C H APT E RDeclaring the Everglades a national park has had bothgood and bad effects. On the positive side, boardwalksand other facilities such as bird watching towers, informa-tion boards and wildlife viewing trams have been built.Such facilities enable visitors to see the Everglades whilecausing little damage to plant and animal life (figure5.106). Another positive effect is that more people are en-couraged to visit the Everglades and thus understandtheir biophysical environment.

Ironically, encouraging visitors is also a negative factor.Although tourists are only allowed to enter some partsof the park in organised groups, some environmentaldamage cannot be avoided (figure 5.107). The Evergladesattracts hundreds of thousands of visitors each year.Some of these visitors camp in their mobile homes, whileothers are day trippers keen to view the wildlife by tramor air boat (figure 5.108).

5.108 Tourist facilities at the Eoerglades.

QUESTION BLOCK 5T

1. Explain ichat j~ meant lly 'enrichc« u-itl: nutrient» '.

2. Has making the Et'ergl(/d('~ !7 national par): llc/pcd ,11' hurtthe quality oiit» enriroumcnt? GiPt' rcasonsio: your

Case Study of Water Conflict at the Interna-tional Scale - The Colorado River in Mexicoand the U:SA

The Colorado River drains much the south-westernUnited States and a small part of Mexico. Its source is inthe Rocky Mountains of north-east Colorado and it flowsin a generally south-western direction for 2,334 kilometresto the Gulf of California (also known as the Sea of Cortez).The river flows through the US states of Colorado, Utah,and Arizona, and it marks the boundary between Arizonaand Nevada and California. The final 120 kilometres ofthe river flows through Mexico into the Gulf of California(figure 5.110).

The area where the river flows is a region of very lowrainfall. Indeed, much of the course of the river flowsthrough desert, including the spectacular gorge of theGrand Canyon, which was carved by the Colorado River(figure 5.109).

5.109 The Colorado River in the Grand Canyon.

In the early 20th century, the warm climate made the areaattractive to farmers wishing to grow crops using irriga-tion. This is not unique, of course, such as parts of Egyptwhich have almost no rainfall but very successful cropgrowing using the Nile River's water for irrigation.Australia and Israel have also converted large areas tofarming using irrigation water brought from areas ofsurplus rainfall. However, the large demand for water inan area of scarcity led to significant international tensionsbetween the US and Mexico over issues of water quantityand water quality.

As a result of the large-scale use of water for irrigationand urban use in the south-western USA, the ColoradoRiver effectively dries up before it even reaches the sea.Furthermore, the water that does reach Mexico is of suchpoor quality that the Mexican Government has com-plained. For example, salinity at the headwaters of theColorado is 50 parts per million (ppm). However, at thepoint -where the Colorado River =osses the border into

Mexico, salinity was about 400ppm in the early 19005 (asone of the tributaries of the Colorado flowed across a

223 freshwater issues and conflicts

~~

5.110 Enhanced satellite image of the Colorado River (after Google Earth).

layer of rock salt), but this figure rose to 1200 ppm in the1960s as a result of increased irrigation runoff. Earlyagreements between the us and Mexico dealt with thequantity of water in the Colorado River that the USagreed to deliver. However, with the decrease in the qual-ity of water, Mexico pursued new negotiations that wouldensure a maximum level of salinity in water reachingMexico from the us.

Background to the conflict

The conflict over water in the Colorado River arises be-cause the aridity of the area makes water a scarce re-source. The aridity is caused by the cool ocean currentsthat travel south along the Canadian and United Statescoastline from Alaska. Moisture blowing onshore fromthe Pacific Ocean bring high rainfall as they meet thecoastal ranges in the north of California, but as they blowmainly from inland in southern California there is littlemoisture left. The descending winds near Los Angeles arevery dry and, for many months each year, quite hot.

Ironically, it is this dry, warm, coastal climate that leads toa water shortage that has attracted people to the area inever increasing numbers. At the end of World War II thestate of California had approximately the same popula-tion as the whole of Australia - about seven million peo-ple. Now this one state has over 37 million people, withLos Angeles alone having over 15 million in its metropoli-tan area. In fact the dry southern one-third of Californiahas more than 25 million people, or two-thirds of the total

state population. In nearby states such as Nevada newcities were being established in the desert, one of thelargest being the tourism and gambling centre of LasVegas (figure 5.111) .

5.111 Las Vegas, a city in the Nevada Desert, survives 011 water pipedin from the Colorado River.

At the same time as the increasing urban population wasdemanding more water, the state's farmers were alsoneeding more water to expand the area under cultivation(figure 15.112). Increasing affluence has added to thewater shortages, and in the area around Palm Springsalone, which is a desert in its natural state, more than 70golf courses stand out for their rich green colour, whilesurrounding urban areas are dotted with lakes while thesurrounding homes of the wealthy are pictures of waterylushness.

Freshwater issues and conflicts 224

C H APT E R

5.112 Farmland near Yuma, Arizona, that is irrigated with ColoradoRiver water.

The whole built environment stands beside desert sandsfrom below which the water is pumped. This is commonin California as a whole where close to half the water usedfor irrigation is from aquifers or underground supplies.The difference with Palm Springs is the great depth fromwhich the water is pumped. This suggests it is geologi-cally trapped water and will not be replaced. In the Cen-tral Valley, water being pumped to the surface is replacedby surface water soaking down to refill the aquifer.

How did the water shortage evolve?

To the casual observer, regulating the allocation of waterof the Colorado River might seem a simple task. After all,if too much water is being used by upstream users, whynot simply restrict access to water by upstream people toallow sufficient flow for downstream users, includingthose south of the international border with Mexico.

Perhaps surprisingly given the problems experienced bydownstream users, this approach has been followed sincethe early days of using Colorado River waters. Attemptswere made to measure the flow of the river as early as the1890s, and several measuring stations were built at vari-ous points on the river from the 1890s to the 1920s.

On the basis of these measurements, the Colorado Riverbasin was divided into two sections, the upper basin andthe lower basin, with the boundary being placed. some-what arbitrarily at Lees Ferry, a point in the channel of theColorado River in Nevada, about 50 kilometres south ofthe Utah-Arizona boundary, immediately downstream ofthe Glen Canyon Dam.

Each US state with the Colorado flowing through it en-tered into an agreement known as the 'Colorado RiverCompact' in November 1922. The allocation of water be-tween the two parts of the basin were based on an esti-mated annual river flow of about 18.5 billion cubic metres(18,502,228,000 m"). It was known that the annual flow ofthe Colorado River fluctuates greatly, so this figure wasobtained by taking the average of several years of meas-

urements at Lees Ferry in the years leading up to the sign-ing. According to the Colorado River Compact, 9.25 bil-lion cubic metres of water per year from the ColoradoRiver was allocated to each of the upper and lower basinsin perpetuity. The needs of Mexico were not considered.

5.113 The Parker Dam, Colorado River, USA.

Signing the Colorado River Compact cleared th~ way for .a large number of dams to be built along the river to regu-late the flow {figure 5.113}.Some dams.were built to pro~ .vide hydroelectric power, while others were built for .flood control, to provide water for irrigation, recreation,and municipal use. One of the dams, the 221 metre highHoover Dam, is the largest producer of hydroelectricpower and the main flood-control dam (figure 5.114). Tocarry the irrigation water from the dams to urban andfarming areas, a network of long canals was also con-structed. These include the Colorado River Aqueduct,which goes all the way to the southern California coast,the All American Canal, which carries water just north ofthe US-Mexican border to California's Imperial Valley, andthe Gila Canal, in Arizona (figure 5.115).

The engineering behind the works is impressive,and in-cludes tunnels through the Continental Divide to bringwater from the Colorado River to cities and farmlands onthe high plains of Arizona. Despite the impressive engi-neering, the problem of insufficient water persisted in thelower basin and especially in Mexico.

Recent studies in the Colorado River Basin using dendro-chronology (analysis of tree rings), which measures theextent of wet and dry years over long periods by examin-ing the thickness of the annual growth in tree trunks, haveshown that the early 1920s was a period with unusuallywet conditions in the mountains near the source of theriver. Tree ring analyses for the past 300 years indicatethat the correct long-term average flow of the ColoradoRiver is about about 16.65 billion cubic metres. Further-more, it seems that the river's discharge is highly erratic,ranging from 5.4 billion m3 to over 27 billion m3. There-fore, the assumed annual flow of 18.5 billion m3 seems tohave been an over-estimate of the typical flow, whichwould explain the water deficiency in the lower sectionsof the river into Mexico.

225 Freshwater issues and conflicts

PLANET GEOGRAPHY

The water shortages in the lower Colorado River led torepresentations from the Mexican Government, and as aresult, the United States and Mexico entered into a treatyon February 3, 1944 which guaranteed Mexico 1.85 billioncubic metres of Colorado River water annually, this figurebeing subject to increase or decrease under circumstancesprovided for in the treaty.

Nonetheless, over-allocation of water in the US meansthat the 1.85 billion cubic metres allocation does not arriveevery year. Consequently, the Colorado River often soaksinto its river bed and evaporates before reaching the sea.Many regard this as an environmental tragedy becausethis area, which is now often a dry salt flat, was a vastwetland, teeming with more than 400 species of plantsand animals, before the waters of the Colorado werediverted.

The river's delta was also the traditional home of theCopacha Indians, who lived by fishing in the estuary.Today, many of the fishing boats are stranded and the In-dians and Mexicans share widespread poverty as a resultof the water shortages.

Unfortunately, much of the water that does reach Mexicocontains runoff from alfalfa and cotton farms in Arizonaand California. Many of the soils in these areas are salty,as they comprise an ancient sea bed. Therefore, thewaters that reach Mexico are heavily saline and polluted.

When salinity levels of Colorado River water flowinginto Mexico reached 1200 ppm in 1961, the MexicanGovernment complained to US officials that the poorwater quality was reducing crop yields in the MexicaliValley. As a result, the United States agreed to limit thesalinity of water flowing into Mexico to a level less than

115ppm.

This promise was put into effect with the constructionjust over 20 years later of the Yuma Desalting Plant, whichprocesses 270 million litres of water per day using aprocess known as reverse osmosis. Although completedin 1992, the high costs of operation forced its closure forevery year except one during the period 1993 to 2008.The Mexicans, whose protests 47 years earlier in 1961 hadled to the construction of the plant, are perhaps under-standably disappointed by the continuing poor quality ofthe water they receive.

5.115 A section of the All American Canal, channelling waterwestwards from the CoLoradoRiver just 'norin of (and parallel to) theMexican border,

The future-

Climatic records across the Colorado River basin over thepast century suggest that temperatures in the region arerising. If this trend continues, the higher temperatures areexpected to result in less precipitation in the upper basinof the Colorado River. As much of the precipitation inthis area falls and is stored as snow, the combination ofreduced precipitation and increased losses due to evapo-ration could shift the timing of peak spring snow melt toearlier in the year. The overall effect of this could be toreduce discharge and water availability in the future, thusmaking Mexico's problems even more severe. Reduceddischarge could also contribute to greater frequency ofdroughts, with such droughts becoming longer and moresevere.

QUESTION BLOCK 5U

1. Describe the physical features of the Colorado River basin.

2. Explain why the Colorado River often dries up before itreaches the sea.

3. What is the cause of the Colorado River's salinity?

4. Explain why the Colorado River Compact allocated morewater to US states than was usually available in the river ..

5. Describe the impact on Mexico of the management of theColorado River in the LIS.

Freshwater issues and conflicts 226