USGS Science⌕ Search

Geology topics

Lloyd E. Dunlap

Publications and source records attributed to Lloyd E. Dunlap.

5 recordsLinked to original sources
USGS1981

Analysis and computer simulation of stream-aquifer hydrology, Arkansas River valley, southwestern Kansas

A study was made, in cooperation with the Division of Water Resources, Kansas State Board of Agriculture, to determine geohydrologic conditions underlying nearly 110,000 acres of the Arkansas River Valley between the Colorado-Kansas State line and the Bear Creek Fault zone in southwestern Kansas. The Arkansas River meanders atop and interacts hydraulically with the area's unconfined sand and gravel aquifer. Owing to decreasing recharge and increasing discharge during the 1970's, water levels declined an average of 4 feet during 1970-79. Average annual streamflow at Syracuse, Kansas, also decreased from 232 cubic feet per second during 1951-69 to 85 cubic feet per second during 1970-79.

Kansas↗
USGS1980

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.

Kansas↗
USGS1980

Geohydrology and model analysis for water-supply management in a small area of west-central Kansas

The Ogallala Formation in the intensive-study area, an area of 12 square miles in northeastern Wichita County, west-central Kansas, has had a substantial decrease in saturated thickness since the development of irrigation. The annual water-level decline during 1950-78 ranged from 1.08 to 2.22 feet per year. The hydrologic system was investigated to study methods of conserving the remaining ground water in the intensive-study area. During 1977-78, the average annual ground-water withdrawal was 7,400 acre-feet, and the water-level decline ranged from 0.91 to 5.05 feet. The saturated thickness in 1977 ranged from about 40 to 80 feet, and aquifer storage was about 61,000 acre-feet. Natural recharge is estimated to be 0.28 inch per year. Projections from a digital ground-water flow model were used to indicate the additional water-level decline that might occur from 1978 to 1988 if pumpages in the 480-square-mile model area were one-half, equal to, or double the 1977 pumpage rate. The additional water-level declines in the intensive-study area would range from 5 to 15 feet if pumpages were one-half, 15 to 30 feet if pumpages were equal to, and 25 to 40 feet if pumpages were double the 1977 rate. Projections also were used to indicate the water-level declines if pumpages in the model area were equal to the 1977 rate and if pumpages in the intensive-study area were one-half or double the 1977 rate. Additional water-level declines in the intensive-study area would range from 10 to 20 feet if pumpages were one-half and from 20 to 25 feet if pumpages were doubled. Decreased pumpage in the area could reduce the water-level declines, but continued pumpage in adjacent areas would cause declines to be greater near the edge than near the center. The digital model was more sensitive to changes in pumpage than to changes in hydraulic conductivity, specific yield, and recharge.

Kansas↗