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This report, which is one of a series of reports for Alaska, lists stations in Yukon Basin, Alaska, at which streamflow and water quality data have been collected by the U.S. Geological Survey. Included are a hydrologic subregion map of Yukon Basin, Alaska, and a table listing the types of data collected and periods of record. (USGS)
This report, which is one of a series of reports for Alaska, lists stations in south-central Alaska at which streamflow and water quality data have been collected by the U.S. Geological Survey. Included are a hydrologic subregion map of south-central Alaska and a table listing the types of data collected and periods of record. (USGS)
The watersheds studied include mined and reclaimed; mined and unreclaimed; and unmined, agricultural land uses, and are each < 3 sq mi in area. Surface water, groundwater, and meteorologic data for the 1981 and 1982 water years were used to describe and compare hydrologic systems of the six watersheds and to identify hydrologic effects of mining and reclamation. Peak discharges were greater at the agricultural watersheds than at the unreclaimed watersheds, primarily because of large final-cut lakes in the unreclaimed watersheds. Annual runoff was greatest at the unreclaimed watersheds, intermediate at the agricultural watersheds, and least at the reclaimed watersheds. Hydrologic effects of mining were identified by comparing the hydrologic systems at mined and unreclaimed watersheds with those at unmined, agricultural watersheds. Comparisons of the hydrologic systems of these watersheds indicate that surface coal mining without reclamation has the potential to increase annual runoff, base flow, and groundwater recharge to the bedrock; reduce peak flow rates and variation in flow; lower the water table in upland areas; change the relation between surface water and groundwater divides; and create numerous, local flow systems in the shallow groundwater. Hydrologic effects of reclamation were identified by comparing the hydrologic systems at mined and reclaimed watersheds with those at mined and unreclaimed watersheds. Reclamation has the potential to decrease annual runoff, base flow, and recharge to the bedrock; increase peak flow rates, variation in flow, and response to thunderstorms; reestablish the premining relation between surface and groundwater divides; and create fewer local flow systems in the shallow groundwater.
The Lower and Combined Aquifers of the Eastbank Aquifer system, located in a river-terrace deposit along the Columbia River near Rocky Reach Dam, Washington, are primarily recharged by the Columbia River and provide water to the Eastbank Hatchery and the regional water system servicing the cities of Wenatchee, East Wenatchee, and parts of unincorporated Chelan and Douglas Counties. In 2006, mean annual pumpage from the aquifers by the hatchery and regional water system was about 43 and 16 cubic feet per second, respectively. Reportedly, temperatures of ground water pumped by the hatchery have been increasing, thereby making water potentially too warm for salmonid fish production. An evaluation of hourly ground-water and river temperatures from January 1991 through August 2007 indicates increasing interannual trends in temperatures in most of the Lower and Combined Aquifers from 1999 through 2006 that correspond to increasing trends in the annual mean and annual maximum river temperatures during the same period of 0.07 and 0.17?C per year, respectively. There were no trends in the annual minimum river temperatures from 1999 through 2006, and there were no trends in the annual minimum, mean, and maximum river temperatures from 1991 through 1998 and from 1991 through 2007. Increases in river temperatures from 1999 through 2006 are within the natural variability of the river temperatures. Most of the Lower and Combined Aquifers reached thermal equilibrium?defined by constant time lags between changes in river temperatures and subsequent changes in ground-water temperatures?during 1991?98. The only exceptions are the Combined Aquifer north of the well field of the regional water system, which had not reached thermal equilibrium by 2006, and the Lower Aquifer west of the well fields of the hatchery and the regional water system, which reached thermal equilibrium prior to 1991. Because most of the Lower and Combined Aquifers were in thermal equilibrium from 1999 through 2006 and seasonal pumpage patterns were relatively stable, reported trends of increasing temperatures of water pumped by the hatchery well field are most likely explained by increasing trends in river temperatures. Most of the water pumped by the hatchery well field recharges in an area west to southwest of the well field about 2 months prior to the time it is pumped from the aquifer. The northern extent of the hatchery well field may pump some colder water from a bedrock depression to the north and west of the well field. The conceptual model of hydrologic and thermal conditions is supported by analyses of historical water temperatures, water-level data collected on July 18, 2007, and dissolved-constituent and bacterial concentrations in samples collected on August 20?22, 2007.
The Guanella Pass road, located about 40 miles west of Denver, Colorado, between the towns of Georgetown and Grant, has been designated a scenic byway and is being considered for reconstruction. The purpose of this report is to present an assessment of hydrologic and water-quality conditions in the Guanella Pass area and provide baseline data for evaluation of the effects of the proposed road reconstruction. The data were collected during water years 1995-97 (October 1, 1995, to September 30, 1997). Based on Colorado water-quality standards, current surface-water quality near Guanella Pass road was generally acceptable for specified use classifications of recreation, water supply, agriculture, and aquatic life. Streams had small concentrations of dissolved solids, nutrients, trace elements, and suspended sediment. An exception was upper Geneva Creek, which was acidic and had relatively large concentrations of iron, zinc, and other trace elements related to acid-sulfate weathering. Concentrations of many water-quality constituents, especially particle-related phases and suspended sediment, increased during peak snowmelt and rainstorm events and decreased to prerunoff concentrations at the end of runoff periods. Some dissolved (filtered) trace-element loads in Geneva Creek decreased during rainstorms when total recoverable loads remained generally static or increased, indicating a phase change that might be explained by adsorption of trace elements to suspended sediment during storm runoff. Total recoverable iron and dissolved zinc exceeded Colorado stream-water-quality standards most frequently. Exceedances for iron generally occurred during periods of high suspended-sediment transport in several streams. Zinc standards were exceeded in about one-half the samples collected in Geneva Creek 1.5 miles upstream from Grant. Lake-water quality was generally similar to that of area streams. Nitrogen and phosphorus ratios calculated for Clear and Duck Lakes indicated that phytoplankton in the lakes were probably phosphorus-limited. Measures of trophic status (secchi depth, total phosphorus, and chlorophyll- a ) indicated that Duck and Clear Lakes were oligotrophic in 1997. Ground water had relatively low specific conductance (range 24 to 584 microsiemens per centimeter) and did not exceed U.S. Environmental Protection Agency drinking-water standards, except for samples collected from a single well, which exceeded the Proposed Maximum Contaminant Level for uranium. Runoff from the Guanella Pass road enters streams through surface channels connected to culverts and roadside ditches. Fifty-six percent of the total number of culvert and roadside-ditch drainage features on the Guanella Pass road showed evidence of recent surface runoff connection to an adjacent stream. Road runoff is generated during snowmelt and during summer rainstorms. At a road cross-drain culvert monitored continuously for discharge (water years 1996-97), most runoff (77 to 96 percent) was a result of snowmelt, and runoff from the road preceded the basinwide peak streamflow, resulting in sediment and water-quality constituent inputs to the stream when the stream’s capacity for dilution of the road runoff was low. Specific conductance of road-runoff samples ranged from 14 to 468 microsiemens per centimeter. Major-ion composition of some samples indicated effects from deicing salt (sodium chloride) and dust inhibitor (magnesium chloride) applied to sections of the road, but changes in the stream concentrations that might be attributed to the runoff were brief and relatively small. Nutrients were commonly measured in road-runoff samples at larger concentrations than in streamflow. Concentrations of nitrate and ammonia, especially during rainfall-generated road runoff, were more similar to the concentrations in precipitation than to the concentrations in stream water. Concentrations of ammonia plus organic nitrogen (total as N) (range less than 0.2 to 24 milligrams per liter) and total phosphorus (range 0.024 to 7.2 milligrams per liter) in road runoff were generally large in snowmelt and rainstorm samples and were related to abundant particulate organic material and suspended sediment in the road runoff. Trace-element data indicated that total recoverable trace-element concentrations in road runoff were substantially larger (by several times) than dissolved trace-element concentrations, indicating that most trace elements were particulate. Most of the stream trace-element standards would not likely be exceeded as a result of road-runoff constituents discharged into streams because the standards apply primarily to dissolved-phase (filtered) constituents, and the predominant phase associated with Guanella Pass road runoff is particulate. The suspended-sediment concentrations in snowmelt-generated road runoff ranged from 66 to 7,360 milligrams per liter. Rainstorm-runoff concentrations ranged from 34 to 38,800 milligrams per liter. The sediment was primarily fine grained, which facilitated transport of the sediment. The median percentage of silt and clay (finer than 0.062 millimeter) in road-runoff samples analyzed for size fractions was greater than 90 percent for snowmelt samples and 88 percent for rainstorm samples. Dilution of estimated road runoff to South Clear Creek upstream from Naylor Creek as a result of snowmelt on the road in early May (prior to peak watershed streamflows) ranged from approximately 10 to 100 times. During peak snowmelt in the watershed (early June), dilution of road runoff was estimated to be greater than 1,000 times. Dilution factors for late-summer-rainstorm road runoff were in the range of 10 to 500 times. Given the large concentrations of suspended sediment in road runoff, the potential water-quality effects of road runoff could be substantial during the low streamflows of early snowmelt and late summer base flow (low dilution capacity) but inconsequential during high streamflows (high dilution capacity). The median bulk deposition rate of filterable solids is probably related to dust deposition from roads. The median deposition rate at sites near unpaved roads was 105 times the median rate at an undisturbed reference site (located at least 500 feet away from a road), and the rate at sites near paved roads was 3 times the undisturbed reference site median rate. During August to September 1997, bulk atmospheric deposition directly on the active channel of a reach of Geneva Creek was estimated to be 1.7 tons, or about 1 percent of the estimated 165 tons of suspended sediment transported past the nearby stream-monitoring site near Grant during the same period. The estimate of 1.7 tons indicates little potential effect from direct settling of bulk atmospheric solids on suspended-sediment transport in Geneva Creek, a stream that closely parallels the Guanella Pass road.
This report presents hydrologic and geologic data collected by the U.S. Geological Survey during an investigation of water resources in the Shetucket River basin of Connecticut in cooperation with the Connecticut Water Resources Commission. The Shetucket River basin occupies about 507 square miles in the eastern part of the State, including the towns of Andover, Ashford, Chaplin, Coventry, Mansfield, Scotland, Sprague, Windham, and Willington, and parts of Bolton, Canterbury, Columbia, Eastford, Ellington, Franklin, Lebanon, Lisbon, Hampton, Hebron, Norwich, Pomfret, Stafford, Tolland, Union, Vernon, and Woodstock. A companion interpretive report, Connecticut Water Resources Bulletin ll, (Thomas, and others, 1967), evaluates the water resources of the basin. 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 1962 through December 1964. Streamflow records from continuous-record gaging stations in the basin for this period 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 1964, including those made as part of this investigation, are published in Connecticut Water Resources Bulletin 7 (Meikle and Baker, 1965). 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 1962 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. Plate A includes the locations of 98 sites where 2 to 6 miscellaneous measurements of streamflow were made during 1963 and 13 other sites where continuous records are maintained. Data for these sites have already been published in "Surface Water Records of Connecticut" and are not repeated here. Data presented~ unless otherwise noted, were collected by U.S. Geological Survey personnel.
This report presents hydrologic and geologic data collected by the U.S. Geological Survey during an investigation of water resources in the lower Thames and southeastern coastal river basins in cooperation with the Connecticut Water Resources Commission. The report area occupies about 440 square miles in the southeastern part of the State; it includes about 5 square miles in southwestern Rhode Island. It includes the towns of Bozrah, Groton, Ledyard, Montville, New London, Stonington, and Waterford, and parts of Columbia, Colchester, East Lyme, Franklin, Lebanon, North Stonington, Norwich, Old Lyme, Preston, Salem, and Voluntown. A companion interpretive report, Connecticut Water Resources Bulletin No. 15, (Thomas and others, in preparation), evaluates the water resources of the area. 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 from 1963 to 1965. Streamflow records from continuous~record gaging stations in the report area for this period 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 those made as part of this investigations are published in Connecticut Water Resources Bulletin No. 7 (Meikle and Baker~ 1965) and Connecticut Water Resources Bulletin No. 13 (Melklee 1967). Most other data collected during this investigation are tabulated on the following pages. Included are some previously unpublished data collected prior to the start of this study. The locations of sites at which data were collected are shown on Plate A in the pocket at the back of the report. Plate A includes the locations of 42 miscellaneous sites where measurements of streamflow were made during 1963 and 1964 and 6 other sites where continuous records are maintained. Data for 25 of the 42 miscellaneous sites are included in this report: data for the remaining 17 miscellaneous sites and for 5 of the 6 continuous-record sites have already been published in "Surface Water Records of Connecticut." Streamflow records for Pawcatuck River at Westerly~ Rhode Island have been previously published in "Surface Water Records of Massachusetts, New Hampshire, Rhode Island, and Vermont." Data presented, unless otherwise noted, were collected by U.S. Geological Survey personnel.
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.
This report presents hydrologic and geologic data collected by the U.S. Geological Survey during an investigation of water resources in the Quinebaug River basin of Connecticut in cooperation with the Connecticut Water Resources Commission. The Quinebaug River basin occupies about 425 square miles in the northeastern part of the State, including the towns of Brooklyn, Griswold, Killingly, Plainfield, Pomfret, Putnam, Sterling, and Thompson, and parts of Canterbury, Hampton, Lisbon, North Stonington, Preston, Voluntown, and Woodstock. A companion interpretive report evaluating the water resources of the basin will be published as Connecticut Water Resources Bulletin 8. 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.
The U.S. Geological Survey (USGS) collects streamflow, groundwater levels, and water-quality data for the State of Illinois and the Nation. Much of these data are collected every 15 minutes (real-time) as a part of the national network, so that water-resource managers can make decisions in a timely and reliable manner. Coupled with modeling and other water-resource investigations, the USGS provides data to the State during droughts and other hydrologic events. The types of data, capabilities, and presentation of these materials are described in this document as USGS Real-Time Data, Supplementary Data Collection and Analysis, and National Resources Available.
The U.S. Geological Survey (USGS) has been collecting data on the occurrence of pesticides in California surface and ground water since the 1970’s. The design of these studies benefited from the availability of the Pesticide Use Reporting (PUR) database of the California Department of Pesticide Regulation. Actual locations and dates of applications of active ingredient allow for effective design of studies that seek to understand which compounds can be mobilized from the point of application as well as the hydrological or climate-related factors that enhance the off-site transport. Key studies from the 1970’s to the present are discussed here and demonstrate how the USGS both designed studies and improved their analytical methodology to keep up with changes in how pesticides are used in California.
This 18-month field study addresses the seasonal and spatial patterns and processes controlling methylmercury (MeHg) production, bioaccumulation, and export from natural and agricultural wetlands of the Yolo Bypass Wildlife Area (YBWA). The data were collected in conjuntion with a Proposition 40 grant from the State Water Resources Control Board in support of the development of Best Management Practices (BMP's) for reducing MeHg loading from agricultural lands in the wetland-dominated Yolo Bypass to the Sacramento-San Joaquin River Delta. The four managemenr-based questions addressed in this study were: 1. Is there a different among agricultural and managfed wetland types in terms of Me Hg dynamic (production, degradation, bioaccumulation, or export)? 2. Does water residence time influence MeHg dynamics? 3. Does the application of sulfate-based fertilizer impact MeHg production rates? 4. Does the presence (or absence) of vegetation influence MeHg production rates? Measurements of MeHg concentrations in sediment, water, and biota (plants, invertebrates, and fish) were made to assess management-level patterns in five wetland types, which included three type of shallowly-flooded agricultural wetlands (white rice, wild rice, and fallow) and two types of managed wetlands (permanently and seasonally flooded). To strengthen our understanding of the processes underlying the seasonal and spatial patterns of MeHg cycling, additional exploratory factors were measured including ancillary sediment and water quality parameters, stable isotope fractionation (oxygen, sulfur, carbon, and nitrogen), photodemethylation rates, and daily-integrated hydrologic budgets. Samples and field data were collected from May 2007 to July 2008, and nearly all sample analyses were completed by September 2008 as per the Quality Assurance Program Plan (QAPP) requirements. Although wetland type was a major factor that drove the study design, within-field hydrology also proved to be an important factor controlling aqueous MeHg and total mercury (THg) concentrations and export. Overall, agricultural wetlands exhibited higher MeHg concentrations in overlying water, sediment, and biota than did managed seasonal and permanent wetlands. This appears to be partly due to higher rates of sediment in microbial production of MeHg on agricultural wetlands during the fall through spring period. Both sulfate- and iron-reducing bacteria have been implicated in the MeHg production process, and both were demonstrably active in all wetlands studied; however, sulfate-reducing bacteria were not stimulated by the addition of sulfate-based fertilizer to agricultural wetlands, suggesting that easily-degraded (labile) organic matter, rather than sulfate, was limiting their activity in these field types. The data suggest that agriculturally-managed soils promoted MeHg production through 1) enhanced microbial activity via higher temperatures and larger pools of labile carbon, and 2) enhanced pools of microbially available inorganic divalent mercury (Hg(II)) resulting from a decrease in reduced-sulfur, solid-phase minerals under oxic or only mildly reducing conditions. MeHg mass balances were assessed by comparing filed-specific MeHg loads for inlets vs. outlet flows. The overall mass balance for MeHg in surface water during the summer irrigation period (June - September 2007) indicated little to no net MeHg export from the six agricultural wetlands taken as a whole. Of the six agricultural wetlands, there was net overall MeHg export from two fields (one fallow and one white rice) during August, and from four of the six fields (one fallow, one white rice, and two wild rice) during September) Over the entire summer irrigation period, two of the fields (one fallow and one wild rive) showed net MeHg export, and the other four fields showed wither net import or no significant change. Rates of measured photomethylation and exchange between sediment and water pools suggest that both processes may be responsible for the lack of MeHg export. Despite significant differences during winter months between fields in surface water concentrations of MeHg, MeHg loads were not calculated in mid-winter because flood waters had overtopped field boundaries and field fidelity could not be established. During the summer 2007 irrigation season, surface water out-flows from agricultural wetlands were 9%-36% of inlet flows, and evaporation rates explained most of this water loss, with infiltration likely accounting for the remainder. Unfiltered aqueous MeHg concentrations increased from <1 ng L -1 in source waters to up to 10 ng L -1 in agricultural wetland drains during the summer irrigation period. Increases in solute concentration caused by evapoconcentration were estimated by determining concentration factors (outflow/inflow) for chloride (a conservative dissolved constituent) and by measuring oxygen isotope ratios ( 18 O/ 16 O, expressed as δ 18 O) in water. Increases in MeHg concentration from inflows-to-outflows exceeded those caused by evapoconcentration on several fields during the summer irrigation season. This was especially true when initial surface water MeHg concentrations were low, as seen in the southern block of fields receiving irrigation water directly from the Toe Drain. The northern block of fields received irrigation water from Greens Lake, which included Toe Drain water plus recirculated drain water from other agricultural fields within the Yolo Bypass and west of the Yolo Bypass; as such, the northern fields showed a smaller percentage increase in MeHg concentration because initial MeHg concentrations in surface water inflows were greater than in inputs to the southern fields. Mercury concentrations in fish were greater in agricultural wetlands white rice and wild rice) than in the two permanently flooded wetlands. Additionally, Hg concentrations in biota showed a general increase from inlets to outlets withing agricultural wetlands, but not within permanent wetlands. This was particular evident in white rice fields where caged western mosquitofish at the outlets had Hg concentrations that were more than 4 times higher than in caged fish held at the inlets. Similar spatial patterns in Hg bioaccumulation in agricultural and permanent wetlands were seen for wild populations of western mosquitofish and Mississippi silversides. In contrast to fish, invertebrates, such as water-boatman (Corixidae) and back swimmers (Notonectidae), had greater Hg concentrations in permanent wetlands than in tempoarirly flooded agricultural wetlands, Fish THg concentrations were weakly correlated with water MeHg,a and not correlated with sediment MeHg. In contrast, invertebrate MeHg concentrations were more strongly correlated with sediment MeHg than with water MeHg concentrations. These results illustrate the complexity of MeHg bioaccumulation through food webs and indicate the importance of simultaneously using multiple biosentinels when monitoring MeHg production and bioaccumulation. Despite high sediment production rates and water concentrations in agricultural wetlands, MeHg export was physically limited by hydrologic export for all wetlands studied. We suggest that load reduction is maximized by limiting water throughout, but that on-site biota exposure is maximized by this loner water residence time. While field-specific hydrologic loads could not be fully quantified during flood conditions in February 2008, we suggest that the primary period of MeHg export from Yolo Bypass Wildlife Area is during those winter flooding periods when overall microbial activity and MeHg production in agricultural soils is fueled by the decomposition of rice straw, and when hydrologic flowthrough is maximal. Local stakeholders participated in two workshops related to this study, demonstrating an interest in understanding factors controlling MeHg production, export, and bioaccumulation. The results of this field study show that permanently flooded, naturally vegetated wetlands are unlikely to a large source of MeHg production within the YBWA, in contrast with agriculturally-managed wetlands. MeHg loading to Toe Drain waters of the Yolo Bypass may be reduced by lowering rated of hydrologic export from agricultural wetlands during the growing season and especially during rice harvest, However, under these water-holding conditions, biota living within agricultural wetlands may thus be exposed to higher MeHg concentrations in surface water, As observed in this study, rapid bioacculumaltion over a 2-month period led to MeHg concentrations in invertebrates and fish more than 6 and 11 times higher, respectively, than proposed TMDL target values to protect wildlife (0.03 ppm ww). The results of this field study, together with the information from YBWA stakeholders, provide a more definitive understanding of how MeHg cycling and bioaccumulation respond to habitat differences and specific management practices. These results directly address 4 core components of CBDA's Mercury Strategy for the Bay-Delta Ecosystem (Wiener et al., 2003a): a) Quantification and evaluation of THg and MeHg sources, b) Quantification of effects of ecosystem restoration on MeHg exposure, c) Assessment of ecological risk, and d) Identification and testing of potential management approaches for reducing MeHg contamination. In addition, the quantitative results reported here assess the effect of current land use practices in the Yolo Bypass MeHg production, bioaccumulation and export, and provide process-based advice towards achieving current goals of the RWQCB-CVR's Sacramento -- San Joaquin Delta Estuary TMDL for Methyl & Total Mercury (Wood et al., 2010b). Further work is necessary to evaluate biotic exposure in the Yolo Bypass Wildlife Area at higher trophic levels (e.g. birds), to quantify winter hydrologic flux of MeHg to the larger Delta ecosystem, and to evaluate rice straw management options to limit labile carbon supplies to surface sediment during winter months. In summary, agricultural management of rice fields -- specifically the periodic flooding and production of easily degraded organic matter -- promotes the production of MeHg beyond rates seen in naturally vegetated wetlands, whether seasonally or permanently flooded., The exported load from MeHg from these agricultural wetlands may be controlled by limiting hydrologic export from fields to enhance on-site MeHg removal processes, but the tradeoff is that this impoundement increases Me Hg exposure to resident organisms.
Aquifers are the primary source of water for drinking and agricultural purposes in western Oklahoma. Health concerns about consuming nitrogen and an increased reliance on ground water for drinking necessitate a better understanding of the cause and effect of contamination from nutrients. The purpose of this project was to compile nutrients data from the National Water Information System data base for the alluvial aquifers west of longitude 98 degrees W. and from three bedrock aquifers, High Plains, Rush Springs, and Blaine, and provide this information in a report for future projects and for the facilitation of nutrient source management. The scope of the work consisted of (1) compiling ground-water quality data concerning nitrogen and phosphorus ions, (2) constructing boxplots illustrating data variability, (3) maps for each aquifer showing locations of wells when nitrogen and phosphorus ions were measured in ground water and where concentrations of nitrate and nitrite, reported as nitrogen, exceed the maximum contaminant level, and (4) calculating summary statistics. Nutrient data were obtained from the U.S. Geological Survey data base called the National Water Information System. Data were restricted to ground-water samples, but no restrictions were placed on well and water use or date and time of sampling. Compiled nutrient data consist of dissolved and total concentrations of the common nitrogen and phosphorus ions measured in ground water. For nitrogen these ions include nitrate, nitrite, ammonium, and nitrite plus nitrate. All concentrations are reported in milligrams per liter as nitrogen. Phosphorus in ground water is measured as the orthophosphate ion, and is reported in milligrams per liter as phosphorus. Nutrient variability is illustrated by a standard boxplot. The data are presented by aquifer or hydrologic subregion for alluvial aquifers, with one boxplot constructed for each nutrient compound if more than four analyses are present. Maps for each aquifer show where nitrogen and phosphorus have been measured in ground water and where the concentrations of nitrate and nitrite exceed the maximum contaminant level. A statistical summary for each aquifer and subregion show if censored data were present, number of samples in each data set, largest minimum reporting level for each nutrient compound, percentiles used to construct boxplots, and minimum and maximum values. Also given are the number of wells sampled in each aquifer and the number of wells exceeding the maximum contaminant level.
Three models of the aquifer in the southern High Plains were compared to determine the effect of grid size on simulated water levels. The first model, calibrated prior to this study, had 10-mi grid spacing. The mean difference between the simulated and measured pre-development water levels in this model was +0.28 ft with a standard deviation of 25.8 ft. The second model, calibrated during this study independently of the first model, had 5-mi grid spacing. The mean difference between the simulated and measured pre-development water levels was -0.01 ft with a standard deviation of 44.4 ft. For 1980 water levels, the mean difference was +8.22 ft with a standard deviation of 27.9 ft. The results from the first and second models were compared. The standard deviation of the differences in simulated water levels was 19.0 ft for the pre-development period and 21.8 ft for 1980. There appeared to be no hydrologic significance to the pattern of the differences. A third model, constructed by aggregating the data from the second model, had 10-mi grid spacing. The mean difference in simulated pre-development water levels between the second and third models was +0.86 ft with a standard deviation of 8.9 ft. For the 1980 water levels, the mean difference between the models was +0.39 ft with a standard deviation of 4.4 ft. The study found that the same hydrologic conclusions would have been reached had 5-mi grid spacing or 10-mi grid spacing been used. It was further concluded that the difference in simulated water levels between models with 5-mi grid spacing or 10-mi grid spacing was five to six times smaller than the differences between the simulated and measured water levels. (Author 's abstract)
This map and accompanying table show Hydrologic Units that are basically hydrographic in nature. The Cataloging Units shown will supplant the Cataloging Units previously used by the U.S. Geological Survey in its Catalog of Information on Water Data (1966-72).
Introduction The South Florida Ecosystem Restoration Program is an intergovernmental effort to reestablish and maintain the ecosystem of south Florida. One element of the restoration effort is the development of a firm scientific basis for resource decision making.The U.S. Geological Survey (USGS) provides scientitic information as part of the South Florida Ecosystem Restoration Program. The USGS began its own project, called the South Florida Ecosystem Project in fiscal year 1995 for the purpose of gathering hydrologic, cartographic, and geologic data that relate to the mainland of south Florida, Florida Bay, and the Florida Keys and Reef ecosystems. Historical changes in water-management practices to accommodate a large and rapidly growing urban population along the Atlantic coast, as well as intensive agricultural activities, have resulted in a highly managed hydrologic system with canals, levees, and pumping stations. These structures have altered the hydology of the Everglades ecosystem on both coastal and interior lands. Surface-water flows in a direction south of Lake Okeechobee have been regulated by an extensive canal network, begun in the 1940's, to provide for drainage, flood control, saltwater intrusion control, agricultural requirements, and various environmental needs. Much of the development and subsequent monitoring of canal and river discharge south of Lake Okeechobee has traditionally emphasized the eastern coastal areas of Florida. Recently, more emphasis has been placed on providing a more accurate water budget for internal canal flows.
Winter cover crops are an effective conservation management practice with potential to improve water quality. Throughout the Chesapeake Bay Watershed (CBW), which is located in the Mid-Atlantic US, winter cover crop use has been emphasized and federal and state cost-share programs are available to farmers to subsidize the cost of winter cover crop establishment. The objective of this study was to assess the long-term effect of planting winter cover crops at the watershed scale and to identify critical source areas of high nitrate export. A physically-based watershed simulation model, Soil and Water Assessment Tool (SWAT), was calibrated and validated using water quality monitoring data and satellite-based estimates of winter cover crop species performance to simulate hydrological processes and nutrient cycling over the period of 1991–2000. Multiple scenarios were developed to obtain baseline information on nitrate loading without winter cover crops planted and to investigate how nitrate loading could change with different winter cover crop planting scenarios, including different species, planting times, and implementation areas. The results indicate that winter cover crops had a negligible impact on water budget, but significantly reduced nitrate leaching to groundwater and delivery to the waterways. Without winter cover crops, annual nitrate loading was approximately 14 kg ha −1 , but it decreased to 4.6–10.1 kg ha −1 with winter cover crops resulting in a reduction rate of 27–67% at the watershed scale. Rye was most effective, with a potential to reduce nitrate leaching by up to 93% with early planting at the field scale. Early planting of winter cover crops (~30 days of additional growing days) was crucial, as it lowered nitrate export by an additional ~2 kg ha −1 when compared to late planting scenarios. The effectiveness of cover cropping increased with increasing extent of winter cover crop implementation. Agricultural fields with well-drained soils and those that were more frequently used to grow corn had a higher potential for nitrate leaching and export to the waterways. This study supports the effective implement of winter cover crop programs, in part by helping to target critical pollution source areas for winter cover crop implementation.