Fluctuating Water Levels as Indicators of Global
Change: Examples from Around the World
Cynthia A. Evans, Joe Caruana, David L. Amsbury,
and Kamlesh P. Lulla
Office of Earth Sciences
NASA Johnson Space Center
Houston, Texas USA
Astronauts participating in the Shuttle-Mir program from 1996 through 1998 documented the interaction between short-term climate variability and longer term human demands on water resources in many regions of the world. Several high-use watersheds experienced rapid changes and extremes - both floods and drought - during this period. In Asia, astronauts documented the continued desiccation of the Aral' Sea, and effects of flooding along the shores of the Caspian (see Chapters 9 to 19). Southwestern North America went from drought in 1996 to flooding in 1997 and 1998, while the Ohio-Mississippi Valley flooded in spring of 1997. In Africa, heavy monsoons flooded Lake Nasser in late 1996 to its highest level ever, resulting in new developments in the Egyptian desert. Similarly, heavier-than-usual precipitation in early 1998 filled new reservoirs on the Euphrates River in Turkey, and El Niņo-related rains in early 1998 flooded much of northeast Africa. We also tracked water levels in Lake Chad, seasonal changes along the inland delta of the Niger River, and the Okavango swamp in Botswana. Because astronauts on long-duration flights develop detailed knowledge about the status of water bodies, they are able to recognize and record changes. The image data collected during the Shuttle-Mir long-duration flights allowed differentiation of seasonal variability, annual climate variations, and some human-induced changes.
Comparative analyses of these images with historical imagery allowed changes to be quantified in several large reservoirs and catchment basins. For example, the Aral' Sea continued to shrink by roughly 5000 km2 between 1996 and 1998, now covering an area of only 27,000 km2. The area of Lake Amistad on the Rio Grande was reduced by more than half during the 1996 drought in western North America. In Egypt, a newly flooded depression covers 256 km2. These images and the simple analyses resulting from them can become tools for rapid assessment of changing conditions in high-use watersheds around the world.
Citation for the published article
Evans, C. A., J. Caruana, D. L. Amsbury, and K. P. Lulla, 2000. Fluctuating water levels as indicators of global change: Examples from around the world, in Dynamic Earth Environments: Remote Sensing Observations from Shuttle-Mir Missions (K. P. Lulla and L. V. Dessinov, eds.), John Wiley & Sons, New York, pp. 43-60, 262, 271-272.
Links to Color Images
|Figure 4.1 Map of significant precipitation anomalies in 1997. The boxes numbered 2 to 9 correspond to Figures 4.2 to 4.9, and identify locations of examples discussed in the text. (Modified from Climate Prediction Center, 1998.)|
|Figure 4.2 Aral' Sea. This set of four photographs (NASA photographs STS51F-36-059, STS047-79-082, NM21-762-025A, and NASA6-707-034) provides a pictorial time series of water-level drops in the Aral' Sea from 1985 through early 1998. Note that the sequence includes the cutoff near the Syr Darya delta (a) between the northern and southern basins between 1985 and 1992. Also note the shape of the Amu Darya deltaic coastline (b) and the progresively increased size of Vozrozhdeniya Island (c). Finally, between 1996 and 1998, Barsakel'mes Island, the arrow-shaped island (d), joins with the mainland to become a peninsula.|
|Figure 4.3 Areal coverage of the Aral' Sea, mapped from the photographs in Figure 4.2. The images were rectified to a common map base (K. Knowlton, unpublished data), and areas were measured from these projections.|
|Figure 4.4 Amistad Reservoir, Texas-Mexico border. The 1996 drought in the southwestern United States resulted in a 50-ft drop in water level of Amistad Reservoir. View (B), taken in August 1996, shows the former shoreline of the lake (white region circling the reservoir) and its diminished size (calculated to cover roughly 75 kmē) after the drought (NASA photograph NM22-705-059). For comparison, view (A), taken in October 1989, shows normal water levels covering an area of nearly 200 kmē (NASA photograph STS034-74-101).|
|Figure 4.5 Floods in the Ohio and Mississippi Rivers. Top right: Ohio River flooding at Evansville, Indiana on March 9,1997 (NASA photograph NM23-705-321). The feature on the left side is a Mir solar array. Top left: Flooding from the confluence of the Ohio and Mississippi Rivers to Memphis, Tennessee on March 15, 1998 (NASA photograph NM23-712-438). The area inside the white box, which includes the city of Memphis, is given in detail below. Bottom left: Detailed view of the area inside the box (NASA photograph NM23-712-438). The extent of flooding around Memphis is obvious. Bottom right: FOr comparison, image showing the same area during normal river flow in September 1996 (NASA photograph STS079-812-086).|
|Figure 4.6 Lake Nasser and New Valley development, Egypt. The left photo (NASA photograph STS087-758-086) is an oblique view showing most of Lake Nasser in November 1997. On the right, the top two photos (NASA photograph NM22-705-079 and NM23-703-232) compare the relative water levels in the same section of central Lake Nasser in August 1996 and March 1997. The white boxes define the section of Lake Nasser analyzed in this paper. The lake areas within the box are 870 kmēin August 1996 and 970 kmē in March 1997. After the rise in the lake, the New Valley Project (bottom right, NASA photograph STS088-719-002) was implemented, tapping Lake Nasser from the west and transporting water into a formerly barren wadi. The project was not visible as late as June 7, 1998. The December 1998 photograph shows the recently flooded New Valley. The area of the flooded region is calculated to be about 400 kmē.|
|Figure 4.7 Euphrates River and the Ataturk Dam: (A) map showing the upper Euphrates River and location of the photo (box); (B) photograph (NASA photograph NASA7-703-56K) showing the recent hydrologic modifications in Turkey and the proximity of the Turkish Ataturk Dam to the Syrian Euphrates Dam (marked "Dam").|
|Figure 4.8 Inland delta of the Niger River. (A) In October 1996 (NASA photograph NM22-736-055) the dark green vegetation is luch when water from the summer rains pass through the region. Although vegetation cover lasts only a few months, it provides a strong visual contrast with the surrounding desert countryside. (B) By April 1997, the wetlands have dried up, and the inland delta is a uniform tan color (NASA photograph NM23-730-271). The white box outlines the area covered by view (A).|
|Figure 4.9 Okavango Delta. Vegetation cover in the Okavango delta in mid-October 1996 (NASA photograph NM22-723-083) and early July 1997 (NASA photograph NASA5-707-089). The left-hand view is a synoptic photograph of the Okavango, taken with the 100-mm lens in mid October 1996. Note that the distal ends of many of the delta fingers are dry, especially on the western side of the river. The white box on the photo depicts the area analyzed in the detailed sections on the right for change in vegetation cover between October 1996 (1840 kmē of vegetation) and July 1997 (2750 kmē of vegetation). Although many distributaries are still dry in July 1997, more vegetation filled the center part of the delta and extended farther out the distributaries, compared with the October 1996 view.|
|Figure 4.10 Patagonian glaciers. This composite of two photographs (NASA photographs NM22-737-091 and NM22-737-092) taken in the sunglint, shows the position of several glaciers flowing from the ice field of Patagonia (the Darwin Cordillera) into the Pacific fjords. Taken during southern hemisphere summer, the glaciers are calving andthe sunglint pattern suggests that there is water covering parts of some of the glaciers (arrows).|
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