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At least 1,747 records · Page 97Linked to original sources
USGS2006

Effects of irrigation practices on water use in the groundwater management districts within the Kansas high plains, 1991-2003

Data compiled for the High Plains region of Kansas that includes five Groundwater Management Districts (GMDs) were analyzed for trends in irrigation water use, acres irrigated, precipitation, irrigation system types, and irrigated crop types to determine the effects of irrigation practices on water use over time. For the study period 1991 through 2003, precipitation decreased significantly (with 95-percent confidence) in northwestern and west-central Kansas but not in the southwestern and south-central parts of the State. Irrigation water use had no statistically significant trend during this period. There was a good (R= -0.77) relation between average regional precipitation and total GMD irrigation water use. When irrigation water use was adjusted for this relation, there was a positive trend (90-percent confidence level) in the adjusted irrigation water use. Another adjustment to water use was made using the ratio of annual precipitation to 1991-2005 average precipitation, which resulted in a negative trend (95-percent confidence level) in irrigation water use. This demonstrated the contradictory nature of precipitation adjustments to water use, making their utility somewhat suspect. GMD 3 in southwestern Kansas used 63 percent of the total acre-feet of irrigation water within all the GMDs. When all GMDs are considered, the number of irrigated acres for flood and center pivot systems without drop nozzles decreased significantly during the study period. At the same time the number of drop nozzle irrigated acres increased significantly. The number of irrigated acres of water-intensive crops (corn, alfalfa, and soybeans) also increased significantly, whereas the number of less- or non-water-intensive crops (grain sorghum and wheat), and multiple crop type acres decreased. Drop nozzle irrigation systems used approximately 2 percent less water in a year-by-year comparison than center pivot systems and 8 to 11 percent less water than flood irrigation. The best estimator of irrigation water use incorporated total acres irrigated and annual average or March-October regional precipitation. A conclusion that can be drawn from the trend analyses described in this report is that, although irrigation water use for all GMDs showed no statistically significant trend, an apparent increased efficiency of center pivots irrigation systems with drop nozzles has allowed more water-intensive crops to be grown on more irrigated acres.

Scientific Investigations Report↗
USGS2008

Conceptual Model of Hydrologic and Thermal Conditions of the Eastbank Aquifer System near Rocky Reach Dam, Douglas County, Washington

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.

Scientific Investigations Report↗
USGS2008

Statistical analysis of major ion and trace element geochemistry of water, 1986-2006, at seven wells transecting the freshwater/saline-water interface of the Edwards aquifer, San Antonio, Texas

This report by the U.S. Geological Survey, in cooperation with the San Antonio Water System, describes the results of a statistical analysis of major ion and trace element geochemistry of water at seven wells transecting the freshwater/saline-water interface of the Edwards aquifer in San Antonio, Texas, either over time or in response to variations in hydrologic conditions. The data used in this report were collected during 1986–2006. The seven monitoring wells are screened at different depths in the aquifer at three sites that form a generally north-to-south transect. The three wells of the southern site and the deeper of the two middle-site wells are open to the freshwater/saline-water transition zone, which contains saline water. The shallower well of the middle site and the two wells of the northern site are open to the freshwater zone. Mean specific conductance (SC) values were greater at transition-zone wells than at freshwater-zone wells, but SC did not vary systematically with depth. Concentrations of all major ions except bicarbonate were greater at transition-zone wells than at freshwater-zone wells, but concentrations tended to be more variable at freshwater-zone wells. Mean molar ratios of magnesium:calcium, sulfate:chloride, and sodium:chloride were similar at transition-zone wells and freshwater-zone wells. Concentrations of trace elements for many water samples at the seven transect wells were below the laboratory analytical reporting level. Detections of trace elements were more frequent at transition-zone wells, and mean concentrations of cadmium, chromium, copper, lead, and silver were elevated at transition-zone wells relative to freshwater-zone wells. All strong correlations between SC and major ions were positive, and in general there were more and stronger correlations between SC and major ions in the water from the freshwater-zone wells than from the transition-zone wells. Except for the shallowest transition-zone well, the transition-zone wells had relatively few strong correlations overall. The lack of a strong correlation indicates that much of the variability in the major ion concentrations at these wells might be a result of analytical variability caused by the multiple laboratory analytical methods used. In most cases, strong correlations between concentrations of trace elements were positive, and transition-zone wells and freshwater-zone wells had water with a similar number of significant correlations. Principal components analysis indicates dilution of ground water by low-ionic-strength meteoric water at the three freshwater-zone wells and at the shallowest transition-zone well. At the two deeper transition-zone wells at the southern site, principal components analysis indicates that there is no systematic variation in major ion concentrations. At three transition-zone wells, there was a general trend toward less salinity over the 21-year period of sampling. Trends in SC at the freshwater-zone wells were less consistent. There is no systematic change in the direction of trend in SC by water type (saline or fresh), between sites, or with depth. In general, trends in major ion concentrations corresponded to those in SC. For each trace element over the 21-year sampling period, there was either no trend or a downward trend. Relations between SC, major ions, and major ion molar ratios and hydrologic indicators (concurrent or prior time-averaged measures of water level and effective rainfall) were investigated. Correlations between geochemical variables and measures of water level in the freshwater-zone wells were much more frequent than correlations between geochemical variables and measures of water level in the transition-zone wells. There were correlations between SC and all measures of water level at the two freshwater-zone wells at the northern site, but there were no correlations between SC and any measures of water level at any transition-zone wells. SC was correlated with effective rainfall at all freshwater-zone wells and at one transition-zone well. The statistical analyses taken together indicate that the geochemistry at the freshwater-zone wells is more variable than that at the transition-zone wells. The geochemical variability at the freshwater-zone wells might result from dilution of ground water by meteoric water. This is indicated by relatively constant major ion molar ratios; a preponderance of positive correlations between SC, major ions, and trace elements; and a principal components analysis in which the major ions are strongly loaded on the first principal component. Much of the variability at three of the four transition-zone wells might result from the use of different laboratory analytical methods or reporting procedures during the period of sampling. This is reflected by a lack of correlation between SC and major ion concentrations at the transition-zone wells and by a principal components analysis in which the variability is fairly evenly distributed across several principal components. The statistical analyses further indicate that, although the transition-zone wells are less well connected to surficial hydrologic conditions than the freshwater-zone wells, there is some connection but the response time is longer.

Texas↗
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↗
USGS2013

Summary and interpretation of discrete and continuous water-quality monitoring data, Mattawoman Creek, Charles County, Maryland, 2000-11

Discrete samples and continuous (15-minute interval) water-quality data were collected at Mattawoman Creek (U.S. Geological Survey station number 01658000) from October 2000 through January 2011, in cooperation with the Charles County (Maryland) Department of Planning and Growth Management, the Maryland Department of the Environment, and the Maryland Geological Survey. Mattawoman Creek is a fourth-order Maryland tributary to the tidal freshwater Potomac River; the creek’s watershed is experiencing development pressure due to its proximity to Washington, D.C. Data were analyzed for the purpose of describing ambient water quality, identifying potential contaminant sources, and quantifying nutrient and sediment loads to the tidal freshwater Mattawoman estuary. Continuous data, collected at 15-minute intervals, included discharge, derived from stage measurements made using a pressure transducer, as well as water temperature, pH, specific conductance, dissolved oxygen, and turbidity, all measured using a water-quality sonde. In addition to the continuous data, a total of 360 discrete water-quality samples, representative of monthly low-flow and targeted storm conditions, were analyzed for suspended sediment and nutrients. Continuous observations gathered by a second water-quality sonde, which was temporarily deployed in 2011 for quality-control purposes, indicated substantial lateral water-quality gradients due to inflow from a nearby tributary, representing about 10 percent of the total gaged area upstream of the sampling location. These lateral gradients introduced a time-varying bias into both the continuous and discrete data, resulting in observations that were at some times representative of water-quality conditions in the main channel and at other times biased towards conditions in the tributary. Despite this limitation, both the continuous and discrete data provided insight into the watershed-scale factors that influence water quality in Mattawoman Creek. Annual precipitation over the study period was representative of the long-term record for southern Maryland. The median value of continuously measured discharge was 25 cubic feet per second (ft 3 /s), and the maximum observed value was 3,210 ft 3 /s; there were 498 days, or about 15 percent of the study period, when flow was zero or too low to measure. Continuously measured water temperature followed a seasonal trend characteristic of the geographic setting; the trend in dissolved oxygen was inverted relative to temperature, and reflected nearly saturated conditions year round. Relations between discharge and both pH and specific conductance indicate that stream water can be conceptualized as a mixture of acidic, dilute precipitation with pH-neutral groundwater of higher conductance. Specific conductance data showed a pronounced winter peak in both median and extreme measurements, indicating the influence of road salt. However, this influence is minor relative to that observed in the Northeast Branch Anacostia River (U.S. Geological Survey station number 01649500), a nearby, more heavily urbanized comparison basin. The median suspended-sediment concentration in discrete samples was 24 milligrams per liter (mg/L), with minimum and maximum concentrations of 1 mg/L and 2,890 mg/L, respectively. Total nitrogen ranged from 0.21 mg/L to 4.09 mg/L, with a median of 0.69 mg/L; total phosphorus ranged from less than 0.01 mg/L to 0.98 mg/L, with a median of 0.07 mg/L. Total nitrogen was dominated by the dissolved organic fraction (49 percent based on median species concentrations); total phosphorus was predominantly particulate (70 percent). Seasonal trends in suspended-sediment concentration indicate a supply subsidy in late winter and spring; this could be linked to flood-plain interaction, mobilization of sediment from the channel or banks, or anthropogenic input. Seasonal trends for both total phosphorus and total nitrogen generally corresponded to seasonal trends for suspended sediment, indicating a common underlying physical control, likely acting in synchrony with seasonal biological controls on total nutrient concentrations. Speciation of phosphorus, including proportional concentration of the biologically available dissolved inorganic fraction, did not vary seasonally. The speciation of nitrogen reflected demand for inorganic nitrogen and associated transformation into organic nitrogen during the growing season. Stepwise regression models were developed, using continuous data corresponding to collection times for discrete samples as candidate surrogates for suspended sediment, total phosphorus, and total nitrogen. Turbidity and discharge were both included in the model for suspended sediment (R 2 = 0.76, n = 185); only turbidity was selected as a robust predictor of total phosphorus and nitrogen (R 2 = 0.68 and 0.61, respectively, n = 186 for both). Loads of sediment and nutrients to the downstream Mattawoman estuary were computed using the U.S. Geological Survey computer program LOADEST. Load estimation included comparison of a routinely applied seven-parameter regression model based on time, season, and discharge, with an eight-parameter model that also includes turbidity. Adding turbidity decreased total load estimates, based on hourly data for a fixed 2-month period, by 21, 8, and 3 percent for suspended sediment, total phosphorus, and total nitrogen, respectively, in addition to decreasing the standard error of prediction for all three constituents. The seasonal pattern in specific conductance, reflecting road salt application, is the strongest evidence of the effect of upstream development on water quality at Mattawoman Creek. Accordingly, ongoing continuous monitoring for trends in specific conductance would be the most reliable means of detecting further degradation associated with increased development.

Charles County, Maryl↗
USGS2013

Computed statistics at streamgages, and methods for estimating low-flow frequency statistics and development of regional regression equations for estimating low-flow frequency statistics at ungaged locations in Missouri

The weather and precipitation patterns in Missouri vary considerably from year to year. In 2008, the statewide average rainfall was 57.34 inches and in 2012, the statewide average rainfall was 30.64 inches. This variability in precipitation and resulting streamflow in Missouri underlies the necessity for water managers and users to have reliable streamflow statistics and a means to compute select statistics at ungaged locations for a better understanding of water availability. Knowledge of surface-water availability is dependent on the streamflow data that have been collected and analyzed by the U.S. Geological Survey for more than 100 years at approximately 350 streamgages throughout Missouri. The U.S. Geological Survey, in cooperation with the Missouri Department of Natural Resources, computed streamflow statistics at streamgages through the 2010 water year, defined periods of drought and defined methods to estimate streamflow statistics at ungaged locations, and developed regional regression equations to compute selected streamflow statistics at ungaged locations. Streamflow statistics and flow durations were computed for 532 streamgages in Missouri and in neighboring States of Missouri. For streamgages with more than 10 years of record, Kendall’s tau was computed to evaluate for trends in streamflow data. If trends were detected, the variable length method was used to define the period of no trend. Water years were removed from the dataset from the beginning of the record for a streamgage until no trend was detected. Low-flow frequency statistics were then computed for the entire period of record and for the period of no trend if 10 or more years of record were available for each analysis. Three methods are presented for computing selected streamflow statistics at ungaged locations. The first method uses power curve equations developed for 28 selected streams in Missouri and neighboring States that have multiple streamgages on the same streams. Statistical estimates on one of these streams can be calculated at an ungaged location that has a drainage area that is between 40 percent of the drainage area of the farthest upstream streamgage and within 150 percent of the drainage area of the farthest downstream streamgage along the stream of interest. The second method may be used on any stream with a streamgage that has operated for 10 years or longer and for which anthropogenic effects have not changed the low-flow characteristics at the ungaged location since collection of the streamflow data. A ratio of drainage area of the stream at the ungaged location to the drainage area of the stream at the streamgage was computed to estimate the statistic at the ungaged location. The range of applicability is between 40- and 150-percent of the drainage area of the streamgage, and the ungaged location must be located on the same stream as the streamgage. The third method uses regional regression equations to estimate selected low-flow frequency statistics for unregulated streams in Missouri. This report presents regression equations to estimate frequency statistics for the 10-year recurrence interval and for the N-day durations of 1, 2, 3, 7, 10, 30, and 60 days. Basin and climatic characteristics were computed using geographic information system software and digital geospatial data. A total of 35 characteristics were computed for use in preliminary statewide and regional regression analyses based on existing digital geospatial data and previous studies. Spatial analyses for geographical bias in the predictive accuracy of the regional regression equations defined three low-flow regions with the State representing the three major physiographic provinces in Missouri. Region 1 includes the Central Lowlands, Region 2 includes the Ozark Plateaus, and Region 3 includes the Mississippi Alluvial Plain. A total of 207 streamgages were used in the regression analyses for the regional equations. Of the 207 U.S. Geological Survey streamgages, 77 were located in Region 1, 120 were located in Region 2, and 10 were located in Region 3. Streamgages located outside of Missouri were selected to extend the range of data used for the independent variables in the regression analyses. Streamgages included in the regression analyses had 10 or more years of record and were considered to be affected minimally by anthropogenic activities or trends. Regional regression analyses identified three characteristics as statistically significant for the development of regional equations. For Region 1, drainage area, longest flow path, and streamflow-variability index were statistically significant. The range in the standard error of estimate for Region 1 is 79.6 to 94.2 percent. For Region 2, drainage area and streamflow variability index were statistically significant, and the range in the standard error of estimate is 48.2 to 72.1 percent. For Region 3, drainage area and streamflow-variability index also were statistically significant with a range in the standard error of estimate of 48.1 to 96.2 percent. Limitations on the use of estimating low-flow frequency statistics at ungaged locations are dependent on the method used. The first method outlined for use in Missouri, power curve equations, were developed to estimate the selected statistics for ungaged locations on 28 selected streams with multiple streamgages located on the same stream. A second method uses a drainage-area ratio to compute statistics at an ungaged location using data from a single streamgage on the same stream with 10 or more years of record. Ungaged locations on these streams may use the ratio of the drainage area at an ungaged location to the drainage area at a streamgage location to scale the selected statistic value from the streamgage location to the ungaged location. This method can be used if the drainage area of the ungaged location is within 40 to 150 percent of the streamgage drainage area. The third method is the use of the regional regression equations. The limits for the use of these equations are based on the ranges of the characteristics used as independent variables and that streams must be affected minimally by anthropogenic activities.

Missouri↗
USGS2014

Aquifers of Arkansas: protection, management, and hydrologic and geochemical characteristics of groundwater resources in Arkansas

Sixteen aquifers in Arkansas that currently serve or have served as sources of water supply are described with respect to existing groundwater protection and management programs, geology, hydrologic characteristics, water use, water levels, deductive analysis, projections of hydrologic conditions, and water quality. State and Federal protection and management programs are described according to regulatory oversight, management strategies, and ambient groundwater-monitoring programs that currently (2013) are in place for assessing and protecting groundwater resources throughout the State. Physical attributes, groundwater geochemistry, and groundwater quality are described for each of the 16 aquifers of the State. Information in regard to the hydrology and geochemistry of each of the aquifers is summarized from about 550 historical and recent publications. Additionally, more than 8,000 sites with groundwater-quality data were obtained from the U.S. Geological Survey National Water Information System and the Arkansas Department of Environmental Quality databases and entered into a spatial database to investigate distribution and trends in chemical constituents for each of the aquifers. The 16 aquifers of the State were divided into two major physiographic regions of the State: the Coastal Plain Province (referred to as Coastal Plain) of eastern and southern Arkansas, which includes 11 of the 16 aquifers, and the Interior Highlands Division (referred to as Interior Highlands) of western Arkansas, which includes the remaining 5 aquifers. The 11 aquifers in the Coastal Plain consist of various geologic units that are Cenozoic in age and consist primarily of Cretaceous, Tertiary, and Quaternary sands, gravels, silts, and clays. Groundwater in the Coastal Plain represents one of the most valuable natural resources in the State, driving the economic engines of agriculture, while also supplying abundant water for commercial, industrial, and public-supply use. In terms of age from youngest to oldest, the aquifers of the Coastal Plain include Quaternary alluvial aquifers, including the Mississippi River Valley alluvial aquifer (the most important aquifer in Arkansas in terms of volume of use and economic benefits), the Jackson Group (a regional confining unit that served for decades as an important source of domestic supply), and the Cockfield, Sparta, Cane River, Carrizo, Wilcox, Nacatoch, Ozan, Tokio, and Trinity aquifers. The Mississippi River Valley alluvial aquifer accounts for approximately 94 percent of all groundwater used in the State, and the aquifer is used primarily for irrigation purposes. The Sparta aquifer is the second most important aquifer in terms of use, and the aquifer was used in the past dominantly as a source of public and industrial supply, although increasing irrigation use is occurring because of critically declining water levels in the Mississippi River Valley alluvial aquifer. Other aquifers of the Coastal Plain generally are used as important local sources of domestic, industrial, and public supply, in addition to other minor uses. Water quality generally is good for all aquifers of the Coastal Plain, except for elevated iron concentrations and localized areas of high salinity. The high salinity results from intrusion from underlying formations, evapotranspiration processes in areas of low recharge, and inadequate flushing in downgradient areas of residual salinity from deposition in marine environments. Trends in the spatial distribution of individual chemical constituents are related to position along the flow path for most aquifers of the Coastal Plain. These trends include elevated iron and nitrate concentrations with lower pH values and dissolved solids in groundwater from the outcrop areas, transitioning to lower iron and nitrate (related to changes in redox) and higher pH and dissolved solids (dominantly from the dissolution of carbonate minerals) in groundwater downgradient from outcrop areas. Groundwater generally trended from a calcium- to a sodium-bicarbonate water type with increasing cation exchange along the flow path. The Interior Highlands of western Arkansas has less reported groundwater use than other areas of the State, reflecting a combination of factors. These factors include prevalent and increasing use of surface water, less intensive agricultural uses, lower population and industry densities, lesser potential yield of the resource, and lack of detailed reporting. The overall low yields of aquifers of the Interior Highlands result in domestic supply as the dominant use, with minor industrial, public, and commercial-supply use. Where greater volumes are required for growth of population and industry, surface water is the greatest supplier of water needs in the Interior Highlands. The various aquifers of the Interior Highlands generally occur in shallow, fractured, well-indurated, structurally modified bedrock of this mountainous region of the State, as compared to the relatively flat-lying, unconsolidated sediments of the Coastal Plain. In terms of age from youngest to oldest, the aquifers of the Interior Highlands include: the Arkansas River Valley alluvial aquifer, the Ouachita Mountains aquifer, the Western Interior Plains confining system, the Springfield Plateau aquifer, and the Ozark aquifer. Spatial trends in groundwater geochemistry in the Interior Highlands differ greatly from trends noted for aquifers of the Coastal Plain. In the Coastal Plain, the prevalence of long regional flow paths results in regionally predictable and mappable geochemical changes along the flow paths. In the Interior Highlands, short, topographically controlled flow paths (from hilltops to valleys) within small watersheds represent the predominant groundwater-flow system. As such, dense data coverage from numerous wells would be required to effectively characterize these groundwater basins and define small-scale geochemical changes along any given flow path for aquifers of the Interior Highlands. Changes in geochemistry generally were related to rock type and residence time along individual flow paths. Dominant changes in geochemistry for the Ouachita Mountains aquifer and the Western Interior Plains confining system are attributed to rock/water interaction and changes in redox zonation along the flow path. In these areas, groundwater evolves along flow paths from a calcium- to a sodium-bicarbonate water type with increasing reducing conditions resulting in denitrification, elevated iron and manganese concentrations, and production of methane in the more geochemically evolved and strongest reducing conditions. In the Ozark and Springfield Plateau aquifers, rapid influx of surface-derived contaminants, especially nitrogen, coupled with few to no attenuation processes was attributed to the karst landscape developed on Mississippian- and Ordovician-age carbonate rocks of the Ozark Plateaus. Increasing nitrate concentrations are related to increasing agricultural land use, and areas of mature karst development result in higher nitrate concentrations than areas with less karst features.

Arkasas↗
USGS2016

Modern (1992–2011) and projected (2012–99) peak snowpack and May–July runoff for the Fort Peck Lake and Lake Sakakawea watersheds in the Upper Missouri River Basin

Mountain snowpack is an important contributor to runoff in the Upper Missouri River Basin; for example, high amounts of winter and spring precipitation in the mountains and plains in 2010–11 were associated with the peak runoff of record in 2011 in the Upper Missouri River Basin. To project trends in peak mountain snowpack and runoff in the upcoming decades, multiple linear regression models of peak mountain snowpack and total May–July runoff were developed for the Fort Peck Lake (above Fort Peck Dam) and lower Lake Sakakawea watersheds (between Fort Peck and Garrison Dams) in the Upper Missouri River Basin. Input to regression models included seasonal estimates of precipitation, air temperature, and total reference evapotranspiration stratified by elevation. Calibration was based on records from 107 weather stations from 1991 to 2011. Regressed annual peak mountain snowpack was used as input to the transfer function of May–July runoff. Peak snowpack and May–July runoff were projected for 2012–99 on the basis of air temperature and precipitation from the Community Climate System Model (CCSM) output. Two estimates of projected peak snowpack and May–July runoff for 2012–99 were computed: one estimate was based on output from the CCSM, version 3.0 (CCSM3), and the second estimate was based on output from the CCSM, version 4.0 (CCSM4). The significance of projected trends was based on the Kendall’s tau nonparametric test. Annual peak snowpack was projected to have a downward trend for the Fort Peck Lake watershed and an upward trend for the lower Lake Sakakawea watershed. Projections of May–July runoff had a significant downward trend for the Fort Peck Lake, lower Lake Sakakawea, and Lake Sakakawea (combination of Fort Peck Lake and lower Lake Sakakawea) watersheds. Downward trends in projected May–July runoff indicated that power production at Fort Peck Dam might be affected particularly in the later part of the simulation (2061–99); however, confidence in projected May–July runoff for the later part of the simulation was less certain because bias-corrected air temperatures from CCSM3 and CCSM4 commonly fell outside of the observed range used for calibration. Projected May–July runoff combined for the Fort Peck Lake and lower Lake Sakakawea watersheds were on the order of magnitude of the 2011 flood for 1 simulation year for each of the CCSM-based simulations. High peak snowpack and precipitation in April, May, and June in the plains was associated with large May–July runoff events; therefore, high precipitation at lower elevations in the Fort Peck Lake and lower Lake Sakakawea watersheds was a factor in the simulation of extreme runoff events at the magnitude of the 2011 flood.

Montana, North Dakota, Wyoming↗
USGS2019

Sediment storage and transport in the Nooksack River basin, northwestern Washington, 2006–15

The Nooksack River is a dynamic gravel-bedded river in northwestern Washington, draining off Mount Baker and the North Cascades into Puget Sound. Working in cooperation with the Whatcom County Flood Control Zone District, the U.S. Geological Survey studied topographic, hydrologic, and climatic data for the Nooksack River basin to document recent changes in sediment storage, long-term bed elevation trends, rates of sediment transport, and factors influencing surficial drainage in order to support ongoing river management. Differences in elevations between topographic and bathymetric surveys in 2005/06 and 2013/15 indicate the active channel aggraded about 1–2 feet locally near the cities of Ferndale and Everson but was primarily stable between them. The active channel upstream of Nugent’s Corner generally incised. Total incision upstream of Nugent’s Corner to Glacier Creek generated 2.3 ± 1.7 million cubic yards of sediment from 2005/06 to 2013 and likely represented a significant source of coarse sediment to the lower mainstem river over that time. Long-term records of local channel-bed elevation, derived from U.S. Geological Survey streamgage data, show bed-elevation changes of about 1–3 feet. The river bed at most streamgages exhibits long-term trends, with relatively consistent rates of change on the order of 1 foot per decade that persist years to decades. Lagged correlations in bed-elevation trends at all seven streamgages in the North Fork Nooksack and mainstem Nooksack suggest that decadal periods of persistent aggradation and incision originate in the North Fork and translate downstream. The channel-change signal propagates downstream 0.5–2.5 miles per year, with the rate of propagation scaling closely with channel slope. The pattern of incision and aggradation in the North Fork correlates with regional climate, where persistent incision follows extended cold and wet periods, and persistent aggradation follows extended warm and dry periods. Climate-driven variation in coarse-sediment delivery, primarily from the North Fork Nooksack, then appears to be a strong control on long-term vertical channel adjustments at sites downstream. The downstream-translating climate signal generated in the North Fork would account for recently observed aggradation at Everson and Ferndale but not the observed incision in unconfined reaches upstream of Nugent’s Corner from 2005–06 to 2013. This mismatch indicates that understanding how changes in sediment-supply influence those unconfined reaches remains a key uncertainty for predicting future channel change. Continuous turbidity monitoring integrated with suspended sediment and limited bedload sampling were used to calculate annual sediment loads at five sites in the basin. The sediment load in the lower river at Ferndale ranged from 0.78 to 1.17 million tons per year and averaged 0.97 million tons per year for WYs 2012–17. Suspended sediment made up 93 percent of the load, and bedload made up 7 percent. Most of the fine sediment load of the lower river is supplied from headwaters of the North, Middle, and South Fork Nooksack basins, with relatively little net increase in fine sediment loads in the lower mainstem basin. The three forks supply approximately equal proportions of the lower-river fine sediment load. However, the glacially sourced North and Middle Fork Nooksack basins carry a notably sandier suspended-sediment load than the South Fork Nooksack. A comparison of monthly streamflow and precipitation trends since 1981 indicate statistically significant increases in total spring precipitation and the number of spring days with measurable precipitation in much of the basin, as well as increases in mean spring river stage near Ferndale. Since no trends in mean spring discharge are observed, the trends in river stage are attributed primarily to observed changes in bed elevation. Changes in bed elevation and precipitation may then both have plausibly impacted field drainage in the lower river below Ferndale.

Washington↗
USGS2019

Flood-frequency estimates for Ohio streamgages based on data through water year 2015 and techniques for estimating flood-frequency characteristics of rural, unregulated Ohio streams

Estimates of the magnitudes of annual peak streamflows with annual exceedance probabilities of 0.5, 0.2, 0.1, 0.04, 0.02, 0.01, and 0.002 (equivalent to recurrence intervals of 2-, 5-, 10-, 25-, 50-, 100-, and 500-years, respectively) were computed for 391 streamgages in Ohio and adjacent states based on data collected through the 2015 water year. The flood-frequency estimates were computed following guidance outlined in Bulletin 17C, developed by the Advisory Committee on Water Information. The Bulletin 17C guidelines retain the basic statistical framework of the superseded Bulletin 17B guidelines; however, the Bulletin 17C guidelines add several enhancements including an improved method of moments approach for fitting the log-Pearson Type III (LPIII) distribution to the flood peaks (called the expected moments algorithm), a generalization of the Grubbs Beck low-outlier test (called the Multiple Grubbs Beck test) that permits identification of multiple potentially influential low floods, and new methods for estimating regional skew and uncertainty. Equations for estimating flood-frequency characteristics at ungaged sites on rural, unregulated streams in Ohio were developed with a two-step process involving ordinary least-squares and generalized least-squares regression techniques. Data from 333 streamgages with 10 or more years of unregulated record were screened for redundancy and a regression dataset was selected that was composed of flood-frequency and basin-characteristic data for 275 streamgages in Ohio and adjacent states. Two sets of equations were developed—one set, referred to as the “simple model,” uses regression region and drainage area as regressor variables, and a second set, referred to as the “full model,” uses regression region, drainage area, main-channel slope, and the percentage of the watershed covered by water and wetlands as regressor variables. The average standard errors of prediction ranged from about 40.5 to 46.5 percent for the simple-model equations and from about 37.2 to 40.3 percent for the full-model equations. For sites meeting the rural, unregulated criteria, flood-frequency estimates determined by means of LPIII analyses are reported along with weighted flood-frequency estimates, computed as a function of the LPIII estimates and the regression estimates. For sites with homogenous periods of regulation, flood-frequency estimates determined by means of LPIII analyses are reported. Ninety-five percent confidence limits are reported for all estimates. Values of regressor variables were determined from digital spatial datasets by means of a geographic information system (GIS). The GIS datasets and the new full-model equations have been incorporated into Ohio’s StreamStats application, a web-based, GIS-backed system designed to facilitate the estimation of streamflow statistics at ungaged locations on streams. Seasonal patterns in peak flows were assessed for 295 streamgages in Ohio. Annual peak flows occurred most frequently between January and April, with March having the highest frequency of occurrence. The month with the fewest number of annual peaks was October. Peak-of-record flows occurred most frequently in March, followed by January (months in which two of Ohio’s most severe widespread floods in recent history occurred). None of the peak-of-record flows occurred in October and only two occurred in November. Temporal trend in annual peak flows were assessed for 133 streamgages on unregulated streams in Ohio with 30 or more years of systematic record. Trends were assessed by computing the rank correlation (as measured with the two-sided Kendall’s tau statistic) between time and annual peak flows. Weak but statistically significant trends were indicated at 15 of the 133 streamgages. Of the 15 streamgages with significant trend in annual peak flows, 12 had an upward trend (positive tau) and 3 had a downward trend (negative tau). All 12 streamgages with positive tau values were at latitudes north of 40°33', and streamgages with negative tau values were at latitudes south of 40°33'.

Ohio↗
USGS2019

Aquifer storage change and storage properties, 2010–2017, in the Big Chino Subbasin, Yavapai County, Arizona

The Big Chino Subbasin is a groundwater basin that includes the Verde River headwaters in Yavapai County in north-central Arizona. Groundwater in the southern part of the subbasin is found primarily in the Big Chino and Williamson Valleys. The former is a potential municipal water source for growing communities in Yavapai County, particularly groundwater from the Big Chino Water Ranch, about 15 miles northwest of the community of Paulden. Groundwater in the Big Chino Valley discharges to wells (by pumping), by evapotranspiration, and to the upper Verde River springs, which form the headwaters of the Verde River. Groundwater also discharges to short perennial reaches of Williamson Valley Wash, Walnut Creek, and a small number of small, ungaged springs and seeps. To monitor changes in groundwater storage and to identify aquifer-storage properties, a network of repeat microgravity stations and groundwater-level monitoring stations was established in the Big Chino and Williamson Valleys in 2010. Small decreases in groundwater storage were observed throughout the study area from 2010 to 2017. Annual groundwater withdrawals for agricultural use varied between 2,800 and 4,000 acre-ft between 2013 and 2016, with an additional amount, probably less than 1,000 acre-ft, withdrawn for domestic use, primarily in the Paulden and Williamson Valley Wash areas. No local recharge events from sustained rainfall were observed during 2010 to 2017, and base-flow discharge in the Verde River near Paulden and Williamson Valley Wash near Paulden was consistently below the long-term average (for years 1964 to 2017 and 1966 to 2017, respectively) at each site. Relations between groundwater-level changes and aquifer-storage changes (determined from repeat microgravity data) indicate monitoring wells are representative primarily of semiconfined aquifer conditions in the Paulden area, the area west of Big Chino Wash, and the Big Chino Water Ranch area. Unconfined aquifer conditions are monitored in the Williamson Valley Wash area and at two sites in the Paulden area. Specific yield was estimated at five wells and ranged between 0.04 and 0.34, with a median value of 0.23. Negative groundwater-level trends (increasing depth to water) were observed between 2010 and 2017 at all sites where trends were identified using the Mann-Kendall trend test, except for the northernmost reaches of Big Chino Wash within and to the north of the Big Chino Water Ranch. Groundwater storage trends were negative at all sites where trends were identified except for one site in the foothills of the Santa Maria mountains west of Big Chino Wash. Declining storage in the Big Chino Water Ranch area, where water levels show no trend or are increasing, are likely the result of drying conditions in the unsaturated zone and (or) aquifers located above the aquifer(s) monitored by wells.

Arizona↗
USGS2021

Water-level conditions in the confined aquifers of the New Jersey Coastal Plain, 2013

The Coastal Plain aquifers of New Jersey provide an important source of water for more than 3.5 million people. In 2013, groundwater withdrawals from 10 confined aquifers of the New Jersey Coastal Plain totaled about 190 million gallons per day. Steadily increasing withdrawals from the late 1800s to the early 1990s resulted in declining water levels and the formation of regional cones of depression in many confined Coastal Plain aquifers. Starting in 1978, the U.S. Geological Survey (USGS) began mapping the potentiometric surfaces of the major confined Coastal Plain aquifers every 5 years to provide a regional assessment of groundwater conditions. In a study conducted by the USGS, in cooperation with the New Jersey Department of Environmental Protection, water levels in 10 confined aquifers of the New Jersey Coastal Plain were measured and evaluated to provide a regional overview of groundwater conditions during fall 2013. Water levels were measured in 987 wells in New Jersey, and parts of Pennsylvania and Delaware. Potentiometric-surface maps were prepared for, in ascending order of age, the confined Cohansey aquifer of Cape May County, Rio Grande water-bearing zone, Atlantic City 800-foot sand, Piney Point aquifer, Vincentown aquifer, Wenonah-Mount Laurel aquifer, Englishtown aquifer system, and the Upper, Middle, and Lower aquifers of the Potomac-Raritan-Magothy (PRM) aquifer system. Persistent, regionally extensive cones of depression were present in the potentiometric surfaces of the Englishtown aquifer system and Wenonah-Mount Laurel aquifer in Ocean and Monmouth Counties; Wenonah-Mount Laurel and Upper, Middle, and Lower PRM aquifers in Camden County; and Atlantic City 800-foot sand in Atlantic County. Changes in water levels from 2008 to 2013 were measured in many Coastal Plain aquifers in New Jersey. In some areas, water levels continued to decline as a result of pumping, but in other areas water levels continued to recover as a result of regulated decreases in groundwater withdrawals. Since 2008, in the confined Cohansey aquifer in Cape May County, water levels generally did not change; however, cones of depression in the potentiometric surface of the Piney Point aquifer in some areas of Cumberland County deepened by more than 20 feet (ft). In Critical Area 1, an area of restricted withdrawals, measured water levels in the Wenonah-Mount Laurel aquifer declined in parts of southern Monmouth County by more than 10 ft; however, rises in water levels of more than 10 ft were measured in parts of northern Ocean and Monmouth Counties. Since 2008, in Critical Area 2, also an area of restricted withdrawals, measured water levels in the Wenonah-Mount Laurel aquifer rose more than 20 ft in parts of western Burlington County and more than 20 ft in parts of western Camden County. Since 2008, in Critical Area 1, measured water levels in the Englishtown aquifer system declined in parts of eastern Ocean County by more than 10 ft and in southeastern Monmouth County by more than 20 ft; however, rises in water levels of more than 10 ft were measured in other parts of Ocean and Monmouth Counties. In general, since 2008 in Critical Area 2, in the Upper PRM aquifer, measured water levels continued to rise by 10 ft or more in central and western Burlington and central Camden Counties. In the Middle PRM aquifer in Critical Area 2, measured water levels rose in parts of central Camden County by 10 ft or more. However, measured water levels in the Lower PRM aquifer in Critical Area 2 were more than 10 ft lower in the center of the cone of depression in central Camden County, but measured water levels continued to rise updip from this area in Critical Area 2. Seasonal water-level fluctuations are presented in time-series hydrographs for 77 wells during 1978–2013. Analyses of long-term water-level changes for the period 2008–13 indicate downward water-level trends at 14 wells (18 percent), upward trends at 34 wells (44 percent), and no substantial change at 29 wells (38 percent). Downward trends were most often observed for wells screened in the Piney Point aquifer and the Atlantic City 800-foot sand. Upward water-level trends were most often measured for wells screened in the PRM aquifer system. Upward water-level trends also were measured for wells in the Englishtown aquifer system and the Wenonah-Mount Laurel aquifer in Critical Area 1 in some areas; however, downward trends and no substantial changes were measured in other areas.

New Jersey↗
USGS2020

Estimating flood magnitude and frequency on streams and rivers in Connecticut, based on data through water year 2015

The U.S. Geological Survey, in cooperation with the Connecticut Department of Transportation, updated flood-frequency estimates with 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities (2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-year recurrence intervals, respectively) for 141 streamgages in Connecticut and 11 streamgages in adjacent States using annual peak-flow data through water year 2015. Peak-flow regression equations were derived for estimating flows at ungaged stream sites with annual exceedance probabilities from 50 to 0.2 percent. Methods for estimating prediction intervals for the peak-flow regression equations are presented. The regression equations are applicable for basins in Connecticut with drainage areas ranging from 0.69 to 325 square miles that are not affected by flood-control regulation or flow diversions. The flood discharges for select annual exceedance probabilities were estimated following new (2018) national guidelines for flood-frequency analyses. New guidelines have improved statistical methods for flood-frequency analysis including (1) the expected moments algorithm to help describe uncertainty in annual peak flows and to better represent missing and historical record and (2) the generalized multiple Grubbs-Beck test to screen out potentially influential low outliers and to better fit the upper end of the peak-flow distribution. Additionally, a new regional skew (0.37) derived for New England was used in the flood-frequency analysis for the streamgages. Annual peak flows were analyzed for trends for four time periods (30, 50, 70, and 90 years) through 2015. Trend results show some statistical evidence of increasing peak flows in each of the time periods analyzed; however, multidecadal climate cycles may be influencing the number and magnitude of the trends. Historical peak-flow trends in and near Connecticut do not offer clear and convincing evidence for incorporating trends into flood-frequency analyses. For this study, the traditional assumption of stationarity is used with no adjustment for trends. Generalized least squares regression techniques were used to develop the final set of multivariable regression equations for estimating flood discharges with 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities. The standard error of prediction for the regional regression equations ranged from 26.3 to 45.0 percent. The standard error of prediction was slightly smaller in the current study compared to the 2004 study, indicating an improvement in the predictive ability of the equations (6 percent smaller at the 50-percent annual exceedance probability to about 1 percent smaller at the 1-percent annual exceedance probability). Generalized least squares regression techniques also were used to develop a one-variable (drainage-area-only) equation. Drainage-area-only equations can be used as an alternative to the multiexplanatory variable statewide regression equations if decreased accuracy is acceptable. The revised statistical procedures and additional streamgage data applied in the current study result in a more accurate representation of peak-flow conditions in Connecticut than was previously available. The regional regression equations will be integrated in the U.S. Geological Survey StreamStats program, which estimates basin and climatic characteristics and streamflow statistics at user-selected ungaged stream sites.

Connecticut↗
USGS2023

Characterization of streamflow and nutrient occurrence in the upper White River Basin, Colorado, 1980–2020

In 2016, Colorado Parks and Wildlife identified filamentous algae collected from the main stem White River as Cladophora glomerata , a pervasive nuisance aquatic alga. Excessive levels of filamentous algae can compromise aesthetic quality, limit recreational activities, and have negative effects on aquatic life including strong fluctuations in dissolved oxygen levels and a reduction in overall biodiversity. To increase understanding of the biology of the upper White River Basin in Colorado, identify potential factors promoting or limiting nuisance algal abundance, and outline information to aid in the understanding and protection of water resources, the U.S. Geological Survey (USGS), in cooperation with the White River and Douglas Creek Conservation Districts and the White River Algae Technical Advisory Group, initiated a study to collect and analyze physical, chemical, and biological information for the upper White River Basin. The report describes long-term changes and spatial variations in streamflow and nutrient concentrations and loads in the upper White River Basin and identifies possible nutrient sources in the basin. Long-term streamflow and nutrient data indicate that conditions in the upper White River Basin have become more favorable to benthic algae over varying timescales. Upward trends in total phosphorus concentrations and loads were found at three sites across the basin from 2000 to 2020. Total phosphorus loads increased around 50 percent, ranging from 18 to 48 pounds per year. Annual estimated concentrations of total phosphorus from 2005 to 2020 were above algal-specific nutrient criteria at the North Fork White River at Buford, Colo., indicating that phosphorus concentrations at this site likely promote algal growth. Discrete concentrations of total phosphorus exceeded algal-specific nutrient criteria on the South Fork and main stem White River during the summer season, though less frequently than samples collected from the North Fork White River. Nitrogen to phosphorus molar ratios collected from July to September indicate movement from colimitation (10–22) to nitrogen limited (less than 13) conditions at the North Fork White River at Buford, Colo. and the South Fork White River at Buford, Colo. starting in 2012. The magnitude of trends in phosphorus loads were generally greater than trends in concentrations across all sites, indicating that the largest changes in concentrations occurred during greater streamflow periods. At White River above Coal Creek, near Meeker, Colo., significant downward trends in streamflow were found in August and September for mean streamflow (15 and 14 percent per decade, respectively) and 7-day minimum streamflows (23 and 22 percent per decade, respectively). Significant downward trends in annual 7-day minimum streamflows of 24 percent per decade, or 66 percent over the 40-year period of analysis, were also observed. Though not significant based on 90-percent confidence intervals, downward trends in 1-day maximum and mean streamflows in May and June and corresponding increases in April may indicate a shift toward earlier snowmelt runoff, as observed across western North America and the Colorado River Basin. Alteration of the annual hydrograph can influence factors that influence algae including nutrient input and dilution potential, water temperature, dissolved oxygen, light availability, and physical disturbance. Results from a synoptic-style sampling identified the lower North Fork White River subbasin as a large source of phosphorus to the downstream system. Large increases in phosphorus loads were observed below Marvine Creek. Synoptic samples and samples collected during spring and summer of 2019 and 2020 also show large increases in total nitrogen, orthophosphate, and total phosphorus occurring at the furthest three downstream sites on the White River. To further evaluate sources of nitrogen in the upper White River Basin, the dual isotopic composition of nitrate was compared across four sites. The isotopic compositions of nitrate were all within the expected range of typical soil-derived nitrate, though the same values can also be derived from a mixture of agricultural fertilizer and manure or septic sources.

Colorado↗
USGS2025

Groundwater-level elevations in the Denver Basin bedrock aquifers and Upper Black Squirrel Creek alluvial aquifer, El Paso County, Colorado, 2021–24

El Paso County is the second-most populous county in Colorado and is projected to grow another 15 percent by 2030. Within El Paso County is the Upper Black Squirrel Creek Designated Groundwater Basin (Black Squirrel Basin), an area where surface water is scarce and water users rely primarily on groundwater from five different aquifers (the Upper Black Squirrel Creek alluvial aquifer and four bedrock aquifers within the Denver Basin aquifer system: the lower Dawson, Denver, Arapahoe, and Laramie-Fox Hills aquifers) to meet their needs. Currently (2024), land within the Upper Black Squirrel Creek Basin is primarily used for rural grazing and agriculture; however, municipal development is ongoing. In 2021, the U.S. Geological Survey, in cooperation with the Upper Black Squirrel Creek Ground Water Management District, began a study to establish a baseline dataset and assess the groundwater resources of the aquifers within the Black Squirrel Basin. A network of 39 wells was established in 2021; discrete groundwater-level measurements were made bimonthly. Nine of the 39 wells were equipped with pressure transducers to record hourly groundwater-level data. Seven wells had statistically significant seasonal trends, and trends at 3 wells were negative. For the discrete data, 16 wells had a significant trend for the study period, and 4 wells had negative trends. For the time-series data, 8 wells had significant trends, and 3 wells had negative trends. Potentiometric surface maps were created for this study using discrete, static groundwater levels measured in April 2023. These maps showed the estimated groundwater flow direction from the north-northwest to the south-southeast in the alluvial aquifer and from the northwest to the east-southeast for the lower Dawson and Denver aquifer wells. This study indicates the potential benefit of monitoring wells in the areas near municipal pumping. Additional monitoring could lead to a better understanding of connectivity between aquifers and be an important tool for assessing long-term sustainability of groundwater use.

Colorado↗
USGS2001

Hydrology of the coastal springs ground-water basin and adjacent parts of Pasco, Hernando, and Citrus Counties, Florida

The coastal springs in Pasco, Hernando, and Citrus Counties, Florida consist of three first-order magnitude springs and numerous smaller springs, which are points of substantial ground-water discharge from the Upper Floridan aquifer. Spring flow is proportional to the water-level altitude in the aquifer and is affected primarily by the magnitude and timing of rainfall. Ground-water levels in 206 Upper Floridan aquifer wells, and surface-water stage, flow, and specific conductance of water from springs at 10 gaging stations were measured to define the hydrologic variability (temporally and spatially) in the Coastal Springs Ground-Water Basin and adjacent parts of Pasco, Hernando, and Citrus Counties. Rainfall at 46 stations and ground-water withdrawals for three counties, were used to calculate water budgets, to evaluate long-term changes in hydrologic conditions, and to evaluate relations among the hydrologic components. Predictive equations to estimate daily spring flow were developed for eight gaging stations using regression techniques. Regression techniques included ordinary least squares and multiple linear regression techniques. The predictive equations indicate that ground-water levels in the Upper Floridan aquifer are directly related to spring flow. At tidally affected gaging stations, spring flow is inversely related to spring-pool altitude. The springs have similar seasonal flow patterns throughout the area. Water-budget analysis provided insight into the relative importance of the hydrologic components expected to influence spring flow. Four water budgets were constructed for small ground-water basins that form the Coastal Springs Ground-Water Basin. Rainfall averaged 55 inches per year and was the only source of inflow to the Basin. The pathways for outflow were evapotranspiration (34 inches per year), runoff by spring flow (8 inches per year), ground-water outflow from upward leakage (11 inches per year), and ground-water withdrawal (2 inches per year). Recharge (rainfall minus evapotranspiration) to the Upper Floridan aquifer consists of vertical leakage through the surficial deposits. Discharge is primarily through springs and diffuse upward leakage that maintains the extensive swamps along the Gulf of Mexico. The ground-water basins had slightly different partitioning of hydrologic components, reflecting variation among the regions. Trends in hydrologic data were identified using nonparametric statistical techniques to infer long-term changes in hydrologic conditions, and yielded mixed results. No trend in rainfall was detected during the past century. No trend in spring flow was detected in 1931-98. Although monotonic trends were not detected, rainfall patterns are naturally variable from month to month and year to year; this variability is reflected in ground-water levels and spring flows. A decreasing trend in ground-water levels was detected in the Weeki Wachee well (1966-98), but the trend was statistically weak. At current ground-water withdrawal rates, there is no discernible affect on ground-water levels and spring flows. Sporadic data records, lack of continuous data, and inconsistent periods of record among the hydrologic components impeded analysis of long-term changes to the hydrologic system and interrelations among components. The ongoing collection of hydrologic data from index sites could provide much needed information to assess the hydrologic factors affecting the quantity and quality of spring flow in the Coastal Springs Ground-Water Basin.

Water-Resources Investigations Report↗
USGS2002

Sediment deposition and selected water-quality characteristics in Cedar Lake and Lake Olathe, Northeast Kansas, 2000

The Lake Olathe watershed, located in northeast Kansas, was investigated using bathymetric survey data and reservoir bottom-sediment cores to determine sediment deposition, water-quality trends, and transport of nutrients (phosphorus and nitrogen species), selected trace elements, selected pesticides, and diatoms as indicators of eutrophic (organic-enriched and depleted oxygen supply) conditions. To determine sediment deposition and loads, bathymetric data from Cedar Lake and Lake Olathe, both located in the Lake Olathe watershed, were collected in 2000 and compared to historical topographic data collected when the lakes were built. Approximately 338 acre-feet of sediment deposition has occurred in Cedar Lake since dam closure in 1938, and 317 acre-feet has occurred at Lake Olathe since 1956. Mean annual sediment deposition was 5.45 acre-feet per year (0.89 acre-feet per year per square mile) for Cedar Lake and 7.0 acre-feet per year (0.42 acre-feet per year per square mile) for Lake Olathe. Mean annual sediment loads for the two reservoirs were 9.6 million pounds per year for Cedar Lake and 12.6 million pounds per year for Lake Olathe. Mean concentrations of total phosphorus in bottom-sediment samples from Cedar Lake ranged from 1,370 to 1,810 milligrams per kilogram, and concentrations in bottom-sediment samples from Lake Olathe ranged from 588 to 1,030 milligrams per kilogram. The implication of large total phosphorus concentrations in the bottom sediment of Cedar Lake is that inflow into Cedar Lake is rich in phosphorus and that adverse water-quality conditions could affect water quality in downstream Lake Olathe through discharge of water from Cedar Lake to Lake Olathe via Cedar Creek. Mean annual phosphorus loads transported from the Lake Olathe watershed were estimated to be 14,700 pounds per year for Cedar Lake and 9,720 pounds per year for Lake Olathe. The mean annual phosphorus yields were estimated to be 3.74 pounds per acre per year for Cedar Lake and 0.91 pound per acre per year for Lake Olathe. Phosphorus yields in the Cedar Lake watershed were largest of the six Kansas impoundment watersheds recently studied. Concentrations of total ammonia plus organic nitrogen as nitrogen in bottom sediment increased from upstream to downstream in both Cedar Lake and Lake Olathe. Mean concentrations of total ammonia plus organic nitrogen as nitrogen (N) ranged from 2,000 to 2,700 milligrams per kilogram in bottom-sediment samples from Cedar Lake and from 1,300 to 2,700 milligrams per kilogram in samples from Lake Olathe. There was no statistical significance between total ammonia plus organic nitrogen as nitrogen and depth of bottom sediment. Concentrations of six trace elements in bottom sediment from Cedar Lake and Lake Olathe (arsenic, chromium, copper, lead, nickel, and zinc) exceeded the U.S. Environmental Protection Agency Threshold Effects Levels (TELs) sediment-quality guidelines for aquatic organisms in sediment except for one lead concentration. Probable Effects Levels (PELs) for trace elements, however, were not exceeded at either lake. Organochlorine and organophosphate insecticides were not detected in bottom-sediment samples from either Cedar Lake or Lake Olathe, but the acetanilide herbicides alachlor and metolachlor were detected in sediment from both lakes. The U.S. Environmental Protection Agency has not proposed TEL or PEL guideline concentrations for bottom sediment for any of the organophosphate, acetanilide, or triazine pesticides. The diatoms (microscopic, single-celled organisms) Cyclotella bodanica , an indicator of low organic-enriched water, and Cyclotella meneghiniana , an indicator of organic-enriched water, were both present in bottom sediment from Lake Olathe. The presence of both of these diatoms suggests varying periods of low and high eutrophication in Lake Olathe from 1956 to 2000. The concentrations of two species in bottom sediment from Cedar Lake, Aulacoseira cf alpigena and Cyclotella meneghiniana , as well as two species in sediment from Lake Olathe, Aulacoseira cf alpigena and Stephanodiscus nigare , increased in sediment cores from the older bottom material to the more recent deposition near the top of the sediment cores. These diatom species indicate eutrophic conditions, and the increased concentration of these diatom species from the bottom of the cores to the sediment/water interface suggests that historically these lakes have been and continue to be eutrophic at times. Comparison of constituent trends between Cedar Lake and Lake Olathe using reservoir bottom sediment was not possible because sediment from Cedar Lake was suspected of having been disturbed. However, trends that may be reflective of historical changes in water quality were not detected in sediment from either Cedar Lake or Lake Olathe for total phosphorus, trace elements (except lead), and organochlorine or organophosphate pesticides. A slight increasing trend in the concentration of total ammonia plus organic nitrogen as nitrogen was seen in the sediment profile from Lake Olathe but not in the profile from Cedar Lake. The acetanilide herbicides alachlor and metolachlor were more prevalent in more recently deposited sediment in Cedar Lake and Lake Olathe, as was the triazine herbicide atrazine in Lake Olathe bottom sediment, suggesting a possible increasing trend in lake-inflow water concentrations. Trends in water-quality characteristics can be used by the Lake Olathe watershed managers to document historical changes in the watershed such as changes in land use, the suspension of the use of chlorinated insecticides, such as DDT and chlordane, and the use of hydrophobic fertilizers. The investigation described in this report provides a baseline of water-quality information to compare future changes in water quality or other watershed activities. With the addition of bathymetric surveys and the inclusion of additional reservoirs, reservoir sediment investigations can be used to estimate historical loads of phosphorus and other constituents in future water-quality assessments throughout Kansas.

Kansas↗
USGS1995

Streamflow analysis of the Apalachicola, Pearl, Trinity, and Nueces River basins, southeastern United States

Annual mean streamflow and annual minimum and maximum daily mean streamflows were compared with associated annual index precipitation for sites on the main channels and tributaries of four major rivers that discharge directly into the Gulf of Mexico. Long- and short-term precipitation trends were identified for selected streamflow stations with at least 40 years of record. Long-term temporal trends in annual mean streamflow and annual maximum daily mean streamflow to the Gulf were not identified from the Apalachicola River Basin for the period of record studied. Annual mean and maximum streamflow to the Gulf increased with time from the Pearl River Basin and decreased from the Trinity River Basin. Annual mean streamflow showed varied trends and annual maximum streamflow decreased from the Nueces River Basin. Annual minimum streamflow to the Gulf increased in all of the basins studied. The annual index precipitation associated with the most downstream station also increased during the periods of record studied in all four of the basins. Short-term trends in streamflow generally corresponded to trends in associated annual index precipitation for each station. For some streamflow stations in the Trinity River Basin, short-term trends in annual minimum streamflow increased while annual maximum streamflow decreased. Total reported surface-water withdrawals have increased more than fourfold in the Trinity River Basin since 1940. Surface-water withdrawals from the Trinity River Basin in 1988 represent about one-fourth of the annual mean streamflow near the mouth. Total withdrawals increased more than eightfold in the Nueces River Basin since 1940. Surface-water withdrawals from the Nueces River Basin in 1988 represent about one-third of the annual mean streamflow near the mouth. Effects of selected reservoirs on streamflow in the four basins also were studied. Predicted peak streamflow into the Gulf from the Apalachicola River was about 23 percent less for the 50- year peak streamflow after reservoir construction. Although one large reservoir was built on the Pearl River and many reservoirs have been built on the Trinity River and its tributaries, peak streamflow into the Gulf of Mexico from these rivers has not been affected during the past 50 years. Estimates from a water-budget analysis showed that the annual mean streamflow to the Gulf from the Nueces River was reduced by about 24 percent from 1985 through 1990 as a result of filling and evaporation at Choke Canyon Reservoir.

Apalachicola, Nueces, Pearl, and Trinity River bas↗