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USGS2004

Evaluation of strategies for balancing water use and streamflow reductions in the upper Charles River basin, eastern Massachusetts

The upper Charles River basin, located 30 miles southwest of Boston, Massachusetts, is experiencing water shortages during the summer. Towns in the basin have instituted water-conservation programs and water-use bans to reduce summertime water use. During July through October, streamflow in the Charles River and its tributaries regularly falls below 0.50 cubic foot per second per square mile, the minimum streamflow used by the U.S. Fish and Wildlife Service as its Aquatic Base Flow standard for maintaining healthy freshwater ecosystems. To examine how human water use could be changed to mitigate these water shortages, a numerical ground-water flow model was modified and used in conjunction with response coefficients and optimization techniques. Streamflows at 10 locations on the Charles River and its tributaries were determined under various water-use scenarios and climatic conditions. A variety of engineered solutions to the water shortages were examined for their ability to increase water supplies and summertime streamflows. Results indicate that although human water use contributes to the problem of low summertime streamflows, human water use is not the only, or even the primary, cause of low flows in the basin. The lowest summertime streamflows increase by 12 percent but remain below the Aquatic Base Flow standard when all public water-supply pumpage and wastewater flows in the basin are eliminated in a simulation under average climatic conditions. Under dry climatic conditions, the same measures increase the lowest average monthly streamflow by 95 percent but do not increase it above the Aquatic Base Flow standard. The most promising water-management strategies to increase streamflows and water supplies, based on the study results, include wastewater recharge to the aquifer, altered management of pumping well schedules, regional water-supply sharing, and water conservation. In a scenario that simulated towns sharing water supplies, streamflow in the Charles River as it exits the basin increased by 18 percent during July through September and an excess water-supply capacity of 13.4 cubic feet per second, above and beyond average use, would be available to all towns in the basin. These study results could help water suppliers and regulators evaluate strategies for balancing ground-water development and streamflow reductions in the basin.

Massachusetts↗
USGS2004

Biological assessment of streams in the Indianapolis Metropolitan Area, Indiana, 1999-2001

During 1999?2001, benthic invertebrates and fish were sampled to describe biological communities in the White River and selected tributaries in the Indianapolis Metropolitan Area in Indiana. Twelve sites (six on the White River and six on tributaries) were sampled biannually for benthic invertebrates and annually for fish. The information complements water-chemistry data collected by the Indianapolis Department of Public Works in the study area. Evaluation of the habitat for sites in the study area was done, using a Qualitative Habitat Evaluation Index (QHEI) developed by the Ohio Environmental Protection Agency. The QHEI scores basin and habitat characteristics for each site, with a maximum possible score of 100. Higher scores indicate better habitat conditions for biotic communities. The QHEI scores for sites on the White River ranged from 55 at the Harding site to 71 at the Waverly site; scores on the tributaries ranged from 45 on Pogues Run to 82 on Williams Creek. A total of 151 taxa were identified from the benthic-invertebrate samples. The Ephemeroptera, Plecoptera, and Trichoptera (EPT) Index scores for sites on the White River ranged from 0 at the Harding site to 15 at the Nora site. The Nora site, which is upstream from Indianapolis, generally scored the highest of all White River sites. Sites in the immediate vicinity of Indianapolis scored the lowest and indicate a negative effect on benthic-invertebrate communities in that reach. EPT Index scores increased in the farthest downstream reaches, which indicate that water-quality conditions had improved in comparison to sites in Indianapolis. For the tributary sites, EPT Index values ranged from 0 at Pogues Run to 16 at Buck Creek. Tributary sites on Fall Creek, Pleasant Run, and Pogues Run consistently scored 7 or lower; sites on Buck Creek, Eagle Creek, and Williams Creek scored 7 or higher. Hilsenhoff Biotic Index (HBI) scores ranged from 4.9 (good) to 9.6 (very poor) for the White River sites and from 5.2 (good) to 8.0 (poor) for the tributary sites. The lowest scores among the White River sites were at the Nora site, indicating the best water-quality conditions were where the White River enters Marion County. The highest HBI scores were at the Morris and Harding sites, indicating the least-favorable water-quality conditions of all the White River sites. Of the tributary sites, HBI scores for Buck, Eagle, and Williams Creeks indicate fair water-quality conditions; HBI scores for Pleasant Run and Pogues Run were the highest, indicating relatively poor water-quality conditions. On the White River, the highest Invertebrate Community Index (ICI) scores, which indicate the best benthic-invertebrate conditions, were at the Nora site. Conditions were fair to poor in the downtown Indianapolis area; ICI scores indicate slight improvement in the downstream reaches of the study area. Of the tributary sites, Buck Creek was the only site with ICI scores indicating exceptional water quality. Williams Creek ICI scores indicate good water quality; the remaining tributary-site scores reflect fair conditions. A total of 74 species and 3 hybrids of fish were identified during the study period. The Cyprinidae (carps and minnows) was the largest group of fish identified and consisted of more than half of all fish collected. The most numerous species was the central stoneroller (Campostoma anomalum), which accounted for almost 25 percent of the fish identified. Two nonnative species, the koi carp (Cyprinus carpio) and the western mosquitofish (Gambusia affinis), and one species classified as an Indiana species of special concern, the northern studfish (Fundulus catenatus), also were collected during the study. Indiana Index of Biotic Integrity (IBI) and Ohio Index of Biotic Integrity scores were calculated to show the condition of the fish communities at each site. Results of the Indiana IBI calculations showed no apparent differences in scores among the Wh

Water-Resources Investigations Report↗
USGS2003

Evaluation of Streamflow Requirements for Habitat Protection by Comparison to Streamflow Characteristics at Index Streamflow-Gaging Stations in Southern New England

Streamflow characteristics and methods for determining streamflow requirements for habitat protection were investigated at 23 active index streamflow-gaging stations in southern New England. Fish communities sampled near index streamflow-gaging stations in Massachusetts have a high percentage of fish that require flowing-water habitats for some or all of their life cycle. The relatively unaltered flow condition at these sites was assumed to be one factor that has contributed to this condition. Monthly flow durations and low flow statistics were determined for the index streamflow-gaging stations for a 25- year period from 1976 to 2000. Annual hydrographs were prepared for each index station from median streamflows at the 50-percent monthly flow duration, normalized by drainage area. A median monthly flow of 1 ft 3 /s/mi 2 was used to split hydrographs into a high-flow period (November–May), and a low-flow period (June–October). The hydrographs were used to classify index stations into groups with similar median monthly flow durations. Index stations were divided into four regional groups, roughly paralleling the coast, to characterize streamflows for November to May; and into two groups, on the basis of base-flow index and percentage of sand and gravel in the contributing area, for June to October. For the June to October period, for index stations with a high base-flow index and contributing areas greater than 20 percent sand and gravel, median streamflows at the 50-percent monthly flow duration, normalized by drainage area, were 0.57, 0.49, and 0.46 ft 3 /s/mi 2 for July, August, and September, respectively. For index stations with a low base-flow index and contributing areas less than 20 percent sand and gravel, median streamflows at the 50-percent monthly flow duration, normalized by drainage area, were 0.34, 0.28, and 0.27 ft 3 /s/mi 2 for July, August, and September, respectively. Streamflow variability between wet and dry years can be characterized by use of the interquartile range of median streamflows at selected monthly flow durations. For example, the median Q50 discharge for August had an interquartile range of 0.30 to 0.87 ft 3 /s/mi 2 for the high-flow group and 0.16 to 0.47 ft 3 /s/mi 2 for the low-flow group. Streamflow requirements for habitat protection were determined for 23 index stations by use of three methods based on hydrologic records, the Range of Variability Approach, the Tennant method, and the New England Aquatic-Base-Flow method. Normalized flow management targets determined by the Range of Variability Approach for July, August, and September ranged between 0.21 and 0.84 ft 3 /s/mi 2 for the low monthly flow duration group, and 0.37 and 1.27 ft 3 /s/mi 2 for the high monthly flow duration group. Median streamflow requirements for habitat protection during summer for the 23 index streamflow-gaging stations determined by the Tennant method, normalized by drainage area, were 0.81, 0.61, and 0.21 ft 3 /s/mi 2 for the Tennant 40-, 30-, and 10-percent of the mean annual flow methods, representing good, fair, and poor stream habitat conditions in summer, according to Tennant. New England Aquatic-Base-Flow streamflow requirements for habitat protection during summer were determined from median of monthly mean flows for August for index streamflow-gaging stations having drainage areas greater than 50 mi 2 . For five index streamflow-gaging stations in the low median monthly flow group, the average median monthly mean streamflow for August, normalized by drainage area, was 0.48 ft 3 /s/mi 2 . Streamflow requirements for habitat protection were determined for riffle habitats near 10 index stations by use of two methods based on hydraulic ratings, the Wetted-Perimeter and R2Cross methods. Hydraulic parameters required by these methods were simulated by calibrated HEC-RAS models. Wetted-Perimeter streamflow requirements for habitat protection, normalized by drainage area, ranged between 0.13 and 0.58 ft 3 /s/mi 2 , and had a median value of 0.37 ft 3 /s/mi 2 . Streamflow requirements determined by the R2Cross 3-of-3 criteria method ranged between 0.39 and 2.1 ft 3 /s/mi 2 , and had a median of 0.84 ft 3 /s/mi 2 . Streamflow requirements determined by the R2Cross 2-of-3 criteria method, normalized by drainage area, ranged between 0.16 and 0.85 ft 3 /s/mi 2 and had a median of 0.36 ft 3 /s/mi 2 , respectively. Streamflow requirements determined by the different methods were evaluated by comparison to streamflow statistics from the index streamflow-gaging stations.

Water-Resources Investigations Report↗
USGS2004

Microbiological Water Quality in Relation to Water-Contact Recreation, Cuyahoga River, Cuyahoga Valley National Park, Ohio, 2000 and 2002

The microbiological water quality of a 23-mile segment of the Cuyahoga River within the Cuyahoga Valley National Park was examined in this study. This segment of the river receives discharges of contaminated water from stormwater, combined-sewer overflows, and incompletely disinfected wastewater. Frequent exceedances of Ohio microbiological water-quality standards result in a health risk to the public who use the river for water-contact recreation. Water samples were collected during the recreational season of May through October at four sites on the Cuyahoga River in 2000, at three sites on the river in 2002, and from the effluent of the Akron Water Pollution Control Station (WPCS) both years. The samples were collected over a similar range in streamflow in 2000 and 2002. Samples were analyzed for physical and chemical constituents, as well as the following microbiological indicators and pathogenic organisms: Escherichia coli (E. coli), Salmonella, F-specific and somatic coliphage, enterovirus, infectious enterovirus, hepatitis A virus, Clostridium perfringens (C. perfringens), Cryptosporidium, and Giardia. The relations of the microorganisms to each other and to selected water-quality measures were examined. All microorganisms analyzed for, except Cryptosporidium, were detected at least once at each sampling site. Concentrations of E. coli exceeded the Ohio primary-contact recreational standard (298 colonies per 100 milliliters) in approximately 87 percent of the river samples and generally were higher in the river samples than in the effluent samples. C. perfringens concentrations were positively and significantly correlated with E. coli concentrations in the river samples and generally were higher in the effluent samples than in the river samples. Several of the river samples that met the Ohio E. coli secondary-contact recreational standard (576 colonies per 100 milliliters) had detections of enterovirus, infectious enterovirus, hepatitis A virus, and Salmonella, indicating that there are still risks even when the E. coli standard is not exceeded. River samples in which the secondary-contact recreational standard for E. coli was exceeded showed a higher percentage of the co-occurrence of pathogenic organisms than samples that met the standard. This indicates that in this study area, E. coli is a useful indicator of human health risk. Detections of hepatitis A virus tended to be associated with higher median concentrations of somatic coliphage, F-specific coliphage, and infectious enterovirus. In addition, geometric mean C. perfringens concentrations tended to be higher in samples where hepatitis A virus was present than in samples where hepatitis A virus was absent. Hepatitis A virus was not detected in samples collected upstream from the Akron WPCS; all downstream detections had coincident detections in the Akron WPCS effluent, suggesting that Akron WPCS was a principal source of hepatitis A virus at the downstream sites. Geometric mean concentrations of E. coli were calculated on the basis of analytical results from at least five samples collected at each river site during May, July, and September of 2000. In each case, the Ohio geometric-mean primary-contact recreational standard of 126 col/100 mL was exceeded. E. coli concentrations were significantly correlated with streamflow and increased with streamflow at sites upstream and downstream from the Akron WPCS. This indicates that E. coli loads from sources upstream from the Akron WPCS have the potential to appreciably influence the frequency of attainment of recreational water-quality standards at downstream locations.

Water-Resources Investigations Report↗
USGS2004

Analysis of streamflow and water-quality data at two long-term monitoring sites on the St. Croix River, Wisconsin and Minnesota

Streamflow of the St. Croix River has been monitored on a long-term basis by the U.S. Geological Survey (USGS) at streamflow-gaging stations on the St. Croix River at Wisconsin State Highway 35 near Danbury, Wisconsin and below the dam at St. Croix Falls, Wisconsin. Trend analysis indicates that annual streamflow peaks, annual mean flows, and annual 7-day low flows have remained relatively stable at the Danbury (upstream) station from 1914 to 2001 but have increased by 0.45 to 0.55 percent per year at the St. Croix Falls (downstream) station from 1902 to 2001. Water-quality sampling conducted by the USGS at two associated water-quality monitoring sites from 1964 to 2001 have included analysis for nutrients, suspended sediments, metals, bacteria, and pesticides. The water-quality data at the two sites had considerable temporal variation and was often limited in extent by the data-collection needs of previous projects. The absence of consistent long-term water-quality data made detection of statistically significant trends in the water-quality data difficult. Nutrient, suspended-sediment, and major ion concentrations and field parameters were generally higher and more variable at the St. Croix Falls site than at the Danbury site. However, disparate sampling periods and strategies could cause possible biases in the comparison of water quality between sites. Access data at http://wi.waterdata.usgs.gov/nwis

Minnesota, Wisconsin↗
USGS2004

Results of a Two-Dimensional Hydrodynamic and Sediment-Transport Model to Predict the Effects of the Phased Construction and Operation of the Olmsted Locks and Dam on the Ohio River near Olmsted, Illinois

The Olmsted two-dimensional hydrodynamic and sediment-transport model was developed in cooperation with the U.S. Army Corps of Engineers, Louisville District. The model was used to estimate the effects that the phased-construction sequence and operation of the Olmsted Locks and Dam had on sediment-transport patterns in the 11.9-mile study reach (Ohio River miles 962.6 to 974.5), particularly over an area of endangered orange-footed pearly mussel (Plethobasus cooperianus) beds beginning approximately 2 miles downstream of the dam construction. A Resource Management Associates?2 (RMA-2) two-dimensional hydrodynamic model for the reach was calibrated to a middle-flow hydraulic survey (350,000 cubic feet per second) and verified with data collected during low- and high-flow hydraulic surveys (72,500 and 770,000 cubic feet per second, respectively). The calibration and validation process included matching water-surface elevations at the construction site and velocity profiles at 15 cross sections throughout the study reach. The sediment-transport aspect of the project was simulated with the Waterways Experiment Station's Sed2D model for a 6-year planned-construction period (construction-phase modeling) and a subsequent 3-year operational period (operational-phase modeling). The sediment-transport results from the construction and operational models both were compared to results of concurrent baseline simulations to determine the changes in erosional and depositional patterns induced by the dam construction and operation throughout the study reach and more importantly over the area of the endangered mussel beds. Simulation of the phased-in-the-wet Olmsted Locks and Dam construction and subsequent operation period resulted in a maximum additional deposition of approximately 2 feet over a localized region of the mussel beds when compared to the bed change simulated with baseline conditions (river conditions that included only the completed locks section). Most areas on the mussel beds experienced less than 0.5 feet of cumulative bed change between the baseline and construction phases during the nine annual hydrographs. The bed change over the 9 year Olmsted Locks and Dam simulation reveals a continuous downstream progression and deepening of the main channel and deposition along the right bank with limited lateral migration toward the more densely populated mussel-bed areas. The sensitivity of the mussels to sediment deposition is difficult to quantify; therefore, the effect of simulated deposition on the welfare of the mussels is uncertain. The model also will provide the U.S. Army Corps of Engineers a tool to predict the locations of high deposition in navigable sections, which can save engineers time and resources when monitoring the need for dredging operations.

Water-Resources Investigations Report↗
USGS2005

Use of discrete-zone monitoring systems for hydraulic characterization of a fractured-rock aquifer at the University of Connecticut Landfill, Storrs, Connecticut, 1999 to 2002

The U.S. Geological Survey, in cooperation with the University of Connecticut, used a suite of hydraulic methods to characterize the hydrogeology of a fractured-rock aquifer near the former landfill and chemical-waste disposal pits at the University of Connecticut, Storrs, Connecticut. Multiple methods were used to determine head, driving potential, and transmissivity, including manual open-hole water-level and discretezone water-level measurements from 11 boreholes; continuous discrete-zone water-level measurements from 6 of the boreholes; estimated head and transmissivity for 11 boreholes using heat-pulse flowmeter profiles and pumping records; and differential head testing using a straddle-packer apparatus from 4 boreholes. These data were analyzed to identify and characterize relations between long-term water-level patterns and precipitation, topographic setting, contaminant distribution at the site, and a conceptual ground-water flow model. Data collected using the heat-pulse flowmeter, the straddle-packer apparatus, and discrete-zone monitoring (DZM) systems helped to establish, refine, and verify a conceptual model of ground-water flow in the study area. Monitoring of DZM systems installed in 11 boreholes provided a method for longterm monitoring of hydraulic head and water quality of the aquifer at fracture zones of different depths. These data were used to help define the conceptual site model for ground-water flow and to determine and explain the distribution of contamination. Hydrographs constructed for discretely isolated zones in the boreholes showed the magnitude of seasonal changes of water levels and driving potential in response to precipitation and drought. Heads in discrete zones and in different boreholes varied both in magnitude of response and in timing of response to precipitation. Water levels in open boreholes and in DZM systems showed a semi-diurnal pattern that coincides with gravimetric tidal plots generated for this area. No fluctuations that might indicate pumping were identified in the continuous water-level records. Lack of hydraulic response between boreholes during cross-hole testing in the area of the former chemical-waste disposal pits indicates poor hydraulic connection between the boreholes that were tested. In general, data indicated the presence of downward driving potentials in the recharge areas and in the area of the ground-water divide, and upward driving potentials in discharge areas north and south of the landfill. The results of this study illustrate the importance of discrete-zone isolation and monitoring in fractured-rock aquifers to prevent cross contamination while permitting head measurements and water-quality sampling that can be used to identify and characterize contamination or pathways for contaminant migration in a fractured-rock aquifer. Without DZM systems installed in the boreholes, only open-hole heads can be measured. The open-hole heads may be misleading when determining potential flow directions at contamination sites, because they are a composite of the heads associated with each of the fractures intersecting the borehole. The flowmeter tool and straddle-packer apparatus are effective screening tools for generating a snapshot of the hydraulic conditions, including vertical flow, transmissivity, and heads; however, they cannot prevent flow and potential cross-contamination and cannot easily be used to monitor long-term conditions. This work was conducted as part of a larger multidisciplinary investigation to characterize the nature and extent of contamination in the soil, surface water, and ground water in the overburden and fractured bedrock in the area of the landfill and former chemical-waste disposal pits near the University of Connecticut. The methods and hydraulic data presented in this report were used along with surface- and borehole-geophysical data and geochemical data to understand and characterize the ground-water flow in overburden and fractured bedrock; to assess possible chemical migration; to develop a site conceptual ground-water flow model; and to assess remediation alternatives.

Connecticut↗
USGS2001

Effects of Pumping on Ground-Water Flow Near Water-Supply Wells in the Lower Potomac-Raritan-Magothy Aquifer, Pennsauken Township, Camden County, New Jersey

Since the 1970's, hexavalent chromium has been detected in concentrations as great as 1.0 milligram per liter in wells at the Puchack well field operated by the Camden City Department of Utilities, Water Division (Water Department), forcing the Water Department to progressively remove five of its six wells from service between 1975 and 1988. The wells in the Puchack well field range in depth from 140 to 220 feet and are screened in the Lower Potomac-Raritan-Magothy aquifer. The Water Department has continued to pump Puchack Well 1 to maintain a hydraulic gradient toward the well field in an attempt to limit contaminant migration. In late 1997, concerns about treating the water withdrawn from Puchack Well 1 led water managers to consider temporarily discontinuing the pumping. In the spring of 1998, the U.S. Geological Survey (USGS), in cooperation with the New Jersey Department of Environmental Protection, began a preliminary assessment of the potential effects of temporarily removing Puchack Well 1 from service. Water levels in the Lower Potomac-Raritan-Magothy aquifer were measured during both pumping and nonpumping conditions to determine the direction and velocity of ground-water flow and the results were compared. Data collected in late March and early April 1998 indicate the presence of a ground-water divide between the Puchack well field and the Morris and Delair well fields when Puchack Well 1 was being pumped. A similar divide also was present when the well was not being pumped. The position and persistence of this divide limits the probability that contaminants in the vicinity of the Puchack well field will reach the Delair and Morris well fields during either pumping condition. Another divide southeast of Puchack Well 1 while the well was being pumped was no longer evident when the pumping was stopped and water levels had recovered. Under non-pumping conditions, ground water between Puchack Well 1 and this divide could begin to migrate toward other large pumping centers to the southeast. The average linear ground-water velocity along an arbitrarily selected southeast-trending flow path was estimated to be from 221 to 332 feet per year. This estimate indicates that any contaminated ground water that may be present within the area influenced by pumping at Puchack Well 1 may begin to move toward the pumping centers less than 2 miles to the southeast if Puchack Well 1 is either temporarily or permanently removed from service.

Water-Resources Investigations Report↗
USGS2000

Aquifer-system compaction and land subsidence: Measurements, analyses, and simulations – The Holly Site, Edwards Air Force Base, Antelope Valley, California

Land subsidence resulting from ground-water-level declines has long been recognized as a problem in Antelope Valley, California. At Edwards Air Force Base (EAFB), ground-water extractions have caused more than 150 feet of water-level decline, resulting in nearly 4 feet of subsidence. Differential land subsidence has caused sinklike depressions and earth fissures and has accelerated erosion of the playa lakebed surface of Rogers Lake at EAFB, adversely affecting the runways on the lakebed which are used for landing aircraft such as the space shuttles. Since 1990, about 0.4 foot of aquifer-system compaction has been measured at a deep (840 feet) borehole extensometer (Holly site) at EAFB. More than 7 years of paired ground-water-level and aquifer-system compaction measurements made at the Holly site were analyzed for this study. Annually, seasonal water-level fluctuations correspond to steplike variations in aquifer-system compaction; summer water-level drawdowns are associated with larger rates of compaction, and winter water-level recoveries are associated with smaller rates of compaction. The absence of aquifer-system expansion during recovery is consistent with the delayed drainage and resultant delayed, or residual, compaction of thick aquitards. A numerical one-dimensional MODFLOW model of aquitard drainage was used to refine estimates of aquifer-system hydraulic parameters that control compaction and to predict potential future compaction at the Holly site. The analyses and simulations of aquifer-system compaction are based on established theories of aquitard drainage. Historical ground-water-level and land-subsidence data collected near the Holly site were used to constrain simulations of aquifer-system compaction and land subsidence at the site for the period 1908-90, and ground-water-level and aquifer- system compaction measurements collected at the Holly site were used to constrain the model for the period 1990-97. Model results indicate that two thick aquitards, which total 129 feet or about half the aggregate thickness of all the aquitards penetrated by the Holly boreholes, account for most (greater than 99 percent) of the compaction measured at the Holly site during the period 1990-97. The results of three scenarios of future water-level changes indicate that these two thick aquitards account for most of the future compaction. The results also indicate that if water levels decline to about 30 feet below the 1997 water levels an additional 1.7 feet of compaction may occur during the next 30 years. If water levels remain at 1997 levels, the model predicts that only 0.8 foot of compaction may occur during the same period, and even if water levels recover to about 30 feet above 1997 water levels, another 0.5 foot of compaction may occur in the next 30 years. In addition, only a portion of the compaction that ultimately will occur likely will occur within the next 30 years; therefore, the residual compaction and associated land subsidence attributed to slowly equilibrating aquitards is important to consider in the long-term management of land and water resources at EAFB.

California↗
USGS2000

Storage capacity and sedimentation of Loch Lomond Reservoir, Santa Cruz County, California, 1998

In 1998, a bathymetric survey was done to determine the storage capacity and the loss of capacity owing to sedimentation of Loch Lomond Reservoir in Santa Cruz County, California. Results of the survey indicate that the maximum capacity of the reservoir is 8,991 acre-feet in November 1998. The results of previous investigations indicate that storage capacity of the reservoir is less than 8,991 acre-feet. The storage capacity determined from those investigations probably were underestimated because of limitations of the methods and the equipment used. The volume of sedimentation in a reservoir is considered equal to the decrease in storage capacity. To determine sedimentation in Loch Lomond Reservoir, change in storage capacity was estimated for an upstream reach of the reservoir. The change in storage capacity was determined by comparing a 1998 thalweg profile (valley floor) of the reservoir with thalweg profiles from previous investigations; results of the comparison indicate that sedimentation is occurring in the upstream reach. Cross sections for 1998 and 1982 were compared to determine the magnitude of sedimentation in the upstream reach of the reservoir. Results of the comparison, which were determined from changes in the cross-sectional areas, indicate that the capacity of the reservoir decreased by 55 acre-feet.

California↗
USGS2000

Concentrations of Escherichia Coli in Streams in the Upper Wabash River Watershed in Indiana, June-September 1998

Water samples collected from 46 stream sites in the Upper Wabash River Watershed from June through September 1998 were analyzed for concentrations of the bacteria Escherichia coli (E. coli). Each site was sampled five times in a 30-day period. Twenty-one sites were sampled during June and July, and 25 sites were sampled during August and September. The concentration of E. coli in 145 of the 230 samples collected exceeded the Indiana standard of 235 colonies per 100 milliliters for a single sample for waters used for recreation. A five-sample geometric mean also was computed for each site. Concentrations in samples from 43 of the 46 sites exceeded the Indiana bacteriological quality standard of 125 colonies per 100 milliliters for a five-sample geometric mean for waters used for recreation. Discharge during sample collection generally was greater than the long-term median daily mean discharge. To determine if the greater discharge affected the concentrations of E. coli, additional samples were collected at two sites. Statistically significant positive correlations between concentrations of E. coli and discharge were determined for these sites, indicating increased concentrations with greater discharge.

Water-Resources Investigations Report↗
USGS2000

Water-quantity and water-quality aspects of a 500-year flood - Nishnabotna River, southwest Iowa, June 1998

Flooding that occurred in southwest Iowa during June 15–17, 1998, was the worst flood ever recorded on the Nishnabotna River, exceeding the theoretical 500-year flood calculated from peak-flow records (1922 to present). This flood was a direct consequence of severe thunderstorm activity that caused more than 4 inches of rain to fall over a large part of the Nishnabotna River Basin. In fact, a new official State record for 24-hour total rainfall (13.18 inches) was set by this storm. The peak streamflow of the Nishnabotna River near Hamburg, Iowa, was 65,100 cubic feet per second, about 20 percent more than any previous recorded peak streamflow at this site. To determine the concentrations of selected contaminants that might be present in this record flooding, water-quality samples were collected within hours of the flood peak. The results from these samples documented the presence of numerous herbicide compounds (11 parent compounds and 12 herbicide degradates). The highest herbicide concentration was 5.06 micrograms per liter (µg/L) for atrazine, followed by metolachlor (1.16 µg/L), metolachlor ESA (1.04 µg/L), acetochlor OA (0.99 µg/L), and acetochlor ESA (0.95 µg/L). The total herbicide concentration (summation of the 23 herbicide compounds detected) was 15.6 µg/L. The timing of the severe thunderstorm activity and flooding, which occurred shortly after chemical application associated with planting of crops, was the principal reason for the large number and concentrations of herbicide compounds found in the flood water. At the time the water-quality samples were collected, the Nishnabotna River was transporting about 6,000 pounds of suspended sediment, 18 pounds of nitrogen, 3 pounds of phosphorus, and 0.02 pound of atrazine each second. These loads were about 10 to 150 times greater than those during a previous runoff event, and about 260 to 4,600 times greater than those during a previous base-flow condition. This sampling demonstrates the importance of collecting both water-quantity and water-quality data during flood events to estimate contaminant loads. Potential environmental effects of a flood can only be understood when both components are measured.

Iowa, Missouri↗
USGS2000

Measurement of stream discharge by wading

Most years the U.S. Geological Survey (USGS) makes over 50,000 stream discharge measurements. Over 75 percent of those measurements are made by wading streams and using the velocity-area method. This PowerPoint presentation describes how stream discharge should be measured when wading and using the velocity-area method. It is intended as a learning and reference tool for anyone responsible for making wading discharge measurements.

Water-Resources Investigations Report↗
USGS2000

Hydrologic treatments affect gaseous carbon loss From organic soils, Twitchell Island, California, October 1995–December 1997

Subsidence of organic soils in the Sacramento-San Joaquin Delta, California, has increased the potential for levee failure and flooding in the region. Because oxidation of the peat soils is a primary cause of subsidence, reversion of affected lands to wetlands has been proposed as a mitigation tool. To test this hypothesis, three 10 x 10 meter enclosures were built on Twitchell Island in the Delta and managed as different wetland habitats. Emissions of carbon dioxide and methane were measured in situ from October 1995 through December 1997, from the systems that developed under the different water-management treatments. Treatments included a seasonal control (SC) under current island management conditions; reverse flooding (RF), where the land is intentionally flooded from early dry season until midsummer; permanent shallow flooding (F); and a more deeply flooded, open-water (OW) treatment. Hydrologic treatments affected microbial processes, plant community and temperature dynamics which, in turn, affected carbon cycling. Water-management treatments with a period of flooding significantly decreased gaseous carbon emissions compared to the seasonal control. Permanent flooding treatments showed significantly higher methane fluxes than treatments with some period of aerobic conditions. Shallow flooding treatments created conditions that support cattail [Typha species (spp.)] marshes, while deep flooding precluded emergent vegetation. Carbon inputs to the permanent shallow flooding treatment tended to be greater than the measured losses. This suggests that permanent shallow flooding has the greatest potential for managing subsidence of these soils by generating organic substrate more rapidly than is lost through decomposition. Carbon input estimates of plant biomass compared to measurements of gaseous carbon losses indicate the potential for mitigation of subsidence through hydrologic management of the organic soils in the area.

California↗
USGS2000

Methyl tert-Butyl Ether (MTBE) in ground water, air, and precipitation at North Windham, Maine

Thirty-one monitoring wells in the Windham aquifer in North Windham, Maine, were sampled for methyl tert-butyl ether (MTBE) from July 1998 to May 1999. MTBE was detected in 35 percent of the wells sampled in the Windham aquifer. MTBE was detected in 64 percent of wells in the high-yielding part of the aquifer; these wells account for 82 percent of all wells with detectable MTBE. Land cover also was found to be associated with MTBE in the wells in the study area, with the urban and low-density residential areas having more MTBE than undeveloped areas. The median concentration in wells with detectable MTBE was 1.13 micrograms per liter. Air and precipitation samples were collected in North Windham along with ground-water samples. Air samples were collected every 10 days from December 1998 to July 1999 (20 samples). MTBE was present in all 20 air samples collected, at concentrations ranging from 0.03 ppbv (parts per billion by volume) to 1.0 ppbv. Before Maine opted out of the reformulated gasoline (RFG) program in the spring of 1999, median concentrations in air at the North Windham site were 0.25 ppbv. After Maine stopped using RFG, the median concentration in air dropped to 0.09 ppbv. No MTBE was detected in four samples of precipitation at North Windham. The lack of rainfall during the study period prevented the collection of an adequate number of samples, and technical difficulties negated the results of some of the analyses of the samples that were collected. Based on the equilibrium partitioning of MTBE from the air into rain, the hypothetical average concentration of MTBE in rainfall during months when recharge typically occurs (March-April and October-December) would be approximately 0.3 to 0.4 micrograms per liter during the time that RFG was being used in Maine. After the phaseout of RFG, the maximum average concentration of MTBE in rainfall during these months would be approximately 0.1 micrograms per liter. The distribution and concentrations of MTBE that were detected in ground water indicate that recharge from precipation containing MTBE is not a likely explanation for the occurrence of MTBE in the Windham aquifer.

Maine↗
USGS2000

Regional equations for estimating mean annual and mean seasonal runoff for natural basins in Texas, base period 1961-90

Regional equations were developed for estimating mean annual and mean seasonal runoff for natural basins in Texas. The equations, which are based on the statistical relation between streamflow and basin characteristics, use streamflow data and basin characteristics from U.S. Geological Survey streamflow-gaging stations within natural basins and with a least 8 years of data during 1961-90. The State was divided into 11 hydrologic regions on the basis of previous studies. The final equations for estimating mean annual and mean seasonal runoff were developed from 228 streamflow-gaging stations. Contributing drainage area and mean annual or mean seasonal precipitation were determined to be the most significant basin characteristics in each region.

Texas↗