Soil moisture mapping of drought in Texas
Date
2013-03-15
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Center for Research in Water Resources, University of Texas at Austin
Abstract
Description
Texas experienced in 2011 one of the worst droughts on record. To better
understand and plan for its
effects, this project aimed
to create a map, available online and updated in real-time, showing the extent of
drought in the state of Texas based on soil moisture content information. This
was
to be accomplished
through a combination of the available water storage data provided by the USDA
Soil Survey Geographic
Database (SSURGO)
and the continuously updated
current soil moisture data made available by NLDAS,
the North American Land Data Assimilation System. The SSURGO dataset is
defined at a detailed county
mapping scale, while the NLDAS model operates on a climate-level scale of
1/8
degree polygons,
necessitating consideration of the appropriate scale at which these two datasets should be joined.
The
combination of these two
datasets resulted in a value of current moisture storage in which the percentage of
moisture was defined by NLDAS, while the upper and lower bounds of the moisture levels were defined by
SSURGO. It was decided, however, that current water storage is most easily understood on a percentage
basis, so a soil wetness index was defined and it was upon this metric that the soil moisture map was based.
The analysis began
with a focus
on Travis County
but
was then expanded to the
remainder
of the state of
Texas. The
soil parameters for each NLDAS grid point were acquired, and an
ArcGIS geoprocessing model
was created to calculate and display the average soil wetness index for each county across the state.
Finally,
a 33-year record of
NLDAS
soil moisture data was obtained,
and the groundwork was laid to
employ this
long-term dataset in calculating the statistical significance of current soil moisture data.
Keywords
soil moisture, drought, Texas, mapping, water storage data, SSURGO, NLDAS