River Management - Colorado River PDF

SEPTEMBER 2005 Online Geo file 501...

SEPTEMBER 2005 Online Geo file 501 Sheila Morris Large-scale river management – the Colorado The Colorado River drainage basin Figure 1: The Colorado Basin covers an area of 621,597 km2 over seven states of south western USA and Key Colorado Basin Mexico. It rises close to the Upper Colorado Basin Continental Divide in the Rocky Gr Mountains of Colorado, and is divided Out of Basin diversions ee nR into Upper and Lower basins at Lees 1 Big Thompson. Ferry below Glen Canyon Dam, close 5 2 Smaller projects Yampa to the Utah/Arizona border. Stretching 3 Frying Pan–Arkansas 1 from the high mountains of the Central 4 San Juan do Utah lora Rockies in Colorado, Wyoming and Project Co 2 5 Central Utah Utah, it flows for 2,304 km and falls 3 6 Colorado Aqueduct over 4,376 m from its source to the S. California Gulf of California. Its chief tributaries Lake Lake 7 Imperial Valley San in the upper basin are the Green, Mead Powell Jua n which rises in Wyoming, the Hoover Dam Grand 4 Gunnison and the San Juan rivers. Glen Canyon Davis Dam Canyon Dam Main tributaries in the lower basin are Lit tle the Virgin, Bill Williams, Gila and Colorado River 6 Lake Co lor Aqueduct Havasu Central ad Little Colorado rivers. Arizona o Project Imperial Dam The river is now one of the most PHOENIX regulated in the world. More water is Gila R. exported from the Colorado basin than Salton Sink 7 YUMA from any other river basin in the US. It TUCSON provides water for urban and industrial Figure 2: Agricultural uses of the Colorado River water State Water allocation Irrigated area Average annual Crops Major projects from Colorado precipitation Water Arizona 3,453 m cu m 226,624 ha 5–30 cm Cotton, alfalfa Central Arizona lettuce,wheat, Gila project, barley, citrus Wellton-Mohawk, fruits,vegetables, Yuma melons. California 5,427 m cu m 364,217 ha 6.5–35.5 cm Canteloupes, dates, Colorado River grapes, oranges, Aqueduct, All American lemons, avocados, Canal, Coachella lettuce, tomatoes, Canal, Imperial Valley vegetables, onions, carrots, alfalfa, wheat and grasses (forage) Colorado 4,748 m cu m 768,900 ha 17.8–147cm Hay, alfalfa, grains, Transbasin transfers, vegetables, fruit Big Thompson Nevada 370 m cu m Water used for 10-16 cm Vegetables, fodder urban needs. (more in north) Agriculture uses ground water. New Mexico 1,040 m cu m 24,685 ha 15- 30 cm Alfalfa , corn, wheat, Navajo-Indian and (San Juan) barley, potatoes, 10 smaller projects, onions San Juan-Chama- Rio Grande Wyoming 1,295 m cu m 133,546 ha 18–152 cm Alfalfa and small grains, pasture, fruit Utah 2,095 m cu m 178,000 ha 30–35 cm Pasture, alfalfa, Central Utah Project, grains, fruit 12 smaller projects Mexico 1,850 m cu m 73,000 ha (delta) 7 cm Alfalfa, cotton, (Delta Region) vegetables Geofile Online © Nelson Thornes 2005 September 2005 no.501 Large-scale river management – the Colorado use to 24 million people living in guaranteed 5,500 million cu m to available surplus water from the major cities including Los Angeles, improve agriculture in lands around Colorado. California frequently Phoenix, Albuquerque, Las Vegas, Salt the Colorado delta and Baja California. extracts more than the allocation Lake City, Denver and San Diego. In Eventually (1944) Mexico was because of demands from both the addition to providing irrigation water guaranteed 1,850 million cu m of urban and agricultural areas. The for 810,000 ha of agricultural land, Colorado water, and in return agreed Agreement: water is pumped through tunnels in to provide water from Mexican the Continental Divide to Denver and tributaries of the Rio Grande for reduces the draw down amount to cities on the eastern side of the Front farmers in west Texas. 5,427 million cu m, Range. Within the river basin there is makes special provision for the 74 billion cubic m of storage behind 11 However no provision was made for restoration of the Salton Sea major dams, providing 4,000 water quality, which has now become a megawatts of hydro-electric power contentious issue. Water now delivered This is necessary because of increasing generation capacity. to Mexico has already been used in the salinity and massive die-off of wildlife Wellton-Mohawk Irrigation district that occurred in 1996. The Salton Sea close to the USA-Mexico border. It is is at present replenished by return Major out-of-basin diversions often of high salinity before its transfer water flows (i.e. water originally taken of Colorado River water to Mexico. A desalination plant was from the Colorado River, used in the completed in 1992 at Yuma, Arizona at Imperial Valley and then returned) 1 Southern California and Mexico and the discharge of wastewater into Rapid development of agriculture in a cost of $25 million(£15.6 million), but until early 2004 this was still not the New River. California’s Imperial Valley in the 19th and early 20th centuries created a high fully operational as it was considered The State of California is to buy demand for irrigation water. ‘First in too expensive to run. The long drought 1,973 million cu m of water from time, first in right’ was accepted as a has now made it necessary to the Imperial Irrigation District and principle of water usage. Water from commission the plant. then sell it to the Metropolitan the Colorado bordering Arizona and Water District of Southern California was transferred to the When the Colorado is flowing at California for urban use, making Imperial Valley by a canal that passed normal level the speed of flow and $300 million (£187 million) to help through Mexican territory. Mexico amount of water are sufficient to pay for the Salton Sea restoration. permitted this in return for a portion maintain the salinity at an acceptable The All American and Coachella of the river water. Disastrous floods level. Salty drainage water is diverted canals are to be relined to prevent occurred in 1905 and again in 1910 to the Gulf of California creating a further seepage, saving 95 million when the Colorado broke its banks, marsh area, the Cienga de Santa Clara. cu m of water to be transferred to destroying farmland in the Salton Additional water is drawn down from urban San Diego County. This Sink. For two years the river filled this Lake Mead to help to flush out the salt should provide a reliable water inland depression, creating the Salton concentrations before the water goes to supply for the future. Sea. This led to demands from the Mexico. However during periods of Imperial Valley is also to take California state government and from drought this reduces the storage conservation measures to save farmers for a canal within US territory, available for Arizona. present losses in transfers to San a flood control dam on the lower Diego. It will also have more Colorado and the possibility of Little water now reaches the Colorado finance available from the transfers hydroelectric power to supply Los delta. Prior to the construction of to help to revitalise its economy, Angeles. Agreement was needed from Hoover Dam and Glen Canyon Dam, which depends so heavily on upstream states, who resisted strongly completed in 1935 and 1964, over irrigation agriculture. until the Colorado Compact was 24,669 million cu m passed to the signed in November 1922. 809,000 ha of wetlands in the delta, but 2 The Central Utah Project (CUP) is now less than 10% of the original part of the Colorado River Storage In normal years the river flow and wetlands remain, approximately 73,000 Project (authorised in 1956) to divert storage is adequate for demands being ha. water from the Colorado River made for water from rapidly growing westwards into the Bonneville basin of populations and irrigated areas of In both the Upper and Lower Central Utah. The project area was Southern California and also Arizona. Colorado basins, attempts are being divided originally into six units of 9,250 million cu m annually were made to control salinity and reduce the which the largest – the Bonneville unit allocated to both the upper basin states amounts of salts reaching the river. south of the Great Salt Lake and and the lower basin states in the Sources of salt inputs are being surrounding Utah Lake – started in Compact. The allocations were decided identified and farmers helped to alter 1967 is now almost complete. The on the average flow of 21,585 cu m at their methods; such as using sprinkler project relies on the transfer of water Lees Ferry in 1917. In retrospect, this irrigation more extensively, relining from the headwaters of the Colorado was an above average year, which created canals in irrigation districts to avoid River, including the Duchesne in the difficulties in future allocations of water. waste, piping more water, and carefully Uintah Basin to the east of the observing and recording levels of Wasatch Mountains, to the lands Mexico was not at first included in the salinity on individual farms. around Utah Lake south of Salt Lake Colorado River Compact, though the City. Ten new reservoirs have been United States had tried to provide a In October 2003 California state and constructed with 320 km of aqueducts, minimum of 925 million cu m per year the southern water authorities agreed tunnels and canals. The whole project which was the highest amount used up on the Quantification Settlement will provide water for 80,937 ha of new to then by Mexican farmers. The agreement, meant to last 75 years. This farmland and additional water for Mexican Government wanted a should reduce over-dependence on any 96,719 ha of land. Geofile Online © Nelson Thornes 2005  September 2005 no.501 Large-scale river management – the Colorado Figure 3: Colorado-Big Thompson Project Native American rights to Key Colorado River water Canals Tribes on Indian reservations close to Pipeline the Colorado and its tributaries have Tunnel interests in the waters, mainly for Alva B. agriculture in the bottomlands close to Adams Tunnel the river. They claim ‘senior rights’ i.e. Rocky Mountain prior users’ rights to the water. The National Park Estes Ten Tribes Partnership, formed in Park 1992, is now a strong political voice for Continental Fort the majority of the tribes in the Divide Collins Colorado Basin. The Federal Bi g T h ompso nR government recognised their. Lake importance by allocating money for Estes irrigation canals on reservations as Carter Lake early as 1867. When Parker Dam was Lake constructed in the mid-1930s to do R. Granby provide water for Southern California, lora Co the traditional lands of the Chemuevi Boulder Indians were taken for the dam and reservoir, although suitable alternative land was provided. Rights of the Native Americans were not written Green DENVER into the Colorado Compact, but were Mountain accepted informally. In later discussions between states the Federal government has intervened to protect R. the rights of the tribes. P latte S outh Impact of six years of drought Continental Divide In January 2005 the south western states of the US were into the sixth year of a drought, which is the most CUP supports the growing of fodder Flatiron, Estes, Pole Hill and Green severe since the 1953–56 drought and crops for livestock on irrigated land and Mountain Dams generate hydro- could become the driest period since provides additional water for the electric power for the rapidly growing records began over 100 years ago. It is rangelands in the dry Central Basin, as urban and rural populations on the already worse than the Dust Bowl well as supplying water for urban and Eastern Slope including Denver, period of the 1930s (US Dept of industrial use. Boulder, and Fort Collins. Interior). 3 Colorado-Big Thompson Project In normal years irrigation water is Mountain areas within the Colorado This federally funded project was important in late summer, but in Basin recorded exceptional drought completed in 1959 to divert water from drought years it becomes essential conditions by early January 2004 but the headstreams of the Colorado River throughout the year. Crops produced expected further snow falls. Snow pack to irrigate 291,400 ha in North East under irrigation include sugar beet, conditions, which are essential for Colorado, supply power, and create potatoes, beans, corn and small grains, raising reservoir storage levels, had recreational use on the dams fruit, alfalfa (lucerne), vegetables, dairy improved in the Upper Colorado Basin constructed. Started in 1938 but delayed products, poultry and eggs. Crops such through winter and spring 2004. by the Second World War, water is as sugar beet are used to fatten lambs, However, severe to extreme drought diverted by several dams including the pigs and cattle. persisted. Snow pack conditions in Granby Dam on the Colorado and March 2004 were between 90 –130% of Green Mountain on the Blue River. It is 4 Frying Pan-Arkansas Project normal, following very heavy falls in stored in Granby Reservoir, Shadow This was completed in the 1980s and December and January. This was not Mountain Lake and Grand Lake before diverts water from the Gunnison River enough to break the drought. being pumped through the Alva B. through a tunnel under the Continental Adams Tunnel (13m/21km) at 15.5 cu Divide into the Arkansas Valley. The Throughout 2004 pastures remained m per second to fall 215m via tunnels largest of five storage reservoirs is close poor or very poor throughout the and conduits to Estes Power Plant and to Pueblo in southern Colorado. This region. On western rivers early down the eastern slope of the has become an important recreation snowmelt allowed earlier use of storage Continental Divide into the Big area in addition to providing hydro- and distribution systems to meet water Thompson River, a tributary of the electric power, and the whole scheme requirements. Premature melt means South Platte river. provides irrigation water for 113,000 ha that maximum discharge occurs earlier and municipal and industrial water for and then river levels recede into the Dams near Forth Collins and Estes 430,000 people in the upper Arkansas summer when water supplies are most Park divert water by canals for Basin. needed. agricultural and municipal use. Geofile Online © Nelson Thornes 2005 September 2005 no.501 Large-scale river management – the Colorado Figure 4: Reduced levels at Lake Mead Run-off into Lake Powell was only 53% projects, research into desalination, and (feet) of average in 2003. The elevation of improvements in water management to Lake Powell had dropped to 1,086 m, avoid future water supply crises. All Spillway Crest almost 30.4 m from full, at the end of states in the Colorado Basin must 1225 the summer 2004, and in 2005 was now provide a strategy for more serious only at 43%. In spite of this there is at water shortages. 1200’ present enough water to meet water requirements of the Lower Basin states Population throughout the basin has 1175’ and Southern California, as long as risen rapidly, increasing by 47% demands do not increase. The reduced between 1980 and 2000. Arizona’s head of water for power production population has quadrupled since 1950. 1150’ means that the turbines can only This puts increasing pressures on the Sept 1999 produce 31% capacity (cf record year available power and water supplies. 1125’ 95% capacity 1984 – 93% capacity). Between April and July 2004 the Colorado had 76% normal flow. 1100’ March 2005 63% capacity One advantage of the present situation 1050’ on Lake Powell is that many interesting sites flooded by the water when the dam was created, such as Cathedral of the 1000’ Desert and Gregory’s Natural Bridge, 1982 1987 1992 1997 2002 2005 may now be visited by boat. Fishermen Lake Mead Elevations at Hoover Dam 1982–2005 (March) welcome the improved natural fishing (Bureau of Reclamation data) for bass and other native fish. Large amounts of sediment are retained Drought is ever present in the South behind Glen Canyon dam which means West. There is competition for the a decline in sediment along the Grand melting snow between lowered Canyon. The reduction in numbers of reservoirs and the drought parched native fish such as the humpback chub soils. The warm March weather causes is serious. Introduced species such as snow to be lost directly to the the rainbow and brown trout thrive in atmosphere. Trees and grass start the reservoirs and in the river below growth earlier so further draining scarce Glen Canyon Dam. soil moisture (US Drought Monitor 23 March 2004). This situation was to Conclusion remain until late summer 2004 when Hydrologists believe that it will take at severe thunderstorms and later more least five years of average or above continuous heavy rain (thought to be average rainfall to refill the Colorado linked to a weak El Nino in the Pacific) system. Farmers in the Upper Basin occurred. have already been warned to expect a 20% drop in their water allocations for There has now been a five-month the current year. In 2004 agricultural period when the South West was wetter production in Upper Basin was down than normal bringing the drought to an 40%. Impact on the Lower Basin end. By the end of January 2005 snow farming was less due to the Colorado conditions were better than the Compact law. It is now recognised that previous two years (NOAAnews). attitudes to water use from both urban and agricultural communities will have Water levels in Lake Mead and Lake to alter significantly. In 2003 the US Powell are still at record low levels government launched a major although there have been slight rises programme, ‘Water 2025: Preventing since December 2004. The level of Lake Crises and Conflict in the West’. $21 Mead at Hoover Dam was 347m (59% million (£14 million) initial Federal storage), its lowest level since 1955 (332 funding for 2004 will help co-operation m) and a 21 m drop since June 2000. It between states with conservation is the first time in 40 years that the level has fallen below 359m. In winter 2003/4 ramps for pleasure craft were extended Focus Questions in anticipation of the tourist season, and knowledge that the drought would 1. What methods could be used to reduce the consumption of water in persist. There are restrictions on the use cities such as Las Vegas and Los Angeles? Can the allocations of water to of water in cities such as Las Vegas and urban areas be justified? the prospect of severe restrictions on the use of irrigation water for the next 2. ‘A River No More’ has been used to describe the Colorado. Is this fair? agricultural season. These continued Are there more environmentally acceptable ways in which this river could and have not yet been lifted. be used? Geofile Online © Nelson Thornes 2005