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USGS2002

Geologic framework of the regional ground-water flow system in the Upper Deschutes Basin, Oregon

Ground water is increasingly relied upon to satisfy the needs of a growing population in the upper Deschutes Basin, Oregon. Hydrogeologic studies are being undertaken to aid in management of the ground-water resource. An understanding of the geologic factors influencing ground-water flow is basic to those investigations. The geology of the area has a direct effect on the occurrence and movement of ground water. The permeability and storage properties of rock material are influenced by the proportion, size, and degree of interconnection of open spaces the rocks contain. These properties are the result of primary geologic processes such as volcanism and sedimentation, as well as subsequent processes such as faulting, weathering, or hydrothermal alteration. The geologic landscape in the study area evolved during about 30 million years of volcanic activity related to a north-south trending volcanic arc, the current manifestation of which are today’s Cascade Range volcanoes. The oldest rock unit in the upper Deschutes Basin study area, the John Day Formation, is a sequence of upper Eocene to lower Miocene volcanic and sedimentary rocks. Weathering and alteration of the rocks has resulted in very low permeability; consequently, the unit forms the hydrologic basement for the regional ground- water flow system throughout much of the area. The Deschutes Formation and age-equivalent deposits that overlie the John Day Formation, in contrast, are highly permeable and are the most widely used ground-water-bearing units in the study area. The Deschutes Formation consists of a variety of volcanic and sedimentary deposits ranging in age from late Miocene to Pliocene (approximately 7.5 to 4.0 million years). Three distinct depositional environments previously described for the formation provide useful hydrogeologic subdivisions. The ancestral Deschutes River deposits and some units within the arc- adjacent alluvial-plain region are among the highest yielding units within the Deschutes Formation, with some wells producing up to a few thousand gallons per minute. Opal Springs basalt, Pelton basalt, and the rhyodacite dome complex near Steelhead Falls are particularly productive subunits within the Deschutes Formation and provide tens to hundreds of cubic feet per second of ground-water discharge to the Deschutes and Crooked Rivers, upstream of Round Butte Dam. Most ground-water recharge in the upper Deschutes Basin occurs in Quaternary deposits of the Cascade Range and Newberry Volcano. These deposits are highly permeable, and the fractured character of the lava flows facilitates rapid infiltration of precipitation and snowmelt, as well as movement of ground water to lower elevations. Additional recharge from canal leakage occurs along sections of unlined canals near Bend, constructed on lava flows from Newberry Volcano. Hydrothermal alteration and secondary mineralization at depth beneath the Cascade Range and Newberry Volcano has drastically reduced the permeability of the material in those regions, effectively restricting most ground water to the strata above the altered rocks. The top of the hydrothermally altered region is considered the base of the regional ground-water system beneath the Cascade Range and Newberry Volcano. Structural features influence ground-water flow within the upper Deschutes Basin mainly by juxtaposing materials with contrasting permeability. This juxtaposition can be caused by fault movement or by the influence of a fault on subsequent deposition. Several depositional centers have formed along the base of fault-line scarps or in grabens within the study area, and the infilling sedimentary deposits have permeability that differs from the surrounding rocks. The effects of faults on ground-water flow may be masked in some areas. For example, the water-table gradient changes slope in the vicinity of the Sisters fault zone, but the slope change also corresponds with a major precipitation gradient change; therefore, any influence of the fault zone is unclear. Geologic units in the Deschutes Basin were divided into several distinct hydrogeologic units. In some instances the units correspond to existing stratigraphic divisions. In other instances, hydrogeologic units correspond to different facies within a single stratigraphic unit or formation. The hydrogeologic units include Quaternary sediment, deposits of the Cascade Range and Newberry Volcano, four zones within the Deschutes Formation and age-equivalent rocks that roughly correspond with depositional environments, and pre-Deschutes-age strata.

Water-Resources Investigations Report↗
USGS2002

Trends in selected streamflow and stream-channel characteristics for the Chagrin River at Willoughby, Ohio

Monotonic upward trends in annual mean streamflows and annual 7-day low flows were identified statistically for the streamflow-gaging station on the Chagrin River at Willoughby, Ohio. No monotonic trends were identified for the annual peak streamflow series or partial-duration series of peak streamflows augmented with annual peak streamflows that did not exceed a base discharge of 4,000 cubic feet per second. A plot of cumulative departure of annual precipitation from the long-term mean annual precipitation for the weather-observation station at Hiram, Ohio, indicates a relatively dry period extending from about 1910 to about 1968, followed by a relatively wet period extending from about 1968 to the late 1990s. A plot of cumulative departure of annual mean streamflow from the mean annual streamflow for the Chagrin River at Willoughby, Ohio, closely mimics the shape of the precipitation departure plot, indicating that the annual mean streamflows increased in concert with annual precipitation. These synchronous trends likely explain why upward trends in annual mean streamflows and annual 7-day low flows were observed. A lack of trend in peak streamflows indicates that the intensity and severity of flood-producing storms did not increase appreciably along with the increases in annual precipitation. An analysis of point-of-zero-flow data indicates that the low-water control of the Chagrin River streamflow-gaging station tended to aggrade over the period 1930–93; however, the magnitude of aggradation is sufficiently small that its effect on stages of moderate to large floods would be negligible. Stage values associated with reference streamflows of 500 and 5,000 cubic feet per second tended to remain fairly stable during the period from about 1950 to 1970 and then decreased slightly during the period from about 1970 to 1980, suggesting that the flood-carrying capacity of the stream increased somewhat during the latter period. Since a large flood on May 26, 1989, significant changes have occurred in the relation between stage and streamflow. The most recent relation indicates that stage values associated with streamflows of 500 and 5,000 cubic feet per second are about 0.5 foot and 0.1 foot higher, respectively, than the pre-1989 levels.

Water-Resources Investigations Report↗
USGS2002

Historical contributions of phosphorus from natural and agricultural sources and implications for stream water quality, Cheney Reservoir watershed, south-central Kansas

An examination of soil cores collected from 43 nonagricultural coring sites in the Cheney Reservoir watershed of south-central Kansas was conducted by the U.S. Geological Survey in September 1999. The cores were collected as part of an ongoing cooperative study with the city of Wichita, Kansas. The 43 sites (mostly cemeteries) were thought to have total phosphorus concentrations in the soil that are representative of natural conditions (unaffected by human activity). The purpose of this report is to present the analysis and evaluation of these soil cores, to quantify the phosphorus contributions to Cheney Reservoir from natural and agricultural sources, and to provide estimates of stream-water-quality response to natural concentrations of total phosphorus in the soil. Analysis of soil cores from the 43 sites produced natural concentrations of total phosphorus that ranged from 74 to 539 milligrams per kilogram with a median concentration of 245 milligrams per kilogram in 2-inch soil cores and from 50 to 409 milligrams per kilogram with a median concentration of 166 milligrams per kilogram in 8-inch soil cores. Natural concentrations of total phosphorus in soil were statistically larger in samples from coring sites in the eastern half of the watershed than in samples from coring sites in the western half of the watershed. This result partly explains a previously determined west-to-east increase in total phosphorus yields in streams of the Cheney Reservoir watershed. A comparison of total phosphorus concentrations in soil under natural conditions to the historical mean total phosphorus concentration in agriculturally enriched bottom sediment in Cheney Reservoir indicated that agricultural activities within the watershed have increased total phosphorus concentrations in watershed soil that is transported in streams to about 2.9 times natural concentrations. Retention efficiencies for phosphorus and sediment historically transported to Cheney Reservoir were calculated at 92 and 99 percent, respectively. Most of the phosphorus was retained in bottom sediment. Sediment accumulation in Cheney Reservoir was less than reservoir design-life specifications on the basis of the age of the reservoir. Estimates of mean total phosphorus concentrations for selected streams in the Cheney Reservoir watershed under natural concentrations of total phosphorus in soil and a historic set of watershed conditions indicate that water from two of the five streamflow sampling sites would not meet the total phosphorus water-quality goal of 0.10 milligram per liter established by the Cheney Reservoir Watershed Task Force Committee. These results imply that the water-quality goal for total phosphorus in some streams of the watershed may not be met simply by reducing the amount of phosphorus applied. Instead, meeting the goal could involve a combination of approaches-for example, reducing the agricultural distribution of phosphorus and implementing changes in watershed activities to mitigate phosphorus movement to surface water.

Kansas↗
USGS2002

Hydrogeology and simulation of ground-water flow and land-surface subsidence in the Chicot and Evangeline aquifers, Houston area, Texas

In November 1997, the U.S. Geological Survey, in cooperation with the City of Houston Utilities Planning Section and the City of Houston Department of Public Works & Engineering, began an investigation of the Chicot and Evangeline aquifers in the greater Houston area in Texas to better understand the hydrology, flow, and associated land-surface subsidence. The principal part of the investigation was a numerical finite-difference model (MODFLOW) developed to simulate ground-water flow and land-surface subsidence in an 18,100-square-mile area encompassing greater Houston. The focus of the study was Harris and Galveston Counties, but other counties were included to achieve the appropriate boundary conditions. The model was vertically discretized into three 103-row by 109-column layers resulting in a total of 33,681 grid cells. Layer 1 represents the water table using a specified head, layer 2 represents the Chicot aquifer, and layer 3 represents the Evangeline aquifer. Simulations were made under transient conditions for 31 ground-water-withdrawal (stress) periods spanning 1891–1996. The years 1977 and 1996 were chosen as potentiometric-surface calibration periods for the model. Simulated and measured potentiometric surfaces of the Chicot and Evangeline aquifers for 1977 match closely. Waterlevel measurements indicate that by 1977, large ground-water withdrawals in east-central and southeastern areas of Harris County had caused the potentiometric surfaces to decline as much as 250 feet below sea level in the Chicot aquifer and as much as 350 feet below sea level in the Evangeline aquifer. Simulated and measured potentiometric surfaces of the Chicot and Evangeline aquifers for 1996 also match closely. The large potentiometric-surface decline in 1977 in the southeastern Houston area showed significant recovery by 1996. The 1996 centers of potentiometric-surface decline are located much farther northwest. Potentiometric-surface declines of more than 200 feet below sea level in the Chicot aquifer and more than 350 feet below sea level in the Evangeline aquifer were measured in observation wells and simulated in the flow model. Simulation of land-surface subsidence and water released from storage in the clay layers was accomplished using the Interbed-Storage Package of the MODFLOW model. Land-surface subsidence was calibrated by comparing simulated long-term (1891–1995) and short-term (1978–95) land-surface subsidence with published maps of land-surface subsidence for about the same period until acceptable matches were achieved. Simulated 1996 Chicot aquifer flow rates indicate that a net flow of 562.5 cubic feet per second enters the Chicot aquifer in the outcrop area, and a net flow of 459.5 cubic feet per second passes through the Chicot aquifer into the Evangeline aquifer. The remaining 103.0 cubic feet per second of flow is withdrawn as pumpage, with a shortfall of about 84.9 cubic feet per second supplied to the wells from storage in sands and clays. Water simulated from storage in clays in the Chicot aquifer is about 19 percent of the total water withdrawn from the aquifer. Simulated 1996 Evangeline aquifer flow rates indicate that a net flow of 14.8 cubic feet per second enters the Evangeline aquifer in the outcrop area, and a net flow of 459.5 cubic feet per second passes through the Chicot aquifer into the Evangeline aquifer for a total inflow of 474.3 cubic feet per second. A greater amount, 528.6 cubic feet per second, is withdrawn by wells; the shortfall of about 54.8 cubic feet per second is supplied from storage in sands and clays. Water simulated from storage in clays in the Evangeline aquifer is about 10 percent of the total water withdrawn from the aquifer.

Texas↗
USGS2002

Ground-water resources of the uppermost confined aquifers, southern Wadena County and parts of Ottertail, Todd, and Cass Counties, central Minnesota, 1997–2000

Water managers are concerned about the increase of ground-water withdrawals from high-capacity wells completed in the uppermost confined aquifers in southern Wadena County. The hydrogeologic units of primary interest in the study area are the surficial aquifer, the uppermost confining units, and the uppermost confined aquifers. The surficial aquifer underlies all but portions of the eastern, western, and south-central parts of the study area, and is as much as 70 ft thick. The thickness of the uppermost confined aquifers ranges from 0 to 72 ft. The thickness of the aquifers is greatest in the south-central and west-central parts of the study area, where thicknesses exceed 50 ft. Depth to the top of the uppermost confined aquifers ranges from 23 to 132 ft. The thickness of the uppermost confining units ranges from 4 to 132 ft. The regional direction of flow in the uppermost confined aquifers is to the east, southeast, and southwest toward the Crow Wing River in the eastern part of the study area and toward the Leaf River in the western part. Sources of water to the uppermost confined aquifers are leakage of water through overlying till and clay and ground-water flow from adjoining aquifers outside the study area. Discharge from the uppermost confined aquifers is by withdrawal from wells and to the surficial aquifer in river valleys. The theoretical maximum well yields for the uppermost confined aquifers range from less that 175 gal/min to greater than 2,000 gal/min and are greatest in areas of greatest aquifer thickness and transmissivity. The water budget for the calibrated steady-state simulation indicated that areal recharge to the surficial aquifer is 86.9 percent of the water to the aquifers, with leakage to the uppermost confined aquifers contributing 6.9 percent. The largest discharges from the aquifers are leakage to streams (54.5 percent) and ground-water evapotranspiration (41.4 percent). The simulated transient water budget for 1999 indicated that the principal sources of water to the aquifers were areal recharge to the surficial aquifer and release from storage. The principal discharges were stream-aquifer leakage, addition to storage, and ground-water evapotranspiration. Results of the steady-state simulation with anticipated increases in ground-water withdrawals indicated maximum drawdowns of 0.3 ft in the surficial aquifer and 0.9 ft in the uppermost confined aquifers due to the anticipated increases in ground-water withdrawals. Model results indicate that the anticipated increases in withdrawals during a drought may lower water levels 2 to 4 ft regionally in much of both the surficial and uppermost confined aquifers. Water-level declines in the surficial aquifer of about 6 ft may occur in Wadena and in the central part of the aquifer south of the Leaf River. Results of the transient simulation indicate that the anticipated increases in withdrawals during a drought would increase seasonal declines in the surficial and uppermost confined aquifers less than 1 and 2 ft, respectively. Model results indicate that greater than anticipated increases in withdrawals during periods of normal precipitation will have minimal effects on ground-water levels and streamflow in the area. In the uppermost confined aquifers, for example, water levels may decline an average of 0.13 ft regionally, with maximum declines of 0.8 to 2.1 ft near Wadena and Verndale. Greater than anticipated increases in withdrawals would cause decreases in ground-water discharge to streams of about 1.4 percent (2.5 ft 3 /s) of 1998-99 steady-state conditions.

Minnesota↗
USGS2002

Hydrologic characteristics of Bear Creek near Silver Hill and Buffalo River near St. Joe, Arkansas, 1999-2000

The Buffalo River and its tributary Bear Creek are in the White River Basin in the Ozark Plateaus in north-central Arkansas. Analysis of streamflow measurements and water-quality samples at a site on Bear Creek and a site on the Buffalo River in Searcy County, Arkansas, quantify differences between the two sites during calendar years 1999 and 2000. Streamflow and water quality also vary seasonally at each site. Mean annual streamflow was substantially larger at the Buffalo River site (836 and 719 cubic feet per second in 1999 and 2000) than at the Bear Creek site (56 and 63 cubic feet per second). However, during times of low flow, discharge of Bear Creek comprises a larger proportion of the flow of the Buffalo River. Concentrations of nutrients, fecal-indicator bacteria, dissolved organic carbon, and suspended sediment generally were greater in samples from Bear Creek than in samples from the Buffalo River. Statistically significant differences were detected in concentrations of nitrite plus nitrate, total nitrogen, dissolved phosphorus, orthophosphorus, total phosphorus, fecal coliform bacteria, and suspended sediment. Loads varied between sites, hydrologic conditions, seasons, and years. Loads were substantially higher for the Buffalo River than for Bear Creek (as would be expected because of the Buffalo?s higher streamflow). Loads contributed by surface runoff usually comprised more than 85 percent of the annual load. Constituent yields (loads divided by drainage area) were much more similar between sites than were loads. Flow-weighted concentrations and dissolved constituent yields generally were greater for Bear Creek than yields for the Buffalo River and flowweighted concentrations yields were higher than typical flow-weighted concentrations and yields in undeveloped basins, but lower than flow-weighted concentrations and yields at a site in a more developed basin.

Water-Resources Investigations Report↗
USGS2002

Statistical summaries of streamflow in Oklahoma through 1999

Statistical summaries of streamflow records through 1999 for gaging stations in Oklahoma and parts of adjacent states are presented for 188 stations with at least 10 years of streamflow record. Streamflow at 113 of the stations is regulated for specific periods. Data for these periods were analyzed separately to account for changes in streamflow due to regulation by dams or other human modification of streamflow. A brief description of the location, drainage area, and period of record is given for each gaging station. A brief regulation history also is given for stations with a regulated streamflow record. This descriptive information is followed by tables of mean annual discharges, magnitude and probability of exceedance of annual high flows, magnitude and probability of exceedance of annual instantaneous peak flows, durations of daily mean flow, magnitude and probability of non-exceedance of annual low flows, and magnitude and probability of non-exceedance of seasonal low flows.

Water-Resources Investigations Report↗
USGS2002

Generalized hydrogeology and ground-water budget for the C Aquifer, Little Colorado River Basin and parts of the Verde and Salt River Basins, Arizona and New Mexico

The C aquifer underlies the Little Colorado River Basin and parts of the Verde and Salt River Basins and is named for the primary water-bearing rock unit of the aquifer, the Coconino Sandstone. The areal extent of this aquifer is more than 27,000 square miles. More than 1,000 well and spring sites were identified in the U.S. Geological Survey database for the C aquifer in Arizona and New Mexico. The C aquifer is the most productive aquifer in the Little Colorado River Basin. The Little Colorado River is the primary surface-water feature in the area, and it has a direct hydraulic connection with the C aquifer in some areas. Spring discharge as base flow from the C aquifer occurs predominantly in the lower 13 miles of the Little Colorado River subsequent to downward leakage into the deeper Redwall-Muav Limestone aquifer. Ground-water mounds or divides exist along the southern and northeastern boundaries of the Little Colorado River Basin. The ground-water divides are significant boundaries of the C aquifer; however, the location and persistence of the divides potentially can be affected by ground-water withdrawals. Ground-water development in the C aquifer has increased steadily since the 1940s because population growth has produced an increased need for agricultural, industrial, and public water supply. Ground-water pumpage from the C aquifer during 1995 was about 140,000 acre-feet. Ground-water budget components for the C aquifer were evaluated using measured or estimated discharge values. The system was assumed to be in a steady-state condition with respect to natural recharge and discharge, and the stability of discharge from major springs during the past several decades supported the steady-state assumption. Downward leakage to the Redwall-Muav Limestone aquifer is a major discharge component for the ground-water budget. Discharge from the C aquifer is estimated to be 319,000 acre-feet per year.

Arizona;New Mexico↗
USGS2002

Ground-cover vegetation in wetland forests of the lower Suwannee River floodplain, Florida, and potential impacts of flow reductions

Ground-cover vegetation was surveyed in wetland forests in the lower Suwannee River floodplain, Florida, in a study conducted by the U.S. Geological Survey in cooperation with the Suwannee River Water Management District from 1996 to 1999. Increased water use in the basin, supplied primarily from ground water, could reduce ground-water discharge to the river and flows in the lower Suwannee River. Many of the 282 ground-cover species found in wetland forests of the floodplain have distributions that are related to flow-dependent hydrologic characteristics of forest types, and their distributions would change if flows were reduced. Overall species diversity in the floodplain might decrease, and the composition of ground-cover vegetation in all forest types might change with flow reductions. The study area included forests within the 10-year floodplain of the lower Suwannee River from its confluence with the Santa Fe River to the lower limit of forests near the Gulf of Mexico. The floodplain is divided into three reaches (riverine, upper tidal, and lower tidal) due to variations in hydrology, vegetation, and soils with proximity to the coast. The riverine (non-tidal) reach had the greatest number of total species (203) and species unique to that reach (81). Mitchella repens, Toxicodendron radicans, and Axonopus furcatus were the most frequently dominant species in riverine bottomland hardwoods. Free-floating aquatic species, such as Spirodela punctata and Lemna valdiviana, were the dominant species in the wettest riverine swamps. The upper tidal reach had the lowest number of total species (116), only two species unique to that reach, and the lowest density of ground cover (26 percent). Panicum commutatum and Crinum americanum were frequent dominant species in upper tidal forests. The lower tidal reach had the highest ground-cover density (43 percent) and the second highest number of total species (183) and number of species unique to that reach (55). Saururus cernuus and species of Carex were frequently dominant in lower tidal swamps. Lower tidal hammocks, the most elevated lower tidal forests, were dominated by Osmunda cinnamomea and Chasmanthium laxum. Flow reductions in the lower Suwannee River could change the flow-dependent hydrologic characteristics of wetland forests. Decreases in inundation and saturation in riverine forests could result in a decrease in the number and extent of semi-permanently inundated ponds. As a result, several species of free-floating, aquatic plants that grow only in riverine floodplain ponds might decrease in abundance or disappear if flows were reduced. Decreases in inundation and saturation could also result in a shift to more upland species in all riverine forests and upper tidal bottomland hardwoods. Upland species and some exotic species might increase in abundance in the floodplain, invading forests where hydrologic conditions have been altered by flow reductions. Depth and duration of inundation due to river flooding could decrease in all riverine and upper tidal forests, probably resulting in a shift of species to those that are typically found in forests with shallower, shorter-duration floods. Salinity in the lower tidal reach and adjacent areas of the upper tidal reach might increase with flow reductions, and the distribution of species might change due to varying tolerances of salinity among species. Species with low salt-tolerance unique to the lower tidal reach might disappear from the floodplain, and species with high salinity tolerance could increase in abundance, replacing less salt-tolerant species.

Water-Resources Investigations Report↗
USGS2002

Ground-water quality and discharge to Chincoteague and Sinepuxent Bays adjacent to Assateague Island National Seashore, Maryland

The U.S. Geological Survey, in cooperation with the Maryland Department of the Environment and the Wisconsin State Laboratory of Hygiene, conducted a study to characterize the occurrence and distribution of viral contamination in small (withdrawing less than 10,000 gallons per day) public water-supply wells screened in the shallow aquifer in the Piedmont Physiographic Province in Baltimore and Harford Counties, Maryland. Two hundred sixty-three small public water-supply wells were in operation in these counties during the spring of 2000. Ninety-one of these sites were selected for sampling using a methodology that distributed the samples evenly over the population and the spatial extent of the study area. Each site, and its potential susceptibility to microbiological contamination, was evaluated with regard to hole depth, casing interval, and open interval. Each site was evaluated using characteristics such as on-site geology and on-site land use.Samples were collected by pumping between 200 and 400 gallons of untreated well water through an electropositive cartridge filter. Water concentrates were subjected to cell-culture assay for the detection of culturable viruses and reverse-transcription polymerase chain reaction/gene probe assays to detect viral ribonucleic acid; grab samples were analyzed for somatic and male-specific coliphages, Bacteroides fragilis, Clostridium perfringens, enterococci, Escherichia coli, total coliforms, total oxidized nitrogen, nitrite, organic nitrogen, total phosphate, ortho-phosphate, calcium, magnesium, sodium, potas-sium, chloride, sulfate, iron, acid-neutralizing capacity, pH, specific conductance, temperature, and dissolved oxygen.One sample tested positive for the presence of the ribonucleic acid of rotavirus through poly-merase chain-reaction analysis. Twenty-nine per-cent of the samples (26 of 90) had bacterial con-tamination. About 7 percent of the samples (6 of 90) were contaminated with either male-specific coliphage, somatic coliphage, or bacteriophages of Bacteroides fragilis. About 3 percent of the sam-ples (3 of 87) had oxidized nitrogen concentra-tions that exceeded the U.S. Environmental Protection Agency?s Maximum Contaminant Level of 10.0 milligrams per liter. A statistical analysis showed that no significant relation exists between the presence of bacteria or coliphage and all variables, except the mean temperature of the water sample as measured in the field. Additionally, the concentration of total coliform bacteria had a statistically significant, moderately strong cor-relation with the concentration of sulfate and sample pH as measured at the U.S. Geological Survey National Water-Quality Laboratory in Denver, Colorado.

Water-Resources Investigations Report↗
USGS2002

Streamflow and water-quality data for selected watersheds in the Lake Tahoe basin, California and Nevada, through September 1998

The U.S. Geological Survey, in cooperation with the Tahoe Regional Planning Agency, and the University of California, Davis-Tahoe Research Group, has monitored tributaries in the Lake Tahoe Basin since 1988. This monitoring has characterized streamflow and has determined concentrations of nutrients and suspended sediment, which may have contributed to loss of clarity in Lake Tahoe. The Lake Tahoe Interagency Monitoring Program was developed to collect water-quality data in the basin. In 1998, the tributary-monitoring program included 41 water-quality stations in 14 of the 63 watersheds totaling half the area tributary to Lake Tahoe. The monitored watershed areas range from 1.08 square miles for First Creek to 56.5 square miles for the Upper Truckee River.Annual and unit runoff for 20 primary and secondary streamflow gaging stations in 10 selected watersheds are described. Water years 1988-98 were used to compare runoff data. The Upper Truckee River at South Lake Tahoe, Calif., had the highest annual runoff and Logan House Creek near Glenbrook, Nev., had the lowest. Blackwood Creek near Tahoe City, Calif., had the highest unit runoff and Logan House Creek had the lowest. The highest instantaneous peak flow was recorded at Upper Truckee River at South Lake Tahoe during the January 2, 1997, flood event.Certain water-quality measurements were made in the field. Ranges and median values of those measurements are described for 41 stations. Water temperature ranged from 0 to 23?C. Specific conductance ranged from 13 to 900 microsiemens per centimeter at 25?C. pH ranged from 6.7 to 10.6. Dissolved-oxygen concentrations ranged from 5.2 to 12.6 mg/L and from 70 to 157 percent of saturation.Loads, yields, and trends of nutrients and suspended sediment during water years 1988-98 at the streamflow gaging stations also are described. The Upper Truckee River at South Lake Tahoe had the largest median monthly load for five of the six measured nutrients and of suspended sediment, while Trout Creek at South Lake Tahoe had the largest median monthly load for the remaining nutrient. Logan House Creek near Glenbrook had the smallest median monthly loads for all nutrients and suspended sediment. Seasonal load summaries at selected stations showed nutrient and suspended-sediment loads were greatest in the spring months of April, May and June and least in the summer months of July, August, and September. Monthly load comparisons also were described for five watersheds with multiple stations.Incline Creek had the highest combined rank for all nutrients and sediment. Incline Creek had the largest monthly yields for dissolved nitrite plus nitrate nitrogen and soluble reactive phosphorus. Third Creek had the second highest combined rank and had the largest monthly yields for total nitrogen, total phosphorus, biologically reactive iron, and suspended sediment. Edgewood Creek had the largest monthly yield for dissolved ammonia nitrogen. Logan House Creek had the lowest combined rank and the smallest monthly yields for all nutrients and sediment.Trends in concentrations are either decreasing or not significant for all nutrients in all sampled watersheds, with the exception of biologically reactive iron. Biologically reactive iron and suspended sediment show an increasing trend in three watersheds and decreasing or no significant trend in the other seven watersheds.

Water-Resources Investigations Report↗
USGS2002

Factors affecting ground-water exchange and catchment size for Florida lakes in mantled karst terrain

In the mantled karst terrain of Florida, the size of the catchment delivering ground-water inflow to lakes is often considerably smaller than the topographically defined drainage basin. The size is determined by a balance of factors that act individually to enhance or diminish the hydraulic connection between the lake and the adjacent surficial aquifer, as well as the hydraulic connection between the surficial aquifer and the deeper limestone aquifer. Factors affecting ground-water exchange and the size of the ground-water catchment for lakes in mantled karst terrain were examined by: (1) reviewing the physical and hydrogeological characteristics of 14 Florida lake basins with available ground-water inflow estimates, and (2) simulating ground-water flow in hypothetical lake basins. Variably-saturated flow modeling was used to simulate a range of physical and hydrogeologic factors observed at the 14 lake basins. These factors included: recharge rate to the surficial aquifer, thickness of the unsaturated zone, size of the topographically defined basin, depth of the lake, thickness of the surficial aquifer, hydraulic conductivity of the geologic units, the location and size of karst subsidence features beneath and onshore of the lake, and the head in the Upper Floridan aquifer. Catchment size and the magnitude of ground-water inflow increased with increases in recharge rate to the surficial aquifer, the size of the topographically defined basin, hydraulic conductivity in the surficial aquifer, the degree of confinement of the deeper Upper Floridan aquifer, and the head in the Upper Floridan aquifer. The catchment size and magnitude of ground-water inflow increased with decreases in the number and size of karst subsidence features in the basin, and the thickness of the unsaturated zone near the lake. Model results, although qualitative, provided insights into: (1) the types of lake basins in mantled karst terrain that have the potential to generate small and large amounts of ground-water inflow, and (2) the location of ground-water catchments that could be managed to safeguard lake water quality. Knowledge of how ground-water catchments are related to lakes could be used by water-resource managers to recommend setback distances for septic tank drain fields, agricultural land uses, and other land-use practices that contribute nutrients and major ions to lakes.

Water-Resources Investigations Report↗
USGS2002

Hydrologic investigation of Powell Marsh and its relation to Dead Pike Lake, Vilas County, Wisconsin

An analytic element ground-water-flow model was constructed to help understand the ground- and surface-water hydrology in the vicinity of Dead Pike Lake and Powell Marsh, Vilas County, Wisconsin. The model was used to simulate the effect of removing Powell Marsh control structures (ditches and Vista Pond) on the hydrology of Dead Pike Lake. Measurements and model simulation results show that ground water in the vicinity of Powell Marsh moves to the northwest and west. If Powell Marsh structures are removed from the simulation, it does not affect the general direction of ground-water flow nor the total flow to Dead Pike Lake. Without the simulated structures, slightly more ground-water flow enters Dead Pike Lake and slightly less surface-water flows at the Dead Pike Lake inlet than with the simulated structures. Ground-water levels measured in piezometers installed along a flow path indicated that ground-water flow primarily is horizontal in the marsh and moves upward in the vicinity of a ditch where it discharges. Flow from Vista Pond is downward to the ground-water system but eventually also discharges upward to the ditches. Based on analyses of water samples from piezometers, the ditch, and Vista Pond, it was shown that dissolved iron is transported in the ground water. When ground water is discharged, iron and manganese react with dissolved oxygen, then precipitates, and forms the oxyhydroxide floc present in the Powell Marsh ditches. The processes involved in the transport and floc formation are not unique to the ditches, but are an expected outcome where discharging ground water and oxygenated surface water meet. Therefore, although floc formed in the ditches would no longer be available for transport if ditches were removed, it is likely that the floc formation would be redirected to the near-shore areas of Dead Pike Lake where increased groundwater discharge is expected.

Wisconsin↗
USGS2002

Inventory and review of aquifer storage and recovery in southern Florida

Aquifer storage and recovery in southern Florida has been proposed on an unprecedented scale as part of the Comprehensive Everglades Restoration Plan. Aquifer storage and recovery wells were constructed or are under construction at 27 sites in southern Florida, mostly by local municipalities or counties located in coastal areas. The Upper Floridan aquifer, the principal storage zone of interest to the restoration plan, is the aquifer being used at 22 of the sites. The aquifer is brackish to saline in southern Florida, which can greatly affect the recovery of the freshwater recharged and stored. Well data were inventoried and compiled for all wells at most of the 27 sites. Construction and testing data were compiled into four main categories: (1) well identification, location, and construction data; (2) hydraulic test data; (3) ambient formation water-quality data; and (4) cycle testing data. Each cycle during testing or operation includes periods of recharge of freshwater, storage, and recovery that each last days or months. Cycle testing data include calculations of recovery efficiency, which is the percentage of the total amount of potable water recharged for each cycle that is recovered. Calculated cycle test data include potable water recovery efficiencies for 16 of the 27 sites. However, the number of cycles at most sites was limited; except for two sites, the highest number of cycles was five. Only nine sites had a recovery efficiency above 10 percent for the first cycle, and 10 sites achieved a recovery efficiency above 30 percent during at least one cycle. The highest recovery efficiency achieved per cycle was 84 percent for cycle 16 at the Boynton Beach site. Factors that could affect recovery of freshwater varied widely between sites. The thickness of the open storage zone at all sites ranged from 45 to 452 feet. For sites with the storage zone in the Upper Floridan aquifer, transmissivity based on tests of the storage zones ranged from 800 to 108,000 feet squared per day, leakance values indicated that confinement is not good in some areas, and the chloride concentration of ambient water ranged from 500 to 11,000 milligrams per liter. Based on review of four case studies and data from other sites, several hydrogeologic and design factors appear to be important to the performance of aquifer storage and recovery in the Floridan aquifer system. Performance is m aximized when the storage zone is thin and located at the top of the Upper Floridan aquifer, and transmissivity and salinity of the storage zone are moderate (less than 30,000 feet squared per day and 3,000 milligrams per liter of chloride concentration, respectively). The structural setting at a site could also be important because of the potential for updip migration of a recharged freshwater bubble due to density contrast or loss of overlying confinement due to deformation.

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