Michaela R. Johnson, James F. Cornwall, and Matthew K. Landon 20020207 vector digital data USGS Open-File Report USGS OFR 02-64 Reston, VA U.S. Geological Survey https://water.usgs.gov/lookup/getspatial?ofr0264_aqbase This digital spatial data set consists of the aquifer base elevation contours (50-foot contour interval) for part of the High Plains aquifer in the central United States. This subset of the High Plains aquifer covers the Republican River Basin in Nebraska, Kansas, and Colorado upstream from the streamflow station on the Republican River near Hardy, Nebraska, near the Kansas/Nebraska border. In Nebraska, the digitized contours extend to the South Platte, Platte, and Little Blue Rivers. In Colorado and Kansas, the digital contours extend to the edge of the High Plains aquifer. These boundaries were chosen to simplify boundary conditions for a computer simulation model being used for a hydrologic study of the Republican River Basin. This data set was created to serve as calibration data for a ground-water simulation model of the Republican River Basin. This digital data set consists of the aquifer base elevation contours (50-foot contour interval) for part of the High Plains aquifer in the central United States. This subset of the High Plains aquifer covers the Republican River Basin in Nebraska, Kansas, and Colorado upstream from the streamflow station on the Republican River near Hardy, Nebraska, near the Kansas/Nebraska border. In Nebraska, the digitized contours extend to the South Platte, Platte, and Little Blue Rivers. In Colorado and Kansas, the contours extend to the aquifer boundary, which was determined to be the erosional extent of the geologic units making up the aquifer. These boundaries were chosen to simplify boundary conditions for a computer simulation model of ground-water flow and ground-water/surface-water interaction in the Republican River Basin. The High Plains aquifer consists mainly of hydraulically connected geologic units of late Tertiary or Quaternary age. The late Tertiary-aged rocks include part of the Brule Formation of the White River Group, Arikaree, and Ogallala Formations. The Quaternary-aged deposits included in the aquifer consist of alluvial, dune sand, and valley-fill deposits. The Ogallala Formation is the principal geologic unit in the High Plains aquifer. The Ogallala Formation consists of a heterogeneous sequence of clays, silts, sands, and gravels deposited by streams that flowed eastward from the ancestral Rocky Mountains. Within the Ogallala Formation, zones cemented by calcium carbonate are resistant to weathering and form caprock escarpments that mark the boundary of the High Plains locally. This digital data set was created by digitizing the base of aquifer elevation contours for Colorado and Nebraska and merging the contours with existing digital data for Kansas (Juracek and Hansen, 1995). In Colorado, 50-foot contours were digitized from a 1:500,000 base map (Borman and Meredith, 1983). In Nebraska, the 50-foot contours and aquifer boundaries were digitized from a series of 1:250,000 working maps for the U.S. Geological Survey (USGS) Regional Aquifer System Analysis (RASA) of the High Plains aquifer in Nebraska. These working maps were used in constructing a statewide map of the elevation of the base of the High Plains aquifer with a 100-foot contour interval (Pettijohn and Chen, 1983). In Kansas, the 50-foot contours and aquifer boundaries were extracted from a digital spatial data set obtained from the Kansas Data Access & Support Center (DASC). This digital data set was created by the U.S. Geological Survey (Juracek and Hansen, 1995) to make available in digital format the original source map of the base of the High Plains aquifer in Kansas (Watts and Stullken, 1985). The digital data set provided the base elevation contours (at a 50-foot interval) and the boundary of the High Plains aquifer in Kansas. In a small area of northwestern Kansas, an error in contour elevations was found. To correct this, contours were digitized manually to replace those from the existing digital coverage. These additional contours were digitized from the map "Water Resources of Northwestern Kansas" (Pearl and others, 1972). Contours in parts of Cheyenne, Rawlins, Sherman, and Thomas Counties in Kansas were digitized. Elevation data from each state was processed and merged using Arc/INFO Geographic Information Systems software to create the final digital spatial data set. REFERENCES Borman, R.G., and Meredith, T.S., 1983, Geology, altitude, and depth of the bedrock surface beneath the Ogallala Formation in the northern High Plains of Colorado: U.S. Geological Survey Hydrologic Investigations Atlas HA-669, scale 1:500,000, 1 sheet. Juracek, K.E., and Hansen, C.V., 1995, Digital maps of the extent, base, and 1991 potentiometric surface of the High Plains Aquifer in Kansas: U.S. Geological Survey Open-File Report 95-758, digital data set. Pearl, R.H., Roberts, R.S., Keene, K.M., and McClain, T.J., 1972, Water resources of northwestern Kansas: U.S. Geological Survey Hydrologic Investigations Atlas HA-429, scale 1:250,00, 2 sheets. Pettijohn, R.A., and Chen, H.H., 1983, Geohydrology of the High Plains aquifer system in Nebraska: U.S. Geological Survey Water Resources Investigations Open-File Report 82-502, scale 1:750,000, 3 sheets. Watts, K.R., and Stullken, L.E., 1985, Generalized configuration of the base of the High Plains aquifer in Kansas: U.S. Geological Survey Open-File Report 81-344, scale, 1:500,000, 1 sheet. 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 ArcInfo format, this metadata file may include some ArcInfo-specific terminology. 1972 1985 publication date Complete None Planned -103.99329372 -97.78712813 41.23915327 38.64320091 USGS Thesaurus aquifer base High Plains aquifer ground water Ogallala aquifer Ogallala Formation Brule Arikaree Group inlandWaters ISO 19115 Topic Category geoscientificInformation inlandWaters environment USGS Metadata Identifier USGS:012ccd61-2b69-4f98-b421-02eef7d21129 Geographic Names Information System Republican River Basin Nebraska Hardy, Nebraska Kansas Colorado High Plains Great Plains region United States none This coverage is best used for regional-level analyses at a maximum scale of 1:500,000 because of the small-scale of the source data (1:250,000 and 1:500,000). This is not intended for use in detailed, site-specific investigations. Michaela R. Johnson U.S. Geological Survey GIS Specialist mailing and physical address

Federal Bldg., Room 406

100 Centennial Mall North

Lincoln NE 68508 USA 1-888-275-8747 (402) 437-5139 mrjohns@usgs.gov The Nebraska Republican River Basin Management Districts and the Southwest Nebraska Resource Conservation and Development Area are thanked for their support of this project. The Nebraska Republican River Basin Management Districts include the Upper Republican, Middle Republican, Lower Republican, and Tri-Basin Natural Resources Districts (NRDs), and the Frenchman-Cambridge, Frenchman Valley, Hitchcock and Red Willow, and Nebraska Bostwick Irrigation Districts. The funding for this project was provided by a grant from the Nebraska Environmental Trust Fund to the Nebraska Republican River Basin Management Districts, U.S. Geological Survey cooperative matching funds, and funds from individual NRDs. Windows_NT, 4.0, Intel ArcInfo version 8.1 Accuracy of attributes was verified by cross-checking data against contour labels on source maps. Contours near state boundaries also were checked against those in the neighboring regions to ensure continuity of contour lines and valid entries for elevation values. Accuracy was verified to the same standards as the original source materials. Chain-node topology present. In general, the sources used for this data set were maps showing the elevation of the base of the High Plains aquifer. The base of the aquifer is defined as the upper surface of the geologic units of substantially lower permeability underlying the more permeable High Plains aquifer. In most places within the area of this report, the units underlying the High Plains aquifer are of Cretaceous age, but the White River Group of Tertiary age also underlies the High Plains aquifer. The fractured part of the Brule Formation of the White River Group is included in the High Plains aquifer, but such fractures are not known to exist in the area of this report. Aquifer base elevations for the various source maps were interpreted from drilling logs, seismic data, other geologic data and output from various geophysical techniques. The boundaries of this digital data set in Colorado and Kansas are defined to be the erosional extent of the Ogallala Formation. In Nebraska, the boundary is defined by the South Platte River, the Platte River, and the Little Blue River. These boundaries were selected to include the entire surface drainage basin of the Republican River. Additional regions were selected to provide the appropriate boundary conditions for the ground-water computer simulation model. Horizontal accuracy was maintained as close as possible to the source map standards. Methods for this included obtaining the lowest root mean square error (RMSE) possible for each map sheet digitized (maximum RMSE allowed was 0.010) and ensuring contours were digitized to a positional accuracy of under 2 mm. The only exception to this requirement was for edge-matching prior to joining map sheets, where contours were altered and reshaped to ensure continuity and geologic validity. This coverage is best used for regional-level analyses at a maximum scale of 1:500,000 because of the small-scale of the source data (1:250,000 and 1:500,000). This is not intended for use in detailed, site-specific investigations. R.A. Pettijohn and H.H. Chen, U.S. Geological Survey 1983 map U.S. Geological Survey Water Resources Investigations Open-File Report 82-502 Lincoln, Nebraska U.S. Geological Survey 250,000 clear film 1983 publication date Pettijohn and Chen (1983) Unpublished working maps with 50-foot contours from Pettijohn and Chen (1983) provided the elevation contours of the base of the High Plains aquifer and the boundary of the aquifer in southern Franklin, Webster, and Nuckolls counties in the Nebraska part of the study area. The working maps were on 1:250,000 quadrangles, which included, McCook, North Platte, Grand Island, Lincoln, Scottsbluff, and Sterling, Colorado. The McCook working map included part of the Sterling quadrangle, which was inside the Nebraska state border. The McCook quadrangle does not extend to the Nebraska border. R.G. Borman and T.S. Meredith, U.S. Geological Survey 1983 map U.S. Geological Survey Hydrologic Investigations Atlas series HA-669 Denver, Colorado U.S. Geological Survey 500,000 paper map 1983 publication date Borman and Meredith (1983) This map provided the 50-foot elevation contours of the base of the High Plains aquifer and the boundary of the aquifer within the Colorado part of the study area. K.R. Watts and L.E. Stullken, U.S. Geological Survey 1985 map U.S. Geological Survey Open-File Report OFR 81-344 Lawrence, Kansas U.S. Geological Survey 500,000 paper map 1985 publication date Watts and Stullken (1985) This map provided 50-foot elevation contours for the base of the High Plains aquifer and the boundary of the aquifer within the state of Kansas. The map was digitized by the USGS Kansas District to create a digital spatial data set showing the elevation of the base of the High Plains aquifer in Kansas (Juracek and Hansen, 1995). The digital data set is available from the State of Kansas Geographic Information Systems Initiative's Data Access and Support Center (DASC) web site, (<http://gisdasc.kgs.ukans.edu/dasc.html>). Pearl, R.H., Roberts, R.S., Keene, K.M., and McClain, T.J., U.S. Geological Survey 1972 map U.S. Geological Survey Hydrologic Investigations Atlas series HA-429 Lawrence, Kansas U.S. Geological Survey 250,000 paper map 1972 publication date Pearl and others (1972) This map provided the elevation contours for the base of the High Plains aquifer in a small area of northwestern Kansas. Juracek, K.E., and Hansen, C.V., U.S. Geological Survey 1995 digital vector data Lawrence, Kansas U.S. Geological Survey 500,000 digital vector data 1985 source map publication date, 1985 (Watts and Stullken, 1985) Juracek and Hansen (1995) This digital data, created from Watts and Stulken (1985), set provided the elevation contours for the base of the High Plains aquifer and the boundary of the aquifer in the Kansas part of the study area. The data set was obtained from the DASC web site, (<http://gisdasc.kgs.ukans.edu/dasc.html>). Digitizing Nebraska contours: The five 1:250,000 quadrangles in Nebraska were first digitized from the mylar working maps. The elevation was set as the ARC User-ID (AQBASE83-ID) for each contour line digitized. Once all five quadrangles were completed, the contours were edgematched and the coverages were joined using "APPEND". 19980331 Digitizing Colorado elevation contours: The Colorado map was digitized in the same fashion as Nebraska, using the User-ID code to store the elevation. Once completed, the Colorado contours were edge-matched against the Nebraska data and joined with "APPEND". Edge-matching the Colorado and Nebraska data involved a certain amount of editing contour arcs. An effort was made to minimize alteration of published data, but certain contours had to be moved up to several hundred meters to meet the equivalent contour in the adjacent state. In these cases, contours were adjusted to match at state borders but still be consistent with regional features in the base of aquifer such as ridges and valleys. 19980408 Processing Kansas Digital Coverage: The Kansas data set retrieved from DASC required some processing to merge it with the digitized data sets for Colorado and Nebraska. The data included contour lines, arcs that delineated aquifer boundaries, the State lines, and internal polygons within the aquifer boundary where little or no saturated thickness exists. These extra arc segments were deleted, and the contour arcs were extended across the internal polygons. In the extreme northwestern corner of Kansas, there was a mismatch of several hundred feet between the elevations as digitized from the Nebraska and Colorado maps, and the digital data imported from Kansas. A number of sources were consulted to verify the accuracy of the Colorado, Kansas, and Nebraska data, including several of the original High Plains RASA study personnel. To resolve the mismatch, base of elevation contours for a section of northwestern Kansas were digitized manually from another map (Pearl and others, 1972) to replace the DASC digital coverage. The digitized elevation contours matched closely with the elevation contours in Colorado and Nebraska. The Pearl map displayed the contour lines within the polygons showing areas of little or no saturated thickness. This small segment of contours in northwest Kansas was digitized, edgematched to the Kansas digital coverage and the Colorado/Nebraska coverage, and joined to the Colorado/Nebraska coverage with "APPEND". The final stage in creation of the aquifer base coverage was to match up the item attributes between Kansas and the Colorado/Nebraska/northwest Kansas coverage. The ID field storing the elevation was copied into a field "ALTITUDE_FEET" for consistency with Kansas, the coverages were edgematched, and joined with "APPEND". This coverage was trimmed to the boundary of the Republican study area with the "CLIP" command using the coverage "study_border". 19980420 Corrected discrepancies in elevation values for 5 arc segments and used "DISSOLVE" to reduce the number of arcs from 556 to 374. 19980611 Fixed AQBASE83-ID to contain internal user ID sequential numbers instead of the elevation data that was assigned in the digitizing process. The steps performed were these, tables;sel aqbase83.aat;calc aqbase83-id = aqbase83# - 1;q IDEDIT aqbase83 line 20020115 Copied AQBASE83 to AQBASE 20020130 Ran UNSPLIT in ArcEdit to remove pseudo nodes. ARCEDIT S:\REP_RIV\GIS\AQUIFER\AQBASE 20020130 build aqbase arc 20020130 kill aqbase83 all rename aqbase aqbase83 20020130 copy aqbase83 aqbase clip aqbase s:\rep_riv\gis\boundary\stdybrdr_alb aqbase_clp line 0.001 build aqbase_clp line 20020201 Extend contours along the Platte and Little Blue Rivers to the boundary of the study area. ARCEDIT S:\REP_RIV\GIS\AQUIFER\AQBASE_CLP 20020201 build aqbase_clp line rename AQBASE_CLP AQBASE 20020201 Add in boundary of the aquifer ARCEDIT O:\07900\REPORTS\OFR_AQBASE\AQBASE GET S:\REP_RIV\GIS\BOUNDARY\STDYBRDR_ALB UNSPLIT build aqbase line 20020507 First draft of metadata was created using FGDCMETA.AML ver. 1.2 05/14/98. Descriptive text was added to metadata by Jim Cornwall (USGS) to provide data on source materials, purpose, processing history, etc. 19980619 Second draft of metadata was created by mrjohns using FGDCMETA.AML ver. 1.36 01/16/01 on ArcInfo data set aqbase 20020103 Vector String 440 Albers Conical Equal Area 29.5 45.5 -96 23 0.00000 0.00000 coordinate pair 51.25875854492 51.25875854492 Meters North American Datum of 1983 GRS1980 6378206.4 294.98 > >AQBASE83.AAT: > >COLUMN ITEM NAME WIDTH OUTPUT TYPE N.DEC ALTERNATE NAME > 1 FNODE# 4 5 B - > 5 TNODE# 4 5 B - > 9 LPOLY# 4 5 B - > 13 RPOLY# 4 5 B - > 17 LENGTH 4 12 F 3 > 21 AQBASE# 4 5 B - > 25 AQBASE-ID 4 5 B - > 29 ALTITUDE_FEET 5 5 I - ALTITUDE > 34 LABEL 1 1 I - > > FNODE# - Internal node number of from-node. TNODE# - Internal node number of to-node. LPOLY# - Internal number of the left polygon. RPOLY# - Internal number of the right polygon. LENGTH - Length of arc in meters. AQBASE# - Internal sequence number (i.e. the record number of the arc in the ARC file. AQBASE-ID - Internal feature number. ALTITUDE_FEET - Elevation of the base of the High Plains aquifer; datum is sea level. The value is an integer between 1,150 and 3,850 divisible by 50; the value of -9999 indicates the arc is not a contour. LABEL - Binary attribute used to select a features for labeling for the purpose of illustration. The value is an integer of 0 or 1; the label equals 1 when ALTITUDE_FEET is divisible by 250. none U.S. Geological Survey Michael Ierardi IT Specialist mailing and physical

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Reston Virginia 20192 USA 1-888-275-8747 (1-888-ASK-USGS) mierardi@usgs.gov 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. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Export Full coverage zipped 1 https://water.usgs.gov/GIS/dsdl/ofr0264_aqbase.e00.gz Other sdts coverage zipped 1 https://water.usgs.gov/GIS/dsdl/ofr0264_aqbase.sdts.tgz Shape Shape file zipped 1 https://water.usgs.gov/GIS/dsdl/ofr0264_aqbase_shape.tar.gz None. This dataset is provided by USGS as a public service. 20201117 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) mierardi@usgs.gov FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998