The Use of Remote Sensing in Drought Monitoring


By: Alan Peterson and Richard D. Landzettel

ES 771 Remote Sensing, Fall 2012



Abstract

Remote Sensing helps drought monitoring in many ways. Images produced by Landsat detect multiple bands or wavelengths of the electromagnetic spectrum, each of these bands have different applications. A composite of bands 1, 2 and 3 creates a natural color image that looks similar to what the human eye sees, whereas band 4 detects near-infrared wavelengths which are used for highlighting vegetation and waterbody changes. Band 5 is useful for quantifying soil moisture and temperature. It is also useful for measuring plant stress. It detects mid-infrared wavelengths. Ground based radar data can be used to create precipitation maps and can be compiled to cover daily, monthly and yearly precipitation totals. This data can also be used to create departure from normal precipitation maps.


Contents


Monitoring Waterbody Changes with Landsat Band 4

Landsat images can be used to compare the size of waterbodies, for example: here is a series of images of the Cheyenee Bottoms Refuge located just north of Great Bend Kansas. Cheyenne Bottoms is a closed basin. A diversion canal from the Arkansas River enters the basin on the left side of the image. The reduced flow of the Arkansas River in the past century and the continued pumping of the Ogallalah Aquifer have caused water supply from the canal to be unreliable. The Nature Conservancy manages the wetlands in the northwest corner of the image while the Kansas Department of Wildlife and Parks manages the interior. A difference in management practices can be seen between the two areas. The Nature Conservancy leaves the area to itsself, whereas KDWP has dikes and gates to control water levels in separate water pools. The S-shaped structures seen on the KDWP portion of the basin are manmade structures built to provide bird nesting grounds away from roads and dikes. These images show Landsat band 4 for the years 2007(a wet year), 2010(a normal year), and 2012(a dry year). This location was chosen primarily because it is in the center third of the Landsat scenes, meaning that it has no data gaps due to the failure of the scan line corrector in 2003 on Landsat 7. This Location was also chosen due to the amount of change in the size of the waterbodies.

Precipitation maps

Using radar indicated precipitation measured throughout the year, yearly precipitation maps can be produced and adjusted to show the departure from the climate precipitation normal.


Temporal Composites

A temporal composite of these images can be used to highlight the changes in a waterbody over time. Primary colors show changes between each year, negative colors show areas without change and secondary colors show areas with constant change. This temporal composite of the Cheyenne Bottoms Refuge using band 4, highlights the changes from 2007 to 2010 in green and 2010 to 2012 in red. Band 4 is typically used for measuring biomass and defining water bodies.

This temporal composite highlights the changes from 2007 to 2010 in green and 2010 to 2012 in blue.



Natural Color Composites

Here are composites of Bands 1, 2, and 3 for the years 1987 and 1989 overlooking the North Fork of the Verdigris River area in the Flint Hills of Kansas about 16 miles southwest of Emporia. 1988 and 1989 were drought years in this portion of Kansas. The area is centered on a regional topographic high. Drainage radiates, generally, from the center of the image. The ground in this area is extremely rocky making it unsuitable for farmland. The Flint Hills has the most intact area of tallgrass prairie in North America. It consists primarily of open pasture land making it useful for measuring plant stress and soil moisture as the land use in this area is static. I-35 and the Cottonwood River are visible in the upper left portion of the images.


Monitoring Stream Flow

These charts show stream flow in the Cottonwood River near Plymouth, Kansas from 1986 to 1989. Notice baseflow conditions during the latter part of 1988 and the majority of 1989. The stream gage is just off of the map to the north.


False Color Infrared

This map compilation uses band 5 from 1887 and 1989. It was created by subtracting a haze corrected window of 1987 from 1989. The result shows the difference between the years 1987 and 1989 in the mid-infrared band. 1989 was a hotter drier year.

False Color Thermal

This map compilation uses band 6 from 1887 and 1989. It was created by subtracting a haze corrected window of 1987 from 1989. The result shows the difference between the years 1987 and 1989 in the thermal band.


Discussion

Modern methods for drought monitoring rely heavily on remote sensing. Landsat provides images for multiple electromagnetic wavelengths, each one with different applications. For the purpose of drought monitoring bands 1-5 are used; bands 1, 2 and 3 for real color comparisons, band 4 for monitoring waterbodies and vegetative biomass, and band 5 for soil moisture and land surface temperature which indicates plant stress. Band 4 images for years with above, normal, and below average precipitation in the Cheyenne Bottoms basin clearly indicate the decrease in the size of waterbodies. The departure from normal precipitation maps for the same years as the band 4 images show a progression as the precipitation deficit lead to the circumstances displayed in the band 4 images. The temporal composites of the band 4 images display the changes in the size of the waterbodies between the years shown. Natural color composits for the North Fork of the Verdigris River area show the changes in land cover as our eyes would see them, and the streamflow charts help show the precipitation deficit in the area. False color images composed of subtracted band 5 images help to indicate plant stress through temperature and soil moisture. All of these are examples of the many benefits remote sensing has to offer drought assessment and monitoring.

References

"Advanced Hydrological Prediciton Service." National Weather Service. NOAA, n.d. Web. 14 Nov. 2012. http://water.weather.gov/precip/index.php

"USGS Global Visualization Viewer." Earth Resources Observation and Science Center (EROS), n.d. Web. 14 Nov. 2012. http://glovis.usgs.gov/

"USGS WaterWatch." USGS Streamflow Duration Hydrograph Builder. Site Number 07182250. http://waterwatch.usgs.gov/index.php


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