Chemical Quality Series 5: Ground Water from Lower Cretaceous Rocks in Kansas
Continuing declines in the water table in western Kansas due to the heavy demands of irrigation and municipalities have led to a search for additional supplies of water. Lower Cretaceous rocks (primarily the Cheyenne Sandstone and Dakota Formation) have long supplied water for irrigation and stock.
This survey of the available data on the quantity and quality of ground water available from Lower Cretaceous rocks indicates that an estimated 70-80 million acre-feet of fresh water containing less than 1,000 mg/l (milligrams per liter) dissolved solids and 10-15 million acre-feet of slightly saline water containing 1,000-3,000 mg/l dissolved solids could be obtained. The Kansas Department of Health and Environment recommends less than 500 mg/l dissolved solids for drinking water and will accept up to 1,000 mg/l. Thus, much of the available water could be used as is and even more would be available after desalinization. Water quality tends to be good to the south and the east along the Lower Cretaceous outcrop belt and to gradually decline towards the north and west.
The Lower Cretaceous rocks outcrop in a band from the southwest in a northeasterly direction across the center of the State and are present in the subsurface to the north and west. Their depth increases to 2,600 feet below land surface in the extreme northwest. The thickness of sandstone in the Lower Cretaceous rocks is less than 200 feet in most of Kansas, but is as much as 400 feet in Lane County. The movement of water in Lower Cretaceous sandstones is generally in an easterly or northeasterly direction. The rocks are directly overlain and hydraulically connected with Pliocene and Pleistocene aquifers in parts of southwestern Kansas. Although ground water from the Lower Cretaceous rocks has seen only moderate use to date, there are indications that, locally, pumpage already exceeds recharge.
The ground-water resources in the Lower Cretaceous rocks of western Kansas represent a significant resource for present and future. Additional studies are needed of the regional relationships of the Lower Cretaceous aquifers to overlying Pliocene and Pleistocene aquifers and underlying Jurassic and Permian aquifers with respect to head changes and water-quality changes that may result from water-level declines in the overlying aquifers and pumpage from large numbers of multi-aquifer irrigation wells. Careful planning could result in an extended lifetime for the aquifers.
