U.S. Geological Survey 2010 vector digital data Lincoln, NE U.S. Geologcial Survey Dataset also called sir10-5149_FutDep http://water.usgs.gov/lookup/getspatial?sir10-5149_FutDep This data release includes a polygon shapefile of grid cells attributed with values representing the simulated base-flow, evapotranspiration, and groundwater-storage depletions as a percentage of hypothetical well pumpage for the 2006-2055 time period. Depletions were simulated by the Phase-Two Elkhorn-Loup Model (ELM), constructed using MODFLOW-2005 (Harbaugh, 2005) with the Groundwater Vistas, version 5, software (Environmental Simulations, Inc., 2009). Each polygon represents one model grid cell. All values are estimates and approximations. The Phase-Two ELM simulated the High Plains aquifer in north-central Nebraska from predevelopment (pre-1895) through 2055 (Stanton and others, 2010). The simulation was calibrated using an automated parameter-estimation method to optimize the fit of simulation outputs to three sets of calibration targets: estimated 1939 groundwater levels and base flows (representing pre-1940 conditions), 1945-through-2005 decadal groundwater-level changes, and 1940-through-2005 annual base flows. The calibrated simulation was used to estimate volumetric ratios of the reductions in base flow, evapotranspiration, and groundwater storage to the total volume of water pumped from a hypothetical well for a 50-year future time period. Ratios were then multiplied by 100 to obtain percentages. The 50-year period was selected because base-flow depletion percentages for 40- to 50-year periods are the basis of groundwater and surface-water management decisions in Nebraska. The purpose of this data set is to map the percentage of pumpage from a hypothetical well that causes reductions to base flow, evapotranspiration, and groundwater storage in the Elkhorn and Loup River Basins during the 2006 through 2055 period. This data set also was published to facilitate replicability of the Phase-Two Elkhorn-Loup Model. Irrigated agriculture is vital to the livelihood of communities in the Elkhorn and Loup River Basins in Nebraska, and groundwater is the largest source of water used to irrigate cropland. Concerns about the sustainability of groundwater and surface-water resources have prompted State and regional agencies to evaluate the cumulative effects of groundwater irrigation in this area. Thus, in 2006, the U.S. Geological Survey, the Nebraska Department of Natural Resources, the University of Nebraska's Conservation and Survey Division, and the Lewis and Clark, Lower Elkhorn, Lower Loup, Lower Niobrara, Lower Platte North, Middle Niobrara, Upper Elkhorn, and Upper Loup Natural Resources Districts agreed to cooperatively study the water resources of these basins and to develop the ELM. The initial part of that study, hereinafter referred to as "phase one", was a first step toward understanding long-term average conditions of the stream-aquifer system and developing strategies for management of hydrologically connected groundwater and surface-water supplies in the study area. Phase one, documented by Peterson and others (2008), mainly was limited to pre-existing data to develop a regional groundwater-flow simulation and predict the effects of groundwater irrigation on stream base flow in the Elkhorn and Loup River Basins. Continuation of the study into a second phase was part of a larger, ongoing effort to enhance the knowledge of hydrogeologic characteristics, improve the understanding of stream-aquifer interactions, and compile reliable data describing groundwater system budget components such as groundwater recharge, groundwater pumpage for irrigation, and groundwater discharge to evapotranspiration in the study area. The phase-two study included updates to the groundwater-flow simulation using newly collected data and supporting analyses completed in 2007 and 2008 and advanced simulation calibration methods. The newly collected data include revisions to the base-of-aquifer map based on test-hole drilling and surface and borehole geophysics (McGuire and Peterson, 2008), synoptic base-flow measurements along stream reaches (Peterson and Strauch, 2007), estimates of long-term recharge based on a runoff-recharge watershed model (Strauch and Linard, 2009), and geophysical mapping of resistivity patterns beneath canals (Teeple and others, 2009). In addition to improving the data used for the simulations, advanced parameter-estimation techniques were used for phase-two simulation calibration, providing a more robust calibration. Other enhancements to the simulations included refining the grid discretization, using time-variable estimates of recharge from precipitation, time-variable base-flow estimates, improved estimates of groundwater withdrawals for irrigation, and refined delineation of areas where groundwater was actively evapotranspired. For the phase-two study, a calibrated simulation described the stream-aquifer system from predevelopment through 2005, including predevelopment (pre-1895), early development (1895-1940), and historical development (1940 through 2005) conditions. The predevelopment-through-2005 simulation was calibrated using an automated parameter-estimation method to optimize the fit of simulated water levels and base flows to estimated 1939 groundwater levels and base flows (representing pre-1940 conditions), 1945- through-2005 decadal groundwater-level changes, and 1940-through-2005 annual base flows. The calibrated simulation was used to estimate the percentage of hypothetically pumped volumes that would cause corresponding base-flow, evapotranspiration, and groundwater-storage depletions over a 50-year future time period. Base-flow depletion percentages are of interest because they are used to guide the integrated management of surface water and groundwater in Nebraska. Mapped results of the base-flow depletion analysis conducted for most of the study area indicated that simulated pumpage of one additional hypothetical well over a future 50-year period generally would result in more than 80 percent of pumpage causing base-flow depletion when the well was located close to the stream, except in areas where base-flow depletions were partly offset by reduced groundwater discharge to evapotranspiration or reduced groundwater storage (lower water-table elevations). In many areas, base-flow depletion for the 50-year future period composed greater than 10 percent of the pumped water volume for a hypothetical well placed less than about 10 miles from the stream, though considerable variations existed because of the natural heterogeneity of the system represented by the simulation. For a few streams, future simulated base flows declined substantially. For several small streams, simulated base flows in 2055 were absent. No further base-flow depletion occurred once simulated base flow was absent; therefore, base-flow depletion as a percentage of the volume pumped over 50 years declined from the time the simulated stream went dry until the end of the analysis period. Additional base-flow depletion as a percentage of pumping would be expected if base flow was present through 2055. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in ArcGIS format, this metadata file may include some ArcGIS-specific terminology. 2006 2055 simulated period Complete None planned -101.997799 -97.299951 42.757139 40.770319 ISO 19115 Topic Category inlandWaters geoscientficInformation Water Resources Thesaurus, 3rd ed. streamflow depletion groundwater availability groundwater groundwater potential geohydrology groundwater irrigation groundwater management groundwater storage surface-groundwater relations evapotranspiration hydrologic models Geographic Names Information System (GNIS) Nebraska Elkhorn River Loup River Middle Loup River North Loup River South Loup River Calamus River Dismal River none Elkhorn-Loup Model area High Plains aquifer Ogallala aquifer none This shapefile was constructed from groundwater simulation results, and is only intended to illustrate these results. Not suitable for site-specific uses. U.S. Geological Survey Nebraska Water Science Center mailing and physical address

5231 S 19th St

Lincoln NE 68512 USA 402-328-4100 http://water.usgs.gov/GIS/browse/sir10-5149_FutDep.jpg Illlustration of data set jpg Prepared in cooperation with the Lewis and Clark, Lower Elkhorn, Lower Loup, Lower Platte North, Lower Niobrara, Middle Niobrara, Upper Elkhorn, and Upper Loup Natural Resources Districts. Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 9.3.1.3000 J.S. Stanton S.M. Peterson M.N. Fienen 2010 Scientific Investigations Report 2010-5149 Reston, Virginia U.S. Geological Survey http://pubs.usgs.gov/sir/2010/5149/ A.W. Harbaugh 2005 Techniques and Methods 6-A16 Reston, Virginia U.S. Geological Survey http://pubs.usgs.gov/tm/2005/tm6A16 Environmental Simulations, Inc. 2009 Software released August 24, 2009; accessed August 25, 2009 http://www.groundwatermodels.com S.M. Peterson J.S.Stanton A.T. Saunders J.R. Bradley 2008 Scientific Investigations Report 2008-5143 Reston, Virginia U.S. Geological Survey http://pubs.usgs.gov/sir/2008/5143/ V.L. McGuire S.M. Peterson 2008 Scientific Investigations Map 3042 Reston, Virginia U.S. Geological Survey 1 sheet, scale 1:100,000 http://pubs.usgs.gov/sim/3042 S.M. Peterson K.R. Strauch 2007 Data Series 332 Reston, Virginia U.S. Geological Survey http://pubs.usgs.gov/ds/332/ K.R. Strauch J.I. Linard 2009 Scientific Investigations Report 2009-5075 Reston, Virginia U.S. Geological Survey http://pubs.usgs.gov/sir/2009/5075/ A.P. Teeple J. Vrabel W.H. Kress J.C. Cannia 2009 Scientific Investigations Report 2009-5171 Reston, Virginia U.S. Geological Survey http://pubs.usgs.gov/sir/2009/5171/ Accuracy of attributes was verified by checking the attribute values against all calculated values from the utility program designed to calculate and manage the values. All calculations appeared accurate at time of publication. Estimated accuracy of the calculations is within 2 percent. Assumptions and uncertainties associated with the ELM contribute an unknown amount of error. Each polygon represents a model cell and contains values indicating the estimated percentage of hypothetical volumetric well pumpage causing depletions to stream base flow, evapotranspiration, and groundwater storage. All polygons were checked for closure errors. Values were checked to ensure they matched values in the utility program, were in proper format, and within acceptable ranges. The range of depletion values is 0.0 to 100.0 percent. When a well begins to pump water, the source of that water is initially from storage. As pumping continues, the 3-dimensional zone of effect of the pumping well can expand, potentially causing increased inflow to the aquifer (such as from streamflow) and decreased outflow from the aquifer (such as to evapotranspiration or stream base flow). Base-flow, evapotranspiration, and groundwater-storage depletions as a percentage of hypothetical pumpage were summed to verify that they did not exceed 100.0 percent. 4,973 grid cells were larger than 100.0 percent. The maximum value was 101.7 percent. Values greater than 100.0 percent are likely an outcome of compiling large amounts of rounded data. In addition, some depletion values near the edge of the ELM area could be affected by zero-flow boundary cells. The sum of base-flow, evapotranspiration, and groundwater-storage depletions near the edges or outside of the Elkhorn and Loup Basins will be smaller than 100.0 percent because pumpage causes depletion to features located outside of the Elkhorn and Loup Basins. The sum also can be less than 100.0 percent near fixed-head boundary cells if the boundary cells are supplying water to the hypothetical well. Depletion values were not reported where calculations indicated that fixed-head boundary cells supplied 10 percent or more of the hypothetical pumpage volume. This data set contains estimated base-flow, evapotranspiration, and groundwater-storage depletions caused by pumping a hypothetical well in 22,208 grid cells within the ELM area, during the 2006 through 2055 simulation period only. This data set was produced from one of several simulated outputs for the ELM area. The groundwater system in the ELM area is part of the High Plains Aquifer system. J.S. Stanton S.M. Peterson M.N. Fienen 2010 Scientific Investigations Report 2010-5149 Reston, Virginia U.S. Geological Survey http://pubs.usgs.gov/sir/2010/5149/ online 1895 2055 Range of dates corresponds to the simulation period documented in the publication SIR 2010-5149 Data set was constructed using results from simulations documented in the publication. This data set was derived from the Elkhorn-Loup groundwater model, described in the published SIR 2010-5149. The model uses a grid, 162 rows long and 248 columns wide, comprising more than 40,000 grid cells, each 1-mile by 1-mile in size. Each cell was given a unique identifier that was the combination of its row and column location. The active simulation area, which is smaller than the extent of the model domain, encompasses 29,707 square miles and includes areas with an estimated aquifer saturated thickness of at least 10 feet. Model properties were assigned to each active grid cell by using the unique identifier as the relational key. 2009 A "baseline" simulation was created for the 2006-through-2055 time period. The "baseline" simulation represented estimated future conditions without any changes to groundwater irrigated acres or pumpage after 2008. Simulated groundwater levels from the end of the calibration-period simulation (1940 through 2005) were used as initial groundwater levels in simulating 2006. Future pumpage and additional recharge applied to irrigated-cropland areas were estimated using 2005 land-use data and locations of irrigation wells registered with the Nebraska Department of Natural Resources during 2006, 2007, and 2008. Because future recharge from precipitation rates were unknown, recharge was held constant from 2006 through 2055 at the average 1940-through-2005 rates of recharge from precipitation, as determined during the calibration process. Base-flow, evapotranspiration, and groundwater-storage values from the baseline simulation were imported into an Access database (Microsoft, Redmond, Wash.). 2009 A "pumping-well" simulation was created for the 2006-through-2055 time period. One additional hypothetical well pumping at a continuous rate of 1 cubic foot per second from 2006 through 2055 was added to the baseline simulation. The simulation was run and the total base-flow, evapotranspiration, and groundwater-storage volumes during the simulation were recorded in an Access database. 2009 The reductions in base flow, evapotranspiration, and groundwater storage caused by the addition of one hypothetical pumping well were calculated in the Access database as the cumulative volumetric difference between the baseline simulation and the pumping-well simulation at the end of the 50-year period. 2009 The volumes of base-flow, evapotranspiration, and groundwater-storage reductions were divided by the volume pumped by the hypothetical well to calculate the depletions caused by that well. This task was performed in Access. 2009 Steps 3, 4, and 5 were repeated iteratively, one grid cell at a time, for 22,208 of the 29,707 active simulation grid cells. Each of 22,208 grid cells were used as the location of the hypothetical well. Depletion values were not reported for many grid cells along the edges of the study area because either they were outside of the Elkhorn or Loup Basins and base-flow depletion was less than 10 percent (7,499 cells) or depletion values were affected by fixed water-level boundary cells (297 grid cells). Depletion values are reported for 21,911 grid cells. 2009 Calculated depletion values in the Access database were joined to the polygon shapefile of model grid cell centers in ArcMap, using an attribute join on the unique cell identifier. 2009 Data were re-projected to Nebraska State Plane Coordinates, with units of feet. 2009 Vector G-polygon 21911 State Plane Coordinate System 1983 2600 40.000000 43.000000 -100.000000 39.833333 1640416.666667 0.000000 coordinate pair 0.0010000 0.0010000 survey feet North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 sir10-5149_FutDep Percentage of hypothetical well pumpage causing depletions to simulated base flow, evapotranspiration, and groundwater storage in the Elkhorn and Loup River Basins for 2006-55, for 1-mile square model grid cells U.S. Geological Survey FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. row Grid-cell row numbers locating the features in the model grid U.S. Geological Survey MODFLOW-2005 15 149 column Grid-cell column numbers locating the features in the model grid U.S. Geological Survey MODFLOW-2005 8 246 StrDep Base-flow depletion percentage for the 2006 through 2055 period caused by simulated pumpage of a hypothetical well in the respective model grid cell U.S. Geological Survey 0.0 100.0 percent ETDep Evapotranspiration depletion percentage for the 2006 through 2055 period caused by simulated pumpage of a hypothetical well in the respective model grid cell U.S. Geological Survey 0.0 92.1 percent StorDep Groundwater storage depletion percentage for the 2006 through 2055 period caused by simulated pumpage of a hypothetical well in the respective model grid cell U.S. Geological Survey 0.0 97.8 percent U.S. Geological Survey Ask USGS - Water Webserver Team mailing address

445 National Center

Reston VA 20192 USA 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+sir10-5149_FutDep Downloadable Data Although this data set has been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials. shapefile Polygon shapefile of future depletions in the ELM area .zip 2.842 http://water.usgs.gov/GIS/dsdl/sir10-5149_FutDep.zip None; this data set is provided by the U.S. Geological Survey as a public service. October 2010 unknown 20101027 U.S. Geological Survey Ask USGS - Water Webserver Team mailing address

445 National Center

Reston VA 20192 USA 1-888-275-8747 (1-888-ASK USGS) http://water.usgs.gov/user_feedback_form.html FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998