Ground-Water Resources of the Havana Region in West-Central Illinois

Pleistocene sand and gravel deposits underlying the Havana region of west-central Illinois constitute one of the largest underdeveloped aquifers in the state. The deposits are more than 100 feet thick in most places and were laid down in a wide lowland formed at the junction of several large valleys excavated in bedrock. Where they fill bedrock channels, the deposits locally exceed 150 feet thick. The main aquifer consists of Sankoty Sand (Kansan) and overlying Wisconsinan sand and gravel outwash in much of the region. To the east, where Wisconsinan outwash terminates against Wisconsinan and Illinoian upland tills, the aquifer consists essentially of the Sankoty Sand. Pennsylvanian and Mississippian rocks underlie the Pleistocene deposits and are not developed as a source of ground water where sand and gravel aquifers are present. Rocks below the Mississippian contain water too highly mineralized for most domestic purposes. The average coefficient of permeability of the main sand and gravel aquifer ranges from about 2,000 to 15,000 gallons per day per square foot. Properly designed and developed wells should yield 1 million gallons per day with moderate drawdowns. Recharge from precipitation is received at the average rates of 490,000 gallons per day per square mile in areas where the granular deposits of the aquifer extend to the surface and 270,000 gallons per day per square mile in areas where layers of till overlie the aquifer. The quantity of water stored in the Pleistocene unconsolidated deposits is estimated to be about 7.2 X 10 12 gallons. Total ground-water pumpage in the Havana region was about 21 million gallons per day in 1960; 85 percent of this was pumped for industrial use in the extreme northern part of the region. Pumpage for supplemental irrigation was low in 1960 but is expected to increase at a rapid rate. In most of the region, pumpage has not appreciably affected the water table. The water-yielding character of the sand and gravel deposits, recharge rates from precipitation, and possibilities for induced infiltration of surface water indicate that the potential yield of unconsolidated deposits in the Havana region may be about 350 million gallons per day. I N T R O D U C T I O N A large undeveloped ground-water reservoir underlies an area along the Illinois and Sangamon Rivers in west-central Illinois (fig. 1). The area is called the Havana region in this report. The reservoir consists of thick deposits of sand and gravel saturated with ground water that is of good quality and readily available to wells. The area is geographically situated near the population centers of Illinois and of the United States and is accessible to local and distant markets by river, rail, highway, and air. Mineral resources needed in many industrial processes are close at hand. Soils of the area yield bountiful field and truck-garden crops when supplemental irrigation practices are employed. Although increased demands for industrial and agricultural water in recent years have stimulated the development of available ground-water supplies, the ground-water reservoir has much greater potential.