Page 66 - 2002 DT 12 issues

“. . . nor any drop to drink” ○ years ago when aquifers were absorb- risen substantially since 1995 and may,
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ing water 20 times faster than today; ○ therefore, be accelerating.
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his Blue Planet is blessed with ○ ○ these reservoirs are essentially nonre- ○ Where water is not pumped back
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abundant water, covering about ○ newable resources. The High Plains into the aquifers, subsidence can be
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T 70 percent of its surface. But ○ aquifer underlies a 450,000-square- more considerable. Withdrawal of wa-
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just over 1 percent of that water is ○ kilometer area from North Dakota to ter in the desert between Phoenix and
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readily available for human use. Of the ○ the Texas Panhandle. Large areas of its Tucson has caused aquifer levels in
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rest, 95.6 percent is salty ocean, and just ○ groundwater have been more than 50 some small areas to drop more than 90
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over 2 percent is locked up in ice and ○ percent depleted. Even if withdrawals ○ meters and the surface to compact more
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atmospheric vapor. According to Sci- ○ ○ don’t exceed recharge, shallow ground- ○ than 3 m. In the San JoaquinValley of
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ence News, that tiny amount is getting ○ water provides a major source for California, the surface has subsided
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smaller every day. ○ rivers, lakes, and streams in some areas. from at least 30 cm to more than 9 m
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Growing cities, typically located on ○ If significant amounts of river water are over an area of 13,000 square miles.
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the banks of rivers, have been divert- ○ drawn for agriculture or other uses, the ○ According to the World Meteoro-
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ing more and more river flow over the ○ ecology of the rivers can suffer. ○ logical Organization, by the year 2025
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centuries. With greater than 20 per- ○ ○ Water banking, popular in the arid about half (3.5 billion people) of the
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cent diversion of the local river’s flow, Southwest, is creating problems of its world’s projected then-population will
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a region is considered to be ○ ○ live in river basins where water scarcity
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water-scarce. Agriculture, ○ significantly affects household and eco-
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industry, and household uses ○ nomic activity. Add to that the
have far exceeded that limit in ○ contamination effects of untreated water
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heavily populated regions. In ○ in developing nations, along with
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1995, more than one-third of ○ industrial pollution and agricultural run-
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the world’s population of 5.7 ○ ○ off injected into surface waters around
billion people lived in such ar- ○ ○ the world, and the need to understand
eas, says Richard B. Lammers ○ the connections between water sources
of the University of New ○ above and below ground becomes criti-
Hampshire. Of those, 450 mil- ○ ○ cal.
lion lived in areas of severe ○ ○ In time, notes Alley, much of the
water stress. ○ world’s thirst will be slaked by aquifer
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As surface water has ○ water artificially recharged from
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grown more scarce, popula- ○ above—that is, if the water pumped in
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tions are relying more heavily ○ isn’t itself contaminated.
on aquifers. Water sources, ○ ○
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which can reside at a depth of ○
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1 kilometer or more, are esti- ○ AnagramAnagram
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○ own. During wet seasons, excess water
mated to hold in excess of 1,000 times ○ ○ by H. Dan Wray
is pumped into aquifers for withdrawal ○
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more water than falls on the earth’s sur- ○ ○
when needed. The continual cycles of
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face, according to William M. Alley of ○ input and withdrawal cause the ground ○ ry this one: Rear-
the U.S. Geological Survey (USGS). At ○ ○ to compact and subside, then rebound. ○ ○
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least half of the U.S. population and ○ Some of the subsidence is permanent ○ T eleven” to get the
more than one-quarter of people glo- ○ ○ as the grains of rock shift and settle ○ ○
bally obtain their primary drinking wa- ○ closer together, leaving less space for ○ ○ same answer. The solution is
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○ on page 3, but no peeking!
ter from groundwater. ○ recharge the next season. Satellite stud- ○
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Deep aquifers are slow to recharge. ○ ies by the USGS show that in the Los ○
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Water collected today likely fell 15,000 Angeles area, the compaction rate has
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Page 2 FORRC/September, 2002