The 54-foot (16 m) paddle wheeler Explorer in the Lt. Joseph Ives expedition up the Colorado River. Period engraving.

Highslide JS

Lithograph of the Explorer in Black Canyon, 1857-58.  Lt. Joseph Christmas Ives explored the lower Colorado River as far upstream as today’s Hoover Dam in 1857-58, in the steamboat Explorer.  He and his party left the river at that point and explored overland south of Grand Canyon and into New Mexico, declaring that the land was absolutely worthless.

Credit: Grand Canyon Museum Collection.

Before the damming of the Colorado, there existed an environment that supported billions of clams and other life has disappeared, since the 1930s, because dams and irrigation projects, like the Parker[1] and Imperial[2] Dams, have reduced the flow of nutrient-laden fresh water to the tidal flats, where the river empties into the Gulf of California.[3]

Satellite images and field data indicate that at least two trillion clamshells make up the area’s beaches and islands.[4]Indeed, at any given time during the last 1,000 years before 1930, there were six billion clams living on the delta.[5]Researchers found that where there were 50 specimens per square meter in the past (about five per square foot); today there are only three per square meter (0.3 per square foot).[6]

Additionally, the inundation of large swaths of geography by Lake Powell, Lake Mead, and other mega-reservoirs drowned not only portions of the Colorado – and in other river systems – but also millions of trees, priceless gorges and canyons, like the Glen Canyon, and segments of beautiful deserts unlike any other in the world.

Moreover, human intervention in the hydrologic basin of the Colorado River eradicated water discharge and sediment supply to the River’s mouth and its delta.[7] After some 95 years of applying strong flow control policies, the delta’s previous sedimentary budget has diminished. These changes are ultimately responsible for the relocation of massive volumes of the delta’s sediment inventory, and for the serious ecological impact of habitat loss of indigenous species, such as the now endangered Totoaba,[8] a relative of the sea bass, and the critically endangered Vaquita,[9] a cetacean, resembling a porpoise.

All in all, while we may now be re-thinking the idea of dams, much of the damage is permanent – lost species cannot be replaced. Like the lost wetlands in Louisiana, the disappearing portions of the Delta cannot be reclaimed. The price has indeed been high for the Colorado River and its delta. Were it the sole geographic location so impacted one might rejoice that more has not been lost. However, much more has been lost. These stories follow. We begin with two more examples from the United States: the Hungry Horse Damon the Flat Head River, in Montana and the Lower Monumental Lock and Dam on Snake River, in Washington State.


A. The Hungry Horse Dam and the Lower Monumental Lock and Dam

Streams and rivers have a natural cycle which fish and insects, among other creatures, regulate themselves to. However, when dams are built the flow of the water behind the dam is artificial and does not follow nature’s cyclical sequence. Artificially regulated flows produce a number of distinct problems. First, without high flows, silt doesn’t get flushed from streambed gravel, and the many species of fish and insects that need clean, well-oxygenated gravel for their eggs and larvae are harmed.[10]

Second, nature’s relatively constant flows often lead to relatively constant water temperatures, which influence the many species that depend on natural fluctuations in temperature. For example, due to the Hungry Horse Dam[11]“the adults of a vital species of stone fly in the Flathead River in Montana don’t emerge from their larval stage unless cued by mean daily water temperatures of 65 Fahrenheit. Late-summer discharges from Hungry Horse Dam [on the Flathead River] keep the water cooler than is natural, so whole generations of this insect never reach adulthood.”[12]Consequently, fish, which rely on these insects, are deprived of a food source and they too lose generations.

1. Unnatural Swells

Dams can vary water temperatures in other ways that are injurious to wildlife. In most places irrigation water is stored until summer. This creates unnaturally shallow flows below dams at other times of the year, which in turn causes the water to become abnormally warm. As the water warms, it loses oxygen, and river organisms begin to die.[13] By the same token, flows are unnaturally deep and therefore abnormally cold during the summer.

Another common problem occurs when dams release water that is significantly colder or warmer than the river water. For example, releases from the Lower Monumental Lock and Dam,[14] a concrete behemoth on the Snake River in southeastern Washington, “render the Columbia River too cold–some 20 degrees colder than is natural–for most native organisms for more than 250 miles downstream.”[15]

Drayton Chanos chanos illustration

Joseph Drayton’s illustration of a milkfish, labeled “Fig. 10, Chanos chanos (Forsskål). Smithsonian Institution Archives. RU 007186, Box 7, SIA RU007186.

Not only is water flow disrupted by dams, they also practically cut-off the stream of sediment. “When the current dissipates in the reservoir, its load of suspended particles sinks to the bottom, trapped for the life of the dam. Very little slips by a large dam.”[16] Returning to the Colorado, studies there disclose that Glen Canyon Dam captures 99.5 percent of the sediment rolling down the Colorado River. The sediment penned behind the dam includes organic matter, which is vital to downriver food webs. “Sandbars where plants have grown in and alongside a river- important wildlife habitat–constantly erode; without sediment with which to rebuild, they soon vanish. The same holds for riverbanks.”[17]

The absence of new sediment also causes the riverbed to lower, destroying the riparian zone. “As the channel deepens and the elevation of the river drops, the water table beneath the riparian areas drops correspondingly.”[18] This dries up those lush, elongated oases that are such important havens for wildlife.

Cottonwoods, for example, need high groundwater levels. The demise of these riverside staples robs the stream of shade, which can lead to lethally high water temperatures; causes excessive erosion, because the stabilizing influence of the trees’ roots is gone; and deprives the fungi and bacteria at the foundation of the aquatic food web of the nutrients provided by cottonwood leaves, a crucial food source.[19]

2. Stream-Flows Rewritten by Dams

Dams pose an additional challenge: they significantly alter the hydrologic cycle by causing massive evaporation of water. Worldwide “[c]lose to 5000 km3 [cubic kilometers] [or 1.3 billion gallons] of water — nearly 12% of the total annual river runoff — are presently stored in large reservoirs . . . Almost 2800 km3 of water are evaporated from both irrigated fields and from reservoirs each year . . . .”[20] Evaporation of pooled water, such as that found in dam created reservoirs, is especially high in arid climates, such as that in the Southwestern U.S., Egypt’s Aswan Dam, Iraq, Syria and Turkey. If these riparians could harvest this evaporated water, they would not need to build these massive concrete battlements, as they would have more than enough water “saved” for fallow or dry times.

  1. Dark Lessons from the Senegal River

The damage to natural resources is not limited to the United States and other developed countries. Fifty years following the launching of the era of the mega-dam, the developing world has uncritically and unthinkingly leapt into the syndrome of dam construction. Numerous developing nations today face destruction of natural resources. However, by a cruel irony, in an attempt to improve their lot, by building of dams the peoples of the developing world have lost both their customary way of life – a way of life which has sustained them for thousands of years – and the natural resources and venue that kept them alive for millennia. This tragedy is demonstrated by two dams located along Western Africa’s Senegal River, a semi-arid locale: the next stop on our dam excursion.

The Senegal River flows through Guinea Mali, Mauritania and Senegal.[21] In March 1972 following a series of devastating floods and droughts the four riparians entered into an agreement of cooperation. Over a period of fifteen years the parties planned and built two dams. The first is the Manantali Dam and the second is the Diama Dam. The Manantali dam completed in 1987, created a mega-reservoir that holds over 11.3 billion cubic meters of water,[22] and is used for irrigation, to produce hydropower and for maintenance of a navigation channel.[23] The Diama dam, completed in 1986, is twenty-seven kilometers upstream of the Atlantic Ocean. It is used to stop saltwater intrusion flowing upstream during the dry season, in times of drought and for navigation.[24]

The two dams began operation in 1988. Within the first year after the Diama Dam became operational, the people living near the newly irrigated areas along the Senegalese portion of the river suffered a significant increase in waterborne diseases.[25] These included the grave waterborne disease intestinal schistosomiasis.[26] A host snail is required for the schistosomiasis life cycle. Due to the construction of the two dams, ubiquitous pools of fresh water formed in the riverbed and irrigation canals. Unflushed by the river, as would occur naturally, these pools produced an ideal environment for the host snails to flourish.[27] Similar infections from the same snail have been documented in populations living adjacent to Egypt’s Aswan Dam. For example, “the irrigation channels and new permanence of water have led to an epidemic of bilharzia, with infection rates approaching 100 percent in some areas. Egypt is not alone in finding that dams cause disease.”[28]

By 1994, six years after the dams on the Senegal River became operational, “villagers living along the lower reaches of the river demonstrated a 90 percent infection rate from intestinal schistosomiasis. In addition, virtually every person older than the age of five was infected with a more virulent strain.”[29]

A number of other diseases including, malaria, and cholera also increased dramatically during this same time period, all due to the newly created pools of fresh water. For example, within the first two years of operation, in 1988 and 1989, a random field study of 1,000 people in the vicinity of Diama Dam showed a 60 percent prevalence of intestinal schistosomiasis that was not present in this location before Diama Dam.[30] By 1994, 90 percent of the people living near Diama reservoir were infested.[31] Malaria was present before the dam construction, but the year-round standing water dramatically increased the mosquito breeding grounds. Cholera epidemics, which in the past occurred only during the rainy season, became quasi endemic.[32]

The increase in diseases prompted one commentator to suggest that, following construction of the two dams, the human health costs were greater than all the economic benefits of increased irrigation and navigation potential.[33] Moreover, the changes to the local ecosystem have caused an imbalance in the region’s natural resources, as well as other unintended consequences.

Proliferations of these unintended consequences include the starvation of much needed river sediments into marine environments. One well known example is the non-Senegalese Egyptian Aswan High Dam, which was constructed in 1964.Before the High Dam was built, “fifty percent of the Nile flow drained into the Mediterranean.”[34] Indeed, in the course of a typical flood, “the total discharge of nutrient salts was estimated to be approximately 5,500 tons of phosphate and 280,000 tons of silicate. The nutrient-rich floodwater, or Nile Stream, was approximately fifteen kilometers wide and had sharp boundaries. It extended along the Egyptian coast and was detected off the Israeli coast and sometimes off southern Turkey.”[35]

This stream of sediment is now trapped behind the Aswan High Dam. Starved of this much-needed detritus the Egyptian Coast is experiencing acute erosion. The dam has also had an enormous effect on the coastal waters fertility – “It is a landscape [teeming] with life.”[36] The fertilizing impact of the inflow of the nutrient-rich water throughout the flood season once resulted in extraordinarily dense blooms of phytoplankton off the Nile Delta.[37] This far-reaching impact on the transport of fertile silt and sediments not withstanding, the High Dam has been a boon to “Egyptian agriculture and has benefited industry by providing cheap electric power . . .”[38]

1. Famine by Concrete: Dams’ Impacts on Food Production

Returning to the Senegal River, the construction of the Diama and the Manantali dams triggered other problems. These included the infestation of livestock by waterborne parasites, which caused a regional decrease in milk and meat production from goats and death to livestock.[39] Other food sources, such as fish, the major source of protein for the local population declined precipitously because the dams closed access to spawning grounds in the estuary.[40]

Finally, the most significant and well-documented changes occurred in the agricultural cycle. For centuries prior to damming the Senegal, the local populations practiced communal recession agriculture. The annual river flood during the rainy season caused the floodplain soil to become more fertile once the waters receded, allowing for the planting of cereal crops.

Concomitantly, livestock were moved away from the floodplain to pastures and the cereal crops required little maintenance as they thrived in the wet nutrient rich soil. Thus, villagers were free to spend time herding livestock, fishing, gathering wood, and finally to harvest their crops, which allowed them to move their livestock onto the floodplain to graze on the plant stubble.

The genius of this communal system was that this low-cost production method supported a larger population of humans and animals than would normally be possible in this type of semi-arid environment. However, once the dams were built an inconsistent plan to replicate this cycle destroyed the recession farming and led to the loss of livestock because there was no stubble pasture. Wood gathering also declined, due to two factors: the first, because of the loss of the cereal crop, another crop was needed, and vast stands of acacia trees were cleared for rice fields; the second was due to lack of flood waters for the remaining acacia trees, which died due to lack of water. A sustainable lifestyle was lost.

The promise of power production which was supposed to supplement the sustainable life that these villagers had for over one thousand years, also failed to materialize until 2002.Similarly, irrigation for growing rice has yet to reach the projected goal of 375,000 hectares.[41] Moreover, the costs for rice production are significantly higher than recession agriculture and include clearing and leveling land and building extensive berms around fields to facilitate irrigation.

[1] The Parker Dam, constructed between 1934 and 1938, spans the Colorado River between Arizona and California and lies approximately 155 miles downstream of the Hoover Dam.See generally, United States Department of the Interior, Bureau of Reclamation, Parker Dam and Powerplant(Updated Nov. 2006) at

[2] The Imperial Dam, constructed between 1935 and 1938, is located approximately 20 miles northeast of Yuma, Arizona.The dam was constructed as the point of diversion for waters pouring from the Colorado River to the All-American Canal.The latter serves the Coachella and Imperial valleys in California. See generally, The Imperial Irrigation District, IID Water, Imperial Dam (2006) at

[3] River Management Virtually Wipes Out Life on the Colorado River Delta, supra note 93.

[4] Id.

[5] Id.

[6] Id.

[7] J.D. Carriquiry & A. Sanchez, Sedimentation in the Colorado River Delta and Upper Gulf of California After Nearly a Century of Discharge Loss, 158 Marine Geology125 (June 1999).

[8] “The endangered fish, totoaba, a relative of the white seabass . . . can grow to over 200 pounds in weight.” Gene Kira, Unique Ensenada Fish Breeding Lab Struggles for Funding, Western Outdoor News, July 14, 2003, available at

[9] The vaquita is the smallest living cetacean, weighing up to 55 kg (120 lb) . . . It lives in shallow lagoons along the shoreline where there is strong tidal mixing and high productivity of the aquatic plant and animal communities.

The vaquita appears to be a non-selective feeder on small bottom-dwelling fish and squid . . . The vaquita may have formerly occurred in Mexico throughout the Gulf of California. It was considered abundant in the early 20th century. As of the early 1980s, the only recent records of its occurrence were from the northern part of the Gulf of California. Currently it has the most limited distribution of any marine cetacean. It is restricted to the northwestern corner of the Gulf of California.

Animal Information, Vaquita: Profile (Nov. 2, 2005),

[10] See generally, Janet Abramovitz, Imperiled Waters, Impoverished Future 11 (1996).

[11] The Hungry Horse Dam and reservoir are located on the South Fork of the Flathead River in Montana. Construction on the 564-foot-high dam began in mid 1948, and the work was completed July 18, 1953. Bureau of Reclamation, Hungry Horse Project, at Development (undated)

[12] Devine, The Trouble with Dams, supra note 22.

[13] Id.

[14] Lower Monumental Lock and Dam and Lake Herbert G. West, which extends 28 miles (45 km) east to the base of Little Goose Dam, is formed behind the dam is located on the Snake River, and bridges Franklin County and Walla Walla County, in the state of Washington.

Construction began in June 1961. The main structure and three generators were completed in 1969, with an additional three generators finished in 1981. Generating capacity is 810 megawatts, with an overload capacity of 932 MW. The spillway has eight gates and is 572 feet (176 m) long.

The Lower Monumental Dam is part of the Columbia River Basin system of dams.

U.S. Army Corps of Engineers, Coastal & Hydraulics Laboratory, Lower Monumental Lock and Dam Physical Model Study (undated);68.

[15] Imperiled Water supra note 92 at 11 – 12.

[16] Devine, The Trouble with Dams, supra note 22.

[17] Id.

[18] Id.

[19] Id.

[20] Goddard Institute for Space Studies, Science Briefs,Human Impacts on the Global Water Cycle: Effects on Sea-Level and Climate (Mar. 1997) (emphasis added) at

[21] The River rises in the Fouta Djallon Mountains of Guinea, flows through Mali and Mauritania and empties into the Atlantic Ocean via the Senegal delta.

[22] 11.3 billion meters3 converts to the American equivalent of 9.2 billion acre-feet or 9.2 x 109 (trillion) gallons.

[23] Margaret J. Vick, The Senegal River Basin: A Retrospective and Prospective Look at the Legal Regime, 46Nat. Resources J. 211, 216 (2006).

[24] Id.

[25] Id. at 216 – 217.

[26] Scientific Data for Decision Making Toward Sustainable Development, Senegal River Basin Case Study, Summary of Workshop 4 (National Academy of Sciences 2003), available at http:// [hereinafter Case Study].

[27] Vick, The Senegal River Basin, supra note 113 at 217.

[28] Marq de Villiers, Water: The Fate of Our Most Precious Resource 125 (2001).

[29] Vick, The Senegal River Basin, supra note 113 at 217. That strain is known as schistosomiasis mansoni infestation.Id.

[30] Id.

[31] Id.

[32] Id.

[33] Id. at 218.

[34] Sayed El-Sayed and Gert L. van Dijken, The Southeastern Mediterranean Ecosystem Revisited: Thirty Years After the Construction of the Aswan High Dam, 3 Texas A&M Quarterdeck Online, Spring 1995

[35] Id.

[36] Houck, Oh Canada! supra note 40 at 224.

[37] El-Sayed and van Dijken supra note 121.

[38] Id.

[39] Vick, The Senegal River Basin, supra note 113 at 190-91.

[40] Id.

[41] Id. at 192.


Itzchak Kornfeld

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