Climatic changes
together with increases in population, agriculture and industry
are over-using water resources in many parts of the world,
whilst in other regions lives are endangered as a result of
flooding from heavy rainfall, coastal storms and melting snow
and ice.
Satellite imagery can aid the monitoring of water resources
over large areas. Location of surface water and healthy vegetation
are readily identified and mapped with infra-red imagery,
whilst structural geological interpretation of imagery can
aid the search for underground reserves.
Satellite images provide a low cost and potentially rapid
means to monitor and map the devastating effects of flooding.
NPA offer reliable flood mapping services utilising both
optical and microwave satellite data.
Satellite imagery also provides a means to derive bathymetric
contours up to 25m in clear coastal waters. For more information
on this technique, see NPA's bathymetric mapping page.
The changing state of many of the world's inland water bodies can
be monitored accurately over long periods using satellite imagery,
for example the Kara-Bogaz-Gol lagoon, which has been affected
dramatically by the fluctuations of the Caspian Sea:
Kara-Bogaz-Gol, Turkmenistan
Monitoring fluctuations in the
water level of the Kara-Bogaz-Gol using satellite imagery
The
Kara-Bogaz-Gol (KBG) is a large, shallow lagoon of the Caspian
Sea joined by a narrow, steep sided strait, so
the Caspian's fluctuations have affected the KBG dramatically.
Evaporation makes it one of the saltiest bodies of water
in the world and salt from the shores has been used commercially
since at least the 1920s. For the century before 1977,
the net trend of the Caspian's fluctuations was consistently
downward. Then from 1977 it began to rise. In 1980, believing
the rise to be temporary, the Caspian-KBG strait was dammed,
intending to retain water to sustain the salt industry.
But by November 1983 the KBG dried up entirely and construction
crews rushed to build an aquaduct to let water through
the dam. But while the dam was in place, not only did the
KBG's water level rapidly drop by 2m or more, but the bottom
also rose 0.5m, due to the precipitation of salts. As the
dam choked off the KBG's inflow, the resulting "salt
bowl" caused widespread blowing salt, soil poisoning
and health problems hundreds of kilometers downwind to
the east. In the spring of 1992, the President of Turkmenistan
began the dam's demolition. Satellite imagery has helped
monitor and map the KBG as it has disappeared and then
reappeared.
