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At least 937 records · Page 52Linked to original sources
USGS2008

Drier forest composition associated with hydrologic change in the Apalachicola River floodplain, Florida

Forests of the Apalachicola River floodplain had shorter flood durations, were drier in composition, and had 17 percent fewer trees in 2004 than in 1976. The change to drier forest composition is expected to continue for at least 80 more years. Floodplain drying was caused by large declines in river levels resulting from erosion of the river channel after 1954 and from decreased flows in spring and summer months since the 1970s. Water-level declines have been greatest at low and medium flows, which are the most common flows (occurring about 80 percent of the time). Water levels have remained relatively unchanged during large floods which continue to occur about three times per decade. A study conducted by the U.S. Geological Survey compared temporal changes in hydrologic conditions, forest composition, forest characteristics, and individual species of trees, as well as estimated the potential for change in composition of floodplain forests in the nontidal reach of the Apalachicola River. The study was conducted with the cooperation of the Florida Department of Environmental Protection and the Northwest Florida Water Management District. Forest composition and field observations from studies conducted in 1976-1984 (termed “1976 data”) were used as baseline data for comparison with data from plots sampled in 2004-2006 (“2004 data”). Flood durations were shorter in all periods subsequent to 1923-1976. The periods of record used to calculate flood durations for forest data were subsets of the complete record available (1923-2004). At sampled plots in all forest types and reaches combined, flood durations changed an average of more than 70 percent toward the baseline flood duration of the next drier forest type. For all forest types, changes in flood durations toward the next drier type were greatest in the upper reach (95.9 percent) and least in the lower reach (42.0 percent). All forests are expected to be 38.2 percent drier in species composition by 2085, the year when the median age of surviving 2004 subcanopy trees will reach the median age (99 years) of the 2004 large canopy trees. The change will be greatest for forests in the upper reach (45.0 percent). Forest composition changes from pre-1954 to 2085 were calculated using Floodplain Indices from 1976 and 2004 tree-size classes and replicate plots. Species composition in high bottomland hardwood forests is expected to continue to change, and some low bottomland hardwood forests are expected to become high bottomland hardwood forests. Organisms associated with floodplain forests will be affected by the changes in tree species, which will alter the timing of leaf-out, fruiting, and leaf-drop, the types of fruit and debris produced, and soil chemistry. Swamps will contain more bottomland hardwood species, but will also have an overall loss of tree density. The density of trees in swamps significantly decreased by 37 percent from 1976 to 2004. Of the estimated 4.3 million (17 percent) fewer trees that existed in the nontidal floodplain in 2004 than in 1976, 3.3 million trees belonged to four swamp species: popash, Ogeechee tupelo, water tupelo, and bald cypress. Water tupelo, the most important tree in the nontidal floodplain in terms of basal area and density, has declined in number of trees by nearly 20 percent since 1976. Ogeechee tupelo, the species valuable to the tupelo honey industry, has declined in number of trees by at least 44 percent. Greater hydrologic variability in recent years may be the reason swamps have had a large decrease in tree density. Drier conditions are detrimental for the growth of swamp species, and periodic large floods kill invading bottomland hardwood trees. The loss of canopy density in swamps may result in the swamp floor being exposed to more light with an increase in the amount of ground cover present, which in turn, would reduce tree replacement. The microclimate of the swamp floor would become warmer due to the decrease in shade and inundation. Soils would become dehydrated more quickly in dry periods and debris would decompose more quickly. A loss of tree density in swamps would lead to a decrease in tree and leaf litter biomass, which would have additional effects on swamp organisms. The loss of litter would result in a loss of substrate for benthic organisms in the floodplain and, ultimately, in the downstream waters of the river and estuary.

Florida↗
USGS2008

Determination of Baseline Periods of Record for Selected Streamflow-Gaging Stations in New Jersey for Determining Ecologically Relevant Hydrologic Indices (ERHI)

Hydrologic changes in New Jersey stream basins resulting from human activity can affect the flow and ecology of the streams. To assess future changes in streamflow resulting from human activity an understanding of the natural variability of streamflow is needed. The natural variability can be classified using Ecologically Relevant Hydrologic Indices (ERHIs). ERHIs are defined as selected streamflow statistics that characterize elements of the flow regime that substantially affect biological health and ecological sustainability. ERHIs are used to quantitatively characterize aspects of the streamflow regime, including magnitude, duration, frequency, timing, and rate of change. Changes in ERHI values can occur as a result of human activity, and changes in ERHIs over time at various stream locations can provide information about the degree of alteration in aquatic ecosystems at or near those locations. New Jersey streams can be divided into four classes (A, B, C, or D), where streams with similar ERHI values (determined from cluster analysis) are assigned the same stream class. In order to detect and quantify changes in ERHIs at selected streamflow-gaging stations, a 'baseline' period is needed. Ideally, a baseline period is a period of continuous daily streamflow record at a gaging station where human activity along the contributing stream reach or in the stream's basin is minimal. Because substantial urbanization and other development had already occurred before continuous streamflow-gaging stations were installed, it is not possible to identify baseline periods that meet this criterion for many reaches in New Jersey. Therefore, the baseline period for a considerably altered basin can be defined as a period prior to a substantial human-induced change in the drainage basin or stream reach (such as regulations or diversions), or a period during which development did not change substantially. Index stations (stations with minimal urbanization) were defined as streamflow-gaging stations in basins that contain less than 15 percent urban land use throughout the period of continuous streamflow record. A minimum baseline period of record for each stream class was determined by comparing the variability of selected ERHIs among consecutive 5-, 10-, 15-, and 20-year time increments for index stations. On the basis of this analysis, stream classes A and D were assigned a minimum of 20 years of continuous record as a baseline period and stream classes B and C, a minimum of 10 years. Baseline periods were calculated for 85 streamflow-gaging stations in New Jersey with 10 or more years of continuous daily streamflow data, and the values of 171 ERHIs also were calculated for these baseline periods for each station. Baseline periods were determined by using historical streamflow-gaging station data, estimated changes in impervious surface in the drainage basin, and statistically significant changes in annual base flow and runoff. Historical records were reviewed to identify years during which regulation, diversions, or withdrawals occurred in the drainage basins. Such years were not included in baseline periods of record. For some sites, the baseline period of record was shorter than the minimum period of record specified for the given stream class. In such cases, the baseline period was rated as 'poor'. Impervious surface was used as an indicator of urbanization and change in streamflow characteristics owing to increases in storm runoff and decreases in base flow. Percentages of impervious surface were estimated for 85 streamflow-gaging stations from available municipal population-density data by using a regression model. Where the period of record was sufficiently long, all years after the impervious surface exceeded 10 to 20 percent were excluded from the baseline period. The percentage of impervious surface also was used as a criterion in assigning qualitative ratings to baseline periods. Changes in trends of annual base fl

Scientific Investigations Report↗
USGS2008

Precipitation, Ground-water Hydrology, and Recharge Along the Eastern Slopes of the Sandia Mountains, Bernalillo County, New Mexico

The spatial and temporal distribution of recharge to carbonate and clastic aquifers along the eastern slopes of the Sandia Mountains was investigated by using precipitation, water-level, dissolved chloride, and specific-conductance data. The U.S. Geological Survey (USGS), in cooperation with the Bernalillo County Public Works Division, conducted a study to assess ground-water conditions and provide technical data that could be used as a basis for management and future planning of eastern Bernalillo County water resources. The intent of the investigation was to improve the current understanding of subsurface mechanisms controlling recharge dynamics in a geologically complex aquifer system. In the Sandia Mountains, precipitation events are generally limited to snowfalls in winter months and monsoon rainfall in late summer. Monthly meteorological data from weather stations in the study area indicate that monsoon rainfall during July and August constitutes close to one-third of annual precipitation totals. Following precipitation and snowmelt events, daily ground-water level data show low-amplitude, long-duration peaks in hydrographs of wells north and west of the Tijeras Fault. Hydrographs of monthly and biannual water-level data from across the study area show seasonal variation and water-level fluctuations in excess of 30 ft during a period of below-average precipitation. Water level observations in 67 percent of wells showing drought-induced water-level declines rebounded to at or near predrought conditions within 6 months of return to normal climate conditions. Cross-correlation of annual hydrologic data shows aquifer response to periods of monsoon recharge to persist from 1 to 6 months following events. The lag time between precipitation input and response of water levels or solute concentrations was largest near the Tijeras and Gutierrez Faults. These results indicate regional faults hydrologically isolate the Tijeras Graben from groundwater recharge originating at high elevations along the eastern slopes of the Sandia Mountains. Recharge rates calculated by using the chloride-mass-balance method for five springs located at the base of the Sandia Mountains ranged from 1 to 23 percent of annual precipitation.

Scientific Investigations Report↗
USGS2009

Hydrology of Northern Utah Valley, Utah County, Utah, 1975-2005

The ground-water resources of northern Utah Valley, Utah, were assessed during 2003-05 to describe and quantify components of the hydrologic system, determine a hydrologic budget for the basin-fill aquifer, and evaluate changes to the system relative to previous studies. Northern Utah Valley is a horst and graben structure with ground water occurring in both the mountain-block uplands surrounding the valley and in the unconsolidated basin-fill sediments. The principal aquifer in northern Utah Valley occurs in the unconsolidated basin-fill deposits where a deeper unconfined aquifer occurs near the mountain front and laterally grades into multiple confined aquifers near the center of the valley. Sources of water to the basin-fill aquifers occur predominantly as either infiltration of streamflow at or near the interface of the mountain front and valley or as subsurface inflow from the adjacent mountain blocks. Sources of water to the basin-fill aquifers were estimated to average 153,000 (+/- 31,500) acre-feet annually during 1975-2004 with subsurface inflow and infiltration of streamflow being the predominant sources. Discharge from the basin-fill aquifers occurs in the valley lowlands as flow to waterways, drains, ditches, springs, as diffuse seepage, and as discharge from flowing and pumping wells. Ground-water discharge from the basin-fill aquifers during 1975-2004 was estimated to average 166,700 (+/- 25,900) acre-feet/year where discharge to wells for consumptive use and discharge to waterways, drains, ditches, and springs were the principal sources. Measured water levels in wells in northern Utah Valley declined an average of 22 feet from 1981 to 2004. Water-level declines are consistent with a severe regional drought beginning in 1999 and continuing through 2004. Water samples were collected from 36 wells and springs throughout the study area along expected flowpaths. Water samples collected from 34 wells were analyzed for dissolved major ions, nutrients, and stable isotopes of hydrogen and oxygen. Water samples from all 36 wells were analyzed for dissolved-gas concentration including noble gases and tritium/helium-3. Within the basin fill, dissolved-solids concentration generally increases with distance along flowpaths from recharge areas, and shallower flowpaths tend to have higher concentrations than deeper flowpaths. Nitrate concentrations generally are at or below natural background levels. Dissolved-gas recharge temperature data support the conceptual model of the basin-fill aquifers and highlight complexities of recharge patterns in different parts of the valley. Dissolved-gas data indicate that the highest elevation recharge sources for the basin-fill aquifer are subsurface inflow derived from recharge in the adjacent mountain block between the mouths of American Fork and Provo Canyons. Apparent ground-water ages in the basin-fill aquifer, as calculated using tritium/helium-3 data, range from 2 to more than 50 years. The youngest waters in the valley occur near the mountain fronts with apparent ages generally increasing near the valley lowlands and discharge area around Utah Lake. Flowpaths are controlled by aquifer properties and the location of the predominant recharge sources, including subsurface inflow and recharge along the mountain front. Subsurface inflow is distributed over a larger area across the interface of the subsurface mountain block and basin-fill deposits. Subsurface inflow occurs at a depth deeper than that at which mountain-front recharge occurs. Recharge along the mountain front is often localized and focused over areas where streams and creeks enter the valley, and recharge is enhanced by the associated irrigation canals.

Utah↗
USGS2009

Hydrology of the Johnson Creek Basin, Oregon

The Johnson Creek basin is an important resource in the Portland, Oregon, metropolitan area. Johnson Creek forms a wildlife and recreational corridor through densely populated areas of the cities of Milwaukie, Portland, and Gresham, and rural and agricultural areas of Multnomah and Clackamas Counties. The basin has changed as a result of agricultural and urban development, stream channelization, and construction of roads, drains, and other features characteristic of human occupation. Flooding of Johnson Creek is a concern for the public and for water management officials. The interaction of the groundwater and surface-water systems in the Johnson Creek basin also is important. The occurrence of flooding from high groundwater discharge and from a rising water table prompted this study. As the Portland metropolitan area continues to grow, human-induced effects on streams in the Johnson Creek basin will continue. This report provides information on the groundwater and surface-water systems over a range of hydrologic conditions, as well as the interaction these of systems, and will aid in management of water resources in the area. High and low flows of Crystal Springs Creek, a tributary to Johnson Creek, were explained by streamflow and groundwater levels collected for this study, and results from previous studies. High flows of Crystal Springs Creek began in summer 1996, and did not diminish until 2000. Low streamflow of Crystal Springs Creek occurred in 2005. Flow of Crystal Springs Creek related to water-level fluctuations in a nearby well, enabling prediction of streamflow based on groundwater level. Holgate Lake is an ephemeral lake in Southeast Portland that has inundated residential areas several times since the 1940s. The water-surface elevation of the lake closely tracked the elevation of the water table in a nearby well, indicating that the occurrence of the lake is an expression of the water table. Antecedent conditions of the groundwater level and autumn and winter precipitation totals were used to anticipate flooding of Holgate Lake. Several factors affect annual mean flow of Johnson Creek. More precipitation falls in the southeastern area of the basin because of the topographic setting. Runoff from much of the northern and western areas of the basin does not flow into Johnson Creek due to permeable deposits, interception by combined sewer systems, and by groundwater flow away from Johnson Creek. Inflow from Crystal Springs Creek accounts for one-half of the increase in streamflow of Johnson Creek between the Sycamore and Milwaukie sites. Low flows of Johnson Creek vary as a result of fluctuations in groundwater discharge to the creek, although past water uses may have decreased flows. The groundwater contributions to streamflow upstream of river mile (RM) 5.5 are small compared to contributions downstream of this point. Comparison of flows to a nearby basin indicates that diversions of surface water may have resulted in a 50 percent decrease in low flows from about 1955 to 1977. Runoff from the drainage basin area upstream of the Johnson Creek at Sycamore site contributes more to peak streamflow and peak volume than the drainage basin area between the Sycamore and Milwaukie sites. The average increase in annual peak streamflow and annual peak volume between the two sites was 11 and 24 percent, respectively. Decreased contribution in the lower area of the drainage basin is a result of infiltration, interception by drywell and combined sewer systems, and temporary overbank storage. Trends in flow typically associated with increasing urban development were absent in Johnson Creek. Annual, low, and high flows showed no trend from 1941 to 2006. Much of the infrastructure that may affect runoff from agricultural, residential, and urban development was in place prior to collection of hydrologic data in the basin. Management of stormwater in the urban areas by routing runoff from impervious surfaces to dry

Oregon↗
USGS2009

Hydrologic Conditions that Influence Streamflow Losses in a Karst Region of the Upper Peace River, Polk County, Florida

The upper Peace River from Bartow to Fort Meade, Florida, is described as a groundwater recharge area, reflecting a reversal from historical groundwater discharge patterns that existed prior to the 1950s. The upper Peace River channel and floodplain are characterized by extensive karst development, with numerous fractures, crevasses, and sinks that have been eroded in the near-surface and underlying carbonate bedrock. With the reversal in groundwater head gradients, river water is lost to the underlying groundwater system through these karst features. An investigation was conducted to evaluate the hydrologic conditions that influence streamflow losses in the karst region of the upper Peace River. The upper Peace River is located in a basin that has been altered substantially by phosphate mining and increases in groundwater use. These alterations have changed groundwater flow patterns and caused streamflow declines through time. Hydrologic factors that have had the greatest influence on streamflow declines in the upper Peace River include the lowering of the potentiometric surfaces of the intermediate aquifer system and Upper Floridan aquifer beneath the riverbed elevation due to below-average rainfall (droughts), increases in groundwater use, and the presence of numerous karst features in the low-water channel and floodplain that enhance the loss of streamflow. Seepage runs conducted along the upper Peace River, from Bartow to Fort Meade, indicate that the greatest streamflow losses occurred along an approximate 2-mile section of the river beginning about 1 mile south of the Peace River at Bartow gaging station. Along the low-water and floodplain channel of this 2-mile section, there are about 10 prominent karst features that influence streamflow losses. Losses from the individual karst features ranged from 0.22 to 16 cubic feet per second based on measurements made between 2002 and 2007. The largest measured flow loss for all the karst features was about 50 cubic feet per second, or about 32 million gallons per day, on June 28, 2002. Streamflow losses varied throughout the year, and were related to seasonal fluctuations in groundwater levels. When groundwater levels were at their lowest level at the end of the dry season (May and June), there was an increased potential for streamflow losses. During this study, the largest streamflow losses occurred at the beginning of the summer rainy season when discharge in the river increased and large volumes of water were needed to replenish unfilled cavities and void spaces in the underlying aquifers. The underlying geology along the upper Peace River and floodplain is highly karstified, and aids in the movement and amount of streamflow that is lost to the groundwater system in this region. Numerous karst features and fractured carbonates and cavernous zones observed in geologic cores and geophysical logs indicate an active, well-connected, groundwater flow system. Aquifer and dye tests conducted along the upper Peace River indicate the presence of cavernous and highly transmissive layers within the floodplain area that can store and transport large volumes of water in underground cavities. A discharge measurement made during this study indicates that the cavernous system associated with Dover Sink can accept over 10 million gallons per day (16 cubic feet per second) of streamflow before the localized aquifer storage volume is replenished and the level of the sink is stabilized.

Scientific Investigations Report↗
USGS2010

Hydrology, water quality, and causes of changes in vegetation in the vicinity of the Spring Bluff Nature Preserve, Lake County, Illinois, May 2007–August 2008

Agriculture and urbanization have altered the hydrology and water quality of the coastal wetland complex along the shore of Lake Michigan at the Spring Bluff Nature Preserve and Illinois Beach State Park in northeastern Lake County, Ill., and the adjacent Chiwaukee Prairie State Natural Area in southeastern Wisconsin. Culverts, roads, ditches, and berms installed within the wetland complex have altered the natural directions of surface-water flow and likely have increased the natural hydroperiod in the Spring Bluff Nature Preserve and decreased it in the northern part of the Illinois Beach State Park. Relative to presettlement conditions, surface-water runoff into the wetlands likely is greater in quantity and higher in concentrations of several constituents, including chloride, nitrate, phosphorous, and suspended sediment. These constituent concentrations are affected by a variety of factors, including the amount of agricultural and urban land use in the watersheds. Hydrologic, chemical, and biologic processes within the wetland communities reduce the concentrations of these constituents in surface water before the water discharges to Lake Michigan by as much as 75 percent for chloride, 85 percent for nitrate, 66 percent for phosphorous, and more than an order of magnitude for suspended sediment. However, concentrations of phosphorous and suspended sediment in surface water increased within parts of the wetland complex. Given these changes, the floristic quality of these wetlands has been altered from the historic condition. Specifically, Typha spp. and Phragmites australis occur in greater numbers and over a larger area than in the past. The spread of Typha spp. and Phragmites australis appears to be enhanced by anthropogenic alterations within the wetland complex, such as increased water levels and duration of inundation and, possibly, increases in the total concentration of dissolved constituents in water.

Illinois↗
USGS2010

Groundwater Hydrology and Chemistry in and near an Emulsified Vegetable-Oil Injection Zone, Solid Waste Management Unit 17, Naval Weapons Station Charleston, North Charleston, South Carolina, 2004-2009

The U.S. Geological Survey and the Naval Facilities Engineering Command Southeast investigated the hydrology and groundwater chemistry in the vicinity of an emulsified vegetable-oil injection zone at Solid Waste Management Unit (SWMU) 17, Naval Weapons Station Charleston, North Charleston, South Carolina. In May 2004, Solutions-IES initiated a Phase-I pilot-scale treatability study at SWMU17 involving the injection of an edible oil emulsion into the aquifer near wells 17PS-01, 17PS-02, and 17PS-03 to treat chlorinated solvents. The Phase-I injection of emulsified vegetable oil resulted in dechlorination of trichloroethene (TCE) to cis-1,2-dichloroethene (cDCE), but the dechlorination activity appeared to stall at cDCE, with little further dechlorination of cDCE to vinyl chloride (VC) or to ethene. The purpose of the present investigation was to examine the groundwater hydrology and chemistry in and near the injection zone to gain a better understanding of the apparent remediation stall. It is unlikely that the remediation stall was due to the lack of an appropriate microbial community because groundwater samples showed the presence of Dehalococcoides species (sp.) and suitable enyzmes. The probable causes of the stall were heterogeneous distribution of the injectate and development of low-pH conditions in the injection area. Because groundwater pH values in the injection area were below the range considered optimum for dechlorination activity, a series of tests was done to examine the effect on dechlorination of increasing the pH within well 17PS-02. During and following the in-well pH-adjustment tests, VC concentrations gradually increased in some wells in the injection zone that were not part of the in-well pH-adjustment tests. These data possibly reflect a gradual microbial acclimation to the low-pH conditions produced by the injection. In contrast, a distinct increase in VC concentration was observed in well 17PS-02 following the in-well pH increase. Adjustment of the pH to near-neutral values in well 17PS-02 may have made that well relatively favorable to VC production compared with much of the rest of the injection zone, possibly accounting for acceleration of VC production at that well. Following a Phase-II injection in which Solutions-IES, Inc., injected pH-buffered emulsified vegetable oil with an improved efficiency injection approach, 1,1-dichloroethene, TCE, and cDCE rapidly decreased in concentration and are now (2009) undetectable in the injection zone, with the exception of a low concentration (43 micrograms per liter, August 2009) of cDCE in well 17PS-01. In August 2009, VC was still present in groundwater at the test wells in concentrations ranging from 150 to 640 micrograms per liter. The Phase-II injection, however, appears to have locally decreased aquifer permeability, possibly resulting in movement of contamination around, rather than through, the treatment area.

North Carolina↗
USGS2010

Hydrology, water quality, and water-supply potential of ponds at Hunter Army Airfield, Chatham County, Georgia, November 2008-July 2009

The hydrology, water quality, and water-supply potential of four ponds constructed to capture stormwater runoff at Hunter Army Airfield, Chatham County, Georgia, were evaluated as potential sources of supplemental irrigation supply. The ponds are, Oglethorpe Lake, Halstrum Pond, Wilson Gate Pond, and golf course pond. During the dry season, when irrigation demand is highest, ponds maintain water levels primarily from groundwater seepage. The availability of water from ponds during dry periods is controlled by the permeability of surficial deposits, precipitation and evaporation, and the volume of water stored in the pond. Net groundwater seepage (Gnet) was estimated using a water-budget approach that used onsite and nearby climatic and hydrologic data collected during November-December 2008 including precipitation, evaporation, pond stage, and discharge. Gnet was estimated at three of the four sites?Oglethorpe Lake, Halstrum Pond, and Wilson Gate Pond?during November-December 2008. Pond storage volume in the three ponds ranged from 5.34 to 12.8 million gallons. During November-December 2008, cumulative Gnet ranged from -5.74 gallons per minute (gal/min), indicating a net loss in pond volume, to 19 gal/min, indicating a net gain in pond volume. During several periods of stage recovery, daily Gnet rates were higher than the 2-month cumulative amount, with the highest rates of 178 to 424 gal/min following major rainfall events during limited periods. These high rates may include some contribution from stormwater runoff; more typical recovery rates were from 23 to 223 gal/min. A conservative estimate of the volume of water available for irrigation supply from three of the ponds was provided by computing the rate of depletion of pond volume for a variety of withdrawal rates based on long-term average July precipitation and evaporation and the lowest estimated Gnet rate at each pond. Withdrawal rates of 1,000, 500, and 250 gal/min were applied during an 8-hour daily pumping period. At a withdrawal rate of 1,000 gal/min, available pond volume would be depleted in 13-29 days, at a rate of 500 gal/min in 24-60 days, and at a rate of 250 gal/min, in 44 to 130 days. In each case, Halstrum Pond had the largest amount of available pond volume. The water-supply potential at the golf course pond was assessed by measuring flow downstream from the pond during February-July 2009, and examining historic stormflow measurements collected during 1979-87. Streamflow during both of these periods exceeded average daily (2005-2007) golf course water use. Assuming an 8-hour daily irrigation period, the average discharge rate required to meet Golf Course water demand during peak demand months of March-May and July-October exceeds 200 gal/min, with the greatest rate of 531 gal/min during July. During February-July 2009, daily average streamflow downstream of the golf course pond exceeded 238 gal/min 90 percent of the time. Based on samples collected for chemical analysis during April 2009, water from all four ponds at Hunter Army Airfield is fresh and suitable for irrigation supply, with chloride concentrations below 12 milligrams per liter. With the exception of iron in Wilson Gate Pond, constituent concentrations are below U.S. Environmental Protection Agency primary and secondary drinking water maximum contaminant levels. Water in Wilson Gate Pond contained an iron concentration of 419 mg/L, which exceeds the secondary maximum contaminant level of 300 micrograms per liter. Although not a health hazard, when the iron concentration exceeds 300 micrograms per liter, iron staining of sidewalks and plumbing fixtures may occur. Levels of dissolved oxygen were below the Georgia Environmental Protection Divison standard of 4 milligrams per liter for waters supporting warm-water fishes at deeper depths in Oglethorpe Lake, Wilson Gate Pond, and Halstrum Pond, and in the composite sample at the golf course pond.

Georgia↗
USGS2010

Summary of Hydrologic Data for the Tuscarawas River Basin, Ohio, with an Annotated Bibliography

The Tuscarawas River Basin drains approximately 2,600 square miles in eastern Ohio and is home to 600,000 residents that rely on the water resources of the basin. This report summarizes the hydrologic conditions in the basin, describes over 400 publications related to the many factors that affect the groundwater and surface-water resources, and presents new water-quality information and a new water-level map designed to provide decisionmakers with information to assist in future data-collection efforts and land-use decisions. The Tuscarawas River is 130 miles long, and the drainage basin includes four major tributary basins and seven man-made reservoirs designed primarily for flood control. The basin lies within two physiographic provinces-the Glaciated Appalachian Plateaus to the north and the unglaciated Allegheny Plateaus to the south. Topography, soil types, surficial geology, and the overall hydrology of the basin were strongly affected by glaciation, which covered the northern one-third of the basin over 10,000 years ago. Within the glaciated region, unconsolidated glacial deposits, which are predominantly clay-rich till, overlie gently sloping Pennsylvanian-age sandstone, limestone, coal, and shale bedrock. Stream valleys throughout the basin are filled with sands and gravels derived from glacial outwash and alluvial processes. The southern two-thirds of the basin is characterized by similar bedrock units; however, till is absent and topographic relief is greater. The primary aquifers are sand- and gravel-filled valleys and sandstone bedrock. These sands and gravels are part of a complex system of aquifers that may exceed 400 feet in thickness and fill glacially incised valleys. Sand and gravel aquifers in this basin are capable of supporting sustained well yields exceeding 1,000 gallons per minute. Underlying sandstones within 300 feet of the surface also provide substantial quantities of water, with typical well yields of up to 100 gallons per minute. Although hydraulic connection between the sandstone bedrock and the sands and gravels in valleys is likely, it has not been assessed in the Tuscarawas River Basin. In 2001, the major land uses in the basin were approximately 40 percent forested, 39 percent agricultural, and 17 percent urban/residential. Between 1992 and 2001, forested land use decreased by 2 percent with correspondingly small increases in agricultural and urban land uses, but from 1980 to 2005, the 13-county area that encompasses the basin experienced a 7.1-percent increase in population. Higher population density and percentages of urban land use were typical of the northern, headwaters parts of the basin in and around the cities of Akron, Canton, and New Philadelphia; the southern area was rural. The basin receives approximately 38 inches of precipitation per year that exits the basin through evapotranspiration, streamflow, and groundwater withdrawals. Recharge to groundwater is estimated to range from 6 to 10 inches per year across the basin. In 2000, approximately 89 percent of the 116 million gallons per day of water used in the basin came from groundwater sources, whereas 11 percent came from surface-water sources. To examine directions of groundwater flow in the basin, a new dataset of water-level contours was developed by the Ohio Department of Natural Resources. The contours were compiled on a map that shows that groundwater flows from the uplands towards the valleys and that the water-level surface mimics surface topography; however, there are areas where data were too sparse to adequately map the water-level surface. Additionally, little is known about deep groundwater that may be flowing into the basin from outside the basin and groundwater interactions with surface-water bodies. Many previous reports as well as new data collected as part of this study show that water quality in the streams and aquifers in the Tuscarawas River Basin has been degraded by urban, suburban, and rural

Scientific Investigations Report↗
USGS2011

Baseline hydrologic studies in the lower Elwha River prior to dam removal

After the removal of two large, long‑standing dams on the Elwha River, Washington, the additional load of sediment and wood is expected to affect the hydrology of the lower river, its estuary, and the alluvial aquifer underlying the surrounding flood plain. To better understand the surface-water and groundwater characteristics of the river and estuary before dam removal, several hydrologic data sets were collected and analyzed. An experiment using a dye tracer characterized transient storage, and it was determined that the low‑flow channel of the lower Elwha River was relatively simple; 1–6 percent of the median travel time of dye was attributed to transient‑storage processes. Water data from monitoring wells adjacent to the main‑stem river indicated a strong hydraulic connectivity between stage in the river and groundwater levels in the flood plain. Analysis of temperature data from the monitoring wells showed that changes in the groundwater temperature responded weeks or months after water temperature changed in the river. A seepage investigation indicated that water from the river was moving into the aquifer (losing reach) between 1.7 and 2.8 kilometers from the river mouth. Surface‑water measurements and temperature and salinity data collected throughout the estuary helped to characterize the magnitude and nature of water movement in and out of the estuary. Salinity and stage sensors positioned in the estuarine network showed a strong surface‑water connection between the river and estuary waters east of the river. In contrast, there was a weaker connection between the river and estuarine water bodies west of the river.

Washington↗
USGS2011

Estimated hydrologic budgets of kettle-hole ponds in coastal aquifers of southeastern Massachusetts

Kettle-hole ponds in southeastern Massachusetts are in good hydraulic connection to an extensive coastal aquifer system that includes the Plymouth-Carver aquifer system on the mainland and aquifers underlying Cape Cod. The ponds receive water from, and contribute water to, the underlying glacial aquifer; ponds also receive water from precipitation and lose water to evaporation from the pond surface. Some ponds are connected to surface-water drainage systems and receive water from or contribute water to streams or adjacent wetlands. The Massachusetts Department of Environmental Protection currently (2011) is developing Total Maximum Daily Loads of phosphorus for the freshwater ponds in the region to maintain the health of pond ecosystems; the amounts and sources of water fluxes into and out of the ponds are important factors in determining the amount of phosphorus that can be assimilated into a pond. To assist in this effort, the U.S. Geological Survey used groundwater-flow models of the coastal aquifer system to estimate hydrologic budgets-including inflows and outflows from the aquifer system and adjacent streams and wetlands, and recharge from precipitation-for 425 ponds in southeastern Massachusetts. Water fluxes through the ponds are a function of several factors, including the size, shape, and bathymetry of the pond, orientation of the pond relative to the regional hydraulic gradient, and hydrologic setting relative to the proximity of groundwater divides and discharge boundaries. Total steady-state fluxes through the ponds range from more than 3,300,000 to less than 2,000 cubic feet per day. For ponds without surface-water inlets or outlets, groundwater inflow accounts for 98 to 3 percent of total inflow; conversely, recharge onto the pond surface accounts for the remainder of inflow (between 2 and 97 percent). All natural flows from these ponds are through recharge from the pond into the aquifer. In one pond, about 94 percent of the total outflow is removed for water supply. For ponds that are connected to surface-water drainages, most inflow and outflow are through streams. Ponds that receive water from streams receive most (58 to 89 percent) of their water from those streams. Ponds that are drained by streams lose between 5 and 100 percent of their water to those streams.

Scientific Investigations Report↗
USGS2013

Groundwater hydrology and estimation of horizontal groundwater flux from the Rio Grande at selected locations in Albuquerque, New Mexico, 2003-9

The Albuquerque, New Mexico, area has two principal sources of water: groundwater from the Santa Fe Group aquifer system and surface water from the San Juan-Chama Diversion Project. From 1960 to 2002, groundwater withdrawals from the Santa Fe Group aquifer system have caused water levels to decline more than 120 feet in some places within the Albuquerque area, resulting in a great deal of interest in quantifying the river-aquifer interaction associated with the Rio Grande. In 2003, the U.S. Geological Survey in cooperation with the Bureau of Reclamation, the Middle Rio Grande Endangered Species Collaborative Program, and the U.S. Army Corps of Engineers began a detailed characterization of the hydrogeology of the Rio Grande riparian corridor in the Albuquerque, New Mexico, area to provide hydrologic data and enhance the understanding of rates of water leakage from the Rio Grande to the alluvial aquifer, groundwater flow through the aquifer, and discharge of water from the aquifer to the riverside drains. A simple conceptual model of flow indicates that the groundwater table gently slopes from the Rio Grande towards riverside drains and the outer boundaries of the inner valley. Water infiltrating from the Rio Grande initially moves vertically below the river, but, as flow spreads farther into the Rio Grande inner valley alluvial aquifer, flow becomes primarily horizontal. The slope of the water-table surface may be strongly controlled by the riverside drains and influenced by other more distal hydrologic boundary conditions, such as groundwater withdrawals by wells. Results from 35 slug tests performed in the Rio Grande inner valley alluvial aquifer during January and February 2009 indicate that hydraulic-conductivity values ranged from 5 feet per day to 160 feet per day with a median hydraulic-conductivity for all transects of 40 feet per day. Median annual horizontal hydraulic gradients in the Rio Grande inner valley alluvial aquifer ranged from 0.011 to 0.002. Groundwater fluxes through the alluvial aquifer calculated by using median slug-test results (qm slug ) and Darcy's law ranged from about 0.1 feet per day to about 0.7 feet per day. Groundwater fluxes calculated by using the Suzuki-Stallman method (qm heat ) ranged from 0.52 feet per day to 0.23 feet per day. Results from the Darcy's law and Suzuki-Stallman flux calculations were compared to discharge measured in riverside drains on both sides of the river north of the Montaño Bridge on February 26, 2009. Flow in the Corrales Riverside Drain increased by 1.4 cubic feet per second from mile 2 to mile 4, about 12 cubic feet per day per linear foot of drain. Flow in the Albuquerque Riverside Drain increased by 15 cubic feet per second between drain miles 0 and 3, about 82 cubic feet per day per linear foot of drain. The flux of water from the river to the aquifer was calculated to be 2.2 cubic feet per day per linear foot of river by using the median qm slug of 0.09 feet per day at Montaño transects west of the river. The total flux was calculated to be 6.0 cubic feet per day per linear foot of river by using the mean(qm heat of 0.24 feet per day for the Montaño transects west of the river. Assuming the Corrales Riverside Drain intercepted all of this flow, the qm slug or qm heat fluxes account for 18 to 50 percent, respectively, of the increase of flow in the drain. The flux of water from the river to the aquifer was calculated to be 15 cubic feet per day per linear foot of river by using the median qm slug of 0.30 feet per day at the Montaño transects east of the river. The flux of water from the river to the aquifer was calculated to be 17 cubic feet per day per linear foot of river by using the mean flux calculated from the Suzuki-Stallman method for the Montaño East transects of 0.34 feet per day. Assuming the Albuquerque Riverside Drain intercepted all this flow, the qm slug or (qm heat fluxes would only account for 18 to 21 percent, respectively, of the increase in flow in the drain. The comparison of these results with those of previous investigations suggests that calculated flux through the Rio Grande inner valley alluvial aquifer is strongly scale dependent and that the thickness of aquifer through which river water flows may be greater than indicated by the vertical temperature profiles.

Albuquerque, New Mexico↗
USGS2012

Preliminary analysis of the hydrologic effects of temporary shutdowns of the Rondout-West Branch Water Tunnel on the groundwater-flow system in Wawarsing, New York

Flooding of streets and residential basements, and bacterial contamination of private-supply wells with Escherichia coli (E. coli) are recurring problems in the Rondout Valley near the Town of Wawarsing, Ulster County, New York. Leakage from the Rondout-West Branch (RWB) Water Tunnel and above-normal precipitation have been suspected of causing elevated groundwater levels and basement flooding. The hydrology of a 12-square-mile study area within the Town of Wawarsing was studied during 2008-10. A network of 41 wells (23 unconsolidated-aquifer and 18 bedrock wells) and 2 surface-water sites was used to monitor the hydrologic effects of four RWB Water Tunnel shutdowns. The study area is underlain by a sequence of northeast-trending sedimentary rocks that include limestone, shale, and sandstone. The bedrock contains dissolution features, fractures, and faults. Inflows that ranged from less than 1 to more than 9,000 gallons per minute from the fractured bedrock were documented during construction of the 13.5-foot-diameter RWB Water Tunnel through the sedimentary-rock sequence 710 feet (ft) beneath the study-area valley. Glacial sediments infill the valley above the bedrock sequence and consist of clay, silt, sand, and gravel. The groundwater-flow system in the valley consists of both fractured-rock and unconsolidated aquifers. Water levels in both the bedrock and unconsolidated aquifers respond to variations in seasonal precipitation. During the past 9 years (2002-10), annual precipitation at Central Park, N.Y., has exceeded the 141-year mean. Potentiometric-surface maps indicate that groundwater in the bedrock flows from the surrounding hills on the east and west sides of the valley toward the center of the valley, and ultimately toward the northeast. On average, water levels in the bedrock aquifer had seasonal differences of 5.3 ft. Analysis of hydrographs of bedrock wells indicates that many of these wells are affected by the RWB Tunnel leakage. Tunnel-leakage influences (water level and temperature changes) in the bedrock aquifer were measured at distances up to 7,000 ft from the RWB Tunnel. Water levels in the bedrock changed as much as 12 ft within 0.5 hour during tunnel shutdowns. Nine of the 10 wells that responded to the shutdowns showed a water-level response of 5 ft or greater. Changes in water levels ranged from 1.5 to 12 ft, with tunnel-leakage influence delay times ranging from 0.5 to 60 hours. Many of the longest tunnel-influence delay times and smallest water-level changes were in wells located closest to the tunnel in shale. Tunnel-influence response of the bedrock aquifer is consistent with its preliminary characterization as an anisotropic aquifer with greater transmissivity along bedding strike than across bedding strike. This tunnel-influence response is also consistent with the likely presence of discrete high-transmissivity networks along fractured limestone beds that have undergone dissolution. A lack of bedrock observation wells in half of the study area hampered a more thorough analysis of the extent of leakage from the RWB Tunnel in the study area. On average, water levels in the unconsolidated aquifer had a seasonal difference of 5.0 ft. Some unconsolidated-aquifer wells indicated water-level changes due to tunnel leakage. The locations of unconsolidated-aquifer wells with measurable water-level changes due to tunnel leakage correlated with those in the bedrock. Water levels in the unconsolidated aquifer changed as much as 2.5 ft within 18 hours of tunnel shutdowns, but water-level changes in some unconsolidated-aquifer wells were smaller or nonexistent.

New York↗
USGS2012

Water quality, hydrology, and simulated response to changes in phosphorus loading of Mercer Lake, Iron County, Wisconsin, with special emphasis on the effects of wastewater discharges

Mercer Lake is a relatively shallow drainage lake in north-central Wisconsin. The area near the lake has gone through many changes over the past century, including urbanization and industrial development. To try to improve the water quality of the lake, actions have been taken, such as removal of the lumber mill and diversion of all effluent from the sewage treatment plant away from the lake; however, it is uncertain how these actions have affected water quality. Mercer Lake area residents and authorities would like to continue to try to improve the water quality of the lake; however, they would like to place their efforts in the actions that will have the most beneficial effects. To provide a better understanding of the factors affecting the water quality of Mercer Lake, a detailed study of the lake and its watershed was conducted by the U.S. Geological Survey in collaboration with the Mercer Lake Association. The purposes of the study were to describe the water quality of the lake and the composition of its sediments; quantify the sources of water and phosphorus loading to the lake, including sources associated with wastewater discharges; and evaluate the effects of past and future changes in phosphorus inputs on the water quality of the lake using eutrophication models (models that simulate changes in phosphorus and algae concentrations and water clarity in the lake). Based on analyses of sediment cores and monitoring data collected from the lake, the water quality of Mercer Lake appears to have degraded as a result of the activities in its watershed over the past 100 years. The water quality appears to have improved, however, since a sewage treatment plant was constructed in 1965 and its effluent was routed away from the lake in 1995. Since 2000, when a more consistent monitoring program began, the water quality of the lake appears to have changed very little. During the two monitoring years (MY) 2008-09, the average summer near-surface concentration of total phosphorus was 0.023 mg/L, indicating the lake is borderline mesotrophic-eutrophic, or has moderate to high concentrations of phosphorus, whereas the average summer chlorophyll a concentration was 3.3 mg/L and water clarity, as measured with a Secchi depth, was 10.4 ft, both indicating mesotrophic conditions or that the lake has a moderate amount of algae and water clarity. Although actions have been taken to eliminate the wastewater discharges, the bottom sediment still has slightly elevated concentrations of several pollutants from wastewater discharges, lumber operations, and roadway drainage, and a few naturally occurring metals (such as iron). None of the concentrations, however, were high enough above the defined thresholds to be of concern. Based on nitrogen to phosphorus ratios, the productivity (algal growth) in Mercer Lake should typically be limited by phosphorus; therefore, understanding the phosphorus input to the lake is important when management efforts to improve or prevent degradation of the lake water quality are considered. Total inputs of phosphorus to Mercer Lake were directly estimated for MY 2008-09 at about 340 lb/yr and for a recent year with more typical hydrology at about 475 lb/yr. During these years, the largest sources of phosphorus were from Little Turtle Inlet, which contributed about 45 percent, and the drainage area near the lake containing the adjacent urban and residential developments, which contributed about 24 percent. Prior to 1965, when there was no sewage treatment plant and septic systems and other untreated systems contributed nutrients to the watershed, phosphorus loadings were estimated to be about 71 percent higher than during around 2009. In 1965, a sewage treatment plant was built, but its effluent was released in the downstream end of the lake. Depending on various assumptions on how much effluent was retained in the lake, phosphorus inputs from wastewater may have ranged from 0 to 342 lb. Future highway and stormwater improvements have been identified in the Mercer Infrastructure Improvement Project, and if they are done with the proposed best management practices, then phosphorus inputs to the lake may decrease by about 40 lb. Eutrophication models [Canfield and Bachman model (1981) and Carlson Trophic State Index equations (1977)] were used to predict how the water quality of Mercer Lake should respond to changes in phosphorus loading. A relatively linear response was found between phosphorus loading and phosphorus and chlorophyll a concentrations in the lake, with changes in phosphorus concentrations being slightly less (about 80 percent) and changes in chlorophyll a concentrations being slightly more (about 120 percent) than the changes in phosphorus loadings to the lake. Water clarity, indicated by Secchi depths, responded more to decreases in phosphorus loading than to increases in loading. Results from the eutrophication models indicated that the lake should have been negatively affected by the wastewater discharges. Prior to 1965, when there was no sewage treatment plant effluent and inputs from the septic systems and other untreated systems were thought to be high, the lake should have been eutrophic; near the surface, average phosphorus concentrations were almost 0.035 mg/L, chlorophyll a concentrations were about 7 μg/L, and Secchi depths were about 6 ft, which agreed with the shallower Secchi depths during this time estimated from the sediment-core analysis. The models indicated that between 1965 and 1995, when the lake retained some of the effluent from the new sewage treatment plant, water quality should have been between the conditions estimated prior to 1965 and what was expected during typical hydrologic conditions around MY 2008-09. The models also indicated that if the future Mercer Infrastructure Improvement Project is conducted with the best management practices as proposed, the water quality in the lake could improve slightly from that measured during 2006-10. Because of the small amount of phosphorus that is presently input into Mercer Lake any additional phosphorus added to the lake could degrade water quality; therefore, management actions can usefully focus on minimizing future phosphorus inputs. Phosphorus released from the sediments of a degraded lake often delays its response to decreases in external phosphorus loading, especially in shallow, frequently mixed systems. Mercer Lake, however, remains stratified throughout most of the summer, and phosphorus released from the sediments represents only about 6 percent, or a small fraction, of the total phosphorus load to the lake. Therefore, the phosphorus trapped in the sediments should minimally affect the long-term water quality of the lake and should not delay the response in its productivity to future changes in nutrient loading from its watershed.

Wisconsin↗
USGS2013

Hydrogeology, groundwater seepage, nitrate distribution, and flux at the Raleigh hydrologic research station, Wake County, North Carolina, 2005-2007

rom 2005 to 2007, the U.S. Geological Survey and the North Carolina Department of Environment and Natural Resources, Division of Water Quality, conducted a study to describe the geologic framework, measure groundwater quality, characterize the groundwater-flow system, and describe the groundwater/surface-water interaction at the 60-acre Raleigh hydrogeologic research station (RHRS) located at the Neuse River Waste Water Treatment Plant in eastern Wake County, North Carolina. Previous studies have shown that the local groundwater quality of the surficial and bedrock aquifers at the RHRS had been affected by high levels of nutrients. Geologic, hydrologic, and water-quality data were collected from 3 coreholes, 12 wells, and 4 piezometers at 3 well clusters, as well as from 2 surface-water sites, 2 multiport piezometers, and 80 discrete locations in the streambed of the Neuse River. Data collected were used to evaluate the three primary zones of the Piedmont aquifer (regolith, transition zone, and fractured bedrock) and characterize the interaction of groundwater and surface water as a mechanism of nutrient transport to the Neuse River. A conceptual hydrogeologic cross section across the RHRS was constructed using new and existing data. Two previously unmapped north striking, nearly vertical diabase dikes intrude the granite beneath the site. Groundwater within the diabase dike appeared to be hydraulically isolated from the surrounding granite bedrock and regolith. A correlation exists between foliation and fracture orientation, with most fractures striking parallel to foliation. Flowmeter logging in two of the bedrock wells indicated that not all of the water-bearing fractures labeled as water bearing were hydraulically active, even when stressed by pumping. Groundwater levels measured in wells at the RHRS displayed climatic and seasonal trends, with elevated groundwater levels occurring during the late spring and declining to a low in the late fall. Vertical gradients in the groundwater discharge area near the Neuse River were complex and were affected by fluctuations in river stage, with the exception of a well completed in a diabase dike. Water-quality data from the wells and surface-water sites at the RHRS were collected continuously as well as during periodic sampling events. Surface-water samples collected from a tributary were most similar in chemical composition to groundwater found in the regolith and transition zone. Nitrate (measured as nitrite plus nitrate, as nitrogen) concentrations in the sampled wells and tributary ranged from about 5 to more than 120 milligrams per liter as nitrogen. Waterborne continuous resistivity profiling conducted on the Neuse River in the area of the RHRS measured areas of low apparent resistivity that likely represent groundwater contaminated by high concentrations of nitrate. These areas were located on either side of a diabase dike and at the outfall of two unnamed tributaries. The diabase dike preferentially directed the discharge of groundwater to the Neuse River and may isolate groundwater movement laterally. Discrete temperature measurements made within the pore water beneath the Neuse River revealed seeps of colder groundwater discharging into warmer surface water near a diabase dike. Water-quality samples collected from the pore water beneath the Neuse River indicated that nitrate was present at concentrations as high as 80 milligrams per liter as nitrogen on the RHRS side of the river. The highest concentrations of nitrate were located within pore water collected from an area near a diabase dike that was identified as a suspected seepage area. Hydraulic head was measured and pore water samples were collected from two 140-centimeter-deep (55.1-inch-deep) multiport piezometers that were installed in bed sediments on opposite sides of a diabase dike. The concentration of nitrate in pore water at a suspected seepage area ranged from 42 to 82 milligrams per liter as nitrogen with a median concentration of 79 milligrams per liter as nitrogen. On the opposite side of the dike, concentrations of nitrate in pore water samples ranged from 3 to 91 milligrams per liter as nitrogen with a median concentration of 52 milligrams per liter. At one of the multiport piezometers the vertical gradient of hydraulic head between the Neuse River and the groundwater was too small to measure. At the multiport piezometer located in the suspected seepage area, an upward gradient of about 0.1 was present and explains the occurrence of higher concentrations of nitrate near the sediment/water interface. Horizontal seepage flux from the surficial aquifer to the edge of the Neuse River was estimated for 2006. Along a 130-foot flow path, the estimated seepage flux ranged from –0.52 to 0.2 foot per day with a median of 0.09 foot per day. The estimated advective horizontal mass flux of nitrate along a 300-foot reach of the Neuse River ranged from –10.9 to 5 pounds per day with a median of 2.2 pounds per day. The total horizontal mass flux of nitrate from the surficial aquifer to the Neuse River along the 130-foot flow path was estimated to be about 750 pounds for all of 2006. Seepage meters were deployed on the bed of the Neuse River in the areas of the multiport piezometers on either side of the diabase dike to estimate rates of vertical groundwater discharge and flux of nitrate. The average estimated daily seepage flux differed by two orders of magnitude between seepage areas. The potential vertical flux of nitrate from groundwater to the Neuse River was estimated at an average of 2.5 grams per day near one of the multiport piezometers and an average of 784 grams per day at the other. These approximations suggest that under some hydrologic conditions there is the potential for substantial quantities of nitrate to discharge from the groundwater to the Neuse River.

North Carolina↗
USGS2013

Geology, water-quality, hydrology, and geomechanics of the Cuyama Valley groundwater basin, California, 2008--12

To assess the water resources of the Cuyama Valley groundwater basin in Santa Barbara County, California, a series of cooperative studies were undertaken by the U.S. Geological Survey and the Santa Barbara County Water Agency. Between 2008 and 2012, geologic, water-quality, hydrologic and geomechanical data were collected from selected sites throughout the Cuyama Valley groundwater basin. Geologic data were collected from three multiple-well groundwater monitoring sites and included lithologic descriptions of the drill cuttings, borehole geophysical logs, temperature logs, as well as bulk density and sonic velocity measurements of whole-core samples. Generalized lithologic characterization from the monitoring sites indicated the water-bearing units in the subsurface consist of unconsolidated to partly consolidated sand, gravel, silt, clay, and occasional cobbles within alluvial fan and stream deposits. Analysis of geophysical logs indicated alternating layers of finer- and coarser-grained material that range from less than 1 foot to more than 20 feet thick. On the basis of the geologic data collected, the principal water-bearing units beneath the monitoring-well sites were found to be composed of younger alluvium of Holocene age, older alluvium of Pleistocene age, and the Tertiary-Quaternary Morales Formation. At all three sites, the contact between the recent fill and younger alluvium is approximately 20 feet below land surface. Water-quality samples were collected from 12 monitoring wells, 27 domestic and supply wells, 2 springs, and 4 surface-water sites and were analyzed for a variety of constituents that differed by site, but, in general, included trace elements; nutrients; dissolved organic carbon; major and minor ions; silica; total dissolved solids; alkalinity; total arsenic and iron; arsenic, chromium, and iron species; and isotopic tracers, including the stable isotopes of hydrogen and oxygen, activities of tritium, and carbon-14 abundance. Of the 39 wells sampled, concentrations of total dissolved solids and sulfate from 38 and 37 well samples, respectively, were greater than the U.S. Environmental Protection Agency’s secondary maximum contaminant levels. Concentrations greater than the maximum contaminant levels for nitrate were observed in five wells and were observed for arsenic in four wells. Differences in the stable-isotopic values of hydrogen and oxygen among groundwater samples indicated that water does not move freely between different formations or between different zones within the Cuyama Valley. Variations in isotopic composition indicated that recharge is derived from several different sources. The age of the groundwater, expressed as time since recharge, was between 600 and 38,000 years before present. Detectable concentrations of tritium indicated that younger water, recharged since the early 1950s, is present in parts of the groundwater basin. Hydrologic data were collected from 12 monitoring wells, 56 domestic and supply wells, 3 surface-water sites, and 4 rainfall-gaging stations. Rainfall in the valley averaged about 8 inches annually, whereas the mountains to the south received between 12 and 19 inches. Stream discharge records showed seasonal variability in surface-water flows ranging from no-flow to over 1,500 cubic feet per second. During periods when inflow to the valley exceeds outflow, there is potential recharge from stream losses to the groundwater system Water-level records included manual quarterly depth-to-water measurements collected from 68 wells, time-series data collected from 20 of those wells, and historic water levels from 16 wells. Hydrographs of the manual measurements showed declining water levels in 16 wells, mostly in the South-Main zone, and rising water levels in 14 wells, mostly in the Southern Ventucopa Uplands. Time-series hydrographs showed daily, seasonal, and longer-term effects associated with local pumping. Water-level data from the multiple-well monitoring sites indicated seasonal fluctuations as great as 80 feet and water-level differences between aquifers as great as 40 feet during peak pumping season. Hydrographs from the multiple-well groundwater monitoring sites showed vertical hydraulic gradients were upward during the winter months and downward during the irrigation season. Historic hydrographs showed water-level declines in the Southern-Main, Western Basin, Caliente Northern-Main, and Southern Sierra Madre zone ranging from 1 to 7 feet per year. Hydrographs of wells in the Southern Ventucopa Uplands zone showed several years with marked increases in water levels that corresponded to increased precipitation in the Cuyama Valley. Investigation of hydraulic properties included hydraulic conductivity and transmissivity estimated from aquifer tests performed on 63 wells. Estimates of horizontal hydraulic conductivity ranged from about 1.5 to 28 feet per day and decreased with depth. The median estimated hydraulic conductivity for the older alluvium was about five times that estimated for the Morales Formation. Estimates of transmissivity ranged from 560 to 163,400 gallons per day per foot and decreased with depth. The median estimated transmissivity for the younger alluvium was about three times that estimated for the older alluvium. Geomechanical analysis included land-surface elevation changes at five continuously operating global positioning systems (GPS) and land-subsidence detection at five interferometric synthetic aperture radar (InSAR) reference points. Analysis of data collected from continuously operating GPS stations showed the mountains to the south and west moved upward about 1 millimeter (mm) annually, whereas the station in the center of the Southern-Main zone moved downward more than 7 mm annually, indicating subsidence. It is likely that this subsidence is inelastic (permanent) deformation and indicates reduced storage capacity in the aquifer sediments. Analysis of InSAR data showed local and regional changes that appeared to be dependent, in part, on the time span of the interferogram, seasonal variations in pumping, and tectonic uplift. Long-term InSAR time series showed a total maximum detected subsidence rate of approximately 12 mm per year at one location and approximately 8 mm per year at a second location, while short-term InSAR time series showed maximum subsidence of about 15 mm at one location and localized maximum uplift of about 10 mm at another location.

California↗
USGS2015

Historical and projected climate (1901–2050) and hydrologic response of karst aquifers, and species vulnerability in south-central Texas and western South Dakota

Two karst aquifers, the Edwards aquifer in the Balcones Escarpment region of south-central Texas and the Madison aquifer in the Black Hills of western South Dakota, were evaluated for hydrologic response to projected climate change through 2050. Edwards aquifer sites include Barton Springs, the Bexar County Index Well, and Comal Springs. Madison aquifer sites include Spearfish Creek and Rhoads Fork Spring. Climate projections at sites were based on output from the Community Climate System Model of global climate, linked to the Weather Research and Forecasting (WRF) model of regional climate. The WRF model output was bias adjusted to match means for 1981–2010 from records at weather stations near Madison and Edwards aquifer sites, including Boerne, Texas, and Custer and Lead, South Dakota. Hydrologic response at spring and well sites was based on the Rainfall-Response Aquifer and Watershed Flow (RRAWFLOW) model. The WRF model climate projections for 2011–50 indicate a significant upward trend in annual air temperature for all three weather stations and a significant downward trend in annual precipitation for the Boerne weather station. Annual springflow simulated by the RRAWFLOW model had a significant downward trend for Edwards aquifer sites and no trend for Madison aquifer sites. Flora and fauna that rely on springflow from Edwards and Madison aquifer sites were assessed for vulnerability to projected climate change on the basis of the Climate Change Vulnerability Index (CCVI). The CCVI is determined by the exposure of a species to climate, the sensitivity of the species, and the ability of the species to cope with climate change. Sixteen species associated with springs and groundwater were assessed in the Balcones Escarpment region. The Barton Springs salamander ( Eurycea sosorum ) was scored as highly vulnerable with moderate confidence. Nine species—three salamanders, a fountain darter ( Etheostoma fonticola ), three insects, and two amphipods—were scored as moderately vulnerable. The remaining six species—four vascular plants, the Barton cavesnail ( Stygopyrgus bartonensis ), and a cave shrimp—were scored as not vulnerable/presumed stable (not vulnerable and evidence does not support change in abundance or range of the species). Vulnerability of eight species associated with streams that receive springflow from the Madison aquifer in the Black Hills was assessed. Of these, the American dipper ( Cinclus mexicanus ) and the lesser yellow lady’s slipper ( Cypripedium parviflorum ) were scored as moderately vulernable with high confidence. The dwarf scouringrush ( Equisetum scirpoides ) and autumn willow ( Salix serissima ) were also scored as moderately vulnerable with moderate to low confidence, respectively. Other species were assessed as not vulnerable/presumed stable or not vulnerable/increase likely (not vulnerable and evidence supporting an increase in abundance or range of the species). Lower vulnerability scores for the Black Hills species in comparison to the Balcones Escarpment species reflect lower endemicity, higher projected springflow than in the historical period, and high thermal tolerance of many of the species for the Black Hills. Importantly, climate change vulnerability scores differed substantially for Edwards aquifer species when RRAWFLOW model projections were included, resulting in increased vulnerability scores for 12 of the 16 species.

South Dakota, Texas↗