Reference for general background reading:

Leslie, Jacques, Running Dry, What happens when the world no longer has enough freshwater? Harpers, pp. 37-52, July, 2000.

List of Projections:

1 - Selected water policy issues by continent and region.
2 - Key Concepts: River discharge highly variable by geographic region, due in large part to general atmospheric circulation dynamics (Hadley Cell, etc); result is very high Q in S America and very low Q in Australia.
3 - Locations of large river basins: World Resources Institute.
4 - Hydroelectricity generation by continental area.
5 - Hydroelectricity generation for selected countries.
6 - South America rivers: Amazon, Orinoco, Parana, Magdalena, Sao Francisco.
7 - North America rivers: Mississippi, St. Lawrence, Columbia, Mackenzie, Yukon, Colorado, Hudson.
8 - Water use for hydroelectricity generation in USA (map).
9 - Columbia River drainage basin with major hydro dams (map).
10 - Regional map for James Bay (Canada) hydroelectricity generation.
11 - Map of the Colorado River Basin
12 - Discharge measurements at Lee's Ferry, downstream of the Glen Canyon Dam
13 - Hydrograph of the Colorado River at Lee's Ferry
14 - Water temperature of the Colorado River
15 - Experimental flood on the Colorado River
 

SELECTED WATER POLICY ISSUES BY REGION (Projection 1).

1. Water policies of primary interest in each region are influenced by interaction of natural, economic & political factors.
2. Many developing countries plan to expand hydropower and irrigation storage capacity.
3. Regions with moderate to high precipitation rates and very large rivers (i.e. much of South America) have quite distinct water policy concerns from those with low rainfall and no large rivers (i.e. much of Australia).
4. Economically advanced countries tend to be more concerned with ecological issues and reduction in exposure to toxic chemical contamination, while less developed countries place higher priority on expanding pathogen-free domestic water supplies and reducing immediate dangers such as flood risks.
5. Planning for water resource management rarely involves serious scrutiny about issues more than a few decades in the future, especially when such issues might present obstacles to major capital investment plans or call in question the freedom for established interests to deplete scarce resources.

KEY FACTORS IN CONTROLLING RIVER DISCHARGE (Projection 2):

Amounts of water discharge (Q) in large rivers are related primarily to
1. drainage basin size,
2. large-scale atmospheric circulation dynamics and
3. topography.
These latter two factors have major influence on the amount of precipitation (P) and evapotranspiration (ET) per unit area. High ratios of P to ET result in higher stream runoff per unit area.

Continents with highest and lowest river discharge amounts are South America and Australia, respectively, due primarily to large-scale atmospheric circulation dynamics and topography.

South Asia rivers have some of the highest concentrations of suspended solids in the world due to intense weathering from monsoon precipitation of the Himalaya mountains, Tibetan plateau, and intensively cultivated lands to the south and east, causing major difficulties for construction and operation of reservoirs.

Dissolved solids in major rivers around the world have a relatively small range of concentrations, with the dominant dissolved ions being Ca⁺⁺ and HCO₃^-.

Much of modern human use of fresh water involves diversions or control of large rivers to provide irrigation water for agriculture, hydroelectric dams, cooling of fossil fuel electric generating stations, and domestic water supplies for cities. Some major watersheds of the world which will be discussed briefly here are shown schematically in a World Resources Institute map (Projection 3).

HYDROELECTRICITY GENERATION: GENERAL ASPECTS.

Construction of dams for flood protection, irrigation water storage and hydroelectricity generation represents one of the major features of economic development during the 20th century in most regions of the world. Approximately 20% of electricity in the world is generated through hydropower, with most of the balance from combustion of fossil fuels or nuclear-fuel fission reactors. The installed capacity of hydropower by continental area (Projection 4) , on a per capita basis (watts per capita), is highest in North & Central America (356) and Oceania (427) and lowest in Asia (57) and Africa (27), with a world average for installed hydropower of 113 watts per capita. Actual production of hydropower occurs at a rate less than the maximum installed capacity, for many reasons, such as lack of rain during some seasons of the year. When a reservoir has water standing at a lower level than maximum pool, the electricity generating potential is also lower (electric power production is proportional to rate of water flow multiplied by height (head) of water above the turbines). On a global basis, electricity generation occurs at about 44% of the maximum installed capacity. With very low installed capacity for hydropower in Africa, especially south of the Sahara Desert, one general development policy issue concerns whether significant new hydro investments should be encouraged and financed there. And if so, when and where? There are a number of complicated aspects about these questions, with few simple answers.

The geography of hydroelectricity capacity is tremendously varied between countries and within countries, as the result of the need for at least three important factors to coexist: substantial river discharge, locations where dams can be constructed across rivers to produce appreciable rise in water levels behind the dams, and large amounts of capital for construction. Countries with very large installed hydro capacity (in 1000 megawatts by 1996)) include (Projection 5): USA (75), Canada (65), China (52), Brazil (51) and Russia (40). On a per capita basis, the countries with the highest installed hydro capacities (in watts per capita) include: Norway (6050), Canada (2230), Sweden (1870) and New Zealand (1470). The USA has about 280 watts per capita, and Bangladesh only about 2 watts per capita of hydro power, despite having two of the largest rivers in the world flowing through the country. These two rivers (Ganges and Brahmaputra) are so large and nearly all of the land surface is so close to sea level that there appears to be no currently feasible way to harness them for hydropower in Bangladesh. Clearly some countries have much greater or lesser advantages concerning the potential for generation of hydropower. Those countries with a very high fraction of electricity generation by hydro will have to expend proportionally less for fuel costs associated with electricity produced from fossil fuels.

SOUTH AMERICAN RIVERS.

Beginning with the highest river discharge continent (Projection 6), the largest river in South America delivers almost 20% all global river discharge to the ocean through this single drainage basin. The Amazon, with Q = 6000 to 7000 km³/year, is a remarkable river in almost every aspect. The combination of a large land mass located directly beneath the ITCZ and a large mountain range, the Andes, situated at the downwind edge of the drainage basin, results in massive amounts of precipitation and subsequent river discharge. This river, situated primarily in Brazil, is so large over nearly all of its course that it exceeds the scale of likely human intervention through dams and other attempts to regulate its flow. Although one fifth of global river discharge occurs through the Amazon, the basin area is only about 2% of global continental area, indicative of how high the rate of runoff per unit area of land can be in tropical climates. Another huge river in South America (SA), the Orinoco in Venezuela, has a mean annual discharge rate (1100 km³/yr) that is almost double the largest river in North America. The third largest river in SA, the Parana has an annual Q (500 km³/yr) almost as large as the Mississippi. If we use the mean annual discharge of the Mississippi River (600 km³/year) as a reference, the Amazon and Orinoco Rivers are greater by factors of about 10 and 2, respectively. With the huge scale of several rivers in SA, relatively low population density compared to other continents, combined with rapidly growing national economies, these rivers have become the focus of some of the largest hydroelectric generation schemes ever conceived. The combined electricity output from the Itaipu hydro stations on the Parana River between Brazil and Paraguay currently exceeds 10,000 megawatts of generating capacity, the largest of any single site in the world and more than a factor of five greater than the total capacity of two large nuclear generation stations at Indian Point on the Hudson River. Dozens of other large hydroelectric generation stations have already been completed in Brazil.

The drainage basins of the Amazon and Orinoco Rivers are also the largest remaining areas of tropical forests and the focus of considerable pressure for development that would in many areas involve removal of the native vegetation for wood products or to establish pasture for animals. The eventual fate of the tropical forests of northern South America are of great interest for preservation of global biodiversity, as well as limiting the amounts of carbon dioxide in the atmosphere. Further hydro development in South America is likely to have substantial influence on biodiversity issues in that region.

The Sao Francisco River in northeastern Brazil is critical for domestic water supplies and irrigation in the most arid region of that country, and has many competing demands, as is true for many rivers in semi-arid climatic zones. Periodic droughts in northeastern Brazil represent a major social problem in the country because of displacement of large populations of rural citizens.

NORTH AMERICAN RIVERS.

In North America (NA), the discharge of fresh water is dominated by the Mississippi (Q = 600 km³/yr) and the St. Lawrence (Q = 440 km³/yr), both of which receive large inputs from the higher precipitation region east of the mountain ranges that dominate the western third of the continent (Projection 7). Other large rivers in NA include the Mackenzie, Columbia and Yukon, two of which discharge into Arctic marine waters. These Arctic rivers have high Qs because they drain large land areas and because the mean rate of ET at high latitudes is quite low.

Most hydro power generation capacity in the USA is concentrated in a few regions of the country, including the Pacific Northwest, Colorado River, and Northeast, especially Niagara Falls (Projection 8). Note that there is very little hydro power generated in the central part of the country, despite the presence of the largest river system in North America (Mississippi). The topography in that region is generally not favorable for dam construction. The Columbia River has been the most intensively developed for hydroelectric generation of any river in North America, due to the combination of relatively high Q and a large elevation range in the basin (Projection 9). There are more than a dozen major dams on the main stem of the Columbia River, and a total of more than 100 dams on tributaries.

The St. Lawrence is perhaps best known for the huge freshwater lakes that dominate the border area between Canada and the USA in the eastern half of the continent. These lakes are all relics of the large continental glacier that formerly covered this region and carved deep basins by ice erosion. Discharge of the enormous quantities of water from the St. Lawrence Great Lakes provides the second largest concentration of hydroelectric generating capacity in North America, after that of the Columbia River. Much of the electricity generated at Niagara Falls on the St. Lawrence is distributed to the New York City area.

Considerable new electricity generation capacity in eastern North America was installed in Quebec over the last two decades. As opposition to construction of new fossil fuel and nuclear generating stations contributed to a very low rate of capital investment for these purposes, electricity demand continued to rise. Today, large amounts of electricity are delivered into the grid which serves NYC from very long transmission corridors leading from an array of hydro stations on rivers which discharge into James Bay (Projection 10). The region in which these dams were constructed has very low topographic relief, and thus the reservoirs cover very large areas, flooding forests, many of which were lands occupied by Native Americans. So the environmental and social consequences for construction were considerable, despite being located far from major population centers. There are a number of economic and environmental consequences to this situation, including at least the following issues:

Positive:

1. Economic assets for Quebec and Ontario, through sales of electricity to the USA and reduction of domestic Canadian demand for fossil fuels.
2. Improved air quality in the NE USA due to lower combustion of fossil fuels for electricity generation.
3. No construction of new nuclear power stations for several decades, hence fewer problems with storage and containment of spent fuels.
4. Less US capital invested in electric power generating stations.

1. Continued costs to US citizens to purchase electricity from Canadian utilities.
2. Construction and other costs of high voltage transmission lines within the NE USA.
3. Flooding of huge areas of forested land in Canada, including those intended for indefinite use by Native Americans.
4. Loss of significant ecosystems in high latitudes of Canada.
5. Mercury contamination of fish in the new reservoirs.
6. Large production of methane gas from the flooded forest areas (addition source of greenhouse gas).

In terms of irrigation demand, the most important river in NA is probably the Sacramento (Q = 40 km³/yr), the basis for most of the agriculture in the northern half of the Central Valley of California. The Colorado, a relatively small river in term of Q (22 km³/yr), has great economic importance because it lies in a region that has very limited water resources. This river delivers domestic water to Los Angeles and urban areas in Arizona, as well as major irrigation districts in both these states, and other states upstream. In terms of dollars of economic return per cubic meter of mean annual river discharge, the Colorado probably represents one of the most valuable rivers in the USA. For both the Sacramento and Colorado Rivers there is now intense competition between irrigation agriculture and urban domestic water districts, with the total demand well beyond the water yield of those river basins. Since urban water uses pay, on the average, at least a factor of ten more per unit volume of water than irrigation users, it is likely that there will be smaller future allocations for farming in that region.

The Hudson River, which also has had considerable historic and economic importance in the development of this region of the USA, has relatively low Q because it drains a very small basin compared to those of the others illustrated. The large cross sectional area of the Hudson in the vicinity of NYC is the result of glacial erosion during the ice ages and not fluvial erosion. The Hudson is an estuary near NYC and has appreciable salinity in that area from marine intrusion.

Examples of public policy issues for water management in North America include:

1. pricing of water for irrigation is now heavily subsidized;
2. depletion of groundwaters, especially in the west-central and SW of the USA is becoming widespread & threatens future crop production in those regions;
3. flood control practices (i.e. permitting construction in flood plain areas of the Mississippi and other rivers) expose the general population to major financial costs due to federal government subsidies of flood insurance;
4. loss of anadromous fish such as salmon, due in part to dams on the Columbia and other rivers, is in direct conflict with the need for continued generation of electricity from non fossil fuel sources;
5. hydropower development in eastern Canada has flooded huge areas of low elevation topography, much of which is Native American lands.

See web site on World Commission on Dams (http://www.dams.org) as listed in Gleick text p. 196, in table entitled Water-Related Web Sites.

RIVER MANAGEMENT IN NORTH AMERICA.

Columbia River management issues.

• one of most intensively controlled rivers in the world, with more than 100 dams in the basin, with more than a dozen on the main stem of the river.

• regional electricity cost lowest in the US, due to intensive hydro development, mostly financed by federal programs.

• loss of most of the salmon fishery in the regional ocean waters & within the river itself, due to obstruction of fish spawning migration by dams, as well as other perturbations.

• proposed removal of dams on the Snake River (tributary to the Columbia R), to help restore fisheries.

• see Gleick text chapters on subject of dam removal, especially on the Snake River.

Sacramento River management issues.

• very intensively managed, including large number of reservoirs in the mountain valleys of the Sierra Nevada; providing water for irrigation, municipal supplies, and hydroelectricity generation.

• most precipitation occurs as winter snow, which typically takes many months to melt, and flow down streams to storage reservoirs, thus serving as "natural" storage in the mountains.

• changing climate (warmer winter conditions, including more rain events in the mountains rather than snow).

• new climate conditions lead to more winter/spring flooding, and reduced water availability in the summer.

• possible policy responses: build additional water storage dams? Will require some response to avoid having reduced irrigation water availability and increased flood risks.

• thus climate change can result in significant additional costs for water management infrastructure.

Colorado River.

The Colorado River basin stretches over 7 states and Mexico [Projection 11] and is essential for the water supply of the south western US. Construction of major dams including Glen Canyon Dam have affected the river in many ways. Construction of the dam flooded Glen Canyon, a major tourist attraction but also sparked economic development along Lake Powell (the reservoir behind the dam). The dam produces about 1300 MW of electric power. Discharge rate [Projection 12, Projection 13] and temperature [Projection 14] of the Colorado River have dramatically changed after the dam was completed. Debris was nor cleared any more because of the missing seasonal floods, exotic vegetation invaded the canyon and native fish were replaced by cold water loving trout. Attempts were made in 1996 and 2000 to create an artificial flood [Projection 15] which had only short term positive effects, such as removing some of the non-native vegetation and restoring some of the sandbanks.

Other issues related to the Colorado River include:

• Diversion of nearly all the water in the Lower Colorado to Nevada, California and Arizona, leaving very little to reach Mexico.

• Desalinization plant at Yuma, Arizona, intended for improving water quality of Colorado River water flowing into Mexico; extremely expensive process & has not been used for its originally intended purposes.

Mississippi River.

• very extensive dike system (levees) to reduce frequency of flooding in basin, constructed thru much of 20th century.

• has reduced frequency of moderate floods, but has made major floods more severe in terms of property damage, due to extensive construction of infrastructure in the former flood plain areas.

• flood insurance is heavily subsidized by federal funds, thus much of the flood costs are paid by the entire society.

• costs of summer 1993 floods estimated at about $16 billion.

Updated September 15, 2003
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