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" (predevelopment year), a year of abnormally high rainfall and minimum pumpage (1966), and the previous year (1978). The "base-reference year" is 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, which represents the recent period of intensified irrigation-well development.

Tables in the report show the depths to water level in 1940, 1944, or 1950 (predevelopment year), 1966, 1974, 1978, and 1979; water-level changes from 1940-79, 1944-79, 1950-79, 1966-79, 1974-79, and 1978-79; and the average annual changes from 1940-79, 1944-79, 1950-79, 1966-79, and 1974-79. Also shown are saturated thicknesses of the deposits in 1940, 1944, or 1950 and in 1979, as well as the percentage change in saturated thickness from 1940-79, 1944-79, or 1950-79.

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 Management'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 are designated in a counterclockwise direction beginning in the northeast quadrant. Where there is more than one well in a 10-acre tract, consecutive numbers, beginning with "2", are added in the order in which the data from the wells are collected.