Hydrologic data related to water level measurements made in approximately 1,350 observation wells in western and south-central Kansas are shown in this report. The measurements were made in mid-winter when pumping was minimal and water levels had recovered, for the most part, form the effects of pumping during the previous irrigation season. Annual hydrologic data are provided for relating water level changes from a ' base-reference year ' (predevelopment year), a year of abnormally high rainfall and minimum pumpage (1966 or 1974), and each of 7 consecutive years of measurement (1979-85). The ' base-reference year ' is designated as 1940 for the southwestern area, 1944 for the south-central area, and 1950 for the northwestern, west-central, and Equus Beds areas. Data also are provided for relating the average annual water level changes, saturated thickness of the deposits, and percentage changes in saturated thickness. (USGS)