Map of the Day: Development of an Erosion-Reduction Management Strategy for Watersheds and Reservoirs in Algeria

…from the ESRI Map Book, Volume 24

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“In Algeria, water is a key component of economic development, and its scarcity necessitates dams for storage and distribution for irrigation and human consumption. The Agence Nationale des Barrages et Transferts (ANBT) plans to build new dams to bring the total to 70 by 2010. However, soil erosion has contributed to a 20 percent reduction in reservoir capacities since their construction.

“In 2003, the ANBT invited Tecsult Inc., a major Canadian engineering firm, to conduct a comprehensive study that would locate the degraded areas of watersheds of twenty-one dams (five existing and sixteen in the detailed planned stage) and to develop watershed management plans to reduce hillside erosion and decrease reservoir siltation (accumulation of silt). The total study area covered more than 23,800 square kilometers (9,190 square miles), and the allowed study time was eighteen months.

“Each watershed was characterized for three types of erosion (sheet erosion, gully erosion, and landslides), and the resulting maps were combined in order to create a consolidated erosion risk map. Using this map and twelve land management measures, a watershed management plan was developed for each dam. Each watershed has also a map locating four kinds of special erosion control actions that aimed to reduce the stream sediment loads before they reach the reservoir. Finally, the budget required for implementing the watershed management plan with the special erosion control actions was estimated for each watershed. It was estimated that the twenty-one management schemes elaborated during this study will yield a total estimated gain of water in their reservoir equivalent to the consumption of water for more than 9 million people in one year.

“Courtesy of Agence Nationale des Barrages et Transferts (ANBT).”