McGuire, V.L. Peterson, S.M. 2008 (Version 1.0, March 04, 2008) 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 V.L. McGuire 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/ 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. TThis 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 contour lines of the base-of-aquifer altitude above the vertical datum (National Geodetic Vertical Datum of 1929). The purpose of this dataset is to serve as the lower aquifer boundary in the ground-water-flow model of the Elkhorn-Loup Model area, north-central Nebraska. This dataset is not intended to be used at scales larger than 1:350,000. The density of registered wells and test holes with data about the depth to the base of aquifer varies greatly across the map area. The accuracy of the base-of-aquifer contours in a given area is related directly to the density distribution and availability of registered well and test-hole data with information about the depth to the base of aquifer in that area. The purpose of this dataset is to serve as the lower aquifer boundary in the ground-water-flow model of the Elkhorn-Loup Model area, north-central Nebraska. 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 -102.127551 -97.275007 42.924407 40.599343 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 This dataset is not intended to be used at scales larger than 1:350,000. 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_ab.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 Pettijohn, R.A. Chen, H.H. 1983 document Open-File Report 82-502 Reston, Va U.S. Geological Survey http://pubs.er.usgs.gov/usgspubs/ofr/ofr82502 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_tw 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_gu 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 mapped base-of-aquifer altitude contours for the principal aquifer in the Elkhorn-Loup Model area were visually compared to published reports, where available. See references listed in source information. The designations of the altitude of 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. Chain-node topology are present. Contour lines were visually inspected for topological errors (contours that cross or touch adjacent contours). No errors were detected. The Arc Workstation labelerror command and U.S. Geological Survey's checkdata.aml program (2005, version 1.4.5) were used to verify that each polygon had one and only one label. No errors were detected. The U.S. Geological Survey's checkdata.aml program reported a number of arcs with dangling nodes; this condition was expected and is not an error. The base-of-aquifer altitude contours for the principal aquifer in the Elkhorn-Loup Model area are based on the stratigraphic information from the test-hole lithologic and borehole geophysical logs interpreted by University of Nebraska-Lincoln, Conservation and Survey Division geologists and by the authors. These contours are approximate, especially in areas where there are few test holes with data about the depth to the base of principal aquifer. The geographic location of the test holes are estimated to be within 10 feet of the actual location. The geographic location of the registered wells are estimated to be within 10 to 100 feet of the actual location. All base-of-aquifer contours honor the altitude of the points (wells or test holes) with such altitude data. The density of registered wells and test holes with data about the depth to the base of aquifer varies greatly across the map area. The accuracy of the base-of-aquifer contours in a given area is related directly to the density distribution and availability of registered well and test-hole data with information about the depth to the base of aquifer in that area. The accuracy of the base of aquifer altitude at the location of a given test hole is estimated to be within 10 feet. The accuracy of the base of aquifer altitude at the location of a given registered well is estimated to be within 15 feet. All base of aquifer contours honor the altitude of the base of aquifer at the test-hole or registered well location. If the base of aquifer data for a given test hole or registered well was substantially different that the base of aquifer data in surrounding wells, the given test hole or registered well was dropped from the set of wells used for the base of aquifer map. 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 Benthall 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 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 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 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 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 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 iJuly 2007 http://dnrdata.dnr.ne.gov/wellssql/ online unknown publication date Registered wells database, Nebraska If the registered well was drilled to or below the base of the aquifer and the geologic log is sufficiently descriptive, the source provides the depth to the base of the aquifer at the well location. Nebraska Oil and Gas Commission 2007 tabular digital data 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 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 Denver, Co Rocky Mountain Section, Society of Economic Paleontologists and Mineralogists Flores, R.M. Kaplan, S.S., eds. 1985 document Denver, Co Rocky Mountain Section, Society of Economic Paleontologists 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 Lincoln, Ne University of Nebraska--Lincoln, Conservation and Survey Division 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 Nebraska Department of Natural Resources 1998 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 10-m DEM This source was used to estimate the land-surface altitude at each test-hole location and at selected registered wells. The published and unpublished stratigraphic data for test holes and wells were assembled from 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 recalculate the land-surface altitude at each test hole and at selected registered wells from the 10-m DEM. The source of the original land-surface altitude in the test-hole data was a digital elevation model of unspecified resolution, the test-hole log, or interpreted by unspecified persons from a U.S. Geological Survey 7.5-minute topographic map. Because of the varied sources for land surface elevation for the test holes, the authors decided to recalculate land-surface altitude using the 10-m DEM. The recalculated land-surface altitude for five test holes varied by more than 25 feet from the published land-surface altitude. For these five test holes, it was assumed the latitude and longitude of the test hole were uncertain, and the published land-surface altitude was used for these five test hole. 2007 For each test hole without published stratigraphic information, the authors reviewed the paper test-hole files 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 generally were based on the borehole geophysical logs, for the possible top of the applicable geologic unit. The two possible altitudes of the top of the applicable geologic unit at the test hole in question were visually compared with the altitude of the top of the applicable geologic unit from 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 model surface of the base of aquifer using (1) the available test-hole and registered well data and (2) the COHYST base-of-aquifer contours. The following specifications 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 gridded base of the aquifer, using the following commands: grid setcell 500 aqbase5 = contour (test5,interval,100,1200) q Defined the projection for the output contour map, using:. 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 Workstation ArcEdit program. The manual modifications were based on interpreting the base-of-aquifer data in cross-reference with 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 geologic unit designation that forms the base of aquifer was anomalous and, if possible, corrected the base-of-aquifer altitude or geologic unit designation to agree with surrounding wells and test holes. Or, if the test-hole or registered well data does not support corrected values and the anomoly is substantial, the test hole or registered well was dropped from the data used to generate the base-of-aquifer altitude or geologic unit designation. Constructed a raster dataset of the base-of-aquifer configuration (using as inputs the current manually modified base-of-aquifer contours and the base-of-aquifer altitude data from test holes and selected registered wells), compared it with the land-surface-elevation surface created in process step #1 using the following Arc Workstation Grid commands: /* Step 1=============construct raster surface, as in process step #4 TOPOGRID aqb_grid 500 ENFORCE ON DATATYPE contour MARGIN 0.0 ITERATIONS 30 TOLERANCES 2.5 1.0 0.0 XYZLIMITS # # # # # # point P:\C8T02\GIS\AQBASE\topo_cohyst AQB_ELEV point P:\C8T02\GIS\AQBASE\topo_suekpp AQB_ELEV point P:\C8T02\GIS\AQBASE\topo_TH2BAS AQB_ELEV contour aqb_use contour BOUNDARY p:\c8t02\gis\aqbase\buff20mi_p END grid setcell 500 aqb_redraw = contour (aqb_grid,interval,100,1200) projectcopy cover COV4PROJCP cover aqb_redraw /* Step 2a=============make a grid of diff betw aqbase & land surface /* grid mape aqb_grid; setcell 500 zdiff_ls_aq = (P:\C8T00\GIS\DEMS\DEM10_SPFT / 100) - aqb_grid /* Step 2b=============Construct polygons around the areas where aqbase is greater than land surface /* zdiff_ls_aq3 = setnull(zDIFF_LS_AQ > 0 , zDIFF_LS_AQ) zdiff_ls_aq3i = int(zdiff_ls_aq3) zdif_ls_aq3ip = gridpoly( zdiff_ls_aq3i, 250) /* Step 3=============Add an attribute to the polygon and set dissolve = 'y' for all polys additem zdif_ls_aq3ip.pat zdif_ls_aq3ip.pat dissolve 1 1 c build zdif_ls_aq3ip poly ae; display 9999 1; mape zdif_ls_aq3ip ; ec zdif_ls_aq3ip ; ef poly; drawe poly; sel all calculate dissolve = 'y' /* Step 4=============Dissolve all nested polygons where aqbase > LSE dissolve ZDIF_LS_AQ3IP dif_lsAQ3ipd dissolve poly /* Step 5=============Replace cells in the aqbase grid (aqb_grid) with DEM10 value (LSE( if aqbase is greater than land surface grid docell if (P:\C8T00\GIS\DEMS\DEM10_SPFT / 100 - aqb_grid < 0 ) { aqb_w_dem = P:\C8T00\GIS\DEMS\DEM10_SPFT / 100 } else aqb_w_dem = aqb_grid end /* Step 6=============Contour new aqbase aqb_corr = contour (aqb_w_dem,interval, 100, 1200) projectcopy cover COV4PROJCP cover aqb_corr Areas where the interpreted base-of-aquifer altitude was above land surface were interpreted as the areas where either the base of aquifer surface was inaccurate or areas where the principal aquifer is thin or not present. The base-of-aquifer contours were manually deleted in these areas. 2007 The base-of-aquifer contours and the designation of the geologic unit that form 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 suggestions were incorporated into the dataset and the map. 2007 Metadata imported. P:\C8T02\GIS\aqbase\20090603_4approval_sim3042_ab.xml 20090604 12253000 Vector Complete chain 568 Label point 23 GT-polygon composed of chains 20 State Plane Coordinate System 1983 2600 40.000000 43.000000 -100.000000 39.833333 1640416.666667 0.000000 coordinate pair 100 100 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_ab.aat Table of feature attributes for base-of-aquifer altitude contours. USGS FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. FNODE# Internal node number for the beginning of an arc (from-node). ESRI Whole numbers that are automatically generated. TNODE# Internal node number for the end of an arc (to-node). ESRI Whole numbers that are automatically generated. LPOLY# Internal node number for the left polygon. ESRI Whole numbers that are automatically generated. RPOLY# Internal node number for the right polygon. ESRI Whole numbers that are automatically generated. LENGTH Length of feature in internal units. ESRI Positive real numbers that are automatically generated. SIM3042_AB# Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. SIM3042_AB-ID User-defined feature number. ESRI Sequential unique whole numbers that were automatically generated. CONTOUR Altitude of the base of the principal aquifer, represented using isolines. Vertical datum is the National Geodetic Vertical Datum of 1929 (NGVD29). USGS 1300 3400 feet REFERENCE Reference for altitude contours of the base of the principal aquifer USGS COHYST, 2006 Published base-of-aquifer altitude contour, Cooperative Hydrology Study data, 2006 USGS USGS SIM 3042 Base-of-aquifer altitude contour reinterpreted for this study USGS Modified from Bentall and others, 1971; CSD, 1979 Base-of-aquifer altitude contour based on Bentall and others (1971) and CSD (1979( USGS Modified from CSD, 1979; Burchett and others, 1988 Base-of-aquifer altitude contour based on CSD (1979) and Burchett and others (1988) USGS Modified from COHYST, 2006 Base-of-aquifer altitude contour based on data from the Cooperative Hydrology Study (2006) USGS Modified from CSD, 1979 Base-of-aquifer altitude contour based on University of Nebraska, Conservation and Survey Division (1979) USGS Modified from Souders, 2000 Base-of-aquifer altitude contour based on Souders (2000) USGS Modified from Swinehart and Diffendal, 1998 Base-of-aquifer altitude contour based on Swinehart and Diffendal (1998) USGS Modified from CSD, 1979; Souders, 2000 Base-of-aquifer altitude contour based on CSD (1979) and Souders (2000) USGS Modified from CSD, 1979; Swinehart and Diffendal, 1998 Base-of-aquifer altitude contour based on CSD (1979) and Swinehart and Diffendal (1998) USGS SYMBOL Qualitative assessment of adequacy of stratigraphic information from test-hole and registered wells data to support the base-of-aquifer altitude contour configuration. The base-of-aquifer contours will be dashed in the published map, if there is not adequate distribution of stratigraphic information in the area. USGS 1 Reasonably adequate number and distribution of test-hole or registered wells data with stratigraphic information USGS 2 Minimal number or poor distribution of test-hole or registered wells data with stratigraphic information USGS The relevant attributes for this dataset are: contour, for the interpreted base-of-aquifer altitude, in feet; reference, for an associated reference; and symbol, as a code to indicate a qualitative assessment of the adequacy of test-hole and registered wells data to support the base-of-aquifer-altitude-contour configuration, within stated use constraint. See references listed in source information. 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 1.2 Mbytes http://water.usgs.gov/GIS/dsdl/sim3042ab_e00.zip Shape Shape File zipped 1.0 Mbytes http://water.usgs.gov/GIS/dsdl/sim3042ab_shp.zip None; this dataset is provided by USGS as a public service. 20090603 U.S. Geological Survey Ask USGS - Water Webserver Team mailing

455 National Center

Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+sim3042ab FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 None Unclassified Not applicable