of photochemical oxidation. The percentage change in As(III):As(V) ratios for an EDTA-preserved acid mine drainage (AMD) sample and ground-water sample during a 3-month period was -5 percent and +3 percent, respectively. The bias and variability of the methods were evaluated by comparing results for total arsenic and As(III), As(V), DMA, and MMA concentrations in ground water, AMD, and surface water. Seventy-one ground-water, 10 AMD, and 24 surface-water samples were analyzed. Concentrations in ground-water samples reached 720 ug-As/L for As(III) and 1080 ug-As/L for As(V); AMD samples reached 12800 ug-As/L for As(III) and 7050 ug-As/L for As(V); and surface-water samples reached 5 ug-As/L for As(III) and As(V). Inorganic arsenic species distribution in the samples ranged from 0 to 90 percent As(III). DMA and MMA were present only in surface-water samples from agricultural areas where the herbicide monosodium methylarsonate was applied; concentrations never exceeded 6 ug-As/L. Statistical analyses indicated that the difference between As(III) and As(V) concentrations for samples preserved with EDTA in opaque bottles and field-speciation results were analytically insignificant at the 95-percent confidence interval. There was no significant difference among the methods tested for total arsenic concentration. Percentage recovery for field samples spiked at 50 ug-As/L and analyzed by the laboratory-speciation method (n=2) ranged from 82 to 100 percent for As(III), 97 to 102 percent for As(V), 90 to 104 percent for DMA, and 81 to 96 percent for MMA; recoveries for samples spiked at 100 ug-As/L and analyzed by the field-speciation method ranged from 102 to 107 percent for As(III) and 105 to 106 percent for As(V). Laboratory-speciation results for Environment Canada reference material SLRS-2 closely matched reported concentrations. Laboratory-speciation metho

Water-Resources Investigations Report

Regional Relations in Bankfull Channel Characteristics determined from flow measurements at selected stream-gaging stations in West Virginia, 1911-2002

Three bankfull channel characteristics?cross-sectional area, width, and depth?were significantly correlated with drainage area in regression equations developed for two regions in West Virginia. Channel characteristics were determined from analysis of flow measurements made at 74 U.S. Geological Survey stream-gaging stations at flows between 0.5 and 5.0 times bankfull flow between 1911 and 2002. Graphical and regression analysis were used to delineate an 'Eastern Region' and a 'Western Region,' which were separated by the boundary between the Appalachian Plateaus and Valley and Ridge Physiographic Provinces. Streams that drained parts of both provinces had channel characteristics typical of the Eastern Region, and were grouped with it. Standard error for the six regression equations, three for each region, ranged between 8.7 and 16 percent. Cross-sectional area and depth were greater relative to drainage area for the Western Region than they were for the Eastern Region. Regression equations were defined for streams draining between 46.5 and 1,619 square miles for the Eastern Region, and between 2.78 and 1,354 square miles for the Western Region. Stream-gaging stations with two or more cross sections where flow had been measured at flows between 0.5 and 5.0 times the 1.5-year flow showed poor replication of channel characteristics compared to the 95-percent confidence intervals of the regression, suggesting that within-reach variability for the stream-gaging stations may be substantial. A disproportionate number of the selected stream-gaging stations were on large (drainage area greater than 100 square miles) streams in the central highlands of West Virginia, and only one stream-gaging station that met data-quality criteria was available to represent the region within about 50 miles of the Ohio River north of Parkersburg, West Virginia. Many of the cross sections were at bridges, which can change channel shape. Although the data discussed in this report may not be representative of channelcharacteristics on many or most streams, the regional equations in this report provide useful information for field identification of bankfull indicators.

Water-Resources Investigations Report

Water use in Louisiana, 2015

In 2015, approximately 8,720 million gallons per day (Mgal/d) of water was withdrawn from groundwater and surface-water sources in Louisiana, a 2.6 percent increase from 2010. Total groundwater withdrawals were about 1,750 Mgal/d, an increase of 12 percent from 2010, and total surface-water withdrawals were about 6,970 Mgal/d, an increase of 0.44 percent from 2010 to 2015. Total water withdrawals, in Mgal/d, in 2015 for the various categories of use were as follows: public supply—715, industry—2,155, power generation—4,265, rural domestic—39, livestock—6, rice irrigation—825, general irrigation—225, and aquaculture—490. From 2010 to 2015, Louisiana’s total withdrawals for public supply decreased by 3.4 percent, industry increased by 5.7 percent, power generation decreased by 3.9 percent, rural domestic decreased by 4.1 percent, livestock decreased by 21 percent, rice irrigation increased by 20 percent, general irrigation decreased by 6.0 percent, and aquaculture increased by 58 percent. About 48 percent (approximately 850 Mgal/d) of all groundwater withdrawn was from the Chicot aquifer system and 22 percent (approximately 385 Mgal/d) was withdrawn from the Mississippi River alluvial aquifer. Since 2010, withdrawals from the Chicot aquifer system increased by 30 percent and withdrawals from the Mississippi River alluvial aquifer decreased by 2.9 percent. About 70 percent (4,905 Mgal/d) of all surface water withdrawn was from the Mississippi River mainstem. This value represents a 1.1-percent decrease in withdrawals from 2010 to 2015. All water-withdrawal and water-use data presented in this report should be considered estimates. Because of rounding, totals and percentages presented in the tables, figures, and text in the report may differ slightly from totals or percentages calculated individually

Louisiana

Test drilling and aquifer test in the Marburg schist near Mount Airy, Frederick County, Maryland

This memorandum summarizes briefly the data obtained by test drilling and in an aquifer test at Mount Airy, Md. The tests were a part of the State - Federal cooperative study of the ground-water resources of Frederick County, and it is intended that a more complete analysis of the test data will be included in a future report describing the ground-water resource of Frederick County. The purpose of this memorandum is to make the test data immediately available to the general public. Mount Airy is located along the Carroll-Frederick County boundary bout 2 miles north of the intersection of U.S. Highway 40 with the county boundary. Its population is approximately 1,000. The municipal well field, consisting of two drilled wells (fig. 1) is in a valley about one-half mile west of the center of Mount Airy, within about 400 feet of a small stream, and north of Prospect Road. Well 1, about 40 feet north of Prospect Road, is 125 feet deep, 8 inches in diameter, and reportedly yielded 265 gallons per minute (gpm) in 1947 and 201 gpm in a half hour test in March 1955. The writer determined during the tests described in this memorandum that the well has about 34 feet of casing. Well 2, 85 feet north of well 1, is 96 feet deep, 8 inches in diameter, and reportedly yielded 120 gpm in 1947 and 127 gpm in a half hour test in March 1955. The wells are equipped with deep-well turbine pumps powered by electric motors. Cenorally only well 1 is used, and it is pumped for only a few short intervals each day to meet the water requirements of the town (about 75,000 - 80,000 gallons daily). The reported yields of these wells are considerably higher than the average for crystalline-rock wells in the Piedmont of Maryland. The test drilling was done under contract with Edward I. Brown, well driller, between May 3 and May 12, 1955. Water-supply facilities of the town of Mount Airy were kindly made available for the aquifer tests from May 22 to May 30, 1955. The pumping tests consisted of a step-drawdown and interference test on the public-supply wells on May 30, 1955, and aquifer test in which public-supply well 1 was pumped constantly for 48 hours and the effect of this pumpage was measured in all the wells and test holes on May 23-25.

Maryl

Ground-water resources of Tinian, Commonwealth of the Northern Mariana Islands

Tinian, which lies in the western Pacific Ocean at latitude 15&deg;N and longitude 145&deg;W (fig. 1), is the second largest island (39.2 mi 2 ) in the Commonwealth of the Northern Mariana Islands (CNMI). Fresh ground water is obtained from shallow wells that tap the surface of a freshwater lends found in an aquifer composed mainly of coralline limestone. The main water-supply well withdraws water with a chloride concentration ranging from 160 to 220 mg/L. Current (1999) pumping rates adequately supply the island residents but future demand are expected to be higher.. To better understand the ground-water resources of the island and to learn more about the hydrology of oceanic islands, the U.S. Geological Survey (USGS) entered into a cooperative study with the Municipality of Tinian. The objective of the study, conducted between 1990 and 1997, was to assess the ground-water resources of the is;land. This report presents some of the results of the study including a description of the island's geology and geography, the current land use, the water-production system, the thickness and arcal extent of the freshwater lens, the water-table configuration and directions of ground-water flow. The report also discusses the relation of the changes in water-table elevation to daily and seasonal changes in ocean level.

Tinian Island

Public water supplies of selected municipalities in Florida, 1975

In 1975, the 169 municipalities and 5 county water systems listed in this report supplied 1.037 million gallons of water each day, on the average to 77 percent of the population of the State of Florida. The quantity of water supplied represented 90 percent of the State's public water supply demand. Of the 169 municipalities and 5 county systems, 150 supplied 887 million gallons of ground water and 24 supplied 150 million gallons of surface water each day, on the average, representing 85 percent and 15 percent, respectively, of the total demand of the 174 water systems. Three of the 150 municipal ground-water suppliers are reported to have processed, that year, about 3.2 million gallons of water each day by desalination.

Florida

Estimating the Magnitude and Frequency of Peak Streamflows for Ungaged Sites on Streams in Alaska and Conterminous Basins in Canada

Estimates of the magnitude and frequency of peak streamflow are needed across Alaska for floodplain management, cost-effective design of floodway structures such as bridges and culverts, and other water-resource management issues. Peak-streamflow magnitudes for the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence-interval flows were computed for 301 streamflow-gaging and partial-record stations in Alaska and 60 stations in conterminous basins of Canada. Flows were analyzed from data through the 1999 water year using a log-Pearson Type III analysis. The State was divided into seven hydrologically distinct streamflow analysis regions for this analysis, in conjunction with a concurrent study of low and high flows. New generalized skew coefficients were developed for each region using station skew coefficients for stations with at least 25 years of systematic peak-streamflow data. Equations for estimating peak streamflows at ungaged locations were developed for Alaska and conterminous basins in Canada using a generalized least-squares regression model. A set of predictive equations for estimating the 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year peak streamflows was developed for each streamflow analysis region from peak-streamflow magnitudes and physical and climatic basin characteristics. These equations may be used for unregulated streams without flow diversions, dams, periodically releasing glacial impoundments, or other streamflow conditions not correlated to basin characteristics. Basin characteristics should be obtained using methods similar to those used in this report to preserve the statistical integrity of the equations.

Water-Resources Investigations Report