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than during 1971 even though 1980 was a dryer year than 1971, suggesting that the seasonal component of pumpage for the Prairie du Chien -Jordan aquifer decreased between 1971 and 1980. Water levels in the Mount Simon -Hinckley aquifer indicate that ground water flows from the northwest corner of the study area generally southeast to the vicinity of the Minnesota River and the Mississippi River north of its confluence with the St. Croix and north to that same vicinity from a water - level high south of the study area. Ground water also flows east to the St. Croix and the Mississippi south of its confluence with the St. Croix. However, the natural flow pattern is interrupted by a large cone of depression in the water -level surface near pumping centers in east -central Hennepin and southeas- tern Ramsey Counties. During 1971, the measurable cone of depress_ m was about 25 miles in diameter and 100 to 150 ft deep. The location, depth, and shape of the cone suggest that the Mount Simon -Hinckley aquifer is in poor hydraulic connection with the shallow ground -water system and the major streams. Most of the water that flows into the cores of depression may be derived from leakage through the hydrogeologic units that separate the Mount Simon -Hinckley and Prairie du Chien -Jordan aquifers. Between 1971 and 1980, water levels in the Mount Simon -Hinckley aquifer rose more than 10 ft throughout most of the done of depression and more than 50 ft in the center of the cone, which decreased in area in response to decreased annual pumpage during this period Seasonal water -level declines due to increased summer pumping generally are greater in the Mount Simon -Hinckley aquifer than in the Prairie du Mien - Jordan aquifer and are generally greatest during periods of below -normal pre- cipitation. During 1971, a year of above -average precipitation, water levels in a relatively small area declined more than 10 ft from winter to summer; maximum declines were less than 20 ft. However, during 1980, a year of sig- nificantly below -average precipitation, water levels in the Mount Simon - Hinckley aquifer declined more than 10 ft throughout most of the cone of depression with maximum declines of over 50 ft. This decline in water levels may result from use by municipalities of wells in the Mount Simon -Hinckley aquifer to meet peak demands for water, whereas wells in the Prairie du Chien - Jordan aquifer are used to meet normal demands. In total, the water -level data suggest that (1) annual pumpage from the Prairie du Chien -Jordan aquifer was fairly constant betweer, 1971 and 1980, producing fairly stable water levels; (2) annual pumpage from the Mount Simon - Hinckley aquifer decreased from 1971 to 1980 causing water levels in the aqui- fer to rise; and (3) the seasonal component of pumpage for the Mouni_ Simon - Hinckley aquifer is greater than that for the Prairie du Chien -Jordan, pro- ducing seasonal water -level declines that are larger and more widespread in the Mount Simon -Hinckley than in the Prairie du Chien -Jordan, particularly during d; y years. A large amount of data presently are available to characterize water levels and water -level changes in the Prairie du Chien -Jordan and Mount Simon- 'im_klcl aquifers in the Twin Cities area, but the current data -collection dram has some inadequacies that limit application of the water -level data. ,.If problem is that there are too few observation wells in the Mount Simon- hinckley aquifer, so that there may not be enough control points to accurately 21