Concern regarding contamination migration on Fort Wainwright, Alaska prompted an effort to develop an operational hydrologic model of subsurface flow rates and directions. Hydrology in discontinuous permafrost is extremely complicated and many obstacles were encountered in attempts to model transport plumes. Our approach was through a rigorous field investigation based upon measurements of water table elevations, water chemistry, soil thermal conditions and local meteorologic conditions. Characterization of surface conditions was accomplished through physical measurements of soil temperature and moisture content, precipitation, air temperature and relative humidity. During spring melt, snow surveys were conducted daily to measure rates of snow melt thus enabling us to characterize groundwater recharge rates and locations. This paper presents the results of an investigation on the influence of discontinuous permafrost on recharge patterns. This was accomplished through measurements of precipitation input (rainfall and snowmelt) and the response of soil moisture and groundwater levels.

In this area, the presence of ancient sloughs, discontinuous permafrost, low hydraulic gradients and the rise and fall of the Chena River make this system very complex. The process of infiltration of surface water to the groundwater represents a major question, not just in regard to magnitude, but also in terms of spatial distribution of recharge. Timing of recharge with respect to seasonal frost is also a significant problem which was addressed. We collected data to resolve this question by installing thermistor and TDR probes in strategic locations. These instruments provide adequate data to estimate soil moisture infiltration and for modeling freezing and thawing of the active layer.

Larry D. Hinzman
Water Research Center
University of Alaska
Fairbanks, Alaska  99775-5860
Phone 907-474-7331
FAX   907-474-7979
E-Mail: ffldh@aurora.alaska.edu