Working with nature and not against it: Sandbars

Sandbars are a critical component of the Grand Canyon ecosystem, providing essential habitat, like warm backwaters, for species in the river’s intricate food web. The creation and maintenance of sandbars, however, depend on how much sediment is coming into the system and how fast the water carrying that sediment is flowing.

Prior to construction of Glen Canyon Dam, the Colorado River transported some 60 million tons of sand each year, and flows varied by as much as 600 percent from one year to the next. Each spring, an inundation of meltwater often left new sandbars and beaches in its wake.

Today, the dam has cut off 94 percent of the river’s sand supply and tamed its wildly fluctuating flows, eliminating large spring floods altogether. However, in order to provide water and electricity, the average daily flow is now often higher than before the dam was constructed. 
  
Earth Magazine reports:  http://www.earthmagazine.org/article/releasing-flood-controversy-colorado-river 

Scientists have seen habitat changes reverberating through the Grand Canyon’s food chain. Organic matter from throughout the river’s basin once sustained a diverse group of aquatic insects and formed the base of a complex food web.