Brandon Weihs, Ph.D. Student, Geography
Dr. David Haukos
U.S. Fish and Wildlife Service
Bill Johnson, USFWS
Dr. Steve Sensie, USFWS
Dr. Grant Harris, USFWS
Location: Southern High Plains, Texas and New Mexico
Completion: December 2015
Inundation patterns of playa wetlands are important considerations for alternative energy development on the High Plains.
(1) Develop an accurate spatial remote sensing model to document hydrological condition of playas in the Texas High Plains.
(2) Assess accuracy of results from Landsat analyses.
(3) Construct trends of hydrological conditions of playas and saline lakes since the 1970s.
(4) Test competing models containing available landscape level data to determine if differences between the 1970s and 2000s are due to changes in climatic conditions or perhaps due to other factors (e.g., irrigation).
Progress and Results:
A primary objective of the North American Waterfowl Management Plan is to maintain
(and restore) continental waterfowl populations at 1970s numbers. Playas are the
dominant wetland feature in the Texas High Plains. Historical U.S. Department of
Agriculture soil survey maps suggest there are more than 20,500 playas in this
region. Although playas average only 6.3 ha in size and account for only 2% of the
Texas High Plains landscape, they provide ecological functions critical to the
persistence of nearly all flora and fauna in the region. Timing and duration of
playa hydroperiods drive both plant and invertebrate production. Playas are vital
migratory stop-over and wintering sites for migratory birds. Although current playa
conditions, in terms of availability during midwinter due to natural flooding
events, are increasingly understood, little is known about playa conditions during
the 1970s through 1990s. Historically, playas were actually incorporated into many
furrow irrigation systems, either as catchment basins or as tailwater recovery
basins. Thus, the landscape during the 1970s may have been artificially wet due
to irrigation. If average annual habitat availability, in terms of the percent of
inundated playas, was enhanced due to irrigation runoff, then using waterfowl
numbers during this decade may result in habitat objectives that are simply not
reasonable under natural and current conditions. In 1972 Landsat 1 was the first
orbiting satellite to begin collecting data with the expressed intent to monitor
the Earth's surface, an effort that continues today through Landsat VII. Playa
sample sites required for remote sensing modeling procedures will be selected using
both existing NWI GIS data and digitized historical soil survey data. For the 1970s,
Landsat data from this period is limited to information acquired using the
multispectral scanner system (MSS) sensor. MSS data were acquired with a revisit
time of 18 days at a nominal ground sample distance (GSD) of 60 m2.
Sample results will support modeling efforts run in ERDAS Imagine. Model out-puts
will be incorporated into a GIS to measure the spatial and temporal extent of wet
and dry playa basins across the study area for the time period assessed. These
results should provide reasonable estimates of the annual availability and duration
of inundated playas for this period and better inform regional waterfowl population
Figure 1. Study area showing SHP extent (red line), counties (light grey), and Landsat path/rows used (black line, no-fill polygons).