Soil Moisture Variability and Critical Moisture Levels at Big Meadows, Shenandoah National Park, Virginia
Abstract
Variability in soil moisture is controlled by temporal variability in atmospheric conditions and spatial variability in land surface conditions. Patterns relating the mean moisture content in a field to the variance have been studied using assumed random variations in the land surface variables. Although purely random calculations may describe the relationship between mean and variance, observed spatial patterns are affected strongly by non-random patterns in soil properties and in topography. We used a soil moisture balance model at 75 points at Big Meadows, an upland wetland in Shenandoah National Park, Virginia and captured the land surface variability using soil conductivity measured with an infiltrometer along with slope and aspect derived from a DEM. We calibrated the model using volumetric moisture content measurements made with a TDR probe. We used a series of numerical experiments to examine the effects of rainfall variability on the spatial distribution of soil moisture. A study of critical water stress periods is of particular importance at Big Meadows because this area is extensively used during summer months. To explore how normal climate variability affects the amount of time soil moisture is below the critical moisture content, θc, we ran the model for 3 drought years and 3 wet years. We used stochastically derived time series to reproduce local precipitation and temperature patterns. To explore potential impacts of climate change: we (1) held the total annual precipitation constant, increased the magnitude and decreased the intensity of storms, and we (2) increased the mean annual temperature by 5 degrees C. On average, vegetation is stressed 76.3% of the year in wet years, 80.5% of the year in drought years, and 78.1% of the year in climate change years.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFM.H13A1346L
- Keywords:
-
- 1800 HYDROLOGY;
- 1847 Modeling;
- 1866 Soil moisture