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At least 595 records · Page 33Linked to original sources
USGS2005

Effects of land-use changes and stormflow-detention basins on flooding and nonpoint-source pollution, in Irondequoit Creek basin, Monroe and Ontario counties, New York--application of a precipitation-runoff model

Urbanization of the 150-square-mile Irondequoit Creek basin in Monroe and Ontario Counties, N.Y., continues to spread southward and eastward from the City of Rochester, on the shore of Lake Ontario. Conversion of forested land to other uses over the past 40 years has increased to the extent that more than 50 percent of the basin is now developed. This expansion has increased flooding and impaired stream-water quality in the northern (downstream) half of the basin. A precipitation-runoff model of the Irondequoit Creek basin was developed with the model code HSPF (Hydrological Simulation Program--FORTRAN) to simulate the effects of land-use changes and stormflow-detention basins on flooding and nonpoint-source pollution on the basin. Model performance was evaluated through a combination of graphical comparisons and statistical tests, and indicated 'very good' agreement (mean error less than 10 percent) between observed and simulated daily and monthly streamflows, between observed and simulated monthly water temperatures, and between observed total suspended solids loads and simulated sediment loads. Agreement between monthly observed and simulated nutrient loads was 'very good' (mean error less than 15 percent) or 'good' (mean error between 15 and 25 percent). Results of model simulations indicated that peak flows and loads of sediment and total phosphorus would increase in a rural subbasin, where 10 percent of the basin was converted from forest and grassland to pervious and impervious developed areas. Subsequent simulation of a stormflow-detention basin at the mouth of this subbasin indicated that peak flows and constituent loads would decrease below those that were generated by the land-use-change scenario, and, in some cases, below those that were simulated by the original land-use scenario. Other results from model simulations of peak flows over a 30-year period (1970-2000), with and without simulation of 50-percent flow reductions at one existing and nine hypothetical stormflow-detention basins, indicated that stormflow-detention basins would likely decrease peak flows 14 to 17 percent on Allen Creek and 17 to 18 percent on Irondequoit Creek at Blossom Road. The model is intended as a management tool that water-resource managers can use to guide decisions regarding future development in the basin. The model and associated files are designed to permit (1) creation of scenarios that represent planned or hypothetical development in the basin, and (2) assessment of the flooding and chemical loads that are likely to result. Instream stormflow-detention basins can be simulated in separate scenarios to assess their effect on flooding and chemical loads. This report (1) provides examples of how the model can be applied to address these issues, (2) discusses the model revisions required to simulate land-use changes and detention basins, and (3) describes the analytical steps necessary to evaluate the model results.

Scientific Investigations Report↗
USGS2016

Effects of water-supply reservoirs on streamflow in Massachusetts

State and local water-resource managers need modeling tools to help them manage and protect water-supply resources for both human consumption and ecological needs. The U.S. Geological Survey, in cooperation with the Massachusetts Department of Environmental Protection, has developed a decision-support tool to estimate the effects of reservoirs on natural streamflow. The Massachusetts Reservoir Simulation Tool is a model that simulates the daily water balance of a reservoir. The reservoir simulation tool provides estimates of daily outflows from reservoirs and compares the frequency, duration, and magnitude of the volume of outflows from reservoirs with estimates of the unaltered streamflow that would occur if no dam were present. This tool will help environmental managers understand the complex interactions and tradeoffs between water withdrawals, reservoir operational practices, and reservoir outflows needed for aquatic habitats. A sensitivity analysis of the daily water balance equation was performed to identify physical and operational features of reservoirs that could have the greatest effect on reservoir outflows. For the purpose of this report, uncontrolled releases of water (spills or spillage) over the reservoir spillway were considered to be a proxy for reservoir outflows directly below the dam. The ratio of average withdrawals to the average inflows had the largest effect on spillage patterns, with the highest withdrawals leading to the lowest spillage. The size of the surface area relative to the drainage area of the reservoir also had an effect on spillage; reservoirs with large surface areas have high evaporation rates during the summer, which can contribute to frequent and long periods without spillage, even in the absence of water withdrawals. Other reservoir characteristics, such as variability of inflows, groundwater interactions, and seasonal demand patterns, had low to moderate effects on the frequency, duration, and magnitude of spillage. The reservoir simulation tool was used to simulate 35 single- and multiple-reservoir systems in Massachusetts over a 44-year period (water years 1961 to 2004) under two water-use scenarios. The no-pumping scenario assumes no water withdrawal pumping, and the pumping scenario incorporates average annual pumping rates from 2000 to 2004. By comparing the results of the two scenarios, the total streamflow alteration can be parsed into the portion of streamflow alteration caused by the presence of a reservoir and the additional streamflow alteration caused by the level of water use of the system. For each reservoir system, the following metrics were computed to characterize the frequency, duration, and magnitude of reservoir outflow volumes compared with unaltered streamflow conditions: (1) the median number of days per year in which the reservoir did not spill, (2) the median duration of the longest consecutive period of no-spill days per year, and (3) the lowest annual flow duration exceedance probability at which the outflows are significantly different from estimated unaltered streamflow at the 95-percent confidence level. Most reservoirs in the study do not spill during the summer months even under no-pumping conditions. The median number of days during which there was no spillage was less than 365 for all reservoirs in the study, indicating that, even under reported pumping conditions, the reservoirs refill to full volume and spill at least once during nondrought years, typically in the spring. Thirteen multiple-reservoir systems consisting of two or three hydrologically connected reservoirs were included in the study. Because operating rules used to manage multiple-reservoir systems are not available, these systems were simulated under two pumping scenarios, one in which water transfers between reservoirs are minimal and one in which reservoirs continually transferred water to intermediate or terminal reservoirs. These two scenarios provided upper and lower estimates of spillage under average pumping conditions from 2000 to 2004. For sites with insufficient data to simulate daily water balances, a proxy method to estimate the three spillage metrics was developed. A series of 4,000 Monte Carlo simulations of the reservoir water balance were run. In each simulation, streamflow, physical reservoir characteristics, and daily climate inputs were randomly varied. Tobit regression equations that quantify the relation between streamflow alteration and physical and operational characteristics of reservoirs were developed from the results of the Monte Carlo simulations and can be used to estimate each of the three spillage metrics using only the withdrawal ratio and the ratio of the surface area to the drainage area, which are available statewide for all reservoirs. A graphical user-interface for the Massachusetts Reservoir Simulation Tool was developed in a Microsoft Access environment. The simulation tool contains information for 70 reservoirs in Massachusetts and allows for simulation of additional scenarios than the ones considered in this report, including controlled releases, dam seepage and leakage, demand management plans, and alternative water withdrawal and transfer rules.

Massachusetts↗
USGS2020

Numerical simulation of groundwater availability in central Moloka‘i, Hawai‘i

Since the 1990s, increased chloride concentrations of water pumped from wells (much of which is used for drinking water) and the effects of withdrawals on groundwater-dependent ecosystems have led to concerns over groundwater availability on the island of Molokaʻi, Hawaiʻi. An improved understanding of the hydrologic effects of proposed groundwater withdrawals is needed to ensure effective management of the groundwater resources of Molokaʻi, plan for possible growth, and accommodate cultural, social, and economic concerns. To address the information needs of managers and community stakeholders on Molokaʻi, the U.S. Geological Survey developed a numerical groundwater model capable of simulating salinity change and reduction in groundwater discharge in coastal areas of central and southern Molokaʻi. Estimates of groundwater recharge needed as input to the numerical groundwater model were made using a daily water budget for each decade during 1940−2012 (the period 2000−12 spanned 13 years) and the most current available data, including the distributions of monthly rainfall and potential evapotranspiration. Total island recharge during the decadal periods ranged from a low of about 189 Mgal/d during the 1970s to a high of 278 Mgal/d during the 1960s. These recharge estimates were used to develop an island-wide numerical groundwater model with simplifying assumptions (sharp interface between freshwater and saltwater; two-dimensional flow). The island-wide model provided estimates of groundwater inflows to the main area of interest simulated with a three-dimensional numerical groundwater model. Simulated withdrawal scenarios were selected in consultation with water managers and stakeholders and consisted of: (1) a baseline scenario using average recharge (1978−2007 rainfall and 2010 land cover) and average 2016−17 withdrawals; (2) a scenario using average recharge and withdrawals from existing wells at pending (as of January 2019) water-use permit rates; (3) six scenarios using average recharge and selected withdrawals from existing and proposed wells; and (4) a scenario using reduced recharge and selected withdrawals from existing and proposed wells. Results of the simulated withdrawal scenarios indicate that wells may be capable of producing groundwater with chloride concentrations below 250 mg/L at withdrawal rates exceeding average 2016−17 rates. However, the quality of water withdrawn from production wells is dependent on the rate and distribution of the withdrawals. For all nonbaseline scenarios, simulated groundwater discharge to the nearshore environment is reduced relative to the baseline scenario. Areas of discharge reduction may correspond to areas used for cultural or subsistence purposes. The three-dimensional numerical groundwater model developed for this study utilizes the latest available hydrologic and geologic information and is a useful tool for understanding the hydrologic effects of additional groundwater withdrawals in central Molokaʻi. The model has several limitations, including its nonuniqueness and inability to account for local-scale heterogeneities.

Hawaii↗
USGS2011

Hypolimnetic dissolved-oxygen dynamics within selected White River reservoirs, northern Arkansas-southern Missouri, 1974-2008

Dissolved oxygen is a critical constituent in reservoirs and lakes because it is essential for metabolism by all aerobic aquatic organisms. In general, hypolimnetic temperature and dissolved-oxygen concentrations vary from summer to summer in reservoirs, more so than in natural lakes, largely in response to the magnitude of flow into and release out of the water body. Because eutrophication is often defined as the acceleration of biological productivity resulting from increased nutrient and organic loading, hypolimnetic oxygen consumption rates or deficits often provide a useful tool in analyzing temporal changes in water quality. This report updates a previous report that evaluated hypolimnetic dissolved-oxygen dynamics for a 21-year record (1974-94) in Beaver, Table Rock, Bull Shoals, and Norfork Lakes, as well as analyzed the record for Greers Ferry Lake. Beginning in 1974, vertical profiles of temperature and dissolved-oxygen concentrations generally were collected monthly from March through December at sites near the dam of each reservoir. The rate of change in the amount of dissolved oxygen present below a given depth at the beginning and end of the thermal stratification period is referred to as the areal hypolimnetic oxygen deficit. Areal hypolimnetic oxygen deficit was normalized for each reservoir based on seasonal flushing rate between April 15 and October 31 to adjust for wet year and dry year variability. Annual cycles in thermal stratification within Beaver, Table Rock, Bull Shoals, Norfork, and Greers Ferry Lakes exhibited typical monomictic (one extended turnover period per year) characteristics. Flow dynamics drive reservoir processes and need to be considered when analyzing areal hypolimnetic oxygen deficit rates. A nonparametric, locally weighted scatter plot smooth line describes the relation between areal hypolimnetic oxygen deficit and seasonal flushing rates, without assuming linearity or normality of the residuals. The results in this report are consistent with earlier findings that oxygen deficit rates and flushing-rate adjusted areal hypolimnetic oxygen deficit in Beaver and Table Rock Lakes were decreasing between 1974 and 1994. The additional data (1995-2008) demonstrate that the decline in flushing-rate adjusted areal hypolimnetic oxygen deficit in Beaver Lake has continued, whereas that in Table Rock Lake has flattened out in recent years. The additional data demonstrate the flushing-rate adjusted areal hypolimnetic oxygen deficit in Bull Shoals and Norfork Lakes have declined since 1995 (improved water quality), which was not indicated in earlier studies, while Greers Ferry Lake showed little net change over the period of record. Given the amount of data (35 years) for these reservoirs, developing an equation or model to predict areal hypolimnetic oxygen deficit and, therefore, areal hypolimnetic oxygen content, on any given day during future stratification seasons may be useful for reservoir managers.

Missouri;Arkansas↗
USGS2021

Assessment of groundwater trends near Crex Meadows, Wisconsin

Crex Meadows Wildlife Area (Crex) is a 30,000-acre property in Burnett County, Wisconsin. Crex is managed by the Wisconsin Department of Natural Resources (WDNR) with the goal of providing public recreation opportunities while also protecting the quality of native ecological communities and species on the property. The WDNR’s management strategy includes controlling water levels at flowages in Crex using a system of dikes, water control structures, ditches, and a diversion pump. For the past several decades there has been concern among nearby landowners that the water manage-ment strategy at Crex may be contributing to groundwater flooding in adjacent, privately held properties. This issue has been particularly contentious during periods when regional groundwater elevations are already high. This study was conducted in response to those concerns. For the study, a network of 12 monitoring wells was installed in and to the west of Crex. Groundwater elevations were recorded in the wells before, during, and after water-level changes in the western Crex flowages to assess if groundwater elevations to the west of Crex are detectably affected by the flowage water levels. This study successfully collected groundwater elevations in 11 study wells during a 3-month period in 2019 when water elevations in the Dike 6 flowage and Erickson flowage were lowered and then raised. The data logger at a 12th location failed and no data were recorded. The groundwater elevation trends in these study wells were compared with groundwater elevation trends at a regional U.S. Geological Survey well to provide information for determining if changing the flowage elevations had a noticeable response in the study wells west of Crex Meadows. This analysis was done by (1) evaluating study well groundwater elevation trends compared to the regional well, (2) using a scatter plot of study well and regional well data during raising and lowering periods, (3) assessing horizontal hydraulic gradient data during the study period, and (4) assessing the cumulative departure from the mean groundwater elevation for each well. Overall, regional groundwater elevations had a down-ward trend before and during the flowage lowering period and then had an upward trend during the flowage raising period. This pattern was observed in the regional well and in all the study wells adjacent to and several miles from the flowages. The similarity in patterns indicates that precipitation and regional groundwater flow conditions were the dominant drivers of the system during the study period. The scatter plot and cumulative departure from the mean analysis showed that in addition to regional trends, wells 1, 6, and 7 were likely affected by the changes in the flowage water levels. Overall, at least on the timescale of this study, water management at Crex likely did not have detectable effects on wells outside the Crex property. Wells installed on the Crex property including the wells in the lakebeds of the flowages (wells 1 and 7) and possibly well 6 east of the flowages showed what seems to be minor affects due to water management at Crex.

Wisconsin↗
USGS2015

Applications of optical sensors for high-frequency water-quality monitoring and research

The recent commercial availability of in-situ optical sensors, together with new techniques for data collection and analysis, provides the opportunity to monitor a wide range of water-quality constituents over time scales during which environmental conditions actually change. Traditional approaches for data collection (daily to monthly discrete samples) are often limited by high sample collection, processing, and analytical costs, difficult site access, and logistical challenges, particularly for long-term sampling at a large number of sites. Optical sensors that continuously measure constituents in the environment by absorbance or fluorescence properties (Figure 1) have had a long history of use in oceanography for measuring highly resolved concentrations and fluxes of organic matter, nutrients, and algal material. However, much of the work using commercially-available optical sensors in rivers and streams has taken place in only the last few years. Figure 1. [NOT SHOWN] Optical sensor technology is now sufficiently developed to warrant broader application for research and monitoring in coastal and freshwater systems, and the United States Geological Survey (a U.S. science agency) is now using these sensors in a variety of research and monitoring programs to better understand water quality in-situ and in real-time. Examples are numerous and range from the applications of nitrate sensors for calculating loads to estuaries susceptible to hypoxia (Pellerin et al., 2014) to the use of fluorometers to estimate methymercury fluxes (Bergamaschi et al., 2011) and disinfection byproduct formation (Carpenter et al., 2013). Transmitting these data in real-time provides information that can be used for early trend detection, help identify monitoring gaps critical for water management, and provide science-based decision support across a range of issues related to water quality, freshwater ecosystems, and human health. Despite the value of these sensors, collecting data that meet high-quality standards requires investment in and adherence to tested and established methods and protocols for sensor operation and data management (Pellerin et al., 2013). For example, optical sensor measurements can be strongly influenced by a variety of matrix effects, including water temperature, inner filtering from highly colored water, and scattering of light by suspended particles (Downing et al., 2012). Characterizing and correcting sensors for these effects – as well as the continued development of common methodologies and protocols for sensor use – will be critical to ensuring comparable measurements across sites and over time. In addition, collaborative efforts such as the Nutrient Sensor Challenge (www.nutrients-challenge.org) will continue to accelerate the development, production and use of affordable, reliable and accurate sensors for a range of environments. REFERENCES Bergamaschi .B.A., Fleck J.A., Downing B.D., Boss E., Pellerin B.A., Ganju N.K., Schoellhamer D.H., Byington A.A., Heim W.A., Stephenson M., Fujii R. (2011), Methyl mercury dynamics in a tidal wetland quantified using in situ optical measurements. Limnology and Oceanography, 56(4): 1355-1371. Carpenter K.D., Kraus T.E.C., Goldman J.H., Saraceno J., Downing B.D., Bergamaschi B.A., McGhee G., Triplett T. (2013), Sources and Characteristics of Organic Matter in the Clackamas River, Oregon, Related to the Formation of Disinfection By-products in Treated Drinking Water: U.S. Geological Survey Scientific Investigations Report 2013–5001, 78 p. Downing .B.D., Pellerin B.A., Bergamaschi B.A., Saraceno J., Kraus T.E.K. (2012), Seeing the light: The effects of particles, temperature and inner filtering on in situ CDOM fluorescence in rivers and streams. Limnology and Oceanography: Methods, 10: 767-775. Pellerin B.A., Bergamaschi B.A., Downing B.D., Saraceno J., Garrett J.D., Olsen L.D. (2013), Optical Techniques for the Determination of Nitrate in En

Conference Paper↗
USGS2013

Nutrient concentrations and loads and Escherichia coli densities in tributaries of the Niantic River estuary, southeastern Connecticut, 2005 and 2008–2011

Nutrient concentrations and loads and Escherichia coli (E. coli) densities were studied in 2005 and from 2008 through 2011 in water-quality samples from tributaries of the Niantic River Estuary in southeastern Connecticut. Data from a water-quality survey of the base flow of subbasins in the watershed in June 2005 were used to determine the range of total nitrogen concentrations (0.09 to 2.4 milligrams per liter), instantaneous loads (less than 1 to 62 pounds per day) and the yields of total nitrogen ranging from 0.02 to 11.2 pounds per square mile per day (less than 1 to 7.2 kilograms per hectare per year) from basin segments. Nitrogen yields were positively correlated with the amount of developed land in each subbasin. Stable isotope measurements of nitrate (δ 15 N) and oxygen (δ 18 O) ranged from 3.9 to 9.4 per mil and 0.7 to 4.1 per mil, respectively, indicating that likely sources of nitrate in base flow are soil nitrate and ammonium fertilizers, sewage or animal waste, or a mixture of these sources. Continuous streamflow and monthly water-quality sampling, with additional storm event sampling, were conducted at the three major tributaries (Latimer Brook, Oil Mill Brook, and Stony Brook) of the Niantic River from October 2008 through September 2011. Samples were analyzed for nitrogen and phosphorus constituents and E. coli densities. Total freshwater discharge from these tributaries, which is reduced by upstream withdrawals, ranged from 25.9 to 37.8 million gallons per day. Total nitrogen and phosphorus concentrations generally were low, with the mean values below the U.S. Environmental Protection Agency recommended nutrient concentration values of 0.71 milligram per liter and 0.031 milligram per liter, respectively. Total nitrogen was predominantly in the form of total ammonia plus organic nitrogen at the Oil Mill Brook and Stony Brook sites and in the form of nitrate at Latimer Brook. Annual total nitrogen loads that flowed into the Niantic River estuary from the three major tributaries, calculated with the Load Estimator computer program, ranged from 41,400 to 60,700 pounds, with about 52 to 59 percent of the load as total ammonia plus organic nitrogen. Total phosphorus loads ranged from 1,770 to 3,540 pounds per year. Yields of total nitrogen were highest from Latimer Brook, with the range from the three tributaries between 1,100 and 2,720 pounds per square mile per year. Total phosphorus yields ranged from 52 to 185 pounds per square mile per year. The geometric means of E. coli densities in samples from the three Niantic River tributaries were less than the State of Connecticut water-quality standard of 126 colony-forming units per 100 milliliters; however, individual samples from all three tributaries had densities as high as 2,400 to 2,900 colony-forming units per 100 milliliters. High densities of E. coli were more likely to be present in samples collected during wet weather events.

Connecticut↗
USGS2023

An integrated hydrologic model to support the Central Platte Natural Resources District Groundwater Management Plan, central Nebraska

The groundwater and surface-water supply of the Central Platte Natural Resources District supports a large agricultural economy from the High Plains aquifer and Platte River, respectively. This study provided the Central Platte Natural Resources District with an advanced numerical modeling tool to assist with the update of their Groundwater Management Plan. An integrated hydrologic model, called the Central Platte Integrated Hydrologic Model, was constructed using the MODFLOW-One-Water Hydrologic Model code with the Newton solver. This code integrates climate, landscape, surface water, and groundwater-flow processes in a fully coupled approach. Model framework included 163 rows; 327 columns; 2,640 feet cell sides; and 3 vertical layers. A predevelopment model simulated steady-state hydrologic conditions prior to April 30, 1895, and a development period model discretized into 610 stress periods simulated transient hydrologic conditions from May 1, 1895, to December 31, 2016, using 170 biannual stress periods from 1895 to 1980, and monthly stress periods from May 1, 1980, to December 31, 2016. Calibration of the Central Platte Integrated Hydrologic Model involved two phases: a manual adjustment of parameters, followed by the automated calibration completed using BeoPEST that was facilitated by the employment of the singular value decomposition-assist features of PEST that specified 50 super parameters assembled from the 435 adjustable parameters and Tikhonov regularization. The average absolute groundwater-level residuals for model layers one, two, and three were 6.1, 12.4, and 7.4 feet, respectively. Calibrated horizontal hydraulic conductivity was about 70, 32, and 35 feet per day for layers 1, 2, and 3, respectively. The largest development period inflow to groundwater was recharge from deep percolation past the root zone, averaging 1,122,257 acre-feet per year (2.7 inches per year), and the largest outflow was to irrigation wells, averaging 693,171 acre-feet per year (10.2 inches per year for the Central Platte Natural Resources District). Other substantial groundwater outflows included evapotranspiration and base flow. For the total development period, there was a net change in storage of −122,393 acre-feet per year (−0.3 inch per year). The calibrated Central Platte Integrated Hydrologic Model was used to simulate eight different potential future climate and irrigation pumping conditions from January 1, 2017, to December 31, 2049. Simulated future groundwater levels within the Central Platte Natural Resources District varied significantly between scenarios and locally, from 13.8 feet below to 7.6 feet above baseline 1982 groundwater levels. Most areas exhibited groundwater-level declines for the drought scenarios and rises for the alternate irrigation scenarios. Changes in scenario groundwater levels correlated with the relations between farm net recharge and irrigation pumping. Linear “first order second moment” techniques indicated that the uncertainty in projected groundwater altitudes was reduced by 15.33 feet through model calibration.

Nebraska↗
USGS2024

Numerical model of the groundwater-flow system near the southeastern part of Puget Sound, Washington

Groundwater flow in the active model area (AMA) was simulated using a groundwater-flow model. A steady-state model version of the model simulates equilibrium conditions, and a transient model version simulates monthly variability. The model corresponds to the physical and temporal dimensions of the conceptual model and groundwater budget. The steady-state model version represents average conditions for an 11-year period (January 1, 2005–December 31, 2015), and the transient model represents monthly hydrologic variability within that period. The 13-layer model was constructed using MODFLOW-NWT with a uniformly spaced grid consisting of 416 rows, 433 columns, and cells with a horizontal dimension of 500 feet (ft) on a side. The model was calibrated to measured values of water levels in wells and lakes and estimated base flow for selected streamflow measurement stations, commonly referred to as streamgages. Model calibration was accomplished using a combination of manual and automatic methods, including the Model-Independent Parameter Estimation (PEST) program that adjusted model input parameters with the aim of minimizing the difference between estimated and model-simulated values of hydraulic head and base flow. Model boundary conditions consist of all simulated groundwater inflow to and outflow from the AMA. For example, a stream reach that simulates a gain from or loss to groundwater is a boundary condition that allows water to exit or enter, respectively, the groundwater system. Other boundary conditions include springs, seeps, precipitation recharge, groundwater exchange with lakes and Puget Sound, and groundwater pumping. A comparison of the estimated groundwater budget to that simulated by the steady-state model version indicates that the relative percentages of total inflow or total outflow for six major categories of boundary conditions are similar for the two budgets. The model was used to simulate three suites of scenarios of potential drought and water-use changes. Scenario 1 suite consisted of the steady-state model version that was run with 0, 15, 20, and 25 percent reduction of precipitation recharge to assess the corresponding reductions in base flow with decreasing recharge. The last simulation for the scenario 1 suite consisted of the transient model version simulating 3 years of consecutive seasonal drought, defined by the months of May through September, to assess the corresponding base-flow reductions. Scenario 2 suite consisted of the steady-state model version with all simulated groundwater use removed, compared with a simulation that includes current groundwater use to evaluate changes to potentiometric surfaces and base flows. Scenario 3 suite consisted of a transient model version of the model that simulated pumping increases for four different categories of water-supply wells (compared to no pumping increases) to evaluate resulting reductions in base flow. Although, these scenarios provide examples of model applications and useful insights, many other scenarios could be simulated. A description of how to download the model is described in the body of this report. Uncertainty is associated with most model inputs. Groundwater levels, lake levels, and land-surface altitudes are relatively certain; other model inputs are far less certain, including precipitation recharge, base flow, hydraulic properties, water use, and the three-dimensional structure of subsurface hydrogeologic units. Models are useful not because of high levels of accuracy of all model inputs, but because they combine the best information and estimates available, thereby providing the best predictions available related to physical processes. The model described in this report simulates groundwater flow on a regional scale, which has inherent limitations for simulating hydrologic scenarios at local scales. Model structures and inputs were generalized to be consistent with this regional scale. For example, the actual groundwater system has much greater heterogeneity of hydraulic conductivity than is possible within the model’s degrees of freedom. Variations in hydraulic gradients over distances less than 500 ft cannot be simulated. The distances between model features, such as a pumping well and a stream, must be placed at 500-ft intervals and are co-located if both features are within the same model cell.

Washington↗
USGS2016

Effects of variations in flow characteristics through W.P. Franklin Lock and Dam on downstream water quality in the Caloosahatchee River Estuary and in McIntyre Creek in the J.N. “Ding” Darling National Wildlife Refuge, southern Florida, 2010–13

The U.S. Geological Survey studied water-quality trends at the mouth of McIntyre Creek, an entry point to the J.N. “Ding” Darling National Wildlife Refuge, to investigate correlations between flow rates and volumes through the W.P. Franklin Lock and Dam and water-quality constituents inside the refuge from March 2010 to December 2013. Outflow from Lake Okeechobee, and flows from Franklin Lock, tributaries to the Caloosahatchee River Estuary, and the Cape Coral canal system were examined to determine the sources and quantity of water to the study area. Salinity, temperature, dissolved-oxygen concentration, pH, turbidity, and chromophoric dissolved organic matter fluorescence (FDOM) were measured during moving-boat surveys and at a fixed location in McIntyre Creek. Chlorophyll fluorescence was also recorded in McIntyre Creek. Water-quality surveys were completed on 20 dates between 2011 and 2014 using moving-boat surveys. Franklin Lock contributed the majority of flow to the Caloosahatchee River. Between 2010 and 2013, the monthly mean flow rate at Franklin Lock ranged from 29 cubic feet per second in May 2011 to 10,650 cubic feet per second in August 2013. Instantaneous near-surface salinity in McIntyre Creek ranged from 12.9 parts per thousand on September 26, 2013, to 37.9 parts per thousand on June 27, 2011. Salinity in McIntyre Creek decreased with increasing flow rate through Franklin Lock. Flow rates through Franklin Lock explained 61 percent of the variation in salinity in McIntyre Creek. Salinity data from moving-boat surveys also indicate that an increase in flow rate at Franklin Lock decreases salinity in the Caloosahatchee River Estuary, and a reduction or elimination in flow increases salinity. The FDOM in McIntyre Creek was positively correlated with flow at Franklin Lock, and 54 percent of the variation in FDOM can be attributed to the flow rate through Franklin Lock. Data from moving-boat surveys indicate that FDOM increases when flow volume from Franklin Lock increases. The highest FDOM recorded during a survey was at Billy’s Creek. Chlorophyll fluorescence was positively correlated with flow at Franklin Lock, with 23 percent of the variation explained by the flow rate at Franklin Lock. An increase in flow rate at Franklin Lock resulted in a decrease in pH (21 percent of variation explained by flow rates). Data from the pH surveys indicate an increase in pH with distance from Franklin Lock. Turbidity and dissolved oxygen near the surface in McIntyre Creek were not correlated with flow rate at Franklin Lock. Moving-boat surveys did not document a change in turbidity or dissolved oxygen with a change in distance from the Franklin Lock. Correlations between Franklin Lock flow rate and water quality in McIntyre Creek indicate that releases at Franklin Lock affect water quality in the Caloosahatchee River Estuary and Ding Darling Refuge.

Florida↗
USGS2008

Flow Durations, Low-Flow Frequencies, and Monthly Median Flows for Selected Streams in Connecticut through 2005

Flow durations, low-flow frequencies, and monthly median streamflows were computed for 91 continuous-record, streamflow-gaging stations in Connecticut with 10 or more years of record. Flow durations include the 99-, 98-, 97-, 95-, 90-, 85-, 80-, 75-, 70-, 60-, 50-, 40-, 30-, 25-, 20-, 10-, 5-, and 1-percent exceedances. Low-flow frequencies include the 7-day, 10-year (7Q10) low flow; 7-day, 2-year (7Q2) low flow; and 30-day, 2-year (30Q2) low flow. Streamflow estimates were computed for each station using data for the period of record through water year 2005. Estimates of low-flow statistics for 7 short-term (operated between 3 and 10 years) streamflow-gaging stations and 31 partial-record sites were computed. Low-flow estimates were made on the basis of the relation between base flows at a short-term station or partial-record site and concurrent daily mean streamflows at a nearby index station. The relation is defined by the Maintenance of Variance Extension, type 3 (MOVE.3) method. Several short-term stations and partial-record sites had poorly defined relations with nearby index stations; therefore, no low-flow statistics were derived for these sites. The estimated low-flow statistics for the short-term stations and partial-record sites include the 99-, 98-, 97-, 95-, 90-, and 85-percent flow durations; the 7-day, 10-year (7Q10) low flow; 7-day, 2-year (7Q2) low flow; and 30-day, 2-year (30Q2) low-flow frequencies; and the August median flow. Descriptive information on location and record length, measured basin characteristics, index stations correlated to the short-term station and partial-record sites, and estimated flow statistics are provided in this report for each station. Streamflow estimates from this study are stored on USGS's World Wide Web application 'StreamStats' (http://water.usgs.gov/osw/streamstats/connecticut.html).

Scientific Investigations Report↗
USGS2011

Meteoric precipitation at Yucca Mountain, Nevada: Chemical and stable isotope analyses, 2006-09

Meteoric precipitation samples collected in 2006-09 at Yucca Mountain, Nevada, were analyzed for chemistry and stable isotope composition. Precipitation is the major source of infiltration to the unsaturated zone and of recharge to the saturated zone at Yucca Mountain. On February 28, 2005, seepage of water was observed about 40 to 80 meters below the ground surface within the Tiva Canyon Tuff in the South Ramp of the Exploratory Studies Facility tunnel within Yucca Mountain. This seepage was preceded by a 5-month period of above-average precipitation. Chemical and isotopic analysis of this seepage could not be used to estimate travel time, extent of water-rock interaction, and (or) evaporative water loss during percolation through the unsaturated zone due to the lack of corresponding chemical and isotopic analyses of precipitation inputs to the infiltration events that produced the seepage. In February 2006, collection of precipitation samples for chemical (major ions), delta oxygen-18 (&delta 18 O), and delta deuterium (&deltaD) analyses began at seven meteorological monitoring stations to provide baseline isotopic and chemical analyses. The sampling stations range in elevation from 1,131 to 1,562 meters. Each site has two collectors-one for chemical analysis and the other for isotopic analysis of precipitation. The collectors were sampled and emptied after each precipitation event. In 2006-09, 36 distinct precipitation events, with an average 3- to 4-day duration and an average 9.9 millimeters of accumulation, have been analyzed. The chemical composition of these samples of Yucca Mountain precipitation is relatively dilute but contains measurable and variable concentrations of Na + , Ca 2+ , NH + , NO 3 - , and SO 4 2- . Dust transported by typical winter storms and generated from soil carbonates is the main contributor to this precipitation chemistry. Elevated nitrate and ammonium concentrations may be linked to agriculture in the nearby Amargosa River valley to the south and west of Yucca Mountain. Cumulatively, &delta 18 O values range from 3.0 to -20.4 per mil (%o) and &deltaD values range from 10 to -14%o. Winter-season precipitation commonly has isotopically lighter compositions. The cumulative &delta18O plotted against &deltaD shows that precipitation samples define a line with slope of 6.4, less than the 8 of the Global Meteoric Water Line. This difference in slope, typical of arid environments, is chiefly the result of evaporation of falling raindrops due to warmer air temperatures. ;

Scientific Investigations Report↗
USGS2008

A regression model for computing index flows describing the median flow for the summer month of lowest flow in Michigan

In 2006, Michigan enacted laws to prevent new large capacity withdrawals from decreasing flows to the extent that they would functionally impair a stream's ability to support characteristic fish populations. The median streamflow for the summer month of lowest flow was specified by state decision makers as the index flow on which likely impacts of withdrawals would be assessed. At sites near long-term streamflow-gaging stations, analysis of streamflow records during July, August, and September was used to determine the index flow. At ungaged sites, an alternate method for computing the index flow was needed. This report documents the development of a method for computing index flows at ungaged stream sites in Michigan. The method is based on a regression model that computes the index water yield, which is the index flow divided by the drainage area. To develop the regression model, index flows were determined on the basis of daily flows measured during July, August, and September at 147 streamflow-gaging stations having 10 or more years of record (considered long-term stations) in Michigan. The corresponding index water yields were statistically related to climatic and basin characteristics upstream from the stations in the regression model. Climatic and basin characteristics selected as explanatory variables in the regression model include two aquifer-transmissivity and hydrologic-soil groups, forest land cover, and normal annual precipitation. Regression model estimates of water yield explain about 70.8 percent of the variability in index water yields indicated by streamflow-gaging station records. Index flows computed on the basis of regression-model estimates of water yield and corresponding drainage areas explain about 94.0 percent of the variability in index flows indicated by streamflow-gaging station records. No regional bias was detected in the regression-based estimates of water yield within seven hydrologic subregions spanning Michigan. Thus, the single regression model developed in this report can be used to produce unbiased estimates of index water yield and flow statewide. In addition, a technique is presented for computing prediction intervals about the index flow estimates.

Michigan↗
USGS2014

Use of stable isotopes of nitrogen and water to identify sources of nitrogen in three urban creeks of Durham, North Carolina, 2011-12

A preliminary assessment of nitrate sources was conducted in three creeks that feed nutrient impaired Falls and Jordan Lakes in the vicinity of Durham County, North Carolina, from July 2011 to June 2012. Cabin Branch, Ellerbe Creek, and Third Fork Creek were sampled monthly to determine if sources of nitrate in surface water could be identified on the basis of their stable isotopic compositions. Land use differs in the drainage basins of the investigated creeks—the predominant land use in Cabin Branch Basin is forest, and the Ellerbe and Third Fork Creek Basins are predominantly developed urban areas. Total nutrient concentrations were below 1 milligram per liter (mg/L). All measured nitrate plus nitrite concentrations were below the North Carolina standard of 10 mg/L as nitrogen with the highest concentration of 0.363 mg/L measured in Third Fork Creek. Concentrations of ammonia were generally less than 0.1 mg/L as nitrogen in all creek samples. More than 50 percent of the total nitrogen measured in the creeks was in the form of organic nitrogen. Total phosphorus and orthophosphate concentrations in all samples were generally less than 0.2 mg/L as phosphorus. The isotopic composition of surface water (δ 2 H H20 and δ 18 O H2O ) is similar to that of modern-day precipitation. During July and August 2011 and May and June 2012, surface-water samples displayed a seasonal difference in isotopic composition, indicating fractionation of isotopes as a result of evaporation and, potentially, mixing with local and regional groundwater. The dominant source of nitrate to Cabin Branch, Ellerbe Creek, and Third Fork Creek was the nitrification of soil nitrogen. Two stormflow samples in Ellerbe Creek and Third Fork Creek had nitrate sources that were a mixture of the nitrification of soil nitrogen and an atmospheric source that had bypassed some soil contact through impermeable surfaces within the drainage basin. No influence of a septic or wastewater source was found in Cabin Branch. Results from this study suggest that it is possible to distinguish sources of nitrogen and biogeochemical processes on nitrate using stable isotopes of nitrogen and oxygen in small creeks of Durham County, North Carolina.

North Carolina↗
USGS2016

Methods for estimating streamflow characteristics at ungaged sites in western Montana based on data through water year 2009: Chapter G in Montana StreamStats

The U.S. Geological Survey, in cooperation with the Montana Department of Environmental Quality and the Montana Department of Natural Resources and Conservation, developed regional regression equations based on basin and streamflow characteristics for streamflow-gaging stations through water year 2009 that can be used to estimate streamflow characteristics for ungaged sites in western Montana. The regression equations allow estimation of low-flow frequencies; mean annual and mean monthly streamflows; and the 20-, 50-, and 80-percent durations for annual and monthly duration streamflows for ungaged sites in western Montana that are unaffected by regulation. Regression equations were developed for 54 streamflow characteristics in each of the 4 hydrologic regions generally located in western Montana. Exploratory data analyses determined that of the 40 basin characteristics used as explanatory variables, only 3 were significant in the final equations. These three basin characteristics are contributing drainage area, mean annual precipitation of the drainage basin, and percentage of basin with slopes greater than 50 percent. Low-flow frequency data and daily mean streamflow data from 152 streamflow-gaging stations were used to develop the regression equations. These 152 streamflow-gaging stations were considered to be unregulated (or only the unregulated period of record for regulated streamflow-gaging stations were used). For this study, a streamflow-gaging station is considered to be unregulated if cumulative drainage area upstream from all upstream dams is less than 20 percent of the drainage basin for the streamflow-gaging station, and if no large diversion canals are upstream from the streamflow-gaging station. In addition to the regional regression equations, two methods for estimating streamflow characteristics based on drainage areas of a nearby streamflow-gaging station are provided. Also, spreadsheet tools are provided for calculating streamflow characteristics based on regression equations or the drainage-area ratio method. All of the data used to calculate basin characteristics were derived from publicly available data sources and are available through the U.S. Geological Survey Streamstats program ( http://water.usgs.gov/osw/streamstats/ ) for Montana. The primary purpose of the Montana StreamStats application is to provide estimates of basin characteristics and streamflow characteristics for user-selected ungaged sites on Montana streams. The regional regression equations presented in this report have been loaded to the Montana StreamStats application and can be used to derive streamflow characteristics for ungaged sites.

Montana↗
USGS2018

Monitoring the water-quality response of agricultural conservation practices in the Bucks Branch watershed, Sussex County, Delaware, 2014–16

The purpose of this study was to evaluate the effects of irrigation and cover crops as conservation practices on water quality in groundwater and streams. Bucks Branch, a stream in the Nanticoke River watershed in southwestern Delaware, was identified as having one of the highest concentrations of nitrate in all surface-water sites sampled by the Delaware Department of Natural Resources and Environmental Control (DNREC). The study site is on two adjacent fields bordering Bucks Branch, one that has used irrigation since 2000 and one with dryland farming; both under conservation tillage and long-term rotation of corn, soybean, and small grain crops. A streamgage was installed near the study site fields to measure streamflow and water quality. The study area is typical of farming practices and environmental conditions throughout much of the intensively farmed agricultural land of the Coastal Plain of Delaware and surrounding parts of Maryland. Monitoring was conducted from January 2014 through June 2016. Corn was grown on both fields during the two growing seasons of the study period, and cover crops were planted before or shortly after harvest on both fields. During the second year of data collection, the effects of radish and rye grass cover crops on nutrient transport were studied. The combined results from data collected for this study show that water and nitrate moved below the root zone year round when soil moisture was high, especially after significant rainfall and frequently after irrigation. Soil water sampled 2 to 3 weeks after nutrients were applied had nitrate concentrations greater than 50 milligrams per liter as nitrogen (mg/L as N) and may be a significant source of nitrate to groundwater. Whereas recharge containing elevated nitrate concentrations also occurred under the dryland field, it was less frequent and of lower concentration than recharge under the irrigated field. Nitrate was present in all groundwater samples from these sites. Groundwater estimated to have recharged within 10 years or less had higher median concentrations of nitrate than in older water samples. The oldest groundwater encountered was over 30 years old, and had traveled along the longest, deep flowpaths from upland fields to the stream. The median nitrate concentration was 18 mg/L as N in younger water (less than 10 years old) beneath the irrigated field, compared to about 10 mg/L as N in younger water beneath the dryland field. Samples from the shallow upland wells in both study fields showed little, if any, evidence of denitrification. Several samples from deeper wells and from wells near forested riparian zone wetlands that border both fields did show partial denitrification. A mixing model estimated that between 12 and 22 percent of the nitrate discharging to the stream was lost through uptake and denitrification upstream of the streamgage on Bucks Branch. Continuous data collected at this site and evidence of denitrification in the surface-water samples showed a greater potential for loss of nitrate during the warmer months than the colder months. This pattern was similar to that seen below the streamgage at the most downstream site in the watershed. A mixed cover crop of radishes and rye was planted prior to removal (radishes) and just after harvest (rye) of the corn crop on the irrigated field. Rye grass was planted shortly after crop harvest on the dryland field. Cover crop biomass samples collected while radishes were growing and after they were killed by freezing temperatures indicates that the early planted radish crop effectively scavenged available nitrogen from the soil. Whereas radish biomass initially held more nitrogen than rye, at 55 to 8 pounds per acre, respectively, leaching of inorganic nitrate following radish die-off was minimal. Soil-water nitrate concentrations during the cover-crop growing period were lower than during the growing season prior to planting of the cover crop. There also was an increase in soil fertility and dissolved organic nitrate in samples of soil water that was likely related to increased soil microbial metabolism. Results indicate that cover crops stored plant nutrients over the winter and did not increase shallow groundwater concentrations of nitrate. Although conservation practices such as cover crops and nutrient management have been applied to these fields, there was still significant leaching of nitrate to groundwater, especially under the irrigated field. This will likely continue to be a challenge in this area and other parts of the Coastal Plain where soil moisture capacity is relatively low and managing irrigation around rainfall is difficult. Cover crops, when planted in standing corn, are one practice that can effectively pull nitrate from below the root zone to the top layer of soil, thus limiting the amount of potential nitrate leaching to groundwater. Irrigation management that would lower average soil moisture conditions during the growing season also could potentially limit nitrogen transport.

Delaware↗
USGS2022

Using microbial source tracking to identify fecal contamination sources in Great South Bay on Long Island, New York

The U.S. Geological Survey worked in cooperation with the New York State Department of Environmental Conservation to assess the potential sources of fecal contamination entering a part of Great South Bay (referred to as Great South Bay for the purposes of this report) near the hamlets of West Sayville, Sayville, and Bayport on the southern shore of Suffolk County on Long Island, New York. Water samples are routinely collected by the New York State Department of Environmental Conservation in the bay and analyzed for fecal coliform bacteria, an indicator of fecal contamination, to determine the need for closure of shellfish beds for harvest and consumption. Fecal coliform and other bacteria are an indicator of the potential presence of pathogenic (disease-causing) bacteria. However, indicator bacteria alone cannot determine the biological or geographical sources of contamination; therefore, microbial source tracking was implemented to determine various biological sources of contamination. In addition, information such as the location, weather and season, and surrounding land use where a sample was collected help determine the geographical source and conveyance of land-based water to the embayment. Analysis revealed that the most substantial source of fecal contamination to Great South Bay was discharge from sites draining ponds and wetlands into the tributaries sampled, Brown and Green Creeks, particularly during the summer months. Fecal coliform bacteria at sites where ponds and wetlands drain are increased by stormwater runoff, which is another substantial source of fecal contamination. Sites with high concentrations of fecal coliform bacteria in the summer exacerbated by stormwater include the Brown Creek Culvert at Middle Road, Mill Pond Culvert near South Street, and Green Creek Culvert near Montauk Highway sites. The canine Bacteroides (BacCan) marker was the most frequently detected microbial source tracking marker with 15 positive detections in surface water across the landscape, followed by the waterfowl Helicobacter (GFD) marker with 9 detections and the human Bacteroides (HF183) marker with 4 detections in surface water (excluding 2 detections in sediment). The ruminant Bacteroides (Rum2Bac) marker was not detected in any samples collected during this study. The detection frequency of BacCan was similar for all sampling conditions and seasons, suggesting canine influence is unrelated to weather events and is a year-round occurrence. BacCan was detected in 14 of 16 source samples and only 1 of 16 receptor samples, which suggests that canine fecal contamination is likely diluted in the bay. There was a similar amount of marker detections when comparing weather condition (wet or dry) and season (winter or summer), suggesting that fecal contamination was unrelated to weather events or time of year. Eight waterfowl marker detections were in samples collected during the winter, and only one during the summer, implicating seasonal avian fecal contamination throughout the embayment. The human marker was detected in only one surface-water receptor sample, during the wet winter sampling event at the Green Creek Mid-Bay site. Three of four human marker detections were in the samples collected during the wet winter sampling event, indicating that weather and season may influence the presence of human markers in Great South Bay, but human markers are not overly prevalent.

New York↗
USGS2024

Computation of bromide concentrations at the Kansas River at De Soto, Kansas, January 2021 through October 2023

The Kansas River is an essential water resource that provides drinking water to more than 950,000 people in northeastern Kansas. Water suppliers that rely on the Kansas River as a water-supply source use physical and chemical water-treatment strategies to remove contaminants before distribution. Water District No. 1 of Johnson County, Kansas (WaterOne), is the largest water supplier in the State and uses the Kansas and Missouri Rivers as water-supply sources to provide drinking water to the Kansas City metropolitan area. WaterOne has been using ozone disinfection as a primary water-treatment strategy since the summer of 2020. Water suppliers that rely on ozone disinfection have become increasingly concerned with the presence of elevated dissolved bromide (the negatively charged form of bromine; hereafter referred to as “bromide”) concentrations in their water-supply source. Ozone disinfection of source water containing elevated concentrations of bromide can lead to the formation of bromate, a regulated disinfection byproduct and probable carcinogen. Real-time computations of bromide concentrations upstream from the WaterOne source-water intake in the Kansas River can be used to assist WaterOne with proactive adjustment of water-treatment strategies. These computations can also be used to advance understanding of hydrologic processes affecting ozone disinfection and formation of bromate. This report documents the development of the surrogate-regression model that computes bromide concentrations in real time at De Soto, Kansas, and characterizes daily and monthly bromide concentrations at this location during the study period. The U.S. Geological Survey (USGS), in cooperation with WaterOne, collected specific conductance and discrete bromide sample data at the USGS streamgage Kansas River at De Soto, Kans. (06892350; hereafter referred to as “De Soto”), during January 2021 through October 2023 to develop a surrogate-regression model using ordinary least-squares regression that computes bromide concentrations at De Soto, which is about 15 miles upstream from the WaterOne source-water intake in the Kansas River. Specific conductance explained about 85 percent of the variance in bromide concentrations at De Soto during the study period. The surrogate-regression model documented in this report estimated that bromide concentrations at De Soto were likely to exceed the WaterOne water-treatment level of concern (150 micrograms per liter [μg/L]) when specific conductance was greater than or equal to about 930 microsiemens per centimeter at 25 degrees Celsius. Surrogate-regression model computations of bromide concentrations documented in this report are available at the USGS National Real-Time Water-Quality website ( https://nrtwq.usgs.gov/ ). Bromide concentrations in discrete samples ranged from 31.9 to 251 μg/L and exceeded the water-treatment level of concern in about 34 percent of the 41 samples collected at De Soto during January 2021 through October 2023. Computed daily bromide concentrations ranged from 38.2 to 277 μg/L and exceeded the water-treatment level of concern about 46 percent of the time during January 2021 through October 2023. Generally, an inverse relation was observed between bromide and streamflow during the study period. Higher bromide concentrations were observed during September through February, and lower bromide concentrations were observed during March through August. Seasonal median bromide concentrations were significantly different in all pairwise seasonal combinations, except for summer versus spring. Computed median bromide concentrations were highest during winter, followed by fall, then spring and summer.

Kansas↗