Geography Reference
In-Depth Information
gional trade. After several decades, however, soil salinization—a common problem with ir-
rigation projects in arid regions—caused the system and the city to collapse (Stone and Zi-
mansky 2004). Similarly, gravity-operated water-distribution networks known as
aflaj
sys-
tems were commonly used in Oman and elsewhere in the Middle East to allocate ground-
water for domestic use and agricultural irrigation. Many such systems are still in use today
and rely on a combination of ancient engineering and traditional social management mech-
anisms largely outside the regulation of any state.
11
Dams have occupied a prominent position in states' water-management portfolios for
thousands of years: the remains of the Sadd-el-Kafara earthen dam in Egypt are dated to
2,600
B.C.E
,andRomandamsconstructedofconcreteandmortararenearlyasancient(Sch-
nitter 1994). By the 1600s, the Spanish conquistadors thought they were taking European
knowledge and expertise with them to the New World; when they arrived, however, they
found that the Aztec capital Tenochtitlan was in its own right already a hub of water-en-
gineering projects, including dams and aqueducts. Dams provide people with the oppor-
tunity to harness water for a variety of uses, including irrigation, flood control, household
and commercial consumption, recreation, and navigation. They also equip people with the
capacity to heavily use—and sometimes seriously overexploit—water resources. Dams are
now a ubiquitous part of the landscape in most parts of the world: a georeferenced database
of all dams and reservoirs worldwide shows a dense distribution of dams in almost every
habitable part of the world (Nilsson et al. 2005).
The impacts of this proliferation of dams on the world's rivers have been profound.
Reservoir storageexceeds theannualdischargeinatleast sixmajorriversystems: theMan-
icougan,Colorado,Volta,Tigris-Euphrates,MaeKhlong,andRíoNegro.Anotherfourteen
major rivers are so heavily regulated that more than half of their annual flow is diverted for
reservoir storage and use. Several of the world's great rivers, including the Colorado, the
Nile, and the Yellow, no longer reach the sea year round (Nilsson et al. 2005).
12
In modern times, the construction of dams of all sizes is an integral part of the story of
China's rise to industrial might. In 1949, on the eve of the socialist revolution that brought
the CCP to power, the nation was home to only a handful of hydropower stations and reser-
voirs. In 1950, Mao Zedong approved the Guanting Reservoir Project near Beijing, which
was completed in 1954 as China's first large reservoir project in the modern era (Ma Jun
2004:133). Understanding the prolific growth of dams in China over the past several dec-
ades requires a basic grasp of the nation's transformation from a largely agrarian economy
to a manufacturing powerhouse, a trend that has been supported in part by a massive effort
to regulate and harness rivers throughout the country. Approximately 86,000 dams of vary-
ing sizes were built in China between 1949 and 1990. The vast majority of them were em-
bankment dams of relatively modest scale constructed of earth or rock and used to control
flow, prevent seasonal flooding, or meet irrigation needs in a nation whose population was
still primarily agrarian. Beginning in the 1980s and 1990s, however, the focus shifted to
