Welcome To The United States Geological Survey

The U.S. Geological Survey's (USGS) mission is to provide reliable scientific information about the Nation's natural resources. An integral part of that mission is to provide consistent, long-term water-resources data to customers, cooperators, and the public. To accomplish our mission, we operate a widespread surface and ground-water data collection network as well as research a wide range of scientific issues throughout Iowa.

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Follow the USGS Iowa on Twitter @USGS_IA and Facebook USGS Science in Iowa for the latest news on natural resources, flooding, new scientific reports, and much more.

News & Reports

Predicting Pesticides in Streams and Rivers: Where is Water Quality at Risk?

A new interactive mapping tool provides predicted concentrations for 108 pesticides in streams and rivers across the Nation and identifies which streams are most likely to exceed water-quality guidelines for human health or aquatic life.


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Evaluation of Statistical and Rainfall-Runoff Models for Predicting Historical Daily Streamflow Time Series in the Des Moines and Iowa River Watersheds

Statistical tools and rainfall-runoff methods are evaluated for estimating historical daily streamflow for ungaged watersheds in the Des Moines and Iowa River Basins.


First national-scale reconnaissance of neonicotinoid insecticides in streams across the USA

This study represents the first national-scale study of the presence of neonicotinoids in urban and agricultural land use settings across the Nation and was completed as part of ongoing USGS investigations of pesticide levels in streams. A summer of this study and links to more information can be found at: http://toxics.usgs.gov/highlights/2015-08-18-national_neonics.html


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Modeling groundwater nitrate concentrations in private wells in Iowa

The Virginia Commonwealth University, USGS, Westat, and the National Cancer Institute have collaborated to develop a model for predicting nitrate concentrations in private wells in Iowa.


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2013 Survey of Iowa groundwater and evaluation of public well vulnerability classifications for contaminants of emerging concern: Iowa Geological and Water Survey Technical Information Series 57.

The Iowa Department of Natural Resources, the U.S. Geological Survey, the U.S. Department of Agriculture, the State Hygienic Laboratory, and the Center for Health Effects of Environmental Contamination collaborated on the first ever comprehensive study of contaminants of emerging concern in Iowa's groundwater.


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Learn About the Land: RAGBRAI 2015 Brochures

The 2015 version of Learn About the Land trip logs are now available. Each year the U.S. Geological Survey, Iowa Geological Survey & Iowa Institute of Hydraulic Research, Iowa DNR, and the Iowa Limestone Producers coordinate to provide these brochures that describe interesting landscape, geologic, and other natural resources alaong the RAGBRAI route. Historical features are highlighted in a separate publication produced by the Office of the State Archaeologist. Look for volunteers as they distribute these brochures along the route and in the RAGBRAI campgrounds.

Date Brochure
July 19 Sioux Center to Storm lake
July 20 Storm Lake to Fort Dodge
July 21 Fort Dodge to Eldora
July 22 Eldora to Cedar Falls
July 23 Cedar Falls to Hiawatha
July 24 Hiawatha to Coralville
July 25 Coralville to Davenport


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Chemical Mixtures and Environmental Effects: A Pilot Study to Assess Ecological Exposure and Effects in Streams

The U.S. Geological Survey and the U.S. Environmental Protection Agency are collaborating on a field-based study of chemical mixture composition and environmental effects in stream waters affected by a wide range of human activities and contaminant sources.

More information and report can be found here.


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Comparisons of estimates of annual exceedance-probability discharges for small drainage basins in Iowa, based on data through water year 2013

New USGS comparison study identifies best flood-frequency estimation methods for small drainage basins in Iowa. Comparisons included 80 streamgages and 5 different flood-estimation methods.


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What lies beneath: geophysical mapping of a concealed Precambrian intrusive complex along the Iowa-Minnesota border

This paper describes the geologic interpretation of airborne magnetic and gravity gradient data, constrained by two boreholes and regional geologic concepts, in the vicinity of Decorah, Iowa. The focus is on poorly understood crystalline Precambrian rocks that are buried under several hundreds of meters of younger sedimentary rocks. Several different geologic elements are interpreted, including a Yavapai-age gabbro intrusion, dikes of the Midcontinent Rift system, and a series of mafic-ultramafic and silicic-intermediate intrusions. In particular, a circular intrusion in the vicinity of Decorah is noted for its geophysical similarities to intrusions in Canada that host nickel, copper, and platinum group element deposits.


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Evaluation of the Ott Hydromet Qliner for Measuring Discharge in Laboratory and Field Conditions

The U.S. Geological Survey, in collaboration with the University of Iowa IIHR - Hydroscience and Engineering, evaluated the use of the Ott Hydromet Qliner using laboratory flume tests along with field validation tests. Analysis of the flume testing indicates the velocities measured by the Qliner at a 40-second exposure time results in higher dispersion of velocities from the mean velocity of data collected with a 5-minute exposure time. The percent data spread from the mean of a 100-minute mean of Qliner velocities for a 40-second exposure time averaged 16.6 percent for the entire vertical, and a 5-minute mean produced a 6.2 percent data spread from the 100-minute mean. This 16.6 percent variation in measured velocity would result in a 3.32 percent variation in computed discharge assuming 25 verticals while averaging 4 bins in each vertical. The flume testing also provided results that indicate the blanking distance of 0.20 meters is acceptable when using beams 1 and 2, however be am 3 is negatively biased near the transducer and the 0.20-meter blanking distance is not sufficient. Field testing included comparing the measured discharge by the Qliner to the discharge measured by a Price AA mechanical current meter and a Teledyne RDI Rio Grande 1200 kilohertz acoustic Doppler current profiler. The field tests indicated a difference between the discharges measured with the Qliner and the field reference discharge between -14.0 and 8.0 percent; however the average percent difference for all 22 field comparisons was 0.22, which was not statistically significant.


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Basin-Scale Simulation of Current and Potential Climate Changed Hydrologic Conditions in the Lake Michigan Basin, United States

The Great Lakes Restoration Initiative (GLRI) is the largest public investment in the Great Lakes in two decades. A task force of 11 Federal agencies developed an action plan to implement the initiative. The U.S. Department of the Interior was one of the 11 agencies that entered into an interagency agreement with the U.S. Environmental Protection Agency as part of the GLRI to complete scientific projects throughoutthe Great Lakes basin. The U.S. Geological Survey, a bureau within the Department of the Interior, is involved in the GLRI to provide scientific support to management decisions as well as measure progress of the Great Lakes basin restoration efforts. This report presents basin-scale simulated current and forecast climatic and hydrologic conditions in the Lake Michigan Basin. The forecasts were obtained by constructing and calibrating a Precipitation-Runoff Modeling System (PRMS) model of the Lake Michigan Basin; the PRMS model was calibrated using the parameter estimation and uncertainty analysis (PEST) software suite. The calibrated model was used to evaluate potential responses to climate change by using four simulated carbon emission scenarios from eight general circulation models released by the World Climate Research Programme.s Coupled Model Intercomparison Project phase 3. Statistically downscaled datasets of these scenarios were used to project hydrologic response for the Lake Michigan Basin.

In general, most of the observation sites in the Lake Michigan Basin indicated slight increases in annual streamflow in response to future climate change scenarios. Monthly streamflows indicated a general shift from the current (2014) winter-storage/snowmelt-pulse system to a system with a more equally distributed hydrograph throughout the year. Simulated soil moisture within the basin illustrates that conditions within the basin are also expected to change on a monthly timescale. One effect of increasing air temperature as a result of the changing climate was the appreciable increase in the length of the growing season in the Lake Michigan Basin. The increase in growing season will cause an increase in evapotranspiration across the Lake Michigan Basin, which will directly affect soil moisture and late growing season streamflows. Output from the Lake Michigan Basin PRMS model is available through an online dynamic web mapping service available at (http://pubs.usgs.gov/sir/2014/5175/)

The map service includes layers for the each of the 8 global climate models and 4 carbon emission scenarios combinations for 12 hydrologic model state vari-ables. The layers are pre-rendered maps of annual hydrologic response from 1977 through 2099 that provide an easily accessible online method to examine climate change effects across the Lake Michigan Basin.


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Estimated Use of Water in the United States in 2010

Here are some key facts from the report:
  • Total estimated water withdrawals in 2010 in the U.S. were 355 billion gallons per day, or about 13% less than total estimated withdrawals in 2005. National water use is at the lowest levels since before 1970;
  • In 2010, more than 50 percent of the total withdrawals in the United States were accounted for by 12 states in order of withdrawal amounts: California, Texas, Idaho, Florida, Illinois, North Carolina, Arkansas, Colorado, Michigan, New York, Alabama and Ohio;
  • Florida had the largest saline withdrawals, accounting for 18 percent of the total in the country, mostly saline surface-water withdrawals for thermoelectric power;
  • Oklahoma and Texas accounted for about 70 percent of the total saline groundwater withdrawals in the United States, mostly for mining
  • Withdrawals for all of these uses declined in 2010:
  • Thermoelectric power declined 20% and represented the largest percent decline and the largest water use;
  • Irrigation withdrawals (all freshwater) declined 9%, public-supply withdrawals declined 5%, and self-supplied industrial withdrawals declined 12%;
  • Mining and aquaculture were the only major sectors that reported increases in total withdrawals in 2010. Mining increased 40% and aquaculture increased 7 percent.


USGS and Canada Reach Confluence in Monitoring Streamflow

In a joint effort, the U.S. Geological Survey and the Water Survey of Canada (WSC) have produced the North America WaterWatch (NAWW), an online website that displays streamflow conditions throughout much of North America.

The site provides a fast, easy-to-use, cartographically-based, central web interface for users to access real-time streamflow conditions for both Canada and the United States. NAWW can be accessed online in both English and French.

"North America WaterWatch delivers easily understandable maps and graphics of streamflow conditions and, simultaneously, provides access to real-time and past streamflow data at thousands of streamgages in both nations, said Jerad Bales, USGS Chief Scientist for Water. The portal demonstrates the value of free exchange of water-data through interoperable web services, which is a major strategic focus of the USGS through open-water data activities."

The international collaboration was announced at the American Water Resources Association annual conference in Tysons Corner, Va.

The NAWW site is arranged similarly to USGS Water Watch. Real-time instantaneous flow data are compared against historical daily streamflow percentiles at hydrometric monitoring stations. The stations are then color coded on the map to indicate current flow conditions in relation to normal conditions based on statistical thresholds (i.e. much below normal, below normal, normal, above normal, much above normal, and high). The timely availability of these streamflow indicators is vital to water managers and the general public, as the easily-recognized indicators constitute a direct link between hydrological field information and the assessment of risks.

NAWW displays streamflow conditions in Canada for about 1000 real-time flow stations with more than 20 years of continuous streamflow records selected from three different data sources: the Water Survey of Canada (~ 850), Centre d'expertise hydrique du Qu\351bec (~ 100), and Alberta Environment (~ 60). Streamflow conditions in the United States are shown for roughly 8000 real-time flow stations. The data on the website are updated hourly; daily statistics are updated quarterly.

The publishing of the NAWW website marks another milestone achieved through the cooperation between USGS and WSC.


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The Effects of Missouri River Mainstem Reservoir System Operations on 2011 Flooding Using a Precipitation-Runoff Modeling System Model

In 2011 the Missouri River Mainstem Reservoir System (Reservoir System) experienced the largest volume of flood waters since the initiation of record-keeping in the nineteenth century. The high levels of runoff from both snowpack and rainfall stressed the Reservoir System.s capacity to control flood waters and caused massive damage and disruption along the river. The flooding and resulting damage along the Missouri River brought increased public attention to the U.S. Army Corps of Engineers (USACE) operation of the Reservoir System. To help understand the effects of Reservoir System operation on the 2011 Missouri River flood flows, the U.S. Geological Survey Precipitation-Runoff Modeling System was used to construct a model of the Missouri River Basin to simulate flows at streamgages and dam locations with the effects of Reservoir System operation (regulation) on flow removed. Statistical tests indicate that the Missouri River Precipitation-Runoff Modeling System model is a good fit for high-flow monthly and annual stream flow estimation. A comparison of simulated unregulated flows and measured regulated flows show that regulation greatly reduced spring peak flow events, consolidated two summer peak flow events to one with a markedly decreased magnitude, and maintained higher than normal base flow beyond the end of water year 2011. Further comparison of results indicate that without regulation, flows greater than those measured would have occurred and been sustained for much longer, frequently in excess of 30 da ys, and flooding associated with high-flow events would have been more severe.


Chemicals Found in Treated Wastewater are Transported from Streams to Groundwater

U.S. Geological Survey (USGS) scientists studying a midwestern stream conclude that pharmaceuticals and other contaminants in treated wastewater effluent discharged to the stream are transported into adjacent shallow groundwater. Other mobile chemicals found in wastewater are expected to have similar fates. The study was conducted at Fourmile Creek, a wastewater-dominated stream near Des Moines, Iowa, during two sampling periods, October and December 2012. Wastewater effluent contributed approximately 99 and 71 percent of the flow in Fourmile Creek during these sampling periods, respectively. Persistent dry conditions predominated in the watershed through the study period.


Contaminants of emerging concern in fresh leachate from landfills in the conterminous United States

Landfill leachate contains a variety of chemicals that reflect our daily activities, U.S. Geological Survey (USGS) scientists concluded as a result of a nationwide study. Landfills are a common disposal mechanism for our Nation's solid waste from residential, commercial, and industrial sources. The scientists found that pharmaceuticals, personal-care products, and other contaminants of emerging concern are widespread in water that has passed through landfills, known as leachate. This study is the first national assessment of these chemicals in landfill waste in the United States. The USGS Headline and corresponding Technical Announcement for this paper can be found here.


Widespread occurrence of neonicotinoid insecticides in streams in a high corn and soybean producing region, USA


  • Neonicotinoids prevalent in streams in a corn and soybean region during growing season.
  • Observed temporal patterns suggest seed treatment use contributing to stream concentrations.
  • Frequency of detection: clothianidin (75%) > thiamethoxam (47%) > imidacloprid (23%).
  • Chemical use and precipitation are important driving factors for off-field transport to streams.
  • Concentrations may frequently exceed chronic aquatic toxicity values during growing season.


Learn About the Land: RAGBRAI 2014 Brochures

Once again, the USGS, Iowa Water Science Center, the IDNR Geological & Water Survey, IIHR, Iowa Geological Survey and the Iowa Limestone Producers have teamed up to provide the Learn About The Land daily trip logs describing interesting landscape, geologic, and other natural and historical features and resources along the RAGBRAI trail. Look for volunteers as they distribute these brochures along the route and in the RAGBRAI campgrounds.

Click on each days brochure to learn more about the land of Iowa.


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Summary of U.S. Geological Survey Reports Documenting Flood Profiles of Streams in Iowa, 1963-2012

This report summarizes 47 U.S. Geological Survey flood-profile reports that were published for streams in Iowa during a 50-year period from 1963 to 2012. Flood events profiled in the reports range from 1903 to 2010. The report summarizes flood-profile measurements, changes in flood-profile report content throughout the years, streams that were profiled in the reports, the occurrence of flood events profiled, and annual exceedance-probability estimates of observed flood events. A total of 94 stream reaches have been profiled in U.S. Geological Survey flood-profile reports. Floods were profiled for June flood events for 18 different years, followed by July flood events for 13 years, May flood events for 11 years, and April flood events for 9 years. Multiple large flood events exceeding the 2-percent annual exceedance-probability discharge estimate occurred at 37 of 98 selected streamgages during 1960-2012. Five large flood events were recorded at two streamgages in Ames during 1990-2010 and four large flood events were recorded at four other streamgages during 1973-2010. Results of Kendall's tau trend-analysis tests for 35 of 37 selected streamgages indicate that a statistically significant trend is not evident for the 1963-2012 period of record; nor is an overall clear positive or negative trend evident for the 37 streamgages.


Contaminants of Emerging Concern: New Environmental Challenges

The presentations from the Iowa Groundwater and Public Health Symposium (March 11, 2014, Des Moines, IA) are now available on the web. Dana Kolpin from the USGS Iowa Water Science Center gave the presentation "Contaminants of Emerging Concern: New Environmental Challenges" at this conference.


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Decadal surface water quality trends under variable climate, land use, and hydrogeochemical setting in Iowa, USA,

In the midwestern United States, expansion of corn cropping for ethanol production during the last decade, led to increasing N application rates in the 2000’s during a period of extreme variability of annual precipitation. The analysis of several decades of nitrate concentration and flow data from 10 major Iowa Rivers indicated that flow-normalized concentrations of nitrate+nitrite-N decreased from 2000 to 2012 in all basins. The recent declining concentration trends can be attributed to both very high and very low discharge in the 2000s and to the long (e.g., 8 year) subsurface residence times in some basins. Dilution of N and depletion of stored N occurs in years with high discharge. Reduced N transport and increased N storage occurs in low-discharge years. Central Iowa basins had the greatest reduction in flow-normalized concentrations, likely because of smaller storage volumes and shorter residence times. Effects of land-use changes on the water quality of major Iowa Rivers may not be noticeable for years or decades in peripheral basins of Iowa, and may be obscured in the central basins where extreme flows strongly affect annual concentration trends.


Impact of Climate Variability on Runoff in the North-Central United States

Scientists from the USGS North Dakota Water Science Center and North Dakota State University conducted research on changes in run-off in the north central United States over the last century. Precipitation, temperature and streamflow records were used to compare changes in precipitation potential evapotranspiration to changes in runoff within 25 stream basins including 7 stream basins in Iowa


Research has shown that environmental contamination from pharmaceuticals is a global concern. The USGS Toxic Substances Hydrology Program is a world leader in the study of the occurrence, fate, and effects of pharmaceutical contamination.

To promote the collection and disposal of unused/unwanted drugs in a safe and approved manner, The Great Lakes Clean Water Organization (GLCW) has developed the Yellow Jug Old Drugs/256 Program. GLWC and Stone Bridge Productions, with financial support from Michigan DEQ, teamed up to produce a documentary focusing on the emerging issue of pharmaceuticals in water and what is being done to help prevent such contamination.

As part of this documentary, Dana Kolpin (research hydrologist from the USGS Iowa Water Science Center and team leader of the Toxics Program's Contaminants of Emerging Concern Project) was interviewed to provide his expertise on the topic of pharmaceuticals in the environment. His interview took place at Fourmile Creek in central Iowa (a stream being used by the USGS Toxics Program as a field laboratory to understand fate and effects of pharmaceuticals).

This documentary is being broadcast on all Michigan PBS stations in November and December 2013.

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Occurrence and transport of nutrients in the Missouri River Basin, April through September 2011: Chapter G in 2011 floods of the central United States

Heavy snow and early spring rainfall in the upper part of the Missouri River Basin in 2011 exceeded the storage capacity of the Missouri River main stem reservoirs and unprecedented amounts of water were released into the lower parts of the basin resulting in record floods from June through September on the Missouri River in Iowa and Nebraska and extending into Kansas and Missouri. Runoff from the Missouri River Basin in April through September 2011 was 68,400,000 acre feet that was only exceeded during flooding in 1993 when runoff was 90,700,000 acre feet. Nitrate and total phosphorus concentrations in the Missouri River and selected tributaries during the flood generally were within the expected range of concentrations measured during the last 30 years. The Missouri River transported an estimated 87,700 tons of nitrate and 41,900 tons of total phosphorus to the Mississippi River from April through September 2011. This was less than 20 percent of the combined total nitrate flux and was about 39 percent of the combined total phosphorus flux from the Upper Mississippi and Missouri River Basins. Substantially more nitrate but less total phosphorus was transported from the Missouri River Basin during the historic 1993 than during the 2011 flood.


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Mycotoxins: Diffuse and point source contributions of natural contaminants of emerging concern to streams

A total of 116 water samples were collected at 32 streams and 3 wastewater treatment plants during 2010.

The detections of mycotoxins were nearly ubiquitous (94% of samples) even though basin size spanned 4 orders of magnitude.

The most frequently detected mycotoxins included deoxynivalenol (77%), nivalenol (59%), and beauvericin (43%).

Levels exceeding 100 ng/L were measured during spring snowmelt conditions in agricultural settings and in WWTP effluent.

Both diffuse and point sources are important environmental pathways for mycotoxin transport to streams.


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Nitrate in the Mississippi River and Its Tributaries, 1980–2010: An Update

This report presents estimates of nitrate concentration and flux at eight sites in the Mississippi river basin from 1980 through 2010. It also examines the variability of expected nitrate concentrations in relation to season and streamflow at each of the eight sites for a recent period from 2000 through 2010.


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Streamflow Characterization and Summary of Water-Quality Data Collection during the Mississippi River Flood, April through July 2011

From April through July 2011, the U.S. Geological Survey collected surface-water samples from 69 water-quality stations and 3 flood-control structures in 4 major subbasins of the Mississippi River Basin to characterize the water quality during the 2011 Mississippi River flood. Most stations were sampled at least monthly for field parameters suspended sediment, nutrients, and selected pesticides. Samples were collected at daily to biweekly frequencies at selected sites in the case of suspended sediment. Hydro-carbon analysis was performed on samples collected at two sites in the Atchafalaya River Basin to assess the water-quality implications of opening the Morganza Floodway. Water-quality samples obtained during the flood period were collected at flows well above normal streamflow conditions at the majority of the stations throughout the Mississippi River Basin and its subbasins.


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Optical Techniques for the Determination of Nitrate in Environmental Waters: Guidelines for Instrument Selection, Operation, Deployment, Maintenance, QualityAssurance, and Data Reporting

This report provides information about selection and use of UV nitrate sensors to facilitate the collection of high-quality nitrate nitrogen concentration data. This report addresses the operating principles, key features and sensor design, sensor characterization techniques and typical interferences, and approaches for sensor deployment. Key sections in this report address maintenance and calibration protocols, quality-assurance techniques, and data formats and reporting. Although the focus of this report is UV nitrate sensors, many of the principles can be applied to other in situ optical sensors for water-quality studies.


Learn About the Land: RAGBRAI 2013 Brochures

Once again, the USGS, Iowa Water Science Center, the IDNR Geological & Water Survey and the Iowa Limestone Producers have teamed up to provide the Learn About The Land daily trip logs describing interesting landscape, geologic, and other natural and historical features and resources along the RAGBRAI trail. Look for USGS volunteers as they distribute these brochures in the RAGBRAI campgrounds.

Click on each days brochure to learn more about the land of Iowa.


Welcome to StreamStats

On the Welcome to StreamStats webpage, click on the State Applications link and on the next webpage click on the State of Iowa on the map of the United States to access the introductory page for Iowa StreamStats. Please read the Warnings on the introductory page to become familiar with Iowa StreamStats. Click on the Interactive Map link to open Iowa StreamStats.

StreamStats is a U.S. Geological Survey Web-based Geographic Information System (GIS) that provides users with access to an assortment of analytical tools that are useful for water-resources planning and management, and for engineering design applications, such as the design of bridges. StreamStats allows users to easily obtain streamflow statistics, drainage-basin characteristics, and other information for user-selected sites on streams.Users can select stream site locations of interest from an interactive map and can obtain information for these locations. If a user selects the location of a USGS streamgage, the user will receive previously published information for the streamgage from a database. If a user selects a location where no data are available (an ungaged site), StreamStats will delineate the drainage-basin boundary, measure basin characteristics and estimate streamflow statistics for the site. These estimates assume natural flow conditions at the site. StreamStats also allows users to identify stream reaches that are upstream or downstream from user-selected sites, and to identify and obtain information for locations along the streams where activities that may affect streamflow conditions are occurring.The results are presented in a table and a map showing the basin-boundary outline. The estimates are applicable for stream sites not significantly affected by regulation, diversions, channelization, backwater, or urbanization.


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Comparison Between Two Statistically Based Methods, and Two Physically Based Models Developed to Compute Daily Mean Streamflow at Ungaged Locations in the Cedar River Basin, Iowa

A variety of individuals from water resource managers to recreational users need streamflow information for planning and decisionmaking at locations where there are no streamgages. To address this problem, two statistically based methods, the Flow Duration Curve Transfer method and the Flow Anywhere method, were developed for statewide application and the two physically based models, the Precipitation Runoff Modeling-System and the Soil and Water Assessment Tool, were only developed for application for the Cedar River Basin. Observed and estimated streamflows for the two methods and models were compared for goodness of fit at 13 streamgages modeled in the Cedar River Basin by using the Nash-Sutcliffe and the percent-bias efficiency values.


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Methods for Estimating Annual Exceedance-Probability Discharges for Streams in Iowa, Based on Data through Water Year 2010

A statewide study was performed to develop regional regression equations for estimating selected annual exceedance-probability statistics for ungaged stream sites in Iowa. The study area comprises streamgages located within Iowa and 50 miles beyond the State’s borders. Annual exceedance-probability estimates were computed for 518 streamgages by using the expected moments algorithm to fit a Pearson Type III distribution to the logarithms of annual peak discharges for each streamgage using annual peak-discharge data through 2010. The estimation of the selected statistics included a Bayesian weighted least-squares/generalized least-squares regression analysis to update regional skew coefficients for the 518 streamgages. Low-outlier and historic information were incorporated into the annual exceedance-probability analyses, and a generalized Grubbs-Beck test was used to detect multiple potentially influential low flows. Also, geographic information system software was used to measure 59 selected basin characteristics for each streamgage.

Regional regression analysis, using generalized least-squares regression, was used to develop a set of equations for each flood region in Iowa for estimating discharges for ungaged stream sites with 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities, which are equivalent to annual flood-frequency recurrence intervals of 2, 5, 10, 25, 50, 100, 200, and 500 years, respectively. A total of 394 streamgages were included in the development of regional regression equations for three flood regions (regions 1, 2, and 3) that were defined for Iowa based on landform regions and soil regions.


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Use of the Soil and Water Assessment Tool (SWAT) for Simulating Hydrology and Water Quality in the Cedar River Basin, Iowa, 2000–10

The U.S. Geological Survey, in cooperation with the Iowa Department of Natural Resources, used the Soil and Water Assessment Tool to simulate streamflow and nitrate loads within the Cedar River Basin, Iowa. The goal was to assess the ability of the Soil and Water Assessment Tool to estimate streamflow and nitrate loads in gaged and ungaged basins in Iowa. The Cedar River Basin model uses measured streamflow data from 12 U.S. Geological Survey streamflow-gaging stations for hydrology calibration. The U.S. Geological Survey software program, Load Estimator, was used to estimate annual and monthly nitrate loads based on measured nitrate concentrations and streamflow data from three Iowa Department of Natural Resources Storage and Retrieval/Water Quality Exchange stations, located throughout the basin, for nitrate load calibration. The hydrology of the model was calibrated for the period of January 1, 2000, to December 31, 2004, and validated for the period of January 1, 2005, to December 31, 2010.


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Persistence and potential effects of complex organic contaminant mixtures in wastewater-impacted streams

In this study, Lagrangian sampling, in which the same approximate parcel of water is tracked as it moves downstream, was conducted at Boulder Creek, Colorado and Fourmile Creek, Iowa to determine in-stream transport and attenuation of more than 200 organic contaminants (including metal complexing agents, nonionic surfactant degradates, personal care products, pharmaceuticals, steroidal hormones, and pesticides) discharged from two secondary WWTPs. Similar stream reaches were evaluated, and samples were collected at multiple sites during summer and spring hydrologic conditions. After accounting for in-stream dilution, a complex mixture of contaminants showed little attenuation and was persistent in the receiving streams at concentrations with potential ecosystem implications.


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Electron Donor Concentrations in Sediments and Sediment Properties at the Agricultural Chemicals Team Research Site near New Providence, Iowa, 2006–07

The concentrations of electron donors and sediment propoerties of aquifer sediments near the South Fork Iowa River were conducted on 50 samples collected from below the water table in 11 boreholes. Samples were analyzed for gravel, sand (coarse, medium, and fine), silt, clay, Munsell soil color, inorganic carbon content, and for the following electron donors: organic carbon, ferrous iron, and inorganic sulfide. Sediment mineralogy was analyzed by using x-ray diffraction (XRD)


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