Geology topics

Benjamin J. Dietsch

Publications and source records attributed to Benjamin J. Dietsch.

At least 19 recordsLinked to original sources

USGS2026

Magnitude and frequency of peak and low flows in the Elkhorn River Basin, Nebraska, 1881–2022

Flood-frequency analysis is based on records of annual maximum instantaneous flows observed at long-term streamgages with 10 years or more of operation. Since the last flood-frequency analysis in Nebraska, an additional 30 years of annual peak-flow data have become available, and new flood-frequency analysis techniques have been developed. Moreover, the Elkhorn River Basin in north-central and eastern Nebraska has experienced two of the three highest magnitude floods on record in 2010 and 2019. The U.S. Geological Survey, in cooperation with the Nebraska Department of Transportation, analyzed flow frequency at streamgages in the Elkhorn River Basin in Nebraska. Flow data from the U.S. Geological Survey and the Nebraska Department of Water, Energy, and Environment annual hydrographic reports were utilized to analyze peak flows. The Peak flow FreQuency (PeakFQ) software was used to perform a flood-frequency and nonstationarity analysis on the selected streamgages in the Elkhorn River Basin in Nebraska. Results of the peak-flow nonstationarity analysis indicate that, of the 23 streamgages analyzed for peak-flow frequency, 4 showed trends that were likely increasing for annual peak flows, whereas 3 indicated trends that were somewhat likely to be increasing. For 11 streamgages, the trend was categorized as about as likely as not, meaning there is less than a 70-percent chance of the trend being either upward or downward. Additionally, 2 streamgages exhibited trends that were somewhat likely to be decreasing, and 3 streamgages showed trends that were likely decreasing. Low-flow streamflows and nonstationarity in the Elkhorn River Basin were analyzed for low flow periods representing the 1-day, 7-day, and 30-day flows at 21 streamgages using the Hydrologic Toolbox software. Spatially, the nonstationarity analysis results indicated likely increasing or somewhat increasing trend likelihoods for the 1-day, 7-day, and 30-day low flows for many of the Elkhorn streamgages downstream from the Elkhorn River at Ewing, Nebr., streamgage (U.S. Geological Survey station 06797500) and on eastern tributaries during the period of record.

Nebraska↗

USGS2026

Scenarios to assess the future water availability in the Mississippi River Valley Alluvial Aquifer for the Cache River and Grand Prairie Regions of Arkansas

The U.S. Geological Survey, as part of the Arkansas Groundwater Initiative, developed forecast scenarios using previously calibrated MODFLOW 6 groundwater models that focused on the Cache and Grand Prairie Critical Groundwater Areas to assess the impact of future climate and water management strategies on the Mississippi River Valley alluvial aquifer. A Soil Water Balance model was used to forecast recharge and irrigation water use. The forecast scenario period was from January 1, 2019, through December 31, 2055, with monthly stress periods. Twenty scenarios were simulated and included seven alternate climate forecasts, five 13 general groundwater pumping reduction scenarios (round 1), and groundwater pumping reduction scenarios by crop type and for the Bayou Meto Water Management Project and Grand Prairie Area Demonstration Project (round 2). Declines in saturated thickness within the Cache Critical Groundwater Area were larger for 18 of the 20 scenarios as compared to outside of the Critical Groundwater Area. The largest average increase in saturated thickness inside the Critical Groundwater Area was 6.4 m which occurred for the round 1, 50 percent reduction scenario. Automatic reductions in groundwater pumping by MODFLOW 6 in the Cache simulation ranged from 0.02 to 13.1 percent of total groundwater pumping. For the Grand Prairie model domain, the average change in saturated thickness of the Mississippi River Valley alluvial aquifer inside the Critical Groundwater Area for the forecast period ranged between -6.6 to 1.7 m. The average saturated thickness of the Mississippi River Valley alluvial aquifer inside the Grand Prairie Critical Groundwater Area declined for 16 of the 20 scenarios. The average reduction in requested groundwater pumping for all scenarios inside the Grand Prairie Critical Groundwater Area was 25.1 percent, and the largest reduction was 46.5 percent.

ESS Open Archive↗

USGS2024

Inset groundwater-flow models for the Cache and Grand Prairie Critical Groundwater Areas, northeastern Arkansas

The water resources in the Mississippi alluvial plain, located in parts of Missouri, Kentucky, Tennessee, Mississippi, Louisiana, and Arkansas, supports a multibillion-dollar agricultural industry that relies heavily on pumping of groundwater for irrigation of crops and aquaculture. The primary source of groundwater for agricultural-related pumping is the Mississippi River Valley alluvial aquifer, which has declined in storage for decades; secondary groundwater sources include the middle Claiborne aquifer and Wilcox aquifer system. Two areas in northeastern Arkansas that lie within the Mississippi alluvial plain, part of the Cache and Grand Prairie regions, have been designated as Critical Groundwater Areas owing to decades of groundwater declines that resulted from past and current water use. The multidisciplinary Mississippi Alluvial Plain project, led by the U.S. Geological Survey, and funded by their Water Availability and Use Science Program, included objectives to develop numerical groundwater models in focus regions, including the part of the Cache and Grand Prairie regions of northeastern Arkansas. Two inset models were developed using the child model capabilities of MODFLOW 6, the U.S. Geological Survey’s Modular Hydrologic Model simulation software. Both models, called the Cache model and Grand Prairie model, simulated the groundwater system and surface-water/groundwater interactions for the Mississippi River Valley alluvial aquifer and underlying Tertiary-age aquifers and confining units to the Midway confining unit. Each model was spatially discretized into 500-meter x 500-meter orthogonal cells on a grid with 5-meter constant-thickness vertical layers that represented the Mississippi River Valley alluvial aquifer and increasing thickness layers for the aquifers and confining units below the alluvial aquifer. The Cache and Grand Prairie models were calibrated with the PEST++ iterative ensemble smoother Version 5 and employed high dimensional parameterization schemes of 13,740 and 30,436 parameters, respectively. The Cache mean absolute residual for groundwater-level observations within each model domain for the priority well was 1.58 meters. Grand Prairie mean absolute residuals for the alluvial aquifer and middle Claiborne aquifer groundwater-level observations were 2.71 and 10.78 meters, respectively. The groundwater budgets for the Cache and Grand Prairie models were characterized by substantial outflows to irrigation wells, which constituted about 52 and 54 percent of all outflows, with the primary source of water to those wells being releases from unconfined aquifer storage.

Arkansas↗

USGS2023

Simulation of monthly mean and monthly base flow of streamflow using random forests for the Mississippi River Alluvial Plain, 1901 to 2018

Improved simulations of streamflow and base flow for selected sites within and adjacent to the Mississippi River Alluvial Plain area are important for modeling groundwater flow because surface-water flows have a substantial effect on groundwater levels. One method for simulating streamflow and base flow, random forest (RF) models, was developed from the data at gaged sites and, in turn, was used to make monthly mean streamflow and base-flow predictions at 162 ungaged sites in the study area. Daily streamflow observations and computed base flow from 247 streamgages were used as the basis for the development of these RF models. RF models were constructed from basin and climatic characteristics and related to observed monthly mean streamflow values; models were used to compute monthly base-flow estimates from selected streamgages in and adjacent to the Mississippi River Alluvial Plain extent, which includes streamflows from parts of Alabama, Arkansas, Colorado, Florida, Illinois, Indiana, Kansas, Kentucky, Louisiana, Mississippi, Missouri, New Mexico, Tennessee, and Texas. The explanatory variables for the models were selected to represent physical characteristics and climatic time series for the contributing drainage basins to the streamgages and ungaged locations of interest. The Nash-Sutcliffe efficiency between observed and simulated monthly mean streamflow was greater than 0.80 for 155 of the 247 streamgages, with a median Nash-Sutcliffe efficiency value of 0.83. The streamflow and base-flow simulations can be used to improve inflow values and to verify the Mississippi River Alluvial Plain groundwater flow model. The statistical model, input data, and response data (simulated monthly mean streamflows) are available as a U.S. Geological Survey software release and a U.S. Geological Survey data release.

Alabama, Arkansas, Illinois, Kentucky, Louisiana, ↗

USGS2020

Trends in streamflow and precipitation for selected sites in the Elkhorn River Basin and in streamflow in the Salt Creek and Platte River Basins, Nebraska, 1961–2011

To better understand the streamflow trends at the streamgages in the Elkhorn River Basin in Nebraska, the U.S. Geological Survey (USGS) in cooperation with the Lower Elkhorn Natural Resources District further investigated streamflow trends at the eight streamgages on the Elkhorn River, Salt Creek, and the Lower Platte River that indicated a positive trend in streamflow characteristics and analyzed precipitation trends in the four basins upstream from the Elkhorn River Basin streamgages. An analysis of four streamgages in the Elkhorn River Basin, one streamgage in Salt Creek Basin, and three streamgages in the Lower Platte River Basin that had previously indicated trends in selected annual mean streamflow, annual low flows, fall low flows, and growing season monthly mean streamflows metrics were analyzed for the period from 1961 to 2011. A streamgage in the Upper Elkhorn River Basin (Elkhorn River at Neligh, Nebraska [USGS station 06798500; maintained by USGS from water years 1930 to 1993, maintained by Nebraska Department of Natural Resources from water years 1994 to 2019]) had significant positive trends in annual mean streamflow and insignificant trends for other streamflow metrics whereas the lower three sites (Logan Creek near Uehling, Nebr. [USGS station 06799500]; Maple Creek at Nickerson, Nebr. [USGS station 06800000]; and Elkhorn River at Waterloo, Nebr. [USGS station 06800500]) had significant positive trends for annual mean streamflow, for all durations of the annual low-flow periods (1-day, 2-day, 3-day, 7-day, 14-day, 30-day, 60-day, 90-day, and 183-day periods), for all durations of the low-flow periods in October–November (1-day, 2-day, 3-day, 7-day, 14-day, 30-day, and 60-day periods), and for monthly mean streamflow for July, August, and September. Upstream from the confluence of the Elkhorn River and the Platte River, the Platte River at North Bend, Nebr. (USGS station 06796000), streamgage indicated insignificant trends for most streamflow metrics. A streamgage in the Salt Creek Basin (Salt Creek at Greenwood, Nebr. [USGS station 06803555]) also indicated positive trends in some low-flows metrics. Streamflow at the Platte River at Louisville, Nebr. (USGS station 06805500), streamgage, downstream from the Salt Creek and Elkhorn River inflows, indicated significant positive trends in most annual and all October–November low flows and August mean streamflow but insignificant trends in annual mean streamflow and June, July, and September monthly mean streamflows. Streamflow records for the Platte River near Duncan, Nebr. (USGS station 06774000), streamgage only indicated a significant trend in the August mean streamflow; no other metrics had significant trends at the streamgage. The trend analyses are sensitive to the period that is analyzed for trends. Sites with the most significant trends for low-flow metrics for the period 1961–2011 have fewer significant trends for low-flow metrics for the period after 1980–2011. The results indicate that positive trends in low flows at the Salt Creek and Elkhorn River streamgages may be contributing to positive trends in low flows for the Platte River at Louisville, Nebr., streamgage. Likewise, streamflow in the Salt Creek and Elkhorn River Basins may be contributing to the positive trend in August mean streamflow for the Platte River at Louisville, Nebr., streamgage, three lower Elkhorn River streamgages, and the Salt Creek streamgage. Precipitation was also examined as a primary cause for streamflow trends in the Elkhorn River Basin. For the four streamgages in the Elkhorn River Basin, relations between precipitation and streamflow were examined on an annual and monthly basis using linear regression. In general, the goodness of fit for the linear relations was poor with coefficient of determination values of less than or equal to 0.10 for four of the eight relations. Only one significant increase in annual precipitation upstream from the four streamgages and the frequent detection of significant increases in streamflow after removing the effect of precipitation indicate that other factors besides precipitation may have played a role in the significant positive trends in low-flow periods in the lower Elkhorn River and its tributaries.

Nebraska↗

USGS2019

Flood-inundation maps of the Meramec River from Eureka to Arnold, Missouri, 2018

Libraries of digital flood-inundation maps that spanned a combined 37.2-mile reach of the Meramec River that extended upstream from Eureka, Missouri, to downstream near the confluence of the Meramec and Mississippi Rivers were created by the U.S. Geological Survey (USGS) in cooperation with the U.S. Army Corps of Engineers, Metropolitan St. Louis Sewer District, Missouri Department of Transportation, Missouri American Water, Federal Emergency Management Agency Region 7, and the cities of Pacific, Eureka, Wildwood, and Arnold. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science website at https://water.usgs.gov/osw/flood_inundation/ , depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the cooperative USGS streamgages for the Meramec River near Eureka, Mo. (USGS station 07019000), the Meramec River at Valley Park, Mo. (USGS station 07019130), the Meramec River at Fenton, Mo. (USGS station 07019210), and the Meramec River at Arnold, Mo. (USGS station 07019300). Near-real-time stage data at these streamgages may be obtained from the USGS National Water Information System at https://doi.org/10.5066/F7P55KJN or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at https://water.weather.gov/ahps/ , which also forecasts flood hydrographs at these sites (listed as NWS sites erkm7, vllm7, fnnm7, and arnm7, respectively). Flood profiles were computed for the stream reach by means of a calibrated one-dimensional step-backwater hydraulic model. The model was calibrated using a stage-discharge relation at the Meramec River near Eureka, Mo., streamgage (USGS station 07019000) and documented high-water marks from the flood of December 2015 through January 2016. The calibrated hydraulic model was used to compute water-surface profiles: 1 set for the Meramec River near Eureka, Mo., streamgage (USGS station 07019000); 1 set for the Meramec River at Valley Park, Mo., streamgage (USGS station 07019130); 7 sets for the Meramec River at Fenton, Mo., streamgage (USGS station 07019210) for a range of Mississippi River conditions; and 8 sets for the Meramec River at Arnold, Mo., streamgage (USGS station 07019300) for a range of Mississippi River conditions. The water-surface profiles were produced for stages at 1-foot (ft) intervals referenced to the datum from each streamgage and ranging from the NWS action stage, or near bankfull discharge, to the stage corresponding to the estimated 0.2-percent annual exceedance probability (500-year recurrence interval) flood, as determined at the Meramec River near Eureka, Mo., streamgage (USGS station 07019000). The simulated water-surface profiles then were combined with a geographic information system digital elevation model (derived from light detection and ranging data having a 0.28-ft vertical accuracy and 3.28-ft horizontal resolution) to delineate the area flooded at each simulated 1-ft stage increment. Previously published flood-inundation maps were updated and incorporated in the flood map libraries for USGS stations 07019130 and 07019210 to complete the map sets corresponding to eight Mississippi River conditions. The availability of these maps, along with internet information regarding current stage from the USGS streamgages and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures and for postflood recovery efforts.

Missouri↗

USGS2017

Flood-inundation maps for the Meramec River at Valley Park and at Fenton, Missouri, 2017

Two sets of digital flood-inundation map libraries that spanned a combined 16.7-mile reach of the Meramec River that extends upstream from Valley Park, Missouri, to downstream from Fenton, Mo., were created by the U.S. Geological Survey (USGS) in cooperation with the U.S. Army Corps of Engineers, St. Louis Metropolitan Sewer District, Missouri Department of Transportation, Missouri American Water, and Federal Emergency Management Agency Region 7. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science website at https://water.usgs.gov/osw/flood_inundation/ , depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the cooperative USGS streamgages on the Meramec River at Valley Park, Mo., (USGS station number 07019130) and the Meramec River at Fenton, Mo. (USGS station number 07019210). Near-real-time stage data at these streamgages may be obtained from the USGS National Water Information System at https://waterdata.usgs.gov/nwis or the National Weather Service (NWS) Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/ , which also forecasts flood hydrographs at these sites (listed as NWS sites vllm7 and fnnm7, respectively). Flood profiles were computed for the stream reaches by means of a calibrated one-dimensional step-backwater hydraulic model. The model was calibrated using a stage-discharge relation at the Meramec River near Eureka streamgage (USGS station number 07019000) and documented high-water marks from the flood of December 2015 through January 2016. The calibrated hydraulic model was used to compute two sets of water-surface profiles: one set for the streamgage at Valley Park, Mo. (USGS station number 07019130), and one set for the USGS streamgage on the Meramec River at Fenton, Mo. (USGS station number 07019210). The water-surface profiles were produced for stages at 1-foot (ft) intervals referenced to the datum from each streamgage and ranging from the NWS action stage, or near bankfull discharge, to the stage corresponding to the estimated 0.2-percent annual exceedance probability (500-year recurrence interval) flood, as determined at the Eureka streamgage (USGS station number 07019000). The simulated water-surface profiles were then combined with a geographic information system digital elevation model (derived from light detection and ranging data having a 0.28-ft vertical accuracy and 3.28-ft horizontal resolution) to delineate the area flooded at each flood stage (water level). The availability of these maps, along with internet information regarding current stage from the USGS streamgages and forecasted high-flow stages from the NWS, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures and for postflood recovery efforts.

Missouri↗

USGS2016

Flood-inundation maps for a 12.5-mile reach of Big Papillion Creek at Omaha, Nebraska

Digital flood-inundation maps for a 12.5-mile reach of the Big Papillion Creek from 0.6 mile upstream from the State Street Bridge to the 72nd Street Bridge in Omaha, Nebraska, were created by the U.S. Geological Survey (USGS) in cooperation with the Papio-Missouri River Natural Resources District. The flood-inundation maps, which can be accessed through the USGS Flood Inundation Mapping Science Web site at http://water.usgs.gov/osw/flood_inundation/ , depict estimates of the areal extent and depth of flooding corresponding to selected water levels (stages) at the USGS streamgage on the Big Papillion Creek at Fort Street at Omaha, Nebraska (station 06610732). Near-real-time stages at this streamgage may be obtained on the Internet from the USGS National Water Information System at http://waterdata.usgs.gov/ or the National Weather Service Advanced Hydrologic Prediction Service at http:/water.weather.gov/ahps/ , which also forecasts flood hydrographs at this site. Flood profiles were computed for the 12.5-mile reach by means of a one-dimensional step-backwater model. The model was calibrated by using the current (2015) stage-discharge relation at streamgages for the Big Papillion Creek at Fort Street at Omaha, Nebraska, and the Big Papillion Creek at Q Street at Omaha, Nebraska. The hydraulic model was then used to compute 15 water-surface profiles for flood stages at 1-foot (ft) intervals referenced to the streamgage datum for the Big Papillion Creek at Fort Street and ranging from 18 ft (or near bankfull) to 32 ft, which exceeds the “major flood stage” as defined by the National Weather Service. The simulated water-surface profiles were then combined with a Geographic Information System digital elevation model (derived from light detection and ranging data having a 1.18-ft vertical accuracy and 3.28-ft horizontal resolution) to delineate the area flooded at each flood stage (water level). The availability of these flood-inundation maps, along with Internet information regarding current stage from the USGS streamgage and forecasted high-flow stages from the National Weather Service, will provide emergency management personnel and residents with information that is critical for flood response activities such as evacuations and road closures, as well as for postflood recovery efforts.

Nebraska↗

USGS2015

Topographic and hydrographic survey data for the São Francisco River near Torrinha, Bahia, Brazil, 2014

Navigable inland waterways, including lakes, rivers, and reservoirs, are important transportation routes for people and goods in Brazil. Natural and anthropogenic effects coupled with recent severe droughts have led to decreased inland waterway navigation. The Company for Development of the São Francisco and Parnaíba River Valleys (CODEVASF) has recognized the decrease in waterway navigation and is investing resources to help restore selected reaches of the São Francisco River for navigation. In 2011, CODEVASF signed an agreement with the U.S. Army Corps of Engineers (USACE) seeking technical assistance and engineering expertise in waterway navigation and bank stabilization. The Torrinha-Itacoatiara study reach near Torrinha, Bahia was 1 of 12 conceptual waterway navigation improvement feasibility studies and was the focus of this study. The U.S. Geological Survey, in cooperation with the USACE and CODEVASF, collected topographic and hydrographic data from May 22 to June 12, 2014, to provide baseline data for supporting computational streamflow models. This report presents the surveying techniques and data-processing methods used to collect, process, and disseminate topographic and hydrographic data. All standard and non‑standard data-collection methods, techniques, and data process methods were documented. Additional discussion describes the quality-assurance and quality-control elements used in this study, along with the limitations for the Torrinha-Itacoatiara study reach data. The topographic and hydrographic geospatial data are published along with associated metadata.

Bahia↗

USGS2014

Geomorphic change on the Missouri River during the flood of 2011

The 2011 flood on the Missouri River was one of the largest floods since the river became regulated by a series of high dams in the mid-20th century (greater than 150,000 cubic feet per second during the peak). The flood persisted through most of the summer, eroding river banks, adding sand to sandbars, and moving the thalweg of the channel in many places. The U.S. Geological Survey monitored and assessed the changes in two reaches of the Missouri River: the Garrison Reach in North Dakota, bounded by the Garrison Dam and the Lake Oahe Reservoir, and the Recreational Reach along the boundary of South Dakota and Nebraska bounded upstream by the Gavins Point Dam and extending downstream from Ponca, Nebraska. Historical cross-section data from the Garrison Dam closure until immediately before the flood indicate that the upper reaches of the river near the dam experienced rapid erosion, channel incision, and island/sandbar loss following the dam closure. The erosion, incision, and land loss lessened with time. Conversely, the lower reach near the Lake Oahe Reservoir slackwaters became depositional with channel in-filling and sandbar growth through time as the flow slowed upon reaching the reservoir. Preliminary post-flood results in the Garrison Reach indicate that the main channel has deepened at most cross-sections whereas sandbars and islands have grown vertically. Sandbars and the thalweg migrated within the Recreational Reach, however net scouring and aggradation was minimal. Changes in the two-dimensional area of sandbars and islands are still being assessed using high-resolution satellite imagery. A sediment balance can be constructed for the Garrison Reach using cross-sections, bathymetric data, sand traps for wind-blown material, a quasi-three-dimensional numerical model, and dating of sediment cores. Data collection and analysis for a reach-scale sediment balance and a concurrent analysis of the effects of riparian and island vegetation on sediment deposition currently (2014) is ongoing.

Nebraska, North Dakota, South Dakota↗

USGS2014

Monitoring of levees, bridges, pipelines, and other critical infrastructure during the 2011 flooding in the Mississippi River Basin

During the 2011 Mississippi River Basin flood, the U.S. Geological Survey evaluated aspects of critical river infrastructure at the request of and in support of local, State, and Federal Agencies. Geotechnical and hydrographic data collected by the U.S. Geological Survey at numerous locations were able to provide needed information about 2011 flood effects to those managing the critical infrastructure. These data were collected and processed in a short time frame to provide managers the ability to make a timely evaluation of the safety of the infrastructure and, when needed, to take action to secure and protect critical infrastructure. Critical infrastructure surveyed by the U.S. Geological Survey included levees, bridges, pipeline crossings, power plant intakes and outlets, and an electrical transmission tower. Capacitively coupled resistivity data collected along the flood-protection levees surrounding the Omaha Public Power District Nebraska City power plant (Missouri River Levee Unit R573), mapped the near-subsurface electrical properties of the levee and the materials immediately below it. The near-subsurface maps provided a better understanding of the levee construction and the nature of the lithology beneath the levee. Comparison of the capacitively coupled resistivity surveys and soil borings indicated that low-resistivity value material composing the levee generally is associated with lean clay and silt to about 2 to 4 meters below the surface, overlying a more resistive layer associated with sand deposits. In general, the resistivity structure becomes more resistive to the south and the southern survey sections correlate well with the borehole data that indicate thinner clay and silt at the surface and thicker sand sequences at depth in these sections. With the resistivity data Omaha Public Power District could focus monitoring efforts on areas with higher resistivity values (coarser-grained deposits or more loosely compacted section), which typically are more prone to erosion or scour. Data collected from multibeam echosounder hydrographic surveys at selected bridges aided State agencies in evaluating the structural integrity of the bridges during the flood, by assessing the amount of scour present around piers and abutments. Hydrographic surveys of the riverbed detected scour depths ranging from zero (no scour) to approximately 5.8 meters in some areas adjacent to North Dakota bridge piers, zero to approximately 6 meters near bridge piers in Nebraska, and zero to approximately 10.4 meters near bridge piers in Missouri. Substructural support elements of some bridge piers in North Dakota, Nebraska, and Missouri that usually are buried were exposed to moving water and sediment. At five Missouri bridge piers the depth of scour left less than 1.8 meters of bed material between the bottom of the scour hole and bedrock. State agencies used this information along with bridge design and construction information to determine if reported scour depths would have a substantial effect on the stability of the structure. Multibeam echosounder hydrographic surveys of the riverbed near pipeline crossings did not detect exposed pipelines. However, analysis of the USGS survey data by pipeline companies aided in their evaluation of pipeline safety and led one company to further investigate the safety of their line and assisted another company in getting one offline pipeline back into operation. Multibeam echosounder hydrographic surveys of the banks, riverbed, and underwater infrastructure at Omaha Public Power District power plants documented the bed and scour conditions. These datasets were used by Omaha Public Power District to evaluate the effects that the flood had on operation, specifically to evaluate if scour during the peak of the flood or sediment deposition during the flood recession would affect the water intake structures. Hydrographic surveys at an Omaha Public Power District electrical transmission tower documented scour so that they could evaluate the structural integrity of the tower as well as have the information needed to make proper repairs after flood waters receded.

Missouri River Basin, Mississippi River Basin↗

USGS2014

Repeated multibeam echosounder hydrographic surveys of 15 selected bridge crossings along the Missouri River from Niobrara to Rulo, Nebraska, during the flood of 2011

In 2011, unprecedented flooding in the Missouri River prompted transportation agencies to increase the frequency of monitoring riverbed elevations near bridges that cross the Missouri River. Hydrographic surveys were completed in cooperation with the Nebraska Department of Roads, using a multibeam echosounder at 15 highway bridges spanning the Missouri River from Niobrara to Rulo, Nebraska during and after the extreme 2011 flood. Evidence of bed elevation change near bridge piers was documented. The greatest amount of bed elevation change during the 2011 flood documented for this study occurred at the Burt County Missouri River Bridge at Decatur, Nebraska, where scour of about 45 feet, from before flooding, occurred between a bridge abutment and pier. Of the remaining sites, highway bridges where bed elevation change near piers appeared to have exceeded 10 feet include the Abraham Lincoln Memorial Bridge at Blair, Nebr., Bellevue Bridge at Bellevue, Nebr., and Nebraska City Bridge at Nebraska City, Nebr. Hydrographic surveys at 14 of the 15 sites were completed in mid-July and again in early October or late-November 2011. Near three of the bridges, the bed elevation of locations surveyed in July increased by more than 10 feet, on average, by late October or early November 2011. Bed elevations increased between 1 and 10 feet, on average, near six bridges. Near the remaining four bridges, bed elevations decreased between 1 and 4 feet, on average, from July to late October or early November.

Nebraska↗

USGS2014

Hydrographic survey of Chaktomuk, the confluence of the Mekong, Tonlé Sap, and Bassac Rivers near Phnom Penh, Cambodia, 2012

The U.S. Geological Survey, in cooperation with the U.S. Department of State, Mekong River Commission, Phnom Penh Autonomous Port, and the Cambodian Ministry of Water Resources and Meteorology, completed a hydrographic survey of Chaktomuk, which is the confluence of the Mekong, Tonlé Sap (also spelled Tônlé Sab), and Bassac Rivers near Phnom Penh, Cambodia. The hydrographic survey used a high-resolution multibeam echosounder mapping system to map the riverbed during April 21–May 2, 2012. The multibeam echosounder mapping system was made up of several components: A RESON Seabat™ 7125 multibeam echosounder, an inertial measurement unit and navigation unit, data collection computers, and a Real-Time Kinematic (RTK) Global Navigation Satellite System (GNSS) base station. The survey area was divided into six survey subreaches and each subreach was surveyed within 3 days along survey lines oriented parallel to the flow direction. Complete coverage of the riverbed was the operational objective; however, to obtain broad spatial coverage, gaps between parallel swaths were permitted, especially in wide, shallow areas where multibeam swath widths were narrow. The survey was referenced to two existing bench marks with known geographic coordinates by establishing a GNSS base station on the bench marks each day and using real-time corrections from the base station to correct boat navigation data. The World Geodetic System of 1984 (WGS 84) ellipsoid was used during data collection to reference height, and data were adjusted to the local datum, Ha Tien 1960, during postprocessing. The quality of hydrographic surveys was described by an uncertainty estimate called total propagated uncertainty (TPU). Calculations of TPU were completed for the hydrographic survey data resulting in the maximum TPU of 0.33 meters. The mean and median TPUs were 0.18 meters, and 99.9 percent of TPU values were less than 0.25 meters. Detailed hydrographic maps of Mekong, Tonlé Sap, and Bassac Rivers showing the riverbed elevations surveyed April 21–May 2, 2012, referenced to Ha Tien 1960 were produced. The surveyed area included a 2-km stretch of the Mekong River between the confluence with the Tonlé Sap and Bassac Rivers, and extended 4 km upstream and 3.6 km downstream from the 2,000-m confluence stretch of the Mekong River. In addition, 0.7 km of the Bassac River downstream and 3.5 km of the Tonlé Sap River (from the confluence to Chroy Changvar Bridge) upstream from their confluence with the Mekong River were surveyed. Riverbed features (such as dunes, shoals, and the effects of sediment mining, which were observed during data collection) are visible on the hydrographic maps. All surveys were completed at low annual water levels as referenced to nearby Mekong River Commission streamflow-gaging stations. Riverbed elevations surveyed ranged from 24.08 m below to 1.54 m above Ha Tien 1960.

Phnom Penh↗

USGS2013

Hydrographic surveys of the Missouri and Yellowstone Rivers at selected bridges and through Bismarck, North Dakota, during the 2011 flood

The U.S. Geological Survey (USGS), in cooperation with the North Dakota Department of Transportation and the North Dakota State Water Commission, completed hydrographic surveys at six Missouri River bridges and one Yellowstone River bridge during the 2011 flood of the Missouri River system. Bridges surveyed are located near the cities of Cartwright, Buford, Williston, Washburn, and Bismarck, N. Dak. The river in the vicinity of the bridges and the channel through the city of Bismarck, N. Dak., were surveyed. The hydrographic surveys were conducted using a high-resolution multibeam echosounder (MBES), the RESON SeaBat TM 7125, during June 6–9 and June 28–July 9, 2011. The surveyed area at each bridge site extended 820 feet upstream from the bridge to 820 feet downstream from the bridge. The surveyed reach through Bismarck consisted of 18 miles of the main channel wherever depth was sufficient. Results from these emergency surveys aided the North Dakota Department of Transportation in evaluating the structural integrity of the bridges during high-flow conditions. In addition, the sustained high flows made feasible the surveying of a large section of the normally shallow channel with the MBES. In general, results from sequential bridge surveys showed that as discharge increased between the first and second surveys at a given site, there was a general trend of channel scour. Locally, complex responses of scour in some areas and deposition in other areas of the channel were identified. Similarly, scour around bridge piers also showed complex responses to the increase in flow between the two surveys. Results for the survey area of the river channel through Bismarck show that, in general, scour occurred around river structures or where the river has tight bends and channel narrowing. The data collected during the surveys are provided electronically in two different file formats: comma delimited text and CARIS Spatial Archive TM (CSAR TM ) format.

North Dakota↗

USGS2012

Simulation of streamflow, evapotranspiration, and groundwater recharge in the middle Nueces River watershed, south Texas, 1961-2008

The U.S. Geological Survey—in cooperation with the U.S. Army Corps of Engineers, Fort Worth District; City of Corpus Christi; Guadalupe–Blanco River Authority; San Antonio River Authority; and San Antonio Water System— configured, calibrated, and tested a watershed model for a study area consisting of about 7,726 square miles of the middle Nueces River watershed in south Texas. The purpose of the model is to contribute to the understanding of watershed processes and hydrologic conditions in the middle Nueces River watershed. The model simulates streamflow, evapotranspiration, and groundwater recharge by using a numerical representation of physical characteristics of the landscape and meteorological and streamflow data. Model simulations of streamflow, evapotranspiration, and groundwater recharge were performed for various periods of record depending upon available gaged data for input and comparison, starting as early as 1961. Because of the large size of the study area, the middle Nueces River watershed was divided into eight subwatersheds, and separate Hydrological Simulation Program—FORTRAN models were developed for each subwatershed. Simulation of the overall study area involved running simulations in downstream order. Output from the model was summarized by subwatershed, point locations, stream and reservoir reaches, and the Carrizo– Wilcox aquifer outcrop area. Four long-term U.S. Geological Survey streamflow-gaging stations were used for streamflow model calibration and testing with data from 1990 to 2008. Monthly evaporation estimates from 2001 to 2008 and waterlevel data from 1961 to 2008 at Lake Corpus Christi also were used for model calibration. Additionally, evapotranspiration data for 2006–8 from a U.S. Geological Survey meteorological station in Medina County were used for calibration. Streamflow calibrations were considered poor to very good. The 2000–8 calibration results were characterized as good to very good for total flow volumes and for the volume of the highest 10 percent of daily flows. Calibration results for streamflow volumes of the lowest 50 percent of daily flows were considered poor. The daily streamflow calibration at U.S. Geological Survey streamflow-gaging station 08210000 Nueces River near Three Rivers, Tex., had the lowest (best) root mean square error, and U.S. Geological Survey streamflow-gaging station 08194500 Nueces River near Tilden, Tex., had the highest root mean square error expressed as a percentage of the mean flow rate. The mean daily reservoir volume during 1961–2008 was 182,000 acre-feet. Simulated mean daily reservoir volume was within 9 percent of this computed volume. Selected results of the model include streamflow yields for the subwatersheds and water-balance information for the Carrizo–Wilcox aquifer outcrop area. For the entire model domain, the area-weighted mean streamflow yield from 1961 to 2008 was 1.12 inches/year. The mean annual rainfall on the outcrop area during the 1961–2008 simulation period was 21.7 inches. Of this rainfall, an annual mean of 20.1 inches (about 93 percent) was simulated as evapotranspiration, 1.2 inches (about 6 percent) was simulated as groundwater recharge, and 0.5 inches (about 2 percent) was simulated as surface runoff.

Texas↗

USGS2009

Evapotranspiration Rates of Riparian Forests, Platte River, Nebraska, 2002-06

Evapotranspiration (ET) in riparian areas is a poorly understood component of the regional water balance in the Platte River Basin, where competing demands have resulted in water shortages in the ground-water/surface-water system. From April 2002 through March 2006, the U.S. Geological Survey, Nebraska Platte River Cooperative Hydrology Study Group, and Central Platte Natural Resources District conducted a micrometeorological study of water and energy balances at two sites in central Nebraska near Odessa and Gothenburg to improve understanding of ET rates and factors affecting them in Platte River riparian forests. A secondary objective of the study was to constrain estimates of ground-water use by riparian vegetation to satisfy ET consumptive demands, a useful input to regional ground-water flow models. Both study sites are located on large islands within the Platte River characterized by a cottonwood-dominated forest canopy on primarily sandy alluvium. Although both sites are typical of riparian forests along the Platte River in Nebraska, the Odessa understory is dominated by deciduous shrubs, whereas the Gothenburg understory is dominated by eastern redcedars. Additionally, seasonal ground-water levels fluctuated more at Odessa than at Gothenburg. The study period of April 2002 through March 2006 encompassed precipitation conditions ranging from dry to wet. This study characterized the components of the water balance in the riparian zone of each site. ET was evaluated from eddy-covariance sensors installed on towers above the forest canopy at a height of 26.1 meters. Precipitation was measured both above and below the forest canopy. A series of sensors measured soil-moisture availability within the unsaturated zone in two different vertical profiles at each site. Changes in ground-water altitude were evaluated from piezometers. The areal footprint represented in the water balance extended up to 800 meters from each tower. During the study, ET was less variable than precipitation. Annual ET fluctuated about 7 percent from the 4-year mean, ranging from about 514 to 586 millimeters per year (551 on average) at the Odessa site and 535 to 616 millimeters per year (575 on average) at the Gothenburg site. Conversely, annual precipitation fluctuated by about 35 percent from the 4-year mean, ranging from 429 to 844 millimeters per year at Odessa and 359 to 791 millimeters per year at Gothenburg. Of this precipitation, 14 to 15 percent was intercepted by the forest canopy before it could infiltrate into the soil. For the 4-year period, annual ground-water recharge from the riparian measurement zone averaged 76 and 13 millimeters at Odessa and Gothenburg, respectively, to satisfy the water balance at each site. This indicates that, from an annual perspective, ground-water reductions caused by ET may be minimal. This effect varied somewhat and primarily was affected by fluctuations in precipitation. Ground-water discharge occurred during the driest study year (2002), whereas ground-water recharge occurred from 2003 to 2005. These results do not exclude ground water as an important source of water to riparian vegetation - especially to phreatophytes that have the capability of directly using water from the saturated zone - during periods of high ET in the summer, particularly during periods of lower than normal precipitation. However, the calculations indicate that, on an annual (or longer) net-flux basis, ground-water use by riparian forests is likely to be balanced by periods of recharge from excess precipitation at other times of the year. In contrast to more arid settings, where scientific literature indicates that ground water may supply a large fraction of the water used for ET by riparian vegetation, precipitation along the Platte River of Nebraska was great enough - and generally greater than ET - that most or all of the annual ET demand was satisfied by available precipitation. Crop coefficients developed for 15-

Scientific Investigations Report↗

USGS2009

Occurrence of Selected Organic Compounds in Groundwater Used for Public Supply in the Plio-Pleistocene Deposits in East-Central Nebraska and the Dawson and Denver Aquifers near Denver, Colorado, 2002-2004

The National Water-Quality Assessment Program of the U.S. Geological Survey has an ongoing Source Water-Quality Assessment program designed to characterize the quality of water in aquifers used as a source of drinking-water supply for some of the largest metropolitan areas in the Nation. In addition to the sampling of the source waters, sampling of finished or treated waters was done in the second year of local studies to evaluate if the organic compounds detected in the source waters also were present in the water supplied to the public. An evaluation of source-water quality used in selected groundwater-supplied public water systems in east-central Nebraska and in the south Denver metropolitan area of Colorado was completed during 2002 through 2004. Fifteen wells in the Plio-Pleistocene alluvial and glacial deposits in east-central Nebraska (the High Plains study) and 12 wells in the Dawson and Denver aquifers, south of Denver (the South Platte study), were sampled during the first year to obtain information on the occurrence and distribution of selected organic chemicals in the source waters. During the second year of the study, two wells in east-central Nebraska were resampled, along with the associated finished water derived from these wells, to determine if organic compounds detected in the source water also were present in the finished water. Selection of the second-phase sampling sites was based on detections of the most-frequently occurring organic compounds from the first-year Source Water-Quality Assessment study results. The second-year sampling also required that finished waters had undergone water-quality treatment processes before being distributed to the public. Sample results from the first year of sampling groundwater wells in east-central Nebraska show that the most-frequently detected organic compounds were the pesticide atrazine and its degradate, deethylatrazine (DEA, otherwise known as 2-chloro-4-isopropylamino-6-amino-s-triazine or CIAT), which were detected in 9 of the 15 wells (60 percent of the samples). The second most frequently detected organic compound was tetrachloroethylene, detected in 4 of the 15 wells (27 percent of the samples), followed by chloroform, trichloroethylene, and 2-hydroxyatrazine (2-hydroxy-4-isopropylamino-6-ethylamino-s-triazine, or OIET), present in 3 of the 15 wells (20 percent of the samples). The pesticide compounds deisopropylatrazine (2-chloro-6-ethylamino-4-amino-s-triazine, or CEAT), metolachlor, and simazine and the volatile organic compound cis-1,2-dichloroethylene were detected in 2 of the 15 wells, and the compounds diuron and 1,2-dichloroethane were detected in only 1 of the 15 wells during the first-year sampling. Most detections of these compounds were at or near the minimum reporting levels, and none were greater than their regulatory maximum contaminant level. There were few detections of organic compounds during the first year of sampling groundwater wells in the South Platte study area. The compounds atrazine, deethylatrazine, picloram, tetrachloroethylene, methyl-tert-butyl-ether (MTBE), tris(2-butoxyethyl)phosphate, and bromoform were detected only once in all the samples from the 12 wells. Most detections of these compounds were at or near the minimum reporting levels, and none were greater than their regulatory maximum contaminant level. Second-year sampling, which included the addition of paired source- and finished-water samples, was completed at two sites in the High Plains study area. Source-water samples from the second-year sampling had detections of atrazine and deethylatrazine; at one site deisopropylatrazine and chloroform also were detected. The finished-water samples, which represent the source water after blending with water from other wells and treatment, indicated a decrease in the concentrations of the pesticides at one site, whereas concentrations remained nearly constant at a second site. The trihalomethanes (THMs or disinfec

Scientific Investigations Report↗

USGS2009

Trends in streamflow characteristics of selected sites in the Elkhorn River, Salt Creek, and Lower Platte River Basins, Eastern Nebraska, 1928-2004, and evaluation of streamflows in relation to instream-flow criteria, 1953-2004

The Nebraska Department of Natural Resources approved instream-flow appropriations on the Platte River to maintain fish communities, whooping crane roost habitat, and wet meadows used by several wild bird species. In the lower Platte River region, the Nebraska Game and Parks Commission owns an appropriation filed to maintain streamflow for fish communities between the Platte River confluence with the Elkhorn River and the mouth of the Platte River. Because Elkhorn River flow is an integral part of the flow in the reach addressed by this appropriation, the Upper Elkhorn and Lower Elkhorn Natural Resources Districts are involved in overall management of anthropogenic effects on the availability of surface water for instream requirements. The Physical Habitat Simulation System (PHABSIM) and other estimation methodologies were used previously to determine instream requirements for Platte River biota, which led to the filing of five water appropriations applications with the Nebraska Department of Natural Resources in 1993 by the Nebraska Game and Parks Commission. One of these requested instream-flow appropriations of 3,700 cubic feet per second was for the reach from the Elkhorn River to the mouth of the Platte River. Four appropriations were granted with modifications in 1998, by the Nebraska Department of Natural Resources. Daily streamflow data for the periods of record were summarized for 17 streamflow-gaging stations in Nebraska to evaluate streamflow characteristics, including low-flow intervals for consecutive durations of 1, 3, 7, 14, 30, 60, and 183 days. Temporal trends in selected streamflow statistics were not adjusted for variability in precipitation. Results indicated significant positive temporal trends in annual flow for the period of record at eight streamflow-gaging stations - Platte River near Duncan (06774000), Platte River at North Bend (06796000), Elkhorn River at Neligh (06798500), Logan Creek near Uehling (06799500), Maple Creek near Nickerson (06800000), Elkhorn River at Waterloo (06800500), Salt Creek at Greenwood (06803555), and Platte River at Louisville (06805500). In general, sites in the Elkhorn River Basin upstream from Norfolk showed fewer significant trends than did sites downstream from Norfolk and sites in the Platte River and Salt Creek basins, where trends in low flows also were positive. Historical Platte River streamflow records for the streamflow-gaging station at Louisville, Nebraska, were used to determine the number of days per water year (Sept. 30 to Oct. 1) when flows failed to satisfy the minimum criteria of the instream-flow appropriation prior to its filing in 1993. Before 1993, the median number of days the criteria were not satisfied was about 120 days per water year. During 1993 through 2004, daily mean flows at Louisville, Nebraska, have failed to satisfy the criteria for 638 days total (median value equals 21.5 days per year). Most of these low-flow intervals occurred in summer through early fall. For water years 1953 through 2004, of the discrete intervals when flow was less that the criteria levels, 61 percent were 3 days or greater in duration, and 38 percent were 7 days or greater in duration. The median duration of intervals of flow less than the criteria levels was 4 consecutive days during 1953 through 2004.

Nebraska↗