Landscape Evolution and Shallow Groundwater Hydrology of a Till Landscape in Central Iowa

Abstract

AbstractDeciphering the effects of land use on environmental quality requires detailed knowledge of the processes governing soil and landscape genesis. The objective of this study was to describe the landscape evolution and shallow groundwater hydrology of a glaciated landscape in Iowa and to relate the soil color pattern to water table fluctuations. Stratigraphic and geomorphic maps and cross sections were prepared using characterization data from 128 soil cores collected from a 32‐ha site. One transect crossing several hillslopes was instrumented with 47 piezometers to determine groundwater flow direction. Three strata of surficial 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 alluvium and may be supraglacial sediment draped on the till and later eroded from adjacent hillslopes. The hydrology was characterized by recharge under topographic highs, lateral groundwater flow on sideslopes and discharge in swales. During dry periods, however, portions of higher swales acted as recharge areas and groundwater flow was directed between swales. Morphologic indicators of wetness are better expressed and shallower in soils at footslope and toeslope positions, but some of these features are relict because of the lowering of the water table by artificial drainage.