During 1984, above-normal ground-water levels flooded the fields and basements in the vicinity of the Crex Meadows Wildlife Area. In response to concerns of neighboring farmers and homeowners, the Wisconsin Department of Natural Resources and the U.S. Geological Survey began a cooperative study to assess ground-water conditions in the area and to determine the causes of above-normal ground-water levels in and around the Crex Meadows Wildlife Area.

Data from an inventory of water levels in the Crex Meadows area measured in 1935 and 1937 were compared with data collected in 1986 and 1987. The comparison indicates that 1986 water levels were 5 to 10 feet higher throughout the area than in 1935 and 1937. Water levels declined about 5 feet throughout much of the area during 1987 and were only 0–5 feet higher than in the late 1930's. Hydrographs of water levels measured from 1985 to the fall of 1987 also indicate that water levels rose in 1985 and 1986 and fell abruptly in 1987.

Water levels in two wells, one in northern Burnett County and the other in Polk County, were compared to those in the wildlife area to determine whether the wetland impoundments contributed significantly to above-normal water levels measured in 1986 or whether levels were high throughout northwestern Wisconsin. Water-levels at long-term observation wells Bt-2 (1936–present) and Pk-40 (1951–present) (13 miles northeast and 20 miles southeast of Crex Meadows, respectively) during 1986 were the highest of record.

Long-term discharge records for the St. Croix River upstream (Danbury) and downstream (St. Croix Falls) from Crex Meadows indicate that the river reached its highest historical discharge volume during 1986.

Hydrographs showing cumulative departure from mean annual precipitation at two stations (Danbury and St. Croix Falls) indicate that the above-normal ground-water levels in 1986 were preceded by several years of above-normal precipitation. It is probable that the above-normal ground-water levels and surface- water discharge throughout the area can be attributed to above-normal precipitation. Groundwater- level fluctuations corresponded directly to variations in precipitation during 1985–87.

Chemical analyses of water samples from 20 observation wells indicate that calcium and bicarbonate are the predominant ions in ground water in the Crex Meadows area. Iron concentrations ranged from 45 to 45,000 micrograms per liter, and 17 of 20 samples exceeded the 300-micrograms-per-liter recommended drinking-water standard of the Wisconsin Department of Natural Resources.