HR: 16:30h
AN: H32H-03    [PDF]
TI: Observations and Modeling of Soil Water Storage in Variable Saturation Zones
AU: * Caroline, M H
EM: caroline.masek@hdrinc.com
AF: HDR Engineering, Inc., 2202 North West Shore Boulevard, Suite 250, Tampa, FL 33607 United States
AB: Variable saturation zones occur in shallow water table environments due to the small storage capacity in the soil profile, or the Soil Water Storage Capacity (SWSC). The SWSC is the depth of water required to raise a shallow water table to the land surface. The health of natural and constructed wetland systems depends on the hydroperiod, or the duration of continuous saturation, of the variable saturation zones in the systems. The concept of SWSC is fundamental to hydroperiod development and other hydrologic processes, including surface runoff by saturation excess and estimation of the length of the overland flow plane. Initial conditions, such as the pre-storm soil moisture profile and depth to water table, are critical when predicting runoff in these areas. In this study, we monitored the water table and the soil moisture at different depths in a shallow Floridian sand profile. The relatively high resolution of soil moisture with depth allowed simultaneous observations of encapsulated air and SWSC above a shallow water table. The objectives of this study were 1) to introduce an equation for SWSC as a function of depth to the water table, 2) to assess the influences of the capillary fringe and encapsulated air on SWSC, and 3) to test and validate the concept of SWSC with field data. The main finding is that the profile soil water storage can be expressed as a polynomial function of the depth to water table. The parameters of this function can be derived from the soil hydraulic and physical characteristics. Encapsulated air reduced the available soil storage and resulted in a rapid rise in the water table. Soil storage results including and excluding air are compared as a function of water table depth. Ignoring encapsulated air below the water table may result in significant overestimation of profile water storage.
DE: 1866 Soil moisture
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2003 Fall Meeting