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USGS2007

Effects of the temporal variability of evapotranspiration on hydrologic simulation in central Florida

The transient response of a hydrologic system can be of concern to water-resource managers, because it is often extreme relatively short-lived events, such as floods or droughts, that profoundly influence the management of the resource. The water available to a hydrologic system for stream flow and aquifer recharge is determined by the difference of precipitation and evapotranspiration (ET). As such, temporal variations in precipitation and ET determine the degree of influence each has on the transient response of the hydrologic system. Meteorological, ET, and hydrologic data collected from 1993 to 2003 and spanning 1- to 3 2/3 -year periods were used to develop a hydrologic model for each of five sites in central Florida. The sensitivities of simulated water levels and flows to simple approximations of ET were quantified and the adequacy of each ET approximation was assessed. ET was approximated by computing potential ET, using the Hargreaves and Priestley-Taylor equations, and applying vegetation coefficients to adjust the potential ET values to actual ET. The Hargreaves and Priestley-Taylor ET approximations were used in the calibrated hydrologic models while leaving all other model characteristics and parameter values unchanged. Two primary factors that influence how the temporal variability of ET affects hydrologic simulation in central Florida were identified: (1) stochastic character of precipitation and ET and (2) the ability of the local hydrologic system to attenuate variability in input stresses. Differences in the stochastic character of precipitation and ET, both the central location and spread of the data, result in substantial influence of precipitation on the quantity and timing of water available to the hydrologic system and a relatively small influence of ET. The temporal variability of ET was considerably less than that of precipitation at each site over a wide range of time scales (from daily to annual). However, when precipitation and ET are of similar magnitude, small errors in ET can produce relatively large errors in available water, and accurate estimates of actual ET are more important. Local hydrologic conditions can also be an important factor influencing the hydrologic response to ET variability. Various points along a flow path in a hydrologic system respond differently to temporal variations in ET. For example, soil moisture contents in the root zone are sensitive to daily variations in ET, whereas spring flow responds to only longer term variations in ET. Both the Hargreaves and Priestley-Taylor equations for potential ET, when applied with an annually invariant monthly vegetation coefficient derived from comparison of measured ET with computed potential ET values, can be used with a hydrologic model to produce reasonable predictions of water levels and flows. Baseline-adjusted modified coefficients of efficiency for simulated water levels ranged from 0.0, indicating that water levels were simulated equally as well with approximated ET as with actual ET values, to -0.6, indicating that water levels were simulated better with actual ET values. Simulations using the Hargreaves approximation consistently yielded larger absolute and relative errors than the Priestley-Taylor approximation. However, the differences between the Hargreaves and Priestley-Taylor simulations generally were much smaller than differences between these simulations and the simulations using actual ET. This suggests that the simpler Hargreaves equation may be an adequate substitute for the more complex Priestley-Taylor equation, depending on the level of accuracy required to satisfy the particular modeling objectives.

Florida↗

USGS2010

Flood of April and May 2008 in Northern Maine

Severe flooding occurred in Aroostook and Penobscot Counties in northern Maine between April 28 and May 1, 2008, and was most extreme in the town of Fort Kent. Peak streamflows in northern Aroostook County were the result of a persistent heavy snowpack that caused high streamflows when it quickly melted during the third week of April 2008. Snowmelt was followed by from two to four inches of rainfall over a 2-day period in northern Maine. Peak water-surface elevations resulting from the flood were obtained from 13 continuous-record streamgages and 63 surveyed high-water marks in Aroostook and Penobscot Counties. Peak streamflows were obtained from 20 sites on 15 streams through stage/discharge rating curves or hydraulic flow models. Peak water-surface elevations and streamflows were the highest ever recorded at seven continuous-record streamgages, which had between 25 and 84 years of record in northern Aroostook County. The annual exceedance probability (the percent chance of exceeding the streamflow recorded during the April/May 2008 flood during any given year) at six streamgages in northern Maine was equal to or less than 1 percent. Data from flood-insurance studies published by the Federal Emergency Management Agency were available for five of the locations analyzed for the April/May 2008 flood and were compared to streamflows and observed peak water-surface elevations from the 2008 flood. Water-surface elevations that would be expected given the observed flow as applied to the effective flood insurance studies ranged from between 1 and 4 feet from the water-surface elevations observed during the 2008 flood. Differences were likely the result of up to 30 years of additional data for the calculation of recurrence intervals and the fact that hydraulic models used for the models had not previously been calibrated to a flood of this magnitude.

Scientific Investigations Report↗

USGS2014

Evaluation of the magnitude and frequency of floods in urban watersheds in Phoenix and Tucson, Arizona

Flooding in urban areas routinely causes severe damage to property and often results in loss of life. To investigate the effect of urbanization on the magnitude and frequency of flood peaks, a flood frequency analysis was carried out using data from urbanized streamgaging stations in Phoenix and Tucson, Arizona. Flood peaks at each station were predicted using the log-Pearson Type III distribution, fitted using the expected moments algorithm and the multiple Grubbs-Beck low outlier test. The station estimates were then compared to flood peaks estimated by rural-regression equations for Arizona, and to flood peaks adjusted for urbanization using a previously developed procedure for adjusting U.S. Geological Survey rural regression peak discharges in an urban setting. Only smaller, more common flood peaks at the 50-, 20-, 10-, and 4-percent annual exceedance probabilities (AEPs) demonstrate any increase in magnitude as a result of urbanization; the 1-, 0.5-, and 0.2-percent AEP flood estimates are predicted without bias by the rural-regression equations. Percent imperviousness was determined not to account for the difference in estimated flood peaks between stations, either when adjusting the rural-regression equations or when deriving urban-regression equations to predict flood peaks directly from basin characteristics. Comparison with urban adjustment equations indicates that flood peaks are systematically overestimated if the rural-regression-estimated flood peaks are adjusted upward to account for urbanization. At nearly every streamgaging station in the analysis, adjusted rural-regression estimates were greater than the estimates derived using station data. One likely reason for the lack of increase in flood peaks with urbanization is the presence of significant stormwater retention and detention structures within the watershed used in the study.

Arizona↗

USGS2015

Water levels and water quality in the Mississippi River Valley alluvial aquifer in eastern Arkansas, 2012

During the spring of 2012, the U.S. Geological Survey, in cooperation with the Arkansas Natural Resources Commission and the Arkansas Geological Survey, measured water levels in 342 wells completed in the Mississippi River Valley alluvial aquifer in eastern Arkansas. The Arkansas Natural Resources Commission measured water levels in 11 wells, and the U.S. Department of Agriculture-Natural Resources Conservation Service measured water levels in 239 wells completed in the alluvial aquifer and provided these data to the Arkansas Natural Resources Commission. In 2010, estimated water withdrawals from the alluvial aquifer in Arkansas totaled about 7,592 million gallons per day. Withdrawals more than doubled between 1985 and 2010, about a 115-percent increase. The regional direction of groundwater flow is generally to the south and east except where flow is affected by groundwater withdrawals. East of Crowleys Ridge, water flows from north to south along Crowleys Ridge and northeast to southwest along the Mississippi River. West of Crowleys Ridge, water flows from northeast to southwest along Crowleys Ridge from Clay County to Craighead County. From Craighead County to Monroe County, a depression redirects groundwater flow from all directions. A depression in Arkansas, Lonoke, and Prairie Counties alters groundwater flow from all directions. South of the Arkansas River, the flow is towards the southeast, except near depressions in Lincoln and Desha Counties and Desha and Chicot Counties where flow is towards the depression. In 2012, the lowest water-level altitude was 73 feet (ft) in Arkansas County. The highest water-level altitude was 288 ft in northeastern Clay County on the western side of Crowleys Ridge. The 2012 potentiomentric-surface map shows eight depressions, two large depressions and six small depressions. One large depression begins in southeastern Arkansas County, at the Arkansas and Desha County line, extends north into Prairie County, west into Lonoke County, and east into the westernmost part of Monroe County. The area in Lonoke, Prairie, and White Counties in the northwestern half of the depression has a water-level altitude measurement of 90 ft and has expanded into the northern third of Prairie County. The 2012 potentiometric-surface map shows a general north-south depression with the southern end in central Monroe County through western Lee, St. Francis, Cross, Poinsett, and Craighead Counties and eastern Woodruff and Jackson Counties. There are two deeper areas in this depression, one at the Monroe and Lee County line, with a low water-level altitude measurement of 123 ft, and the second in Poinsett County, with a low water-level altitude measurement of 113 ft. The six small depressions are located in northern Ashley County, in southern Desha and northern Chicot Counties, in eastern Lincoln and western Chicot Counties, at the Arkansas and Desha County line, in northern Phillips County, and in southeastern Greene County. A map showing the difference in water levels was constructed using 541 differences in water levels measured during 2008 and 2012. The difference in measured water levels from 2008 to 2012 ranged from -27.4 ft to 18.7 ft, with a mean of -1.0 ft. The largest decline of -27.4 ft occurred in Lonoke County, and the largest rise of 18.7 ft occurred in Prairie County. Four areas were predominated by declines—west of Crowleys Ridge from Greene County south to Lee County, including Lawrence and southern Woodruff Counties; east of Crowleys Ridge from Clay County south to Poinsett County and Mississippi County; Lonoke and Jefferson Counties; and Ashley, Chicot, Desha, and Drew Counties. Three areas are predominated by rises in measured water levels—east of Crowleys Ridge in Crittenden, Cross, Lee, and St. Francis Counties; Jackson and northern Woodruff Counties; and Arkansas, Monroe, Phillips, Prairie, and White Counties. Long-term water-level changes were evaluated using hydrographs from 319 wells in the alluvial aquifer for the period from 1988 to 2012. The annual rise or decline in water level for the entire study area was -0.45 feet per year (ft/yr) with a range from -2.08 to 0.84 ft/yr. Arkansas County had two different rates of annual decline for the two hydrographs shown, about 0.97 ft/yr and about 0.26 ft/yr. In Craighead, Cross, Lee, Poinsett, and St. Francis Counties, water levels are declining at a greater rate in areas west of Crowleys Ridge than in areas east of Crowleys Ridge. Two hydrographs are shown in each of Craighead, Cross, Lee, Poinsett, and St. Francis Counties, one on the west side of Crowleys Ridge and one on the east side of Crowleys Ridge. The hydrographs west of Crowleys Ridge have annual water-level declines from -0.91 to -1.24 ft/yr. The hydrographs east of Crowleys Ridge have annual water-level declines from -0.07 to -0.40 ft/yr. The mean county annual water-level declines for these counties range from -0.55 to -0.87 ft/yr. Water samples were collected in the summer of 2012 from142 wells completed in the alluvial aquifer and measured onsite for specific conductance, temperature, and pH. Samples were collected from 94 wells for dissolved chloride analysis. Specific conductance ranged from 91 microsiemens per centimeter at 25 degrees Celsius (μS/cm at 25 °C) in Drew County to 984 μS/cm at 25 °C in Monroe County. The mean specific conductance was 547 μS/cm at 25 °C. Temperature ranged from 18.1 degrees Celsius (°C) in Crittenden County to 22.4 °C in Prairie County. The mean temperature was 22.1 °C. The pH ranged from 8.3 in Randolph County to 6.2 in Drew County and had a median of 7.3. Dissolved chloride concentrations ranged from 3.34 milligrams per liter (mg/L) in Randolph County to 182 mg/L in Lincoln County. The mean chloride concentration was 27.6 mg/L.

Arkansas↗

USGS1996

Hydrologic feasibility of water-supply-development alternatives in Cape May County, New Jersey

Increasing public-supply withdrawals in Cape May County, New Jersey associated with increasing residential and seasonal tourist populations have led to regionally lowered ground-water levels, a reversal of ground-water flow directions toward onshore, and landward encroachment of saltwater in the shallow aquifer system. The three aquifers composing the shallow system are, in order of increasing depth, the unconfined Holly Beach water-bearing zone and the confined estuarine sand and Cohansey aquifers. The changes to the ground-water system have been greatest in the confined aquifers near the three major well fields on the Cape May peninsula. Formerly productive water-supply wells have been abandoned because of saltwater contamination. Concern about anthropogenic contamination has prevented shifting of withdrawals to the unconfined aquifer. Surface- water sources have also been little used. Further development on the peninsula involving increased water demand will exacerbate the current saltwater-encroachment problems. The purpose of this study was to test the feasibility of possible water-supply-development alternatives by use of predictive ground-water flow simulations. The alternatives involve (1) injection of tertiary- treated wastewater to replenish aquifer storage and create a hydraulic barrier to saltwater encroachment, (2) withdrawal of brackish water in order to create a hydraulic barrier, (3) conjunctive use of ground water and surface water, enabling the reduction of ground-water withdrawals, and (4) redistribution of withdrawals inland to the unconfined aquifer. Results of these simulations can potentially be used in the design of a water-supply-development strategy that preserves supply and a monitoring program that ensures early warning of saltwater encroachment, thereby allowing sufficient time for development of an alternative supply. The water-supply- development alternatives were evaluated by comparison of results of predictive simulations made with a previously calibrated ground-water flow model of the shallow aquifer system. The quasi-three-dimensional sharp-interface model was calibrated to 1988 annual average hydrologic conditions. The planning period for the predictive simulations is 1989-2049. For the planning period, total public-supply withdrawals were increased 100 percent over average 1983-88 withdrawals. Results of a baseline simulation involving only the increased withdrawals were compared to each of the simulated alternatives, which also include the withdrawals. Hydraulic heads, saltwater- freshwater interface movement, and ground-water flows were compared. Simulation results indicate that the barrier-injection or barrier-withdrawal scheme could be useful in managing the water supply for a specific location. The conjunctive- use scheme would provide a marginal regional hydrologic benefit. Redistribution of withdrawals appears to be the only regional alternative that would result in recovery of ground-water levels and would substantially slow saltwater encroachment; however, anthropogenic land-surface contamination of the unconfined aquifer would have to be considered if the redistribution alternative is acted upon.

Water-Resources Investigations Report↗

USGS2012

Estimates of tracer-based piston-flow ages of groundwater from selected sites: National Water-Quality Assessment Program, 2006-2010

Piston-flow age dates were interpreted from measured concentrations of environmental tracers from 812 National Water-Quality Assessment (NAWQA) Program groundwater sites from 27 Study Units across the United States. The tracers of interest include chlorofluorocarbons (CFCs), sulfur hexafluoride (SF 6 ), and tritium/helium-3 ( 3 H/ 3 He). Tracer data compiled for this analysis were collected from 2006 to 2010 from groundwater wells in NAWQA studies, including: * Land-Use Studies (LUS, shallow wells, usually monitoring wells, located in recharge areas under dominant land-use settings), * Major-Aquifer Studies (MAS, wells, usually domestic supply wells, located in principal aquifers and representing the shallow drinking water supply), * Flow System Studies (FSS, networks of clustered wells located along a flowpath extending from a recharge zone to a discharge zone, preferably a shallow stream) associated with Land-Use Studies, and * Reference wells (wells representing groundwater minimally impacted by anthropogenic activities) also associated with Land-Use Studies. Tracer data were evaluated using documented methods and are presented as aqueous concentrations, equivalent atmospheric concentrations (for CFCs and SF 6 ), and tracer-based piston-flow ages. Selected ancillary data, such as redox data, well-construction data, and major dissolved-gas (N 2 , O 2 , Ar, CH 4 , and CO 2 ) data, also are presented. Recharge temperature was inferred using climate data (approximated by mean annual air temperature plus 1°C [MAAT +1°C]) as well as major dissolved-gas data (N 2 -Ar-based) where available. The N 2 -Ar-based temperatures showed significantly more variation than the climate-based data, as well as the effects of denitrification and degassing resulting from reducing conditions. The N 2 -Ar-based temperatures were colder than the climate-based temperatures in networks where recharge was limited to the winter months when evapotranspiration was reduced. The tracer-based piston-flow ages compiled in this report are provided as a consistent means of reporting the tracer data. The tracer-based piston-flow ages may provide an initial interpretation of age in cases in which mixing is minimal and may aid in developing a basic conceptualization of groundwater age in an aquifer. These interpretations are based on the assumption that tracer transport is by advection only and that no mixing occurs. In addition, it is assumed that other uncertainties are minimized, including tracer degradation, sorption, contamination, or fractionation, and that terrigenic (natural) sources of tracers, and spatially variable atmospheric tracer concentrations are constrained.

Scientific Investigations Report↗

USGS1999

Trends in base flows and extreme flows in the Beaver Kill Basin, Catskill Mountains, New York, 1915-94

Long-term records from five streamflow-gaging stations within and near the 300-square mile Beaver Kill Basin were analyzed to determine whether construction and presence of New York State Route 17 (NY 17), which was completed in the late 1960's, could have altered hydrologic processes in the basin and thereby adversely affected the basin's trout populations. The hypothesis investigated is that NY 17 has altered surface-water and shallow ground-water flowpaths where it parallels the stream and has increased runoff rates and thereby (1) increased the range in stream discharge (prolonged the base flows, decreased the low flows, and increased the high flows), and (2) altered stream-channel morphology through increased volume and velocity of stormflows. Analyses of base flows, discharge-duration curves, stage-to-discharge relations, peak and bankfull discharges, and flow extremes at a downstream (Beaver Kill at Cooks Falls) and a small tributary (Little Beaver Kill at Livingston Manor) site provide only limited evidence that NY 17 affected hydrologic processes within the basin. These effects are best indicated by significant increases in the magnitude and (or) the frequency of moderate to large discharges (exceedence probabilities) on an instantaneous basis at the Beaver Kill at Cooks Falls site after 1965. Increases in stormflows can not be attributed solely to NY 17, however, because the trend was evident long before NY 17 was constructed. Changes in land use in parts of the watershed may have contributed to gradual and continuous increases in stormflows throughout the entire 80 (plus) years of record. Changes in most base-flow and low-flow statistics for the downstream (Beaver Kill at Cooks Falls) site after 1965 are not statistically significant, but, changes in flow-duration curves and annual peak flows are evident. Flow-duration curves at this site indicate that there is a 16 percent increase in average daily flows after 1965. Annual peak flow data indicate that peak flows from storms recurring at 2-year (and longer) intervals after 1965 are significantly larger than those that recur at the same frequencies before 1965. The lack of comparable increases in peak flows from several nearby reference sites after 1965 indicate that the observed increases in peak flows may be unique to the Beaver Kill Basin. Flow-duration curves and many base-flow and high-flow statistics for the small tributary paralleled by NY 17 in the in the upper reaches of the basin (Little Beaver Kill at Livingston Manor) appear to be considerably altered since NY 17 was constructed. Flow-duration curves at this site indicate that there is about a 54 percent increase in average daily flows after 1965. Increases in the ratio of average annual base flow to average annual flow until 1965 then subsequent decreases suggest an extreme affect of NY 17 on hydrology of the subbasin. The effect of NY 17 on hydrology of the Little Beaver Kill subbasin cannot be defined with certainty, however, because the flow record after 1965 is too short; discharge monitoring was discontinued in 1981. The increases in peak stormflows in the lower Beaver Kill basin through the period of record may have increased the rates of bed-sediment erosion (degradation) and deposition and accelerated changes in stream-channel morphology, however, these possible effects were not examined. Suggestions for further investigation of the effects of NY 17 and of other factors on hydrology, channel morphology, fish habitat, and fish populations in the Beaver Kill Basin include (1) addition of streamflow gages or a creststage gage network at critical locations, (2) a review of engineering records and other aerial photographs for indications of changes in channel morphology, (3) compilation of temperature data and modeling spatial extent and magnitude of stressful summer temperatures (to selected trout species), and (4) confirming the extent and severity of toxic thermal episodes using in-situ fish toxicity tests.

Open-File Report↗

USGS1971

Developing a state water plan: Ground-water conditions in Utah, spring of 1971

This report is the eighth in a series of annual reports that describe ground-water conditions in Utah. Reports in this series are prepared cooperatively by the U.S. Geological Survey and the Utah Division of Water Resources and are designed to provide data to enable interested parties such as legislators, administrators, and planners to keep abreast of changing ground-water conditions. This report, like the others (see references, p. 21), contains information on well construction, ground-water withdrawals, water-level changes, and related changes in precipitation and streamflow. It also contains supplementary data that are related to ground-water use in some areas. In reports of this series, the inclusion of such supplementary data as graphs showing chemical quality of water and maps showing water-table configuration is intended only for those years or areas for which applicable data are available and are important to a discussion of changing ground-water conditions. The report includes individual discussions of the most important areas of ground-water withdrawal in the State for the calendar year 1970. Water-level fluctuations, however, are described for the period spring 1970 to spring 1971. Many of the data used in the report were collected by the Geological Survey in cooperation with the Division of Water Rights, Utah Department of Natural Resources.

Utah↗

USGS2002

Contaminants in arctic snow collected over northwest Alaskan sea ice

Snow cores were collected over sea ice from four northwest Alaskan Arctic estuaries that represented the annual snowfall from the 1995-1996 season. Dissolved trace metals, major cations and anions, total mercury, and organochlorine compounds were determined and compared to concentrations in previous arctic studies. Traces (<4 nanograms per liter, ng L-1) of cis- and trans-chlordane, dimethyl 2,3,5,6-tetrachloroterephthalate, dieldrin, endosulfan II, and PCBs were detected in some samples, with endosulfan I consistently present. High chlorpyrifos concentrations (70-80 ng L-1) also were estimated at three sites. The snow was highly enriched in sulfates (69- 394 mg L-1), with high proportions of nonsea salt sulfates at three of five sites (9 of 15 samples), thus indicating possible contamination through long-distance transport and deposition of sulfate-rich atmospheric aerosols. Mercury, cadmium, chromium, molybdenum, and uranium were typically higher in the marine snow (n = 15) in relation to snow from arctic terrestrial studies, whereas cations associated with terrigenous sources, such as aluminum, frequently were lower over the sea ice. One Kasegaluk Lagoon site (Chukchi Sea) had especially high concentrations of total mercury (mean = 214 ng L-1, standard deviation = 5 ng L-1), but no methyl mercury was detected above the method detection limit (0.036 ng L-1) at any of the sites. Elevated concentrations of sulfate, mercury, and certain heavy metals might indicate mechanisms of contaminant loss from the arctic atmosphere over marine water not previously reported over land areas. Scavenging by snow, fog, or riming processes and the high content of deposited halides might facilitate the loss of such contaminants from the atmosphere. Both the mercury and chlorpyrifos concentrations merit further investigation in view of their toxicity to aquatic organisms at low concentrations.

Water, Air, & Soil Pollution↗

USGS2004

Water resources of the Tulalip Indian Reservation and adjacent area, Snohomish County, Washington, 2001-03

This study was undertaken to improve the understanding of water resources of the Tulalip Plateau area, with a primary emphasis on the Tulalip Indian Reservation, in order to address concerns of the Tulalip Tribes about the effects of current and future development, both on and off the Reservation, on their water resources. The drinking-water supply for the Reservation comes almost entirely from ground water, so increasing population will continue to put more pressure on this resource. The study evaluated the current state of ground- and surface-water resources and comparing results with those of studies in the 1970s and 1980s. The study included updating descriptions of the hydrologic framework and ground-water system, determining if discharge and base flow in streams and lake stage have changed significantly since the 1970s, and preparing new estimates of the water budget. The hydrogeologic framework was described using data collected from 255 wells, including their location and lithology. Data collected for the Reservation water budget included continuous and periodic streamflow measurements, micrometeorological data including daily precipitation, temperature, and solar radiation, water-use data, and atmospheric chloride deposition collected under both wet- and dry-deposition conditions to estimate ground-water recharge. The Tulalip Plateau is composed of unconsolidated sediments of Quaternary age that are mostly of glacial origin. There are three aquifers and two confining units as well as two smaller units that are only localized in extent. The Vashon recessional outwash (Qvr) is the smallest of the three aquifers and lies in the Marysville Trough on the eastern part of the study area. The primary aquifer in terms of use is the Vashon advance outwash (Qva). The Vashon till (Qvt) and the transitional beds (Qtb) act as confining units. The Vashon till overlies Qva and the transitional beds underlie Qva and separate it from the undifferentiated sediments (Qu), which are also a principal aquifer of the plateau. The undifferentiated-sediments aquifer is present throughout the entire study area, but is not well defined because few wells penetrate it. Ground water flows radially outward from the center of the Plateau in the Vashon advance outwash aquifer. Water levels fluctuate seasonally in all hydrogeologic units in response to changes in precipitation over the course of the year. However, water levels do not appear to have changed significantly over the long term. There was no statistically significant change between water levels measured in 72 wells in the early 1990s and 2001. Additionally, when a rank sum test was used to compare monthly water levels measured in 18 wells for this study with monthly water levels from the 1970s and 1980s, water levels increased in some wells, decreased in some, and did not change significantly in others. Ground water in the study area is recharged from precipitation that percolates down from the land surface. Average annual recharge, estimated using the chloride-mass-balance method, was 10.4 inches per year. Current streamflow conditions on the Reservation were defined by four continuous-record streamflow-gaging stations operated from April 2001 through March 2003 and monthly measurements of discharge at 12 periodic-measurement sites. Two continuous-record gaging stations (12157250 and 12158040) near the mouths of Mission and Tulalip Creeks, respectively, also were operated during water years 1975-77. Correlations of streamflow for Mission and Tulalip Creeks with the long-term record of streamflow at Mercer Creek (station 12120000) indicate no significant change in streamflow between the mid-1970s and 2001?03 in Mission and Tulalip Creeks. However, comparisons between the percentage of change in precipitation at the Everett precipitation station and percentages of change in streamflow at the Mercer, Mission, and Tulalip Creek gaging stations from the mid-1970s through 2001

Scientific Investigations Report↗

USGS2004

Sedimentation and occurrence and trends of selected chemical constituents in bottom sediment of 10 small reservoirs, Eastern Kansas

Many municipalities in Kansas rely on small reservoirs as a source of drinking water and for recreational activities. Because of their significance to the community, management of the reservoirs and the associated basins is important to protect the reservoirs from degradation. Effective reservoir management requires information about water quality, sedimentation, and sediment quality. A combination of bathymetric surveying and bottom-sediment coring during 2002 and 2003 was used to investigate sediment deposition and the occurrence of selected nutrients (total nitrogen and total phosphorus), organic and total carbon, 26 trace elements, 15 organochlorine compounds, and 1 radionuclide in the bottom sediment of 10 small reservoirs in eastern Kansas. Original reservoir water-storage capacities ranged from 23 to 5,845 acre-feet. The mostly agricultural reservoir basins range in area from 0.6 to 14 square miles. The mean annual net volume of deposited sediment, estimated separately for several of the reservoirs, ranged from about 43,600 to about 531,000 cubic feet. The estimated mean annual net mass of deposited sediment ranged from about 1,360,000 to about 23,300,000 pounds. The estimated mean annual net sediment yields from the reservoir basins ranged from about 964,000 to about 2,710,000 pounds per square mile. Compared to sediment yield estimates provided by a statewide study published in 1965, the estimates determined in this study differed substantially and were typically smaller. A statistically significant positive correlation was determined for the relation between sediment yield and mean annual precipitation. Nutrient concentrations in the bottom sediment varied substantially among the 10 reservoirs. Median total nitrogen concentrations ranged from 1,400 to 3,700 milligrams per kilogram. Median total phosphorus concentrations ranged from 550 to 1,300 milligrams per kilogram. A statistically significant positive trend (that is, nutrient concentration increased toward the top of the sediment core) was indicated in one reservoir for total nitrogen and in two reservoirs for total phosphorus. Also, a possible positive trend for total nitrogen was indicated in two other reservoirs. These trends in nutrient concentrations may be related to a statewide increase in fertilizer use. Alternatively, the trends may be indicative of diagenesis (that is, postdepositional changes in the sediment caused by various processes including decomposition). Nutrient loads and yields also varied substantially among the five reservoirs for which loads and yields were estimated. Estimated mean annual net loads of total nitrogen deposited in the bottom sediment ranged from 4,080 to 49,100 pounds. Estimated mean annual net loads of total phosphorus deposited in the bottom sediment ranged from 1,120 to 20,800 pounds. Estimated mean annual net yields of total nitrogen from the basins ranged from 2,210 to 6,800 pounds per square mile. Estimated mean annual net yields of total phosphorus from the basins ranged from 598 to 2,420 pounds per square mile. Compared to nonenforceable sediment-quality guidelines adopted by the U.S. Environmental Protection Agency, bottom-sediment concentrations of arsenic, chromium, copper, and nickel in samples from all 10 reservoirs typically exceeded the threshold-effects levels (TELs) but were less than the probable-effects levels (PELs). TELs represent the concentrations above which toxic biological effects occasionally occur in aquatic organisms, whereas PELs represent the concentrations above which toxic biological effects usually or frequently occur. Concentrations of cadmium, lead, and zinc exceeded the TELs but were less than the PELs in sediment samples from about one-half of the reservoirs and were less than the TELs in samples from the remaining reservoirs. Mercury concentrations were less than the TEL (information only available for four reservoirs). Silver was not detected in the bottom sediment fro

Scientific Investigations Report↗

USGS2007

Simulation of streamflow and estimation of ground-water recharge in the Upper Cibolo Creek Watershed, south-central Texas, 1992-2004

A watershed model (Hydrological Simulation Program?FORTRAN) was developed, calibrated, and tested by the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers, San Antonio River Authority, San Antonio Water System, and Guadalupe-Blanco River Authority, to simulate streamflow and estimate ground-water recharge in the upper Cibolo Creek watershed in south-central Texas. Rainfall, evapotranspiration, and streamflow data were collected during 1992?2004 for model calibrations and simulations. Estimates of average ground-water recharge during 1992?2004 from simulation were 79,800 acre-feet (5.47 inches) per year or about 15 percent of rainfall. Most of the recharge (about 74 percent) occurred as infiltration of streamflow in Cibolo Creek. The remaining recharge occurred as diffuse infiltration of rainfall through the soil and rock layers and karst features. Most recharge (about 77 percent) occurred in the Trinity aquifer outcrop. The remaining 23 percent occurred in the downstream part of the watershed that includes the Edwards aquifer recharge zone (outcrop). Streamflow and recharge in the study area are greatly influenced by large storms. Storms during June 1997, October 1998, and July 2002 accounted for about 11 percent of study-area rainfall, 61 percent of streamflow, and 16 percent of the total ground-water recharge during 1992?2004. Annual streamflow and recharge also were highly variable. During 1999, a dry year with about 16 inches of rain and no measurable runoff at the watershed outlet, recharge in the watershed amounted to only 0.99 inch compared with 13.43 inches during 1992, a relatively wet year with about 54 inches of rainfall. Simulation of flood-control/recharge-enhancement structures showed that certain structures might reduce flood peaks and increase recharge. Simulation of individual structures on tributaries showed relatively little effect. Larger structures on the main stem of Cibolo Creek were more effective than structures on tributaries, both in terms of flood-peak reduction and recharge enhancement. One simulated scenario that incorporated two main-stem structures resulted in a 37-percent reduction of peak flow at the watershed outlet and increases in stream-channel recharge of 6.6 percent in the Trinity aquifer outcrop and 12.6 percent in the Edwards aquifer (recharge zone) outcrop.

Texas↗

USGS2008

Ground-Water Storage Change and Land Subsidence in Tucson Basin and Avra Valley, Southeastern Arizona, 1998-2002

Gravity and land subsidence were measured annually at wells and benchmarks within two networks in Tucson Basin and Avra Valley from 1998 to 2002. Both networks are within the Tucson Active Management Area. Annual estimates of ground-water storage change, ground-water budgets, and land subsidence were made based on the data. Additionally, estimates of specific yield were made at wells within the monitored region. Increases in gravity and water-level rises followed above-average natural recharge during winter 1998 in Tucson Basin. Overall declining gravity and water-level trends from 1999 to 2002 in Tucson Basin reflected general declining ground-water storage conditions and redistribution of the recent recharge throughout a larger region of the aquifer. The volume of stored ground-water in the monitored portion of Tucson Basin increased 200,000 acre-feet from December 1997 to February 1999; however, thereafter an imbalance in ground-water pumpage in excess of recharge led to a net storage loss for the monitoring period by February 2002. Ground-water storage in Avra Valley increased 70,000 acre-feet during the monitoring period, largely as a result of artificial and incidental recharge in the monitored region. The water-budget for the combined monitored regions of Tucson Basin and Avra Valley was dominated by about 460,000 acre-feet of recharge during 1998 followed by an average-annual recharge rate of about 80,000 acre-feet per year from 1999 to 2002. Above-average recharge during winter 1998, followed by average-annual deficit conditions, resulted in an overall balanced water budget for the monitored period. Monitored variations in storage compared well with simulated average-annual conditions, except for above-average recharge from 1998 to 1999. The difference in observed and simulated conditions indicate that ground-water flow models can be improved by including climate-related variations in recharge rates rather than invariable rates of average-annual recharge. Observed land-subsidence during the monitoring period was less than 1 inch except in the central part of Tucson Basin where land subsidence was about 2-3 inches. Correlations of gravity-based storage and water-level change at 37 wells were variable and illustrate the complex nature of the aquifer system. Storage and water-level variations were insufficient to estimate specific yield at many wells. Correlations at several wells were poor, inverse, or resulted in unreasonably large values of specific yield. Causes of anomalously correlated gravity and water levels include significant storage change in thick unsaturated zones, especially near major ephemeral channels, and multiple aquifers that are poorly connected hydraulically. Good correlation of storage and water-level change at 10 wells that were not near major streams where significant changes in unsaturated zone storage occur resulted in an average specific-yield value of 0.27.

Scientific Investigations Report↗

USGS2011

Geohydrology, simulation of regional groundwater flow, and assessment of water-management strategies, Twentynine Palms area, California

The Marine Corps Air Ground Combat Center (MCAGCC) Twentynine Palms, California, overlies the Surprise Spring, Deadman, Mesquite, and Mainside subbasins of the Morongo groundwater basin in the southern Mojave Desert. Historically, the MCAGCC has relied on groundwater pumped from the Surprise Spring subbasin to provide all of its potable water supply. Groundwater pumpage in the Surprise Spring subbasin has caused groundwater levels in the subbasin to decline by as much as 190 feet (ft) from 1953 through 2007. Groundwater from the other subbasins contains relatively high concentrations of fluoride, arsenic, and (or) dissolved solids, making it unsuitable for potable uses without treatment. The potable groundwater supply in Surprise Spring subbasin is diminishing because of pumping-induced overdraft and because of more restrictive Federal drinking-water standards on arsenic concentrations. The U.S. Geological Survey, in cooperation with the MCAGCC, completed this study to better understand groundwater resources in the area and to help establish a long-term strategy for regional water-resource development. The Surprise Spring, Deadman, Mesquite, and Mainside subbasins are filled with sedimentary deposits of Tertiary age, alluvial fan deposits of Quaternary-Tertiary age, and younger alluvial and playa deposits of Quaternary age. Combined, this sedimentary sequence reaches a maximum thickness of more than 16,000 ft in the Deadman and Mesquite subbasins. The sedimentary deposits of Tertiary age yield a small amount of water to wells, and this water commonly contains high concentrations of fluoride, arsenic, and dissolved solids. The alluvial fan deposits form the principal water-bearing unit in the study area and have a combined thickness of 250 to more than 1,000 ft. The younger alluvial and playa deposits are unsaturated throughout most of the study area. Lithologic and downhole geophysical logs were used to divide the Quaternary/ Tertiary alluvial fan deposits into two aquifers (referred to as the upper and the middle aquifers) and the Tertiary sedimentary deposits into a single aquifer (referred to as the lower aquifer). In general, wells perforated in the upper aquifer yield more water than wells perforated in the middle and lower aquifers. The study area is dominated by extensive faulting and moderate to intense folding that has displaced or deformed the pre-Tertiary basement complex as well as the overlying Tertiary and Quaternary deposits. Many of these faults act as barriers to the lateral movement of groundwater flow and form many of the boundaries of the groundwater subbasins. The principal recharge to the study area is groundwater underflow across the western and southern boundaries that originates as runoff in the surrounding mountains. Groundwater discharges naturally from the study area as spring flow, as groundwater underflow to downstream basins, and as water vapor to the atmosphere by transpiration of phreatophytes and direct evaporation from moist soil. The annual volume of water that naturally recharged to or discharged from the groundwater flow system in the study area during predevelopment conditions was estimated to be 1,010 acre-feet per year (acre-ft/yr). About 90 percent of this recharge originated as runoff from the Little San Bernardino and the Pinto Mountains to the south, and the remainder originated as runoff from the San Bernardino Mountains to the west. Evapotranspiration by phreatophytes near Mesquite Lake (dry) was the primary form of predevelopment groundwater discharge. From 1953 through 2007, approximately 139,400 acre-feet (acre-ft) of groundwater was pumped by the MCAGCC from the Surprise Spring subbasin. A regional-scale numerical groundwater flow model was developed using MODFLOW-2000 for the Surprise Spring, Deadman, Mesquite, and Mainside subbasins. The aquifer system was simulated by using three model layers representing the upper, middle, and lower aquifers. Measured groundwater levels

California↗

USGS2019

Flood-inundation maps of the Meramec River from Eureka to Arnold, Missouri, 2018

Libraries of digital flood-inundation maps that spanned a combined 37.2-mile reach of the Meramec River that extended upstream from Eureka, Missouri, to downstream near the confluence of the Meramec and Mississippi Rivers were created by the U.S. Geological Survey (USGS) in cooperation with the U.S. Army Corps of Engineers, Metropolitan St. Louis Sewer District, Missouri Department of Transportation, Missouri American Water, Federal Emergency Management Agency Region 7, and the cities of Pacific, Eureka, Wildwood, and Arnold. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science website at https://water.usgs.gov/osw/flood_inundation/ , depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the cooperative USGS streamgages for the Meramec River near Eureka, Mo. (USGS station 07019000), the Meramec River at Valley Park, Mo. (USGS station 07019130), the Meramec River at Fenton, Mo. (USGS station 07019210), and the Meramec River at Arnold, Mo. (USGS station 07019300). Near-real-time stage data at these streamgages may be obtained from the USGS National Water Information System at https://doi.org/10.5066/F7P55KJN or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at https://water.weather.gov/ahps/ , which also forecasts flood hydrographs at these sites (listed as NWS sites erkm7, vllm7, fnnm7, and arnm7, respectively). Flood profiles were computed for the stream reach by means of a calibrated one-dimensional step-backwater hydraulic model. The model was calibrated using a stage-discharge relation at the Meramec River near Eureka, Mo., streamgage (USGS station 07019000) and documented high-water marks from the flood of December 2015 through January 2016. The calibrated hydraulic model was used to compute water-surface profiles: 1 set for the Meramec River near Eureka, Mo., streamgage (USGS station 07019000); 1 set for the Meramec River at Valley Park, Mo., streamgage (USGS station 07019130); 7 sets for the Meramec River at Fenton, Mo., streamgage (USGS station 07019210) for a range of Mississippi River conditions; and 8 sets for the Meramec River at Arnold, Mo., streamgage (USGS station 07019300) for a range of Mississippi River conditions. The water-surface profiles were produced for stages at 1-foot (ft) intervals referenced to the datum from each streamgage and ranging from the NWS action stage, or near bankfull discharge, to the stage corresponding to the estimated 0.2-percent annual exceedance probability (500-year recurrence interval) flood, as determined at the Meramec River near Eureka, Mo., streamgage (USGS station 07019000). The simulated water-surface profiles then were combined with a geographic information system digital elevation model (derived from light detection and ranging data having a 0.28-ft vertical accuracy and 3.28-ft horizontal resolution) to delineate the area flooded at each simulated 1-ft stage increment. Previously published flood-inundation maps were updated and incorporated in the flood map libraries for USGS stations 07019130 and 07019210 to complete the map sets corresponding to eight Mississippi River conditions. The availability of these maps, along with internet information regarding current stage from the USGS streamgages and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures and for postflood recovery efforts.

Missouri↗

USGS1980

Technique for estimating the magnitude and frequency of floods in the Houston, Texas, Metropolitan Area

A technique for estimating the magnitude and frequency of floods in the Houston, Texas, metropolitan area was developed by use of a multiple-regression flood-frequency analysis of flow data from unregulated streams in the area. A regression model, relating flood-peak discharge to concurrent rainfall and antecedent soil moisture conditions, was used to simulate 67-year records of annual peak discharges. Flood-frequency characteristics were determined for the simulated annual peaks and for the observed annual peaks at each of 22 gaging stations. Drainage area, bank-full channel conveyance, and percentage of urban development were used as independent variables; and weighted flood-frequency discharges were used as dependent variables in the multiple regression analysis. Relationships applicable to unregulated streams were developed for predicting floods with recurrence intervals of 2, 5, 10, 25, 50, 100, and 500 years. Drainage basins ranged in area from 1.33 to 182 square miles. The percentage of urban development in these basins ranges from 37 to 98.9 percent. The relationships indicate that as a basin changes from a completely natural state to one of complete urbanization, the magnitude of a 2-year peak discharge is increased by a factor of 4.2, the magnitude of a 50-year peak is increased by a factor of 4.9, and the magnitude of a 100-year peak is increased by a factor of 4. 9.

Texas↗

USGS1987

Relation of sediment and nutrient loads to watershed characteristics and land use in the Otisco Lake basin, Onondaga County, New York

Otisco Lake, the smallest and easternmost of New York State 's Finger Lakes, is the source of water supply for several villages in Onondaga County. In recent years, turbidity and algal blooms have periodically impaired the lake 's use for both water supply and recreation. Principal land uses within the Otisco Lake basin are woodland (39%) and cropland (49%). Conservation practices such as contour farming, strip cropping, and diversion ditches are applied to about 47% of the cropland in the basin. Runoff and concentrations of sediment and nutrients in the five major tributaries, which together drain about 70% of the lake 's watershed, were monitored from November 1981 through September 1983, and sediment and nutrient loads from the ungaged areas of the watershed were estimated. Otisco Lake received 10,600 tons of sediment, 20,600 lbs of phosphorus asp, 199,000 lbs of total kjeldahl nitrogen as N, and 236,000 lbs of nitrite plus nitrate as N from the five tributaries and the ungaged area during the 23-month study. Spafford Creek basin (12.0 sq mi) contributed about 72% of the annual sediment load and 46% of the annual nutrient load; the other four subbasins, which range from 2.6 to 3.7 sq mi in area, each contributed 3 to 5% of the annual sediment load and 6 to 16% of the annual nutrient load. The ungaged part of the watershed contributed 12% of the annual sediment load and 28% of the annual nutrient load. Concentrations of ammonia as N were relatively uniform through the year, although some extremely high concentrations occurred during the summer. Total Kjeldahl nitrogen concentrations were highest in the summer and lowest in the fall. Concentrations of nitrite plus nitrate were significantly lower in winter than in the rest of the year. Total phosphorus concentrations were slightly higher in the spring than at other times, and concentrations of dissolved phosphorus were slightly higher in the summer. Storms and snowmelt accounted for 70 to 90% of the runoff, 90 to 99% of the sediment load, and 70 to 98% of the nutrient loads from the tributaries. The largest nutrient loads occurred during the spring of each year, when runoff was highest. About 70% of the sediment, 60% of total Kjeldahl nitrogen, 58% of total phosphorus, and 53% of nitrite plus nitrate were transported during spring high flows. (Lantz-PTT)

Water-Resources Investigations Report↗

USGS2005

Base flow, water quality, and streamflow gain and loss of the Buffalo River, Arkansas, and selected tributaries, July and August 2003

A study of the Buffalo National River in north-central Arkansas was conducted between July 28-30 and August 13-15, 2003, to characterize the base-flow and water-quality characteristics and streamflow gain and loss in the Buffalo River. The study was separated into two time periods because of a precipitation event that occurred on the afternoon of July 30 causing appreciable storm runoff. Streamflow was separated to identify base-flow and surface-runoff components using the Base Flow Index hydrograph separation computer program. Base-flow separation analyses indicated annual variability in streamflow throughout the Buffalo River Basin. Based upon these analyses, total and base flow were below average for the mainstem of the river and Richland Creek during the 2003 water year. Waterquality samples were collected from 25 surface-water sites on the Buffalo River and selected tributaries. Most nutrient concentrations for the mainstem of the Buffalo River were near or below the minimum reporting level and were less than the median flow-weighted concentration for relatively undeveloped stream basins in the United States. Streamflow measurement data were collected at 44 locations along the mainstem of the Buffalo River and at points of inflow (prior to confluence with the mainstem) to identify gaining and losing reaches. Seven gaining and five losing reaches were identified for the Buffalo River. Additionally, surface flow on the mainstem of the Buffalo River was diverted to subsurface flow on the mainstem at two locations (river miles 73.6 and 131.6) where the mainstem was found to be dry. Reaches throughout the length of the river had calculated gains or losses that were less than the sum of measurement errors for the respective reaches of river.

Scientific Investigations Report↗