The watersheds that supply drinking water to 80% of California’s resident cover almost 157
million acres and span 8 states (Figure 1). These watersheds drain lands that include highly
protected areas (e.g., wilderness areas) and those that have been developed (e.g., downtown
Sacramento). From the map, it is clear that the Sierra Nevada mountains are an important
source of water for the state of California, providing snowmelt for the many lakes and rivers
that drain into the Sacramento and San Joaquin rivers. These rivers, in turn, supply water to the
Sacramento-San Joaquin Delta, a water source that serves roughly 25 million Californians via
the State Water Project. In addition, most southern California cities obtain some of their
drinking water from the Colorado River, which originates in the mountains of Wyoming and
Colorado, and then passes through and drains portions of Utah, New Mexico, Arizona, and
Nevada until it reaches Lake Havasu, on the border between Arizona and California. There, it is
diverted into the Metropolitan Water District’s Colorado River Aqueduct which carries the
water 242 miles to southern California.
A single 13ft long by 33ft high net alone can collect 66 gallons of water a day, sufficient for a
family's needs. The water, which is pure and does not need to be filtered, runs down into troughs
and then via pipes into a holding tank.
Large mesh structures, of hundreds of square meters each, could be set up relatively inexpensively; once in place, they cost virtually nothing to operate. They consume no energy, needing only an occasional brushing to remove particles of grit and bugs. “The operating cost is essentially zero,” McKinley says, because “nature has already done the hard work of evaporating the water, desalinating it and condensing the droplets. We just have to collect it.”
Chilean investigators have estimated that if just 4 percent of the water contained in the fog could be captured, that would be sufficient to meet all of the water needs of that nation’s four northernmost regions, encompassing the entire Atacama Desert area. And with the MIT-designed system, Park points out, 10 percent of the fog moisture in the air passing through the new fog collector system can potentially be captured.