Botkin Environmental Science Earth as Living Planet 8th txtbk

18.8 Global Water Shortage Linked to Food Supply 393
(a)
FIGURE 18.21 The concrete Marmot Dam before (a) and during (b) removal in 2007.
(b)
The cost of the dam in 1948 was about $300,000.
The cost to remove the dam and sediment will be more
than ten times that amount.
The perception of dams as permanent edifices, similar
to the pyramids of Egypt, has clearly changed. What is
learned from studying the removal of the Edwards Dam
in Maine, the Marmot Dam in Oregon, and the Matilija
Dam in California will be useful in planning other damremoval
projects. The studies will also provide important
case histories to evaluate ecological restoration of rivers
after removal of dams. In sum, removing dams is simple in
concept, but involves complex problems relating to sediment
and water. It provides an opportunity to restore ecosystems,
but with that opportunity comes responsibility. 31
18.8 Global Water Shortage
Linked to Food Supply
As a capstone to this chapter, we present the hypothesis
that we are facing a growing water shortage linked to our
food supply. This is potentially a very serious problem.
In the past few years, we have begun to realize that iso-
lated water shortages are apparently indicators of a global
pattern. 33 At numerous locations on Earth, both surface
water and groundwater are being stressed and depleted:
Groundwater in the United States, China, India, Pakistan,
Mexico, and many other countries is being mined
(used faster than it is being renewed) and is therefore
being depleted.
Large bodies of water—for example, the Aral Sea—are
drying up (see earlier Figures 18.8–10).
Large rivers, including the Colorado in the United States
and the Yellow in China, do not deliver any water to the
ocean in some seasons or years. Others, such as the Nile in
Africa, have had their flow to the ocean greatly reduced.
Water demand during the past half-century has tripled
as the human population more than doubled. In the
next half-century, the human population is expected to
grow by another 2 to 3 billion. There is growing concern
that there won’t be enough water to grow the food to feed
the 8–9 billion people expected to be inhabiting the planet
by the year 2050. Therefore, a food shortage linked to
water resources seems a real possibility. The problem is