Simulated water-level declines near Marienthal, west-central Kansas

Intensive study in an area of 12-square miles near Marienthal, Kansas, has shown a decrease of 30 to 50 percent in saturated thickness of the Ogallala Formation since the development of irrigation. Projections from a digital model indicated the additional water-level declines that might occur from 1978 to 1989 if the pumpage in the model area was assumed to be one-half, equal to, or double the 1977 rate. The additional declines would range from 5 to 15 feet, 15 to 30 feet, and 25 to 40 feet, respectively. If pumpage only in the intensive-study area were assumed to be one-half or double the 1977 rate, water-level declines would range from 10 to 20 feet and from 20 to 25 feet, respectively. Reducing pumpage only in the intensive-study area could reduce the water-level declines locally. However, declines would be greatest near the edge of the area as a result of continued pumpage by wells outside the area boundary.

The digital model was more sensitive to changes in pumpage than to changes in hydraulic conductivity, specific yield, and recharge.