This report contains hydrologic data on water-level measurements in observation wells in western and south-central Kansas. The measurements were made in mid-winter, mostly in January, when pumping was minimal and water levels had recovered from the effects of pumping during the previous irrigation season. This report also provides basic hydrologic data for relating water-level changes from a "base-reference year" (pre-development year), a year of abnormally high rainfall and minimum pumpage (1966), and the previous year (1979). The "base-reference year" i s designated as 1950 for the northwestern and west-central areas, 1940 for the southwestern area, and 1944 for the south-central area. Water-level data in the south-central area also are compared with data for 1974. "Base-reference-year" water levels are based on measurements made during that year and on interpretation of water-table-contour maps.

Tables in the report show the depths to water level in 1940, 1944, or 1950 (pre-development years), 1966, 1974, 1979, and 1980; water-level changes from 1940-80,1944-80,1950-80,1966-80,1974-80, and 1979-80; and the average annual changes from 1940-80, 1944-80, 1950-80, 1966-80, and 1974-80. Also shown are saturated thicknesses of the deposits in 1940, 1944, or 1950, and in 1980, as well as the percentage change in saturated thickness from 1940-80, 1944-80, or 1950-80.

Maps in the report, drawn by digital plotter, show the location of observation wells where water-level measurements are made. The water-level rise or decline, 1979-80, is given to the nearest 0.01 foot; two values at the same location indicate separate wells in the same 10-acre tract.

The annual water-level measurements are made by personnel of the Division of Water Resources of the Kansas State Board of Agriculture and of the U.S. Geological Survey. State-agency support for this program is provided through the Kansas Geological Survey.

Wells in this report are numbered according to the Bureau of Land Manage- ment's system of land subdivision. In this system, the first set of digits of a well number indicates the township; the second set, the range east or west of the sixth principal meridian; and the third set, the section in which the well is situated. The first letter denotes the 160-acre tract within the section; the second, the 40-acre tract, and the third, the 10-acre tract. The letters, A, B, C, or D, are designated in a counterclockwise direction beginning in the northeast quadrant. Because there may be more than one well in a 10-acre tract, consecutive numbers, beginning with "1", are added in the order in which the data from the wells are collect.

Explanation of geologic units in tables 1 and 2 are: QA, Quaternary alluvium; QU, undifferentiated Quaternary deposits; TO, Ogallala Formation; KN, Niobrara Formation; KU, undifferentiated Lower Cretaceous rocks; KJ, undiffer-rentiated Lower Cretaceous and Upper Jurassic rocks.