V.L. McGuire S.M. Peterson 2008 (Version 1.0, March 04, 2008) vector digital data Scientific Investigations Map SIM_3042 Reston, Va U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?sim3042_tw V.L. McGuire S.M. Peterson 2008 PDF document Scientific Investigations Map SIM 3042 Reston, Va U.S. Geological Survey http://pubs.usgs.gov/sim/3042/ The U.S. Geological Survey (USGS), in cooperation with the Lewis and Clark Natural Resources District (NRD), Lower Elkhorn NRD, Lower Loup NRD, Lower Platte North NRD, Lower Niobrara NRD, Middle Niobrara NRD, Upper Elkhorn NRD, and Upper Loup NRD, have agreed to cooperatively study water resources from prior to the beginning of irrigation development to 2005 in the Elkhorn-Loup Model (ELM) area using a ground-water-flow model. The ELM area covers approximately 30,800 square miles, and extends from the Niobrara River in the north to the Platte River in the south. The western boundary of the ELM area coincides with the western boundary of the Middle Niobrara, Twin Platte, and Upper Loup NRDs; the eastern boundary coincides with the approximate location of the westernmost extent of glacial till in eastern Nebraska. The initial ground-water-flow model was constructed with a single layer vertically to represent the aquifers of the Tertiary-age Ogallala Group and Quaternary-age alluvial deposits, with a uniform node spacing of 2 miles. The model will be calibrated to measured ground-water levels and estimated ground-water discharge to streams for the pre-ground-water development period (approximately 1940) and the simulation of the 1940-2005 period will be calibrated to measure ground-water level changes. The study results will assist Nebraska Department of Natural Resources and the NRDs in the ELM area to develop long-term strategies for managing hydrologically connected waters. This dataset is one of three geospatial datasets that together revise previously published maps of the configuration of the base of the principal aquifer and of the geologic units that form the base of the principal aquifer in the study area; the revisions to the base-of-aquifer altitude are based on currently available or reinterpreted geologic logs of test holes and selected registered wells. The principal aquifer is the High Plains aquifer except in the northeast part of the model area, where the principal aquifer is an unnamed alluvial aquifer. This dataset consists of the location of test holes and registered wells with information about the altitude of the base of the principal aquifer and the identity of the geologic unit that underlies the principal aquifer in the Elkhorn-Loup Model area, north-central Nebraska. The purpose of this data release is to make available the data used to construct the map of the base of aquifer and the map of geologic units that forms the base of aquifer in the Elkhorn-Loup Model area, north-central Nebraska. The dataset was produced in support of the Elkhorn-Loup Model. 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 dataset in nonproprietary form, as well as in ArcGIS format, this metadata file may include some ArcGIS-specific terminology. 2008 publication date Complete None planned -102.105322 -97.291242 42.904199 40.613928 None USGS High Plains aquifer Elkhorn-Loup Model Area aquifer base Ogallala aquifer ISO 19115 Topic Category inlandWaters geoscientificInformation Water Resources Thesaurus Aquifer characteristics Geohydrologic units None Nebraska None Brule Formation White River Group Upper Cretaceous Lower Tertiary Chadron Formation Pierre Shale Niobrara Formation none none McGuire, V.L. U.S. Geological Survey Hydrologist mailing address

5231 South 19th Street

Lincoln NE 68512 USA (402)328-4100 (402)328-4101 Webmaster@ne20dnelnc.cr.usgs.gov http://water.usgs.gov/GIS/browse/sim3042_tw.gif Illustration of dataset GIF This dataset was prepared in cooperation with the Lewis and Clark Natural Resources District (NRD), Lower Elkhorn NRD, Lower Loup NRD, Lower Platte North NRD, Lower Niobrara NRD, Middle Niobrara NRD, Upper Elkhorn NRD, and Upper Loup NRD. The dataset was prepared using published datasets and reports by the Cooperative Hydrology Study, Nebraska Oil and Gas Commission, University of Nebraska-Lincoln, Conservation and Survey Division, and the U.S. Geological Survey and unpublished data in the test-hole files assembled by J.F. Ayers and maintained by the University of Nebraska-Lincoln, Conservation and Survey Division. E.D. Gutentag, U.S. Geological Survey (retired); J.B. Swinehart, University of Nebraska-Lincoln, Conservation and Survey Division; J.C. Cannia, U.S. Geological Survey; R.F. Diffendal, Jr., University of Nebraska-Lincoln, Conservation and Survey Division; and S.O. Lackey, University of Nebraska-Lincoln, Conservation and Survey Division, reviewed the report and provided valuable feedback. In addition, J.W. Goeke, University of Nebraska-Lincoln, Conservation and Survey Division, provided assistance interpreting the unpublished test-hole information and R.M. Joeckel, University of Nebraska-Lincoln, Conservation and Survey Division, provided assistance with the test-hole data. Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog 9.3.0.1770 Steele, G.V. Sibray, S. S. Quandt, K.A. 2007 U.S. Geological Survey Scientific Investigations Report SIR 2007-5086 Reston, Va U.S. Geological Survey http://pubs.usgs.gov/sir/2007/5086 McGuire, V.L. Peterson, S.M. 2009 vector digital data U.S. Geological Survey Scientific Investigations Map 3042 Reston, Va U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?sim3042_gu McGuire, V.L. S.M. Peterson 2008 pdf document U.S. Geological Survey Scientific Investigations Map 3042 Reston, Va U.S. Geological Survey http://pubs.usgs.gov/sim/3042/ McGuire, V.L. Peterson, S.M. 2009 vector digital data U.S. Geological Survey Scientific Investigations Map 3042 Reston, Va U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?sim3042_ab McGuire, V.L. Peterson, S.M. 2008 pdf document U.S. Geological Survey Scientific Investigations Map 3042 Reston, Va U.S. Geological Survey http://pubs.usgs.gov/sim/3042/ The density of registered wells and test-holes data with data about the depth to the base of aquifer varies greatly across the map area. The location and information about the base of the princial aquifer for the test holes and registared wells were reviewed by geologists familiar with the area--E.D. Gutentag, U.S. Geological Survey (retired); J.B. Swinehart, University of Nebraska-Lincoln, Conservation and Survey Division; J.C. Cannia, U.S. Geological Survey; R.F. Diffendal, Jr., University of Nebraska-Lincoln, Conservation and Survey Division; and S.O. Lackey, University of Nebraska-Lincoln, Conservation and Survey Division. Their feedback was incorporated into the report and the map. A feature attribute table is present. The dataset includes only test holes and selected registered wells with base-of-aquifer information for the principal aquifer in the Elkhorn-Loup Model area, north-central Nebraska. The base-of-aquifer information is based on the stratigraphic information from the test-hole lithologic and borehole geophysical logs as interpreted by University of Nebraska-Lincoln, Conservation and Survey Division geologists and by the authors. The accuracy of the horizontal postion of the test holes and registared wells varies. One of several methods were used to determine horizonal position, including interpreting from U.S. Geological Survey topographic quadranges, doing a survey, and using a GPS device. The test holes or registered wells that the authors assumed had a more uncertain horizontal position were those with a reported surface altitude that varied by more than 25 feet from the surface altitude derived from the 10-meter digital elevation model. 10 feet An approximate accuracy value; the actual accuracy varies. The accuracy of the vertical postion of the test holes and registared wells, that is the land-surface altitude, varies because one of several methods were used to estimate vertical position, including interpreting from U.S. Geological Survey topographic quadranges, doing a survey, and using a digital elevation model. The vertical position of the test holes or registered wells was assumed to be accurate within 5 feet, which is generally one-half of the land-surface contour interval on a U.S. Geological Survye topographic map. 5 feet An approximate accuracy value; the actual accuracy varies. Bentall, Ray Dreeszen, V.H Elder, J.A. Jess, J.M. Souders, V.L. Birkel, W.H. Braun, K.J. Ellis, M.J. Engel, G.B. Engberg, R.A. Shaffer, F.B. 1971 document Resource Atlas No. 1 Lincoln, Ne University of Nebraska-Lincoln, Conservation and Survey Division 1000000 paper unknown publication date Bentall and others, 1971 Geologic units in lower Elkhorn River Basin, Nebraska Burchett, R.R. Reed, E.C. Dreeszen, V.H. Prichard, G.E. 1975 raster digital data U.S. Geological Survey Miscellaneous Investigations Series Map I-905 Reston, Va U.S. Geological Survey http://ngmdb.usgs.gov/Prodesc/proddesc_9487.htm 250000 online and paper unknown publication date Map I-905 Extent of bedrock units in the Fremont 1-degree by 2-degree quadrangle. Burchett, R.R. Dreeszen, V.H. Souders, V.L. Prichard, G.E. 1988 raster digital data U.S. Geological Survey Miscellaneous Investigations Series, Map I-1879 Reston, Va U.S. Geological Survey http://ngmdb.usgs.gov/Prodesc/proddesc_9965.htm 250000 online and paper unknown publication date Map I-1879 Extent and altitude of bedrock units in the Nebraska part of the Sioux City 1-degree by 2-degree quadrangle. COHYST 2006 vector digital data Lincoln, Ne Cooperative Hydrology Study http://cohyst.dnr.ne.gov/cohyst_preliminarydata.html online unknown publication date Base of aquifer altitude, COHYST (2006) Configuration of the base of aquifer in the Nebraska Cooperative Hydrology Study (COHYST) area COHYST 2006 tabular digital data Lincoln, Ne Cooperative Hydrology Study Cooperative Hydrology Study data accessed November 2006 http://cohyst.dnr.ne.gov/cohyst_preliminarydata.html online unknown publication date Testholes and wells, COHYST (2006) Wells and testholes used to map the altitude of bedrock and configuration of the base of aquifer in the Nebraska Cooperative Hydrology Study (COHYST) area. Diffendal, Jr., R.F 1991 raster digital data U.S. Geological Survey Miscellaneous Investigations Series Map I-2277 Reston, Va U.S. Geological Survey http://ngmdb.usgs.gov/Prodesc/proddesc_10209.htm 250000 online and paper unknown publication date Map I-2277 Extent and altitude of bedrock units in the North Platte 1-degree by 2-degree quadrangle. Dreeszen, V.H. Reed, E.C. Burchett, R.R. Prichard, G.E. 1973 raster digital data U.S. Geological Survey Miscellaneous Investigations Series Map I-819 Reston, Va U.S. Geological Survey http://ngmdb.usgs.gov/Prodesc/proddesc_9648.htm 250000 online and paper unknown publication date Map I-819 Extent of bedrock units in the Grand Island 1-degree by 2-degree quadrangle. Eversoll, D.A. Dreeszen, V.H. Burchett, R.R. Prichard, G.E. 1988 raster digital data U.S. Geological Survey Miscellaneous Investigations Series Map I-1878 Reston, Va U.S. Geological Survey http://ngmdb.usgs.gov/Prodesc/proddesc_9964.htm 250000 online and paper unknown publication date Map I-1878 Extent of bedrock units in the McCook 1-degree by 2-degree quadrangle. Nebraska Department of Natural Resources 2007 vector digital data Lincoln, Ne Nebraska Department of Natural Resources Nebraska Department of Natural Resources data accessed in July 2007 http://dnrdata.dnr.ne.gov/wellssql/ online unknown publication date Registered wells database, Nebraska If a registered well was drilled to or below the base of the aquifer and the geologic log is sufficiently descriptive, the source provided the depth to the base of aquifer at the well location. Nebraska Oil and Gas Commission 2007 tabular digital data Current database of oil and gas wells Issue identification, not specified Sidney, Ne Nebraska Oil and Gas Commission Nebraska Oil and Gas Commission data accessed May 2007 http://nogcc.ne.gov/ online unknown publication date Nebraska Oil and Gas Commission data Altitude of bedrock units at well locations. Souders, V.L. 2000 vector digital data U.S. Geological Survey Miscellaneous Investigations Series Map I-2725 Reston, Va U.S. Geological Survey http://ngmdb.usgs.gov/Prodesc/proddesc_28120.htm 250000 online and paper unknown publication date Map I-2725 Extent and altitude of bedrock units in the Broken Bow 1-degree by 2-degree quadrangle. Swinehart, J.B. Souders, V.L. DeGraw, H.M. Diffendal, Jr., R.F. 1985 document Flores, R.M. Kaplan, S.S., eds. 1985 document Denver, Co Rocky Mountain Section, Society of Economic Paleontologist and Mineralogists 1250000 paper unknown publication date Cenozoic paleogeography of western Nebraska This source contains a configuration map of the base of the Ogallala Group and of the presence of the Ogallala Group in western Nebraska. This source was used to estimate drainage patterns in the current base-of-aquifer map and to identify areas where the Ogallala Group was not present. Swinehart, J.B. Diffendal, Jr., R.F. 1998 document Resource Atlas No. 5b, p. 29-42 Bleed, A.S. Flowerday, C.A., eds. 1998 document Resource Atlas No. 5b Lincoln, Ne University of Nebraska-Lincoln, Conservation and Survey Division 1000000 paper unknown publication date Geology of the pre-dune strata This source contains a configuration map of the base of the Ogallala Group and of the presence of the Ogallala Group in the Sand Hills area in Nebraska. This source was used to estimate drainage patterns in the current base-of-aquifer contour map and to identify areas where the Ogallala Group was not present. University of Nebraska-Lincoln, Conservation and Survey Division 1979 vector digital data Lincoln, Ne University of Nebraska-Lincoln, Conservation and Survey Division http://snr.unl.edu/Data/NebrGISwater.asp#ConfigurationoftheBase1979 250000 online unknown publication date Base of principal aquifer, Nebraska (CSD 1979) A map of the base of the principal aquifer in Nebraska, except in areas where a principal aquifer was not present. The authors of this map likely considered the Ogallala Formation to be the base of aquifer, where the the Ogallala Formation is present. University of Nebraska-Lincoln, Conservation and Survey Division 2007 tabular digital data Lincoln, Ne University of Nebraska-Lincoln, Conservation and Survey Division University of Nebraska-Lincoln, Conservation and Survey Division data accessed June 2007. http://csd.unl.edu/general/testholes.asp online unknown publication date Nebraska test-hole database Altitude of bedrock units at test-hole locations. U.S. Geological Survey and Nebraska Department of Natural Resources 1998 Series name, not specified Issue identification, not specified Lincoln, Ne U.S. Geological Survey and Nebraska Department of Natural Resources Data accessed June 2006 http://dnr.ne.gov/databank/dem.html 24000 online unknown publication date DEM 10-m This source was used to estimate the land surface altitude at each well and test-hole location. The published and unpublished stratigraphic data were assembled from test-holes and wells records maintained by the Cooperative Hydrology Study; Nebraska Oil and Gas Commission; and the University of Nebraska-Lincoln, Conservation and Survey Division. The Arc Workstation GRID command, Latticespot, was used to estimate the land-surface altitude at each test hole and at selected registered wells on the basis of the DEM-10m surface. The source of the original land-surface altitude in the test-hole data was either a digital elevation model of unspecified resolution, the test-hole log, or map-interpreted from a U.S. Geological Survey 7.5-minute topographic quadrangle. Because of the varied sources for land surface altitude for the test holes, the authors decided to estimate land-surface altitude using the referenced 10-meter digital elevation model. If the estimated land-surface altitude for a test hole differed by more than 25 feet from the published land-surface altitude, it was assumed that the latitude and longitude of the test hole were uncertain, and the published land-surface altitude was used for this test hole. 2007 For each test hole without published stratigraphic information, the authors reviewed the test-hole records at the University of Nebraska-Lincoln, Conservation and Survey Division, to attempt to determine the altitude of the top of the applicable geologic unit. If the altitude of the top of the applicable geologic unit was not obvious from the lithologic description or from the borehole geophysical logs, the authors noted up to two altitudes, which were based on the borehole geophysical logs, for the possible top of the applicable geologic unit. The two altitudes of the possible top of the applicable geologic unit at the test hole in question were visually compared with the altitude of the top of that same geologic unit at surrounding test holes to resolve the altitude of the top of the applicable geologic unit for the test hole in question. 2007 Published contours of the base of the Ogallala Group, the top of the Brule Formation, the top of the Pierre Shale, the top of the Niobrara Formation, and published base-of-aquifer contours were assembled. The Cooperative Hydrology Study's base-of-aquifer contours in the area were used as the initial base-of-aquifer contours for that area. The base-of-aquifer altitude was calculated as feet above the NGVD29 datum. 2007 The Arc Workstation GRID command, Topogrid was used to initially contour the base of aquifer using (1) the available test-hole and registered well data and (2) the COHYST base-of-aquifer contours. The following were input to TOPOGRID: TOPOGRID test5 500 ENFORCE ON DATATYPE spot MARGIN 0.0 ITERATIONS 30 TOLERANCES 2.5 1.0 0.0 XYZLIMITS # # # # # # point P:\C8T02\GIS\AQBASE\topo_suekpp AQB_ELEV point P:\C8T02\GIS\AQBASE\topo_TH2BAS AQB_ELEV point P:\C8T02\GIS\AQBASE\topo_DeepKp AQB_ELEV point P:\C8T02\GIS\AQBASE\topo_DeepBr AQB_ELEV contour P:\C8T02\GIS\AQBASE\pubbase4topo AQB_ELEV BOUNDARY p:\c8t02\gis\aqbase\buff20mi_p END Made a contour map of the base of aquifer. grid setcell 500 aqbase5 = contour (test5,interval,100,1200) q Defined the projection for the output contour map. projectcopy cover COV4PROJCP cover aqbase5 2007 The base-of-aquifer contours were plotted along with the test-hole and registered well data (test-hole or registered well identification number, land surface altitude, geologic unit that forms the base of aquifer, and base-of-aquifer altitude). The base-of-aquifer contours were manually modified using the Arc/Info ArcEdit program by interpreting the base-of-aquifer data using published paleodrainages from contour maps of the base of the Ogallala Group, top of the Brule Formation, top of the Pierre Shale, and top of the Niobrara Formation (Benthall and others, 1971; Map I-1879; Testholes and wells, COHYST, 2006; Map I-2277; Map I-1878; Map I-2725; Cenozoic paleogeography of western Nebraska; Geology of the pre-dune strata). The source data for test holes and selected registered wells were re-examined when the base-of-aquifer altitude or designation for the geologic unit that forms the base of aquifer was anomalous. When needed, corrected values for the base-of-aquifer altitude or geologic unit that forms the base of aquifer were assigned. 2007 The test holes and wells that support the base-of-aquifer contours and the designations of the geologic unit that forms the base of the aquifer were reviewed by geologists familiar with the area--E.D. Gutentag, U.S. Geological Survey (retired); J.B. Swinehart, University of Nebraska-Lincoln, Conservation and Survey Division; J.C. Cannia, U.S. Geological Survey; R.F. Diffendal, Jr., University of Nebraska-Lincoln, Conservation and Survey Division; and S.O. Lackey, University of Nebraska-Lincoln, Conservation and Survey Division. Their feedback was incorporated into the report and the map. Only the test holes and wells used in for the map of the base of aquifer were included in this dataset. 2007 Vector Entity point 1024 State Plane Coordinate System 1983 2600 40.000000 43.000000 -100.000000 39.833333 1640416.666667 0.000000 coordinate pair 10 10 survey feet North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 National Geodetic Vertical Datum of 1929 5 Feet Attribute values sim3042_tw.pat Point-feature attribute table for test holes and registered wells containing information about the altitude of the base of the principal aquifer and the geologic unit that forms the base of the principal aquifer data obtained from the Cooperative Hydrology Study, 2007; Nebraska Oil and Gas Commission, 2007; Nebraska Department of Natural Resourcses, 2007; and University of Nebraska-Lincoln, Conservation and Survey Division, 2007. FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. AREA Area of feature in internal units squared. ESRI Area is always zero for point coverages. Values are automatically generated. PERIMETER Perimeter of feature in internal units. ESRI Perimeter is always zero for point coverages. Values are automatically generated. SIM3042_TW# Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. SIM3042_TW-ID User-defined feature number. ESRI Sequential unique whole numbers that were automatically generated. AQBPTSRC Source of information about the test hole or registered well USGS COHYST Well information from the Cooperative Hydrology Study (2007) USGS CsdOthTh Testhole information from unpublished records on file at the University of Nebraska, Conservation and Survey Division USGS CsdThStrat Testhole information from the test-hole database (University of Nebraska, Conservation and Survey Division, 2007) USGS HoltCo Registered well information interpreted by S.O. Lackey (written commun., University of Nebraska, Conservation and Survey Division, 2007) from the registered wells database (Nebraska Department of Natural Resources, 2007) USGS NEOGC Well information from the Nebraska Oil and Gas Commission (2007) USGS REGNUM If assigned, the Nebraska well-registration number Nebraska Department of Natural Resources, 2007 Blank G-132773 THNUM If assigned, the test-hole number University of Nebraska-Lincoln, Conservation and Survey Division (2007) Blank USBR-9E-65 API_WELLNO If assigned, the American Petroleum Institute well number Nebraska Oil and Gas Commission, 2007 Blank 26117210070000 LSD Land-surface altitude, in feet above the vertical datum See LSD_SRC attribute 1450 3835 feet VDATUM Vertical datum, associated with the land-surface altitude USGS NGVD29 The vertical datum is the National Geodetic Vertical Datum, 1929 USGS LSD_SRC Source of land-surface altitude USGS DEM For test holes located within the 2 mile buffer around the Elkhorn-Loup Model Area, the test-hole surface altitude was derived from a digital elevation model (Nebraska test-hole database) USGS DEM10 For test holes located within the Elkhorn-Loup Model Area, the test-hole surface altitude was derived from the 10-meter digital elevation model (10-m DEM) USGS LOG For test holes located within the 2 mile buffer around the Elkhorn-Loup Model Area, the test-hole surface altitude was wrtten on the test-hole log sheet (Nebraska test-hole database and unpublished test-hole records on file at UNL-CSD) USGS MAP For test holes located within the 2 mile buffer around the Elkhorn-Loup Model Area, the test-hole surface altitude was determined using a topographic map (Nebraska test-hole database) USGS NEOGC For oil and gas wells, the well's surface altitude as stored in the Nebraska Oil and Gas Commission database USGS TOPO For registered wells in Holt county, the land-surface altitude initially was obtained manually using a topographic map. This altitude value was ultimately retained if it differed by more than 25 feet from the land-surface altitude derived from the 10-meter digital elevation model (S.O. Lackey, University of Nebraska-Lincoln, Conservation and Survey Division (written commun., 2007) and 10-m DEM). USGS COHYS For registered wells in the Cooperative Hydrology Study (COHYST) area, the land-surface altitude was obtained from the COHYST data (Testholes and wells, 2006) USGS LAND2AB Depth to base of aquifer from land surface, in feet Cooperative Hydrology Study, 2007; Nebraska Department of Natural Resources, 2007; and University of Nebraska-Lincoln, Conservation and Survey Division, 2007 20 1120 feet AQB_ELEV Calculated altitude of the base of aquifer, in feet above vertical datum. The calculation is AQB_ELEV = LSD - LAND2AB. USGS 1289 3392 feet AQB_UNIT Geologic unit that forms the base of aquifer USGS T10Br The geologic unit that forms the base of aquifer is the Brule Formation. USGS T10Wr The geologic unit that forms the base of aquifer is the White River Group, which includes the Brule and Chadron Formations USGS T11Ch The geologic unit that forms the base of aquifer is the Chadron Formation. USGS T30UK The geologic unit that forms the base of aquifer is of upper Cretaceous age, which included the Pierre Shale, Niobrara Formation of the Colorado Group, and the Carlile Shale of the Colorado Group. USGS T31Kp The geologic unit that forms the base of aquifer is the Pierre Shale USGS T32Kn The geologic unit that forms the base of aquifer is the Niobrara Formation of the Colorado Group USGS T33Kc The geologic unit that forms the base of aquifer is the Carlile Shale of the Colorado Group USGS LOCAL If available, USGS and University of Nebraska, Conservation and Survey Division's local well-number system of the test hole or well. This local well-number system is based on the Public Land Survey System (PLSS) for Nebraska. See figure 6 in U.S. Geological Survey Scientific Investigations Report 2007-5086, availble on the Web at http://pubs.usgs.gov/sir/2007/5086/pdf/SIR2007-5086.pdf, for an illustration of the local well-number system. An example of a local code is 34N 15W 27ABCD, which is township 34 North, range 15 West, section 27, in quarter ABCD, where A is the northeast quarter, B is the northwest quarter of the northeast quarter, C is the southwest quarter of the northwest quarter of the northeast quarter, and D is the southeast quarter of the southwest quarter of the northwest quarter of the northeast quarter. USGS Encoded as [ttN rrW ssQqqq], where the components of the local well-number system code are township number [tt] north of the base line, township direction [N] from the base line, range number [rr] west of the 6th principal meridan, range direction [W] from the principal meridan, section number [ss] from 1 to 36 within a standard 36-square-mile township, and appropriate alpha codes for quarter section [Q] and its subdivisions [qqq]. The local code indexes to the physical planimetric location of the well or test hole, referenced to the PLSS for Nebraska For test holes, the University of Nebraska-Lincoln, Conservation and Survey Division, and, for registared wells, modified by USGS from Nebraska Department of Natural Resources data COUNTY County where the test hole or well is located USGS County name County where the test hole or well is located USGS BASE_GU Geologic unit that forms the base of aquifer in the Elkhorn-Loup Model Area USGS LT Geologic unit of lower Tertiary age USGS UK Geologic unit of upper Cretaceous age USGS DLAT Latitude of test hole or well in decimal degrees, datum is NAD83 USGS 40.64112 42.89994 decimal degrees DLONG Longitude of test hole or well in decimal degrees, datum is NAD83 USGS -102.05798 -97.32943 HDATUM Horizontal datum USGS NAD83 North American Datum of 1983 USGS U.S. Geological Survey Ask USGS - Water Webserver Team mailing address

507 National Center

Reston Va 20192 USA 1-888-275-8747 (1-888-ASK-USGS) http://water.usgs.gov/user_feedback_form.html Contact via email Downloadable Data Although this dataset 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. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. ARCE Spatial and attribute information zipped 0.1 MBytes http://water.usgs.gov/GIS/dsdl/sim3042tw_e00.zip Shape Shape File zipped 0.1 MBytes http://water.usgs.gov/GIS/dsdl/sim3042tw_shp.zip None; this dataset is provided by USGS as a public service. 20090603 U.S. Geological Survey Ask USGS - Water Webserver Team mailing

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Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+sim3042tw FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 None Unclassified Not applicable