The Colorado River Basin

Transcription

1 The Colorado River Basin The iconic Colorado River and its tributaries may be the most heavily managed and legally contested in the world. The Colorado River basin provides at least part of the water supply for an estimated 35 million people in one of the driest regions of North America, irrigates millions of hectares of productive farmland and pasture, and attracts millions of visitors to the Grand Canyon and other landmarks. Yet the intensively managed and diverted river carries a heavy burden, with several aquatic and riparian species extirpated throughout most of their former habitat and increasing challenges facing human users as demand continues to grow while supply is projected to shrink due to climate change. In the past fifteen years, stakeholders and managers have crafted a remarkable set of changes to the rules and regulations governing the river, providing a model for similar basins around the world. Physical and human geography The Colorado River basin, shown in Figure 1, extends across 663,000 km 2, predominantly in the western United States, with some 3,100 km 2 in northwest Mexico. The mainstem of the Colorado River runs 2,300 km from headwaters in the Rocky Mountains to its mouth in the Upper Gulf of California (also known as the Sea of Cortez); including the headwaters of the Green River, a major tributary with an interesting political history, extends the total length of the river to about 2,700 km. Other major tributaries include the San Juan, Little Colorado, Gila, Gunnison, Yampa, White, Duchesne, Virgin, Muddy, Salt, Verde, Dolores, and San Pedro rivers, though several of these are now so heavily developed and diverted that they rarely contribute any flow at all to the river s mainstem. Groundwater use in the basin supports irrigation and municipal supply. In many areas, especially in Arizona and in Mexico, aquifers are in decline due to over-extraction. Groundwater-surface water interactions in the basin are the subject of a new U.S. federal study but to date have not been quantified, with estimates of total groundwater contributions to surface flows ranging broadly from percent. Surface and groundwater from the Colorado River basin support about 35 million people. However, about 25 million of these people live outside of the basin and also receive water from other sources. In fact, 60% of the total number of people receiving at least some of their water supply from the Colorado River basin live outside the basin in the urban corridor stretching from Los Angeles to Tijuana, Mexico. The four metropolitan areas within the basin are Phoenix, Arizona (4.3 million people), Las Vegas, Nevada (2 million), Tucson, Arizona (1 million) and Mexicali, Baja California, Mexico (1 million). The largest city adjacent to the river is Yuma, Arizona (100,000 people), while San Luís Rio Colorado, in Sonora, Mexico (190,000), lies several miles east of the current river channel. The largest city in the upper portion of the basin is Grand Junction, Colorado, with about 30,000 people. With the exception of the four metropolitan areas noted above, the Colorado River basin is very sparsely populated. Yet just outside the basin lie the fast-growing metropolitan areas of southern California and northern Mexico The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 1

2 noted previously, as well as the Denver, Salt Lake City, and Albuquerque metropolitan areas, all importing water from the basin. Figure 1. The Colorado River Basin. Source: Cohen et al Some 1.3 million hectares (ha) of land are irrigated within the Colorado River basin, and another 0.14 million ha of dry-land farming exists within the basin. Water exported from the basin helps irrigate another million ha outside the basin, primarily in northern Colorado. Other land uses within the basin include extensive resource extractive industries including coal and hardrock mining, oil and natural gas extraction, and timber operations. Dams on basin rivers have an estimated 4,200 megawatts of hydropower capacity. The basin also supports a thriving recreation-based economy, including skiing, rafting, fishing, and motorized water activities. A recent report estimated that the Colorado River generates $26 billion in annual recreation-related revenues (Southwick Associates 2012). The total economic productivity of Colorado River water has not been estimated, though it could be said to support the entire economic productivity of Arizona ($231 billion) and Las Vegas ($96 billion), and contributes to the economies of southern California ($970 billion), metropolitan Denver ($168 billion) and metropolitan Salt Lake City ($72 billion), as well as agricultural productivity inside and outside of the basin. The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 2

3 Figure 2 shows the Colorado River basin s boundaries superimposed on an image depicting the ratio of precipitation to potential evaporation in the western United States, highlighting the extreme aridity of most of the basin. The peri-arid regions on the map, shown in brown and dark brown, receive less than 10 cm of precipitation annually but consume about 30% of the mainstem s average annual discharge. About 72% of the Colorado River s flow comes from runoff from elevations above 2,400 m (areas shown in blue in the figure), comprising less than 10% of the total basin area. As shown in the figure below, the U.S. portion of the Colorado River basin is legally divided into an upper and a lower basin; the upper basin produces about 90% of the river s natural flow just above the confluence of the now-dry Gila River, near the border with Mexico. California and Mexico contribute negligible flow to the mainstem, but have combined legal rights to more than 35% of the mainstem s natural flow. Figure 2. Log scale ratio of precipitation to potential evaporation in the Colorado River Basin. Source: The Biota of North America Program, at Hydrology The gage record for the mainstem of the Colorado River extends about a century. Releases from Hoover Dam dictate mainstem river flows for the last 30% of the river s length, and releases from Glen Canyon Dam determine about 95% of mainstem river flows, so actual gage measurements do not reflect the natural undiverted, unregulated flow of the Colorado River, known as the natural flow. Figure 3 shows the reconstructed natural flow for the Colorado River at two locations, as calculated by Jim Prairie of the U.S. Bureau of Reclamation. The total natural flows of the Gila River, the last major tributary in the basin, are under investigation. In the figure, the black line ( Abv Imp Nat l ) represents the reconstructed natural flow of the Colorado River at Imperial Dam, slightly upstream of the confluence with the Gila River. The red line ( Lee s Ferry The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 3

4 Nat l ) represents the reconstructed natural flow of the river at Lee s Ferry, located slightly downstream of Glen Canyon Dam. Lee s Ferry is the conventional measurement point for the river, marking the dividing point between the Upper and Lower basins (discussed in Governance, below). The blue line shows the actual gage record at Lee s Ferry, reflecting the depletions due to upstream diversions and reservoir evaporation and the influence of governance on river flow. Note that in several years, more water actually flowed at Lee s Ferry than would have flowed naturally, despite upstream diversions, because reservoir storage at Glen Canyon Dam supplemented the natural flow. The large difference in flow between natural and actual flows at Lee s Ferry from 1963 to 1979 reflects the filling of the reservoir behind Glen Canyon Dam. Figure 3 also shows the dramatic inter-annual variability in mainstem flow, with reconstructed natural flow ranging from 7.6 to 31.7 km 3 /year above Imperial Dam. Mean natural flow of the river at Lee s Ferry is 17.5 km 3 /year, rising to 19.0 km 3 /year above Imperial. Actual recorded flow of the river at the last gaging station on the river is now zero in most years km Lees Ferry Nat'l Abv Imp Nat'l Actual Lees Ferry Figure 3. Natural and actual Colorado River flows, Data from U.S. Bureau of Reclamation. The Colorado River s dramatic pre-development inter-annual variability was matched by seasonal variability driven by spring snowmelt followed by late summer low flows. This pattern continues in some upper basin tributaries, but today water orders placed by agricultural and municipal contractors determine river flows for much of the basin. However, hydropower generation to meet peak power demands drives river stage at the daily timestep, so daily flow rates immediately below some dams may vary from m 3 /second, causing daily river stage fluctuations in excess of one meter. Less is known about groundwater extraction rates in the basin. The state of Arizona lies almost entirely within the basin; it estimates annual statewide groundwater extraction at about 3.6 km 3. Groundwater extraction within the Mexican portion of the basin approaches 1.0 km 3. Arizona adopted an innovative Groundwater Management Act in 1980, requiring new development in the most populated areas of the state to demonstrate a sustainable 100 year supply of water, though groundwater overdraft continues The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 4

5 to be a problem in many areas of the state. Historically, Colorado River high flow events recharged much of the Mexican aquifer, though in the past 15 years there have not been any such events, so Mexico is attempting to reduce the amount of irrigated land in an effort to minimize groundwater overdraft. California s Coachella Valley, north of the Salton Sea, has suffered from groundwater overdraft and land subsidence for many years. However, there is no basin-wide assessment available describing groundwater conditions over the basin as a whole. The Colorado River, especially within the lower basin, is tightly managed, regulated, and engineered. Most of the river within the lower basin is channelized, its banks covered with riprap to minimize erosion, flowing from one dam and reservoir to the next, disconnected from its floodplain and starved of sediment. Table 1 lists the major dams in the Colorado River basin, in descending order by storage capacity. The mainstem dams on the river, primarily Hoover and Glen Canyon, can store four years average annual flow of the river. Several of the mainstream dams, such as Morelos Dam at the U.S.- Mexico border and Imperial Dam upstream, lack any meaningful storage capacity but divert all or much of the river out of the channel into irrigation canals. The table also lists the year the structures were completed, highlighting the early development of the river and the flurry of dam construction in the 1950s and 1960s. This is not a comprehensive listing of dams in the basin. Figure 4 shows the location of many of the major dams in the basin. Table 1. Major Dams in the Colorado River Basin, by Reservoir Capacity. Reservoir Capacity (KM 3 ) Power Capacity (MW) Annual Generation (MWh) Dam River Completed Hoover Colorado ,079 3,806,000 Glen Canyon Colorado ,296 3,454,000 Flaming Gorge Green ,400 Theodore Roosevelt Salt ,900 Painted Rock Gila N/A N/A Davis Colorado ,147,000 Navajo San Juan ,000 Soldier Creek Strawberry N/A N/A New Waddell Agua Fria Alamo Bill Williams N/A N/A Blue Mesa Gunnison ,000 Coolidge Gila N/A N/A Parker Colorado ,000 Granby Colorado N/A N/A McPhee Dolores ,300 Fontenelle Green ,000 Dillon Blue Horse Mesa Salt ,900 Bartlett Verde N/A N/A Imperial Colorado N/A N/A Morrow Point Gunnison ,000 Morelos Colorado 1950 Laguna Diversion Colorado 1905 Palo Verde Colorado 1958 Headgate Rock Colorado 1941 Grand Valley Diversion Colorado 1916 The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 5

6 Figure 4. Dams in the Colorado River basin. The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to 6

7 A large number of canals, aqueducts, and pumping stations also mark the basin, conveying water away from streams to fields and cities that may lie hundreds of kilometers distant. The largest of these, the All-American Canal, diverts roughly 20% of the mainstem s average annual flow to the Imperial and Coachella valleys. The Central Arizona Project conveys about 10% of the mainstem s average annual flow to Phoenix and Tucson and cotton fields in the middle of that state. California s Colorado River Aqueduct pumps about 8% of the mainstem s flow out of the basin and over to the Los Angeles and San Diego metropolitan areas, consuming roughly 25% of the hydropower generated by Hoover Dam. The state of Colorado boasts some 29 transbasin diversions, conveying water from headwater reaches within the basin across the continental divide to the eastern plains. One of the oldest of these, the Grand Ditch, conveyed water out of the basin as early as Several new pipeline and storage projects have been proposed, such as the Southern Nevada Water Authority s groundwater pipeline and the Lake Powell pipeline to St. George, Utah, but the prospects of these projects are uncertain. Southern Nevada is currently constructing a third intake into Lake Mead, to improve its water supply reliability in the face of declining reservoir storage, but this new intake will not increase the region s legal entitlement. There is an on-going multi-stakeholder workgroup process to explore water conservation opportunities in the urban and agricultural sectors, that will produce initial reports this summer on new opportunities. The current drought in California has increased interest from state and federal governments to fund and implement additional drought response strategies. Water Supply and Demand In December 2012, the Bureau of Reclamation released a major study (Bureau of Reclamation 2012) projecting Colorado River basin supply and demand into the future, with a range of specific projections for the years 2015, 2035, and 2060, based on information supplied by the individual basin states that arose from projections made, in many cases, in 2008 or earlier. Unfortunately, no comprehensive assessment of current water supply and demand in the Colorado River basin exists. Cohen (2011) and Cohen et al. (2013) describe municipal and agricultural water uses, respectively, noting the lack of consistency in reported information. The Bureau of Reclamation publishes Consumptive Uses and Losses Reports for the U.S. portion of the basin on a semi-decadal basis; the most recent report covers the period These reports characterize water use by sector, though the Lower Basin section excludes mainstem uses. These reports also aggregate all water moved out of the basin into a general exports category, challenging efforts to determine total use by sector. Reclamation also publishes annual reports describing diversions and consumptive uses within the Lower Basin, as well as deliveries to Mexico, but does not categorize such uses by type, only by water contractor. Irrigated agriculture consumes about 70% of the developed water supply within the basin itself. Reservoir evaporation consumes roughly 10% of the basin s developed water supply; municipal and industrial uses and system losses (primarily evapotranspiration by riparian vegetation) consumes the rest. According to Reclamation records, roughly 2.4 km 3 /year of water are exported from the basin each year. Within agriculture, about 60% of the 1.3 million hectares within the basin are irrigated pasture and forage crops, used primarily to feed beef and dairy cattle and horses, consuming about 6 km 3 /year of The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 7

8 basin water. Alfalfa alone accounts for about a quarter of all irrigated acreage within the basin. Crop diversity increases markedly in the southern portions of the basin; Mexico s portion of the basin grows the majority of that nation s wheat crop. The Coachella, Imperial, and Yuma valleys account for most of the U.S. winter vegetable crop, all grown with Colorado River water. The upper basin irrigates about 50% more land than does the lower basin, but because the lower basin, especially the three valleys noted above, enjoy year-round growing seasons while the upper basin growing season may be limited to less than five months, lower basin agriculture consumes more than three times as much water as upper basin agriculture (Cohen et al. 2013). Total municipal and industrial water deliveries (not consumptive use) by agencies relying at least in part on water from the basin increased from about 7.5 km 3 in 1990 to about 8.2 km 3 in 2008, despite a population increase of about 10 million (40%). Municipal deliveries of Colorado River basin water rose from 3.4 km 3 to about 4.2 km 3 over this period (Cohen 2011). Note that these volumes represent total deliveries rather than consumptive uses, as reported for agriculture. Per capita water use among agencies relying on basin water varies by more than a factor of four, though in almost all cases such water use remains well above that of other arid regions. Governance A dense, complex set of local, state, federal, and binational treaties, treaty amendments, laws, interstate compacts, rules, regulations, ordinances, and court decisions, known collectively as The Law of the River (described and reproduced in Verburg 2010) govern the management and use of the Colorado River and water in the basin. It is well beyond the scope of this brief overview to describe the Law of the River and its impacts in any detail; suggested readings for those interested are listed at the end of this document. The Colorado River can only be understood in the context of the Law of the River and the institutions that enforce it. Fradkin (1981:xviii) wrote, To me the [Colorado] river, in its present state, is primarily a product of the political process... rather than a natural phenomenon. Rosenberg et al. (1991:3) state that the Politics of water use is a fundamental aspect of life in the Southwest today and is the determinant of the Colorado River s future. The doctrine of prior appropriation forms the foundation for the Law of the River. California gold miners first developed the doctrine of prior appropriation to resolve disputes over mining claims, using the axiom "first in time, first in right." As miners increasingly turned to hydraulic mining, they applied the doctrine to water as well: the first to divert and put a quantity of water to "beneficial use" was entitled to that quantity of water before any subsequent diverter could be satisfied, even if that meant that the stream was entirely dewatered and more junior rights-holders received no water at all (Hundley 1986). Prior appropriation provides clear property rights to water and a recognized order for satisfying these rights, allowing downstream states such as California to claim senior legal rights to Colorado River water even though the state contributes almost no flow to the river. Closely related to the doctrine of prior appropriation is the concept of forfeiture, commonly known as use it or lose it : the concept that water rights not put to beneficial use may be lost, prompting a perverse incentive to use water. The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 8

9 The Law of the River imposes a three-tiered system for allocating Colorado River water. The highest priority is the United States' international obligation to deliver 1.8 km 3 /yr of water, within a prescribed salinity range, to Mexico. The second tier divides the water between the Upper and Lower basins, and to the various states within each basin. The lowest tier is the allocation of water within each state (Wilson 1994). The Colorado River Compact of 1922 and the subsequent 1944 treaty with Mexico allocate a total of about 20 km 3 /year of Colorado River water, exclusive of reservoir evaporation and other system losses more water than actually flows down the river on average. The foundational documents allocating Colorado River water therefore create a structural deficit, with allocations and demand exceeding average annual supply. California s state allocations of Colorado River water exceed the state s normal entitlement by about 20%. Until the mid-1990s, California was able to draw from the unused apportionment of Arizona and Nevada. As these states began to consume their full entitlement, the Lower Basin as a whole exceeded its compact entitlement, causing the federal government and the other six basin states to pressure California to reduce its reliance on the river to its normal year allotment, leading to the landmark Quantification Settlement Agreement of 2003, creating the nation s largest transfer of agricultural water to urban users, various conveyance efficiencies, and other means by which California allocated Colorado River water within the state. Most Colorado River allocations are based on the concept of consumptive use, defined as diversions minus return flows. For example, in 2012 the state of Nevada pumped 0.54 km 3 from Lake Mead, but their consumptive use was only 0.29 km 3 because the state returned 0.25 km 3 to the system. These allocations typically only focus on water quantity; any degradation of water quality that may occur as the water flows over fields or through plumbing fixtures does not affect the consumptive use accounting or individual contractors legal entitlements. In the Lower Basin, the Secretary of the U.S. Department of the Interior is the watermaster, responsible for managing the river and publishing annual accounting reports of Colorado River mainstem use. The Bureau of Reclamation is the Secretary s designee and maintains operational control of the river, making Reclamation a key player in river management. Other major stakeholders include the large municipal water agencies and irrigation districts in the Lower Basin, including the Metropolitan Water District of Southern California (supplying water to more than 19 million people), the Southern Nevada Water Authority, the Central Arizona Project, the Imperial Irrigation District, and, to a lesser extent, state water agencies such as the Arizona Department of Water Resources, the Colorado River Board of California, and the Colorado River Commission of Nevada. Management and river accounting in the Upper Basin differ from the lower: the federal role is diminished, water accounting is estimated based on irrigated acreage as well as measured deliveries to cities and irrigators, and state water agencies play a much stronger role, supplemented by the Upper Basin Commission (comprised of state and federal representation). In recent years, Denver Water and the Colorado River District of Colorado have played a stronger role, with diminished roles played by the other upper basin states. Internationally, the U.S. and Mexican offices of the International Boundary and Water Commission are the key players in binational negotiations, though recent agreements (discussed in the following) also witnessed active participation by a number of state and local water agencies, as well as Reclamation. Historically, Reclamation asserted a much more prominent role in managing the river and constructing dams and The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 9

10 other engineering projects (cf. Reisner 1993), but this role has diminished over the past twenty years as Reclamation began to work more cooperatively with other stakeholders. Parallel and in many cases senior to the water rights established by the 1922 Compact and other appropriative water rights are the reserved rights held by Native American tribes, and to a much lesser degree by some of the federally-managed wildlife reserves along the river. Reserved rights essentially hold that Native American reservations carry with them an implied water right dating to the time the reservation was created, in sufficient volumes to meet the irrigation needs of the reservation. In recent years there have been a large number of settlement agreements, with various tribes, to quantify and resolve long-standing disputes over water rights. Stakeholders The Grand Canyon Protection Act of 1992 marked an important change in the role of stakeholders and in recognition of the value of water left instream. The 1992 Act called upon Reclamation to include nontraditional stakeholders in its management and consultation processes, in addition to the usual water contractors. This opened the door for non-governmental organizations (NGOs) to participate, to the extent that NGO representatives are now routinely included in the development of new rules and regulations for the river. NGOs also played a major role in Minute 319 1, an amendment to the 1944 treaty that, among other provisions relating to shortages for Mexico and creating opportunities for Mexico to store water in Lake Mead, created the March 23 rd, 2014 eight-week pulse flow of water to the Colorado River delta. In a recent newspaper article heralding the release and the cooperation that enabled the event, the Secretary of the U.S. Department of the Interior and her counterpart in Mexico, the Secretary of La Secretaría de Medio Ambiente y Recursos Naturales, wrote that the pulse flow is believed to be the first instance of a binational agreement specifically delivering water across an international boundary for explicit environmental purposes (Jewell and Guerra 2014). Water Quality With the notable exception of salinity, the Law of the River is silent on the issue of water quality. For geologic reasons, several areas of the Colorado River basin suffer from elevated concentrations of salinity. Irrigating land in these areas tends to leach salts from the soil and, through return flows, carry them back to the river and downstream, where evaporation and reuse increase total concentrations. Below Hoover Dam, the Colorado River carried some 8 million metric tons of salts per year. The development of the Wellton-Mohawk Irrigation and Drainage District along the Gila River near its confluence with the Colorado River led to aggressive pumping of the perched saline aquifer underlying district land, greatly increasing the salinity of the water delivered to Mexico, damaging and killing Mexican crops. After a long and acrimonious dispute between Mexico and the U.S. about the quality of this water, the two countries adopted a series of interim agreements culminating in Minute 242 of the International Boundary and Water Commission. Minute 242 states that 1.68 km 3 of annual water deliveries to Mexico would have an average salinity no more than 115 ppm (±33 ppm to account for differences in assaying techniques) greater than the salinity 1 IBWC Minutes are posted at The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 10

11 of the river at Imperial Dam; the remaining 0.17 km 3 would have a salinity substantially the same as that of the waters customarily delivered there. Congress then passed the Colorado River Basin Salinity Control Act of 1974, authorizing measures to comply with Minute 242, including the construction of the $250 million Yuma Desalting Plant. The 1974 Act also authorized the construction of salinity control projects within the U.S., primarily in Upper Basin areas that contributed disproportionately to salinity loadings. Lower Basin water users help fund these projects, which often take the form of lining drainage ditches or piping water, to reduce the volume of water leaching through the region s salty soils. The salinity control program has been very successful, reducing the river s salinity by about 90 mg/l at Imperial Dam (to roughly 720 mg/l) by reducing salt loadings by about 1.2 million tons per year (Colorado River Basin Salinity Control Forum 2011). Water Pricing Users do not pay anything for Colorado River water itself. The price paid for water by end users reflects the costs of conveyance, treatment, administration, and financing. These prices can vary from the $20/acre-foot (roughly $16/1000 m 3 ) paid by Imperial Valley farmers receiving untreated, gravity-fed Colorado River water to the equivalent of about $2,078/1000 m 3 paid by residential consumers in San Diego. Problems/challenges Snowpack in the Upper Basin currently stands at about 120% of average, signaling above-average runoff and at least a brief respite from the 14-year drought that has drawn down reservoirs in the basin by about half, as shown in Figure 4, in a graph created by Brad Udall. With growing indications that a strong El Niño cycle may appear this fall, the prospect of another wet winter affords some hope that previous projections of delivery shortages for Arizona, Nevada, and Mexico may be postponed for another couple of years or more. Figure 4. Contents of Lake Mead and Lake Powell. Source: Udall. The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 11

12 Current hydrology merely masks the underlying structural deficit within the basin. The growing imbalance between water supply and demand poses the major problem facing the Colorado River basin. Climate change exacerbates this problem, both by diminishing expected runoff and especially by increasing evaporation rates, affecting both sides of the supply-demand imbalance. Reclamation s Basin Study (2012) projects that water supply could decrease by roughly 9.5% by the year 2060, even as millions of additional people are projected to rely on water from the basin. The basin study evaluated a large number of proposed options to bridge this imbalance, grouping these into four broad portfolios. Each of these portfolios includes a set of common options, projected to generate almost 5 km 3 of water annually by the year These common options include municipal and industrial water conservation and efficiency projects, increased implementation of water recycling and re-use, and a combination of agricultural water conservation projects and transfer of conserved water from agricultural to municipal users. Many of these options are already in practice in the basin states; the goal is to accelerate their implementation. Reservoir Sedimentation The Colorado River historically carried a tremendous sediment load as it scoured the sandstone canyons of the upper basin. The old adage about the Colorado was that it was too thick to drink, too thin to plow. Dams have captured most of this sediment, starving the river of its normal load and causing it to scour its channel downstream of dams. Glen Canyon dam traps the majority of this sediment, an estimated 60,000 m 3 per year. This is but a small fraction of the reservoir s capacity, though as storage diminishes due to decreasing runoff this sediment will be deposited closer and closer to the dam itself. Some have suggested that the Glen Canyon dam could lose all of its live storage within 60 years (Powell 2010), though Reclamation and others contest this projection. Conclusion Colorado River management has changed dramatically in the past 15 years, with stakeholders moving from active litigation and polarized positions to the current period of cooperation, across state and international boundaries. Native Americans and NGOs have participated much more actively in the development of Colorado River policies, resulting in a number of water rights settlements and landmark agreements on sharing of surplus, shortage, and even providing water for environmental purposes. The basin has developed several important, forward-looking planning documents to address projected shortages and identify options to offset these impacts, providing a model for similar basins around the world. References Bureau of Reclamation, U.S. Department of the Interior Colorado River Basin Consumptive Uses and Losses Report Revised September Available at The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 12

13 Cohen, MJ Municipal Deliveries of Colorado River Basin Water. Pacific Institute. Available at cities-and-agencies/. Cohen, MJ, J Christian-Smith, and J Berggren Water to Supply the Land: Irrigated Agriculture in the Colorado River Basin. Pacific Institute. Available at Colorado River Basin Salinity Control Forum Review: Water Quality Standards for Salinity Colorado River System. October. Available at Hundley, N, jr The West Against Itself: The Colorado River -- an Institutional History. In New Courses for the Colorado River, ed. G.Weatherford and F. Brown, pp Albuquerque: University of New Mexico Press. Jewell, S, and JJ Guerra Abud Colorado River progress flows from cooperative spirit. Arizona Star, April 6. Available at Powell, J Calamity on the Colorado. Orion. July/August. Available at Southwick Associates Economic Contributions of Outdoor Recreation on the Colorado River & Its Tributaries. Prepared for Protect the Flows. Available at River-Recreational-Economic-Impacts-Southwick-Associates _2.pdf. Verburg, KO The Colorado River Documents Interior Dept., Bureau of Reclamation. 960 pp. Additional Resources Bloom, PL Law of the River: A Critique of an Extraordinary Legal System. In New Courses for the Colorado River: Major Issues for the Next Century, ed. G. Weatherford and F. Brown, pp Albuquerque: University of New Mexico Press. Fradkin, PL A River No More: The Colorado River and the West. Tucson: University of Arizona Press. Getches, DH Competing Demands for the Colorado River. University of Colorado Law Review 56: Gleick, PH The Effects of Future Climatic Changes on International Water Resources: The Colorado River, the United States, and Mexico. Policy Sciences 21: Glenn, EP, C Lee, R Felger, and S Zengel Effects of Water Management on the Wetlands of the Colorado River Delta, Mexico. Conservation Biology 10: Harding, BL., TB Sangoyomi, and EA Payton Impacts of a Severe Sustained Drought on Colorado River Water Resources. Water Resources Bulletin 31: Hayes, DL The All-American Canal Lining Project: A Catalyst for Rational and Comprehensive Groundwater Management on the United States-Mexico Border. Natural Resources Journal 31: Holburt, MB The 1983 High Flows on the Colorado River and Their Aftermath. Water International 9: The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 13

14 Hundley, N, jr Dividing the Waters: A Century of Controversy between the United States and Mexico. Los Angeles: University of California Press Water and the West: The Colorado River Compact and the Politics of Water in the American West. Los Angeles: University of California Press The West Against Itself: The Colorado River -- an Institutional History. In New Courses for the Colorado River, ed. G.Weatherford and F. Brown, pp Albuquerque: University of New Mexico Press The Great American Desert Transformed: Aridity, Exploitation, and Imperialism in the Making of the Modern American West. In Water and Arid Lands of the Western United States, ed. M. El-Ashry and D. Gibbons, pp New York: Cambridge University Press. Lord, WB., et al Managing the Colorado River in a Severe Sustained Drought: An Evaluation of Institutional Options. Water Resources Bulletin 31: Meko, D, CW Stockton, and WR Boggess The Tree-Ring Record of Severe Sustained Drought. Water Resources Bulletin 31: Reisner, M Cadillac Desert: The American West and its Disappearing Water. NY: Penguin Books. Sax, JL The Limits of Private Rights in Public Waters. Environmental Law 19: Snow, Robert F Platte River: Reservation and Quantification of Federal Reserved Water Rights - Firefighting and Administrative Purposes Only! Pace Environmental Law Review 11(1): Stegner, Wallace Beyond the Hundredth Meridian. New York: Penguin Books. Waters, Frank The Colorado. New York: Rinehart & Co. Weatherford, GD, and FL Brown, (eds) New Courses for the Colorado River. Albuquerque: University of New Mexico Press. Wilson, F A Fish Out of Water: A Proposal for International Stream Flow Rights in the Lower Colorado River. Colorado Journal of International Environmental Law and Policy 5: Worster, D Rivers of Empire: Water, Aridity, and the Growth of the American West. NY: Pantheon Books. The Colorado River Basin, by MJ Cohen. April 2014 internal SERIDAS draft. Comments to mcohen@pacinst.org 14