Dams and reduction of water storage capacity

Excerpt from the description of a colloquium that I am organizing on Water Infrastructure:

There are 59,000 dams in the world; 1,400 in the state of California alone. While these dams provide fundamental services, such as irrigation (36% of the dams), hydropower (17%), water supply (15%), flood control (13%), recreation (8%), and the remaining part is for navigation, fish farming, among other usages, these comes at an environmental, social, and economic cost. The vast majority of these dams were constructed between the 1890’s and the early 1980’s, before the major environmental and social impacts of dams were fully recognized. For example, historic dam construction did not consider sediment management scenarios in their designs or locations. Many dams were designed as if rivers carry only clean water, however, dams trap 100% of the gravel that rivers carry, while in fact part of the suspended sediments would pass the dams through their outlets. This problem has resulted than reservoirs behind the dams are losing their water storage capacity by filling up with sediments in a rate of 0.5 to 1% per year.

Since 1978 the global dam construction has slowed down due to an increasing awareness of their environmental and social impacts, but still there are about 3,000 new dam projects planned in Asia, Africa, and South America.

Recuperating that global storage capacity costs approximately 13 billion USD per year. On a more local scale, the state of California recently passed a bill that allocates over 2.5 billion USD for water storage projects, including dams and reservoirs. Our undeniable reliance and need for water supply coupled with the social and environmental impacts of existing technologies lead to many questions: How can we ensure water supply security for next generations? How should we adapt our life styles to conserve limited resources?

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