Interbasin transfer


Interbasin transfer or transbasin diversion are terms used to describe man-made conveyance schemes which move water from one river basin where it is available, to another basin where water is less available or could be utilized better for human development. The purpose of such designed schemes can be to alleviate water shortages in the receiving basin, to generate electricity, or both. Rarely, as in the case of the Glory River which diverted water from the Tigris to Euphrates River in modern Iraq, interbasin transfers have been undertaken for political purposes. While ancient water supply examples exist, the first modern developments were undertaken in the 19th century in Australia, India and the United States; large cities such as Denver and Los Angeles would not exist as we know them today without these diversion transfers. Since the 20th century many more similar projects have followed in other countries, including Israel, Canada and China. Utilized alternatively, the Green Revolution in India and hydropower development in Canada could not have been accomplished without such man-made transfers.
Since conveyance of water between natural basins are described as both a subtraction at the source and as an addition at the destination, such projects may be controversial in some places and over time; they may also be seen as controversial due to their scale, costs and environmental or developmental impacts.
In Texas, for example, a 2007 Texas Water Development Board report analyzed the costs and benefits of IBTs in Texas, concluding that while some are essential, barriers to IBT development include cost, resistance to new reservoir construction and environmental impacts. Despite the costs and other concerns involved, IBTs play an essential role in the state's 50-year water planning horizon. Of 44 recommended ground and surface water conveyance and transfer projects included in the 2012 Texas State Water Plan, 15 would rely on IBTs.
While developed countries often have exploited the most economical sites already with large benefits, many large-scale diversion/transfer schemes have been proposed in developing countries such as Brazil, African countries, India and China. These more modern transfers have been justified because of their potential economic and social benefits in more heavily populated areas, stemming from increased water demand for irrigation, industrial and municipal water supply, and renewable energy needs. These projects are also justified because of possible climate change and a concern over decreased water availability in the future; in that light, these projects thus tend to hedge against ensuing droughts and increasing demand. Projects conveying water between basins economically are often large and expensive, and involve major public and/or private infrastructure planning and coordination. In some cases where desired flow is not provided by gravity alone, additional use of energy is required for pumping water to the destination. Projects of this type can also be complicated in legal terms, since water and riparian rights are affected; this is especially true if the basin of origin is a transnational river. Furthermore, these transfers can have significant environmental impacts on aquatic ecosystems at the source. In some cases water conservation measures at the destination can make such water transfers less immediately necessary to alleviate water scarcity, delay their need to be built, or reduce their initial size and cost.

Existing transfers

There are dozens of large inter-basin transfers around the world, most of them concentrated in Australia, Canada, China, India and the United States. The oldest interbasin transfers date back to the late 19th century, with an exceptionally old example being the Roman gold mine at Las Médulas in Spain. Their primary purpose usually is either to alleviate water scarcity or to generate hydropower.

Primarily for the alleviation of water scarcity

Africa

The Central Arizona Project in the USA is not an interbasin transfer per se, although it shares many characteristics with interbasin transfers as it transports large amounts of water over a long distance and difference in altitude. The CAP transfers water from the Colorado River to Central Arizona for both agriculture and municipal water supply to substitute for depleted groundwater. However, the water remains within the watershed of the Colorado River, though transferred into the Gila sub-basin.

Asia

Characteristics of major existing interbasin transfers and other large-scale water transfers to alleviate water scarcity
Year of constructionLengthCapacity Costs
California State Water Project Early 1960s-1990s715 km25 5.2
Colorado River Aqueduct 1933–1941392 km1603.5 ?
Central Arizona Project 1973-93541 km1850.2 3.6
National Water Carrier 1953-64130 km1.7?
Cutzamala System Late 1970s-late 1990s154 km2.1 1.3
All-American Canal 1930s132 km64 ?
Periyar Project Commissioned in 1895?3.5 ?
Indira Gandhi Canal Since 1958650 km??
Telugu Ganga project 1977–2004406 km10.1 ?
Irtysh-Karaganda scheme 1962–1974450 km6.5 ?

For the generation of hydropower

Africa

In Canada, sixteen interbasin transfers have been implemented for hydropower development. The most important is the James Bay Project from the Caniapiscau River and the Eastmain River into the La Grande River, built in the 1970s. The water flow was reduced by 90% at the mouth of the Eastmain River, by 45% where the Caniapiscau River flows into the Koksoak River, and by 35% at the mouth of the Koksoak River. The water flow of the La Grande River, on the other hand, was doubled, increasing from 1,700 m³/s to 3,400 m³/s at the mouth of the La Grande River. Other interbasin transfers include:
;British Columbia
;Manitoba
;New Brunswick
;Newfoundland and Labrador
;Northwest Territories
;Nova Scotia
;Ontario
;Quebec
;Saskatchewan
The Chicago Sanitary and Ship Canal in the US, which serves to divert polluted water from Lake Michigan.

Transfers under construction

The Eastern and Central Routes of the South-North Water Transfer Project in China from the Yangtse River to the Yellow River and Beijing.

Proposed transfers

Nearly all proposed interbasin transfers are in developing countries. The objective of most transfers is the alleviation of water scarcity in the receiving basin. Unlike in the case of existing transfers, there are very few proposed transfers whose objective is the generation of hydropower.

Africa

From the Ubangi River in Congo to the Chari River which empties into Lake Chad. The plan was first proposed in the 1960s and again in the 1980s and 1990s by Nigerian engineer J. Umolu and Italian firm Bonifica. In 1994, the Lake Chad Basin Commission proposed a similar project and at a March, 2008 Summit, the Heads of State of the LCBC member countries committed to the diversion project. In April, 2008, the LCBC advertised a request for proposals for a World Bank-funded feasibility study.

Americas

From the Ebro River in Spain to Barcelona in the Northeast and to various cities on the Mediterranean coast to the Southwest

Ecological aspects

Since rivers are home to a complex web of species and their interactions, the transfer of water from one basin to another can have a serious impact on species living therein.