LANDSCAPE EVOLUTION AND SHALLOW GROUNDWATER HYDROLOGY OF A TILL LANDSCAPE IN CENTRAL IOWA

Deciphering the effects of land use on environmental quality requires detailed knowledge of the processes governing soil and landscape genes is. The objective of this study was to describe the landscape evolutio n and shallow groundwater hydrology of a glaciated landscape in Iowa a nd to relate the soil color pattern to water table fluctuations. Strat igraphic and geomorphic maps and cross sections were prepared using ch aracterization data from 128 soil cores collected from a 32-ha site. O ne transect crossing several hillslopes was instrumented with 47 piezo meters to determine groundwater how direction, Three strata of surfici al sediments overlying till were identified. The upper two strata were slope alluvium deposited after 4300 YBP, which limits the age of the soils to the late Holocene or younger, The lower sediment resembled al luvium and may be supraglacial sediment draped on the till and later e roded from adjacent hillslopes. The hydrology was characterized by rec harge under topographic highs, lateral groundwater Bow on sideslopes a nd discharge in swales, During dry periods, however, portions of highe r swales acted as recharge areas and groundwater flow was directed bet ween swales. Morphologic indicators of wetness are better expressed an d shallower in soils at footslope and toeslope positions, but some of these features are relict because of the lowering of the water table b y artificial drainage.