Others have shown that water can flow through frozen bottomland soil. The purpose of this study is to examine water flow through soil at sideslope positions. The first study was conducted in a farmer's field on Clarion and Nicollet soils. Time domain reflectometry (TDR) waveguides were installed horizontally at several depths to 1 m at the two sites on a hill. Thermocouples were installed horizontally at the upslope (Clarion) site. Liquid soil water content was monitored for the winters of 1993-4 and 1994-5. Then the second study was conducted on experimental station land. The TDR were installed horizontally at four positions on the hillside to a maximum depth of 1.7 m. Thermocouples were installed at the same depths, and monitoring was continued for the winters of 1995-6 and 1996-7. In the farmer's field, the Clarion soil froze more deeply than the Nicollet soil. In December and February in both years there was apparent water accumulation below the depth of freezing. The water accumulation at the lower depths was due to rain and/or snowmelt, and the intermediate frozen layers of soil did not thaw. The fall of 1995 was very dry which resulted in large pores being air-filled during and after freezing. Then when 50 mm of rain fell in January 1996, the rain penetrated the frozen soil, accumulating at lower depths without thawing the soil above. Within a few hours, an arctic cold front went through and temperatures dropped over 20oC. The rain water froze in the large pores, preventing further entry of water through frozen layers. All subsequent rain and snowmelt events were unable to penetrate frozen layers and ran off. These results showed the varying response of water flow through frozen soil, which depended on water content at the time of freezing as well as subsequent ice blockage within larger pores.
Dr. Sally D. Logsdon USDA-ARS-NSTL 2150 Pammel Dr. Ames, IA 50011 Telephone: (515)-294-8265 Fax: (515)-294-8125 E-mail: logsdon@nstl.gov