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On May 11, 2000, the Governor's Division of Emergency Management issued a Fire Risk Assessment for the State of Texas (firerisk05112000.pdf). The report noted the effect of the prolonged drought in West Texas. Lack of rain had decreased plant moistures to much lower levels than desired, greatly increasing fire risk in the area.
Staff from TNRIS and CSR compared water levels in area impoundments, or ponds, using USGS 7.5 minute topographic map sheets, 1995 color infrared 1-meter resolution digital orthoimagery, and a September 30, 1999, Landsat 7 ETM+ scene. The location coordinates for potential water sources were transmitted to the DEM.
With the arrival of Landsat data from the first day of the fire, the water resources were relocated. However, there was little evidence of water. Drought conditions had affected all visible areas of surface water. To fight the fire, water was trucked to the area from other sources.
The graphic above demonstrates how Landsat 7 ETM+ data aided the analysis of surface water conditions in the Glass Mountains. TNRIS maintains an archive of Landsat 7 ETM+ scenes that have been precision terrain corrected to the same ground control used in the Statewide digital orthophotography program. The vertical integration enables analysts to compare datasets of varying temporal and spatial resolution. The details above show multispectral channels (7, 4, and 2) at 30 meter pixel resolution. In the color composite, vegetated areas appear green, and water features are black to deep blue. Six ponds were located in a 34 square mile area in the September 1999 scene. These can be seen to the lower left of the numerals. Topographic map sheets and high resolution digital orthophotography were used to verify pond location. By May 2000, all that could be discerned were green vegetation patches indicating the former location of standing water.
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