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<br />· about 20,000 acres (8,000 ha) of intertidal wetlands,
<br />which can be found up to 34 miles (56 km) upstream
<br />from the Gulf supported by high tides; and
<br />
<br />. la Cienega de Santa, a wetland in the eastern delta
<br />that was unintentionally created by agricultural
<br />return flows from the U.S. and Mexico that arrive via
<br />drainage canals, and the adjacent EI Doctor and EI
<br />Indio wetlands, both of which are supported by
<br />artesian springs - these wetlands encompass some
<br />44,000 acres (18,000 ha).
<br />
<br />RECENT RESEARCH EFFORTS
<br />
<br />During fieldwork in 1997 and 1998, scientists supported
<br />by the Environmental Defense Fund (EDF), the Envi-
<br />ronmental Research Laboratory (ERL) in Arizona, the
<br />Instituto Tecnologico y de Estudios Superiores de
<br />Monterrey (ITESM), and the Sonoran Institute docu-
<br />mented the extent of surviving ecosystems in the
<br />Colorado River, studied their habitat values, and
<br />assessed their overall ecological significance. They also
<br />determined the quantity and quality of water in the
<br />delta. These measurements playa critical role in defin-
<br />ing what is needed to secure the viability of these
<br />remnant delta ecosystems. This report will detail these
<br />findings.
<br />
<br />Researchers also examined the size and periodicity of
<br />floods in the delta. Floods are known to have high value
<br />for riparian and estuary ecosystems (Grimm et aI., 1997).
<br />The cottonwood for instance, an important riparian
<br />species, depends on floods for seed germination. Flood
<br />flows that reached the delta from 1980 to 1987 were up
<br />to ten times higher than normal, and average excess
<br />flows across the border from 1980 to 1993 were three
<br />times higher than Mexico's legal entitlement (Glenn et
<br />aI., 1996).7 These flows have reestablished an active
<br />floodplain, revegetated many areas of the floodplain
<br />within irrigation and flood control levees, and helped
<br />to reestablish riparian forests. Many marine species
<br />depend on freshwater to keep salinity levels low in
<br />estuaries so they can breed and lay eggs, and flood flows
<br />have improved delta shrimp fisheries (Galindo-Beet,
<br />n.d.). Flood releases to the delta can be expected to
<br />continue if reservoirs along the Colorado remain full,
<br />but a string of dry years could eliminate the fragile
<br />ecosystems that have been reestablished.
<br />
<br />7 Delivery requirements to Mexico are discussed at length in Chapter 2.
<br />8 Population figures are based on 1995 data.
<br />
<br />ENvmONMENTAL DHENSE FUND
<br />
<br />PROTECTING THE INTERESTS
<br />OF THE DELTA'S PEOPLE
<br />
<br />People living in the delta region continue to use and
<br />depend on the delta, from fishermen in the Gulf to farm-
<br />ers along its northern margins. Approximately 207,000
<br />people live in the 1127 small settlements within 5 km of
<br />the delta. Most of these settlements (92 percent) have
<br />fewer than 100 inhabitants (Valdes-Casillas et aI., 1998a).
<br />[See Figure 3.] The two largest municipalities in the delta
<br />region are Mexicali (pop. 696,034) and San Luis Rio
<br />Colorado (pop. 133,140).8 The economic promise of these
<br />border cities has led to high rates of immigration from
<br />other regions of Mexico. San Luis Rio Colorado's growth
<br />rate exceeds 3.5 percent annually (Carrillo, 1999)
<br />
<br />Nearly 2.5 million acres (1 million ha) around the delta
<br />are used for agricultural production, relying on water
<br />from the Colorado and its tributaries. The irrigation
<br />district that includes Mexicali and San Luis Rio
<br />Colorado-some 440,000 acres (178,000 ha)-was
<br />recently assessed a value of nearly $3 billion in annual
<br />crop production (Valdes-Casillas et aI., 1998a). The delta
<br />region attracts migrants from central Mexico with the
<br />economic promise of proximity to the international
<br />border and the predominance of irrigated agriculture.
<br />Concentrated in wheat, cotton, and alfalfa production,
<br />it is the region's largest industry, employing upward of
<br />60 percent of the working population.
<br />
<br />The delta generates significant economic activity in
<br />addition to irrigated agriculture. Three communities
<br />- EI Golfo de Santa Clara, San Filipe, and Puerto
<br />PeTIasco - continue to rely on fishing as the basis for their
<br />culture and economy. Sixteen tourist camps located near
<br />the confluence of the Rio Hardy and the Rio Colorado
<br />are used by visitors from Mexicali and the United States
<br />for fishing, hunting, and other water-based recreation,
<br />and local residents work as guides for these visitors.
<br />Many communities in the delta rely on riparian forests
<br />for fuel wood. One community produces catfish in an
<br />aquaculture facility (Valdes-Casillas et aI., 1998a).
<br />
<br />Today, approximately 600 Native Americans live in the
<br />delta region. Of these, some 200 are Cucapa, who own
<br />353,000 acres (143,000 ha) along the Rio Hardy and Rio
<br />Colorado (Valdes-Casillas et aI., 1998a). No longer able
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