Soil Hydrology on an End Moraine and a Dissected Till Plain in West‐Central Indiana

Abstract

Soil hydrologic properties are a function of precipitation (P)‐evapotranspiration relations, stratigraphy, and geomorphology. An understanding of soil hydrology helps us predict many soil and ecosystem properties. We studied soil hydrology on an end moraine and on a dissected till plain in west‐central Indiana. We measured hydraulic head, water table level, redox potential (EH), and temperature, with piezometers (0.25‐, 0.50‐, 1.0‐, 2.0‐, 4.5‐m depth), observation wells, platinum electrodes (0.25‐, 0.50‐, and 1.0‐m), and thermocouples (0.25‐, 0.50‐, 1.0‐, and 2.0‐m), respectively, in soils along two soil toposequences for 9 yr. Water table levels drop rapidly when hardwood trees first leaf out in the spring, and rise rapidly after the trees go dormant in the fall. The Thornthwaite model underestimates evapotranspiration in the forest in the spring. In the dissected plain underlain with dense till, water is held up by the slowly permeable till. Water moves from the interior of the till plain to the dissected bevel where it periodically rises within 1 m of the surface but does not cause redoximorphic features. Soils on the crest of a moraine are similar in morphology to those on the till plain bevel, but have essentially no high water table because there is no upslope contributing area to serve as a water source. In the wetter soils, reduction begins when a soil horizon becomes wet but not saturated, and proceeds more rapidly when the horizon is saturated. There is a lag period of 2 to 8 wk between initial saturation of the soil at 25 cm and minimum EH.