http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
effects of vegetation on the water balance of an Edwards Plateau watershed
Shrub encroachment can reduce water yield from the
Plateau region of Texas through increased
evapotranspirational losses. This has been
demonstrated through a number of small-scale empirical
studies on the effect of vegetation on hydrology. The goal
of this study was to investigate the effect of vegetation
and brush management on the water balance at the landscape-
scale on the Edwards Plateau using a GIS simulation
modeling approach. A comprehensive GIS data base was
developed for the 206 k study area, Cusenbary Draw
watershed on the Edwards Plateau, as a foundation for
assessing the effect of vegetation on water yield.
Vegetation analysis was conducted for the study area using
1955 and 1990 aerial photography, digital image processing
and GIS analysis. The overall woody vegetation cover
remained relatively constant between 1955 and 1990 due to
brush management practices adopted by ranches within the
watershed. Range sites with the highest potential herbaceous
production experienced declines in woody vegetation cover
from 1955 to 1990. Conversely, incremental increases in
woody vegetation cover were observed on range sites as
herbaceous production potential declined. These observed
differences in woody cover change between range sites imply a
investment in brush management within range sites promising
the highest rate of return. Simulation studies using the
SPUR-91 hydrologic model were conducted to systematically
evaluate the effect of vegetation cover and composition on
the water balance of the watershed. Results of the
simulation studies revealed the dynamics of landscape-scale
hydrologic balances as a function of woody vegetation cover
across range sites. The simulation results agreed well with
the findings of similar small-scale and empirical studies.
The simulation studies also revealed limitations of the
SPLJR-91 hydrologic 'c model and suggested ways to improve
the model structure. The results of the 91 simulation
studies were used to assess the hydrologic impacts associated
with two brush management scenarios. In the absence of brush
management a 50% reduction in water yield from 1990 levels
was predicted. However, with the implementation of a
publicly funded brush management program a 180% increase over
"Major subject: Rangeland Ecology and Management".
Issued also on microfiche from Lange Micrographics.
Includes bibliographical references: pages 66-71.