The sand and gravel deposits of Quaternary age constitute the most important ground-water reservoir and are the source of nearly all the water pumped from wells in the area. An estimated 3.5 million acre-feet for good quality water is stored in these deposits and an additional 1.5 million acre-feet is stored in the underlying Dakota Sandstone. Even larger quantities are stored at greater depths in the Paleozoic dolomites and sandstones, but the water is of poorer quality.
Pumpage for irrigation since 1956 is estimated to have ranged from about 2,500 acre-feet (1962) to about 6,000 acre-feet (1957). The town of Wahoo annually pumps about 460 acre-feet, and other towns pump an estimated total of 180 acre-feet. In 1963 the City of Lincoln pumped 27,000 acre-feet from its well field alongside the Platte River in the southeast corner of the area; since then pumpage has increased and probably is likely to continue to do so. Pumping at Lincoln city well field induces recharge from Platte River.
The quantity of ground water pumped to date is very small compared to the amount of water stored in the rocks. Furthermore, most of the ground water withdrawn has been replaced by infiltrating precipitation and by influent seepage from the Platte River. The large quantity of ground water in storage in addition to the flow of the Platte River indicates that the water resources of the area, if managed properly, can be developed much more extensively without appreciably depleting the supply.
