UNITED STATES DEPARTMENT OF THE INTERIOR J. A. Krug, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director Water-Supply Paper 943 GEOLOGY AND GROUND-WATER RESOURCES OF SCOTTS BLUFF COUNTY, NEBRASKA BY L. K. WENZEL, R. C. CADY AND H. A. WAITE Prepared in cooperation with the CONSERVATION AND SURVEY DIVISION OF THE UNIVERSITY OF NEBJRASKA ;\w UNITED STATES GOVERNMENT FEINTING OFFICE WASHINGTON : 1946 For sale by the Superintendent of Documents, U. 8. Government Printing Office, Washington 86, D. C. Price 25 cents CONTENTS Page Abstract.................................................................................................................................. 1 History, scope, and purpose of the investigation........................................................ 2 Geography of Scotts Bluff County.................................................................................. 5 Location..... ..... ................. ................................................................................... 5 Area and population.................................................................................................... 5 Agriculture...-.......................................:......................................................................... 5 Manufacturing................................................................................................................ 6 Transportation .................................................................... .. .. .................... 6 History.................................................................................................................................... 6 Climate...... .. .-.. ................................... ..................... ...................... 9 Soil and vegetation.............................................................................................................. 12 Irrigation................................................................................................................................. 13 Land forms..-.... .- .................................................................. 17 Majorfeatures.......... .................. ................................................................... ....... 17 Asymmetry of the North Platte Valley. .. - .-. 19 Stream processes................................................... ... ..... .... ......... ...... 21 Flood plain.............................................................................................................. 21 Bluffs and pediments...... .. ... ...... ...... .. 23 Terraces.............................................. ......... ................... ................ 28 Higher terraces....----..--..--..........-. - - - 28 Ninth terrace 29 Eighth terrace.. ... ........- ... .. ..-..-- ...... ...... 29 Seventh terrace--.-----.---.--.--...----.-- 31 Sixth terrace. 31 Fifth terrace-----..---.- - - . 32 Summary of higher terraces 36 Lower terraces . 36 Fourth terrace- . - - - . 36 Third terrace 38 Age of the pediment south of the river..-........... ................. 41 Second terrace .- .......... ... ........... .. ..... .......... 41 First terrace - - . 46 Summary of stream processes--..---......-..- 48 Wind processes.............................................................................................................. 50 Loesslike deposit--.......------...--..-...--..-...-.- .. 50 Sand dunes.... ......................................................................................... 51 Wind erosion ........................................... .. .. ...... ..... ...... 51 Summary of erosional history................................ ............................................ 52 Geology .................................................................................................... ....... 53 General features-....--....-...........-............................--.......-.. 53 Cretaceous system--..-..-.-.-....---...-....-. ._.............................. 53 Lance formation.......-.-..................................-......-..-..-..-...... ...... 53 ill IV CONTENTS Page Tertiary system......_..._.......... .. ._. .. ...._. .. ................_......... 59 White Rivergroup. .. .. .......... ............. .. .. 59 Chadron formation...................................................................................... 60 Brule formation............................................................................................ 66 Arikaree group......._.......................................................................................... 70 Gering formation.......................................................................................... 70 Upper sandstones of the Arikaree group. ....................................... 72 Quaternary system...................................................................................................... 75 Sand and gravel........... ...................................................................................... 75 Occurrence of ground water.............................................................................................. 75 Pleistocene and Recent sand and gravel. ........................................................... 76 Brule formation............................................................................................................ 76 Lance formation............................................................................................._............. 78 Hydrologic properties of the water-bearing formations......- ................................ 78 General conditions.____..........................;... ................................................... 78 Pleistocene and Recent sand and gravel._......................................................... 79 Brule formation............................................................................................................ 83 Depth to ground water.__............................................................................................. 86 Fluctuations of water level in wells................-.. ....-.................................................. 89 Method of investigation__.................................................................................... 89 General conditions.__... _.__.._..__.................................................................. 91 Fluctuations caused by seepage from irrigation ditches and irrigated fields..................................................___............................................................... 92 Fluctuations caused by changes of water stored in Lake Minatare............ 96 Fluctuations caused by precipitation__............................................................. 97 Fluctuations caused by changes in flow of the North Platte River............ 98 Fluctuations caused by pumping of wells......__..............................................: 101 Fluctuations caused by changes in atmospheric pressure......... .................... 103 Movement of ground water._......................................................................................... 103 Ground-water discharge. .._.................................................... ...................................... 106 General conditions._................................................................................................. 106 Discharge from wells.................................................................................................. 107 Farm wells.__........................................................................................_.......... 107 Irrigation wells. ......................................................................................... 107 Flowing wells........................................................................................................ 109 Industrial wells.-.-- -.... .. .-..-........ ---.. .- . - .- -. Ill Municipal wells .................................................................................................. 113 Evapo-transpiration.........................................-..........-........... ................................. 116 Springs.__..._.___........-........-.._.............._.....-.._..... ....... ._... ..... ............... 117 Seepage into streams and return flow from irrigation...................................... 120 North Platte River.............................................................................................. 121 Tributaries of the North Platte River.......................................................... 124 Summary....................................................................................-...... ................. 125 Underflow._................................................................................................................. 125 Estimate of annual discharge. ... 126 Ground-water recharge..........__.......................... ............. .... ...... 126 Chemical character of the ground water.......... ..._..................................... .. 126 Logs of test holes. .... ................._............................................................ ........ ...... 131 Well records.__....... .......................................................... ................................... 136 Index...._.._..................... ....................................................................._._............. 149 ILLUSTRATIONS PLATE 1. Topographic map of Scotts Bluff County, Nebr., and adjoining areas showing location of gravel-filled channels by means