Crews are undertaking an annual effort to monitor changes in groundwater levels in western and central Kansas.

The University of Kansas said Tuesday the Kansas Geological Survey will measure 510 wells early next month. The Kansas Department of Agriculture’s Division of Water Resources will measure an additional 897 wells.

The monitoring focuses on the massive High Plains aquifer system, which consists largely of the Ogallala aquifer. The data are used by landowners, state and federal agencies, local groundwater management districts, private entities and the general public.

From the winter of 2011-12 to 2012-13, water levels in the entire network declined by slightly more than 2 feet on average. Southwest Kansas was the hardest hit area, with an average decline of 3.56 feet.