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The Wood River unit is mainly terrace land that lies on the north side of the Platte River between the city of Kearney and the town of Wood River. As irrigation from pumped wells is practiced extensively in the unit and is a major factor in the economy of the area, it is important to know the amount of water pumped annually from the groundwater reservoir and if the amount of discharge is greater than the annual recharge. Measurements of the water level in several observation wells in the area have been made periodically since the fall of 1930* These records show that in parts of the Wood River unit the water level has lowered since 1930; the net decline during the period from 1930-^9 vas about 6.5 ft in one well situated about > miles north of the town of Wood River.-This indicates that the average annual discharge is greater than the average annual recharge, at least in a local area. Water is discharged from the groundwater reservoir by pumping from wells, by seepage into the Platte River and into Wood River, by underflow eastward, and by transpiration and evaporation in the areas of shallow depths tcy-water* All, irrigation^ domestic, stock, municipal, and industrial^water supplies are obtained from wells. The ground water is recharged principally by precipitation that falls-Within the area, by effluent seepage from the Platte Biver and perhaps-locally from Wood River, by underflow from the west, and by return flow from a part of the water pumped from wells for irrigation. A field census, made in the summer of 19^8, showed 1,113 irrigation wells in the Wood River unit in 19^7-Of this total, the kj2 electrically driven pump installations were operated for an average of hr during the 19^7 irrigation season. Discharge measurements were made on 142 representative irrigation wells; the average yield was 856 gpm. The average electrically pumped well discharged 69.7 acre-ft of water during 19^7, the average amount of water applied to each irrigated acre was 1.52 acre-ft and the total annual pumpage was 77>600 acre-ft. Pumping-plant efficiencies were determined for 86 electrically powered pumping plants; the average plant efficiency was 57-3 percent. The report contains three maps, one showing the locations of all irrigation wells and the depths to water below land surface, another showing contours of the water table as of March and September 19^8, and another showing the change in groundwater levels for the period between 1931 and

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Purpose and scope of the investigation._______ ________________ Location and extent of the area-________________________________ Previous investigations________________________________________ Methods of investigation__-_____________-_-________________-___ Well-numbering system________________________________ Acknowledgments. __________________________________________ Geography____ __ __ ______________________ __________ Topography and drainage_____________________________________ Climate. _____________________________________________ Population..____________________________________________ Transportation________________________________________ Agriculture and soils_____________________________________ Mineral resources__________________________________________ Geology-.-----______________________________ Stratigraphic units and their water-bearing properties._____________ Cretaceous system____________________________________ Lower Cretaceous series._____________________________ Dakota sandstone___-______.________________________ Upper Cretaceous series______________________________ Graneros shale____.__________________________________ Greenhorn limestone_--___-________-__-___________-____ Carlile shale__ ____________________ Niobrara formation._______________________________ Tertiary system.______________________________________________ Pliocene series_________________________________________ Ogallala formation_________________________________ Quaternary system__________________________________________ Pleistocene series__________________________________________ Holdrege formation and Red Cloud sand and gravel, ui> differentia ted______________________________________ Grand Island formation________________________________ Sappa formation__________________________________ Crete formation_______________________________________ Loveland formation___________________________________ Todd Valley sand and younger terrace deposits____________ 31 Peorian and younger loesses_________________-___--_-_-31 Recent series____________________________________________

Most of the Big Blue River basin above Crete, Nebr., is underlain by sand and gravel of Pleistocene age that normally yields large quantities of water to wells. Deposits of till underlie the eastern part of the area, and here ground-water supplies are not abundant.Generally, the ground water is of the calcium bicarbonate type; however, some water in the western part of the area has appreciable amounts of sulfate. The high sulfate may be attributed to oxidation of iron sulfides in the Niobrara formation. Because of its low total salt content, low boron content, and low percent sodium, the ground water is suitable for irrigation. Although the water is hard and locally contains high concentrations of iron, it generally is potable and suitable for domestic use.The general movement of the ground water is eastward toward the main stem of the Big Blue River.Principal sources of ground-water recharge are precipitation on the area and underflow from adjacent areas to the west. Streams in the area generally receive water from, rather than contribute water to, the ground-water reservoir. As of 1953, the natural discharge of ground water into streams was about 150,000 acre-feet per year and was much more than the amount pumped from wells.The major use ma^ie of ground water in the area is for irrigation. About 60,000 acres is irrigated annually. The annual withdrawal of ground water for irrigation is about 61,000 acre-feet; for domestic and stock use, about 25,000 acre-feet; and for municipal use, 8,000 acre-feet.The number of irrigation wells increased from 14 in 1938 to 672 by June 30, 1953. During 1948, 140 irrigation wells were constructed, and the average rate of construction from 1944 through 1952 was 53 wells per year.Use of ground water for irrigation is steadily increasing, but in most parts of the area the available supplies are more than sufficient for present withdrawals. The past average annual rate of increase in ground-water withdrawals, if distributed over the area, could continue for perhaps 25 or 30 years without serious depletion of the ground-water reservoir, but the base flow of streams in the area probably would be reduced considerably. Because of the interest in, and the rate of development of, the ground-water resources, systematic collection of more adequate hydrologic data should be undertaken, and detailed quantitative studies should be made so that the perennial yield of the aquifer can be determined before serious depletion of the ground-water supply occurs. 1 2 GEOLOGY AND GROUND WATER, BIG BLUE RIVER BASIN, NEBR. ADAMS' CLAYFIGUKE 1. Index map showing location of the Big Blue River basin above Crete, Nebr. PURPOSE AND SCOPE OP THE INVESTIGATIONNearly all domestic, municipal, industrial, and irrigation water supplies in the area are obtained from wells. The use of ground water for irrigation is rapidly increasing, and this study was made in order to gain a better understanding of the geology and hydrology of the area as they pertain to the replenishment, discharge, storage, and additional develop...