Delta Over-Pumping Led To Present Water “Crisis”

Gov. Brown may strongly endorse the Bay Delta Conservation Plan, however the facts of Delta over-pumping continue to contribute to the complexity of the issue. What the water agencies do not want you to know is that the Department of Water Resources (DWR) allowed the Delta to be over-pumped from 2000 to 2006 in order to allow the Metropolitan Water District (MWD) to make up for its loss of much of its Colorado River allocation (See Graph). 

Decline of Colorado river water and the rise of water pumped from the Delta Credit: Metropolitan Water District
The graph, courtesy of the MWD, shows that from 1976 through 1998, the MWD received on average roughly 700,000 acre feet of Delta water per year. But in 2000, water deliveries doubled to over 1,400,000 acre feet. It dropped to 1,100,000 acre feet over the next year and then shot up to a high of 1,800,000 acre feet in 2004. Overall, the Delta was subjected to about 45,000,000 acre feet of over-pumping in six short years, enough to cover almost all of Southern California to the depth of one foot! And, as the chart shows, the Delta over-pumping matched exactly the MWD’s loss of its Colorado River water allotment.

This massive over-pumping is what created the “crisis” in the Delta. To get a picture of how it happened you have to imagine two gigantic 40-ft. Pumps at the Clifton Court Forebay, at the southern tip of the Delta. Here, water was collected to be pumped south via the Central Valley Project and the Delta-Mendota canals. But every time the two pumps were turned on the suction was so great that it made Delta rivers run in reverse! At the same time literally millions of fish-from Delta Smelt to Chinook Salmon-were killed, mangled in the rotating blades.

This damage to the Delta was bad enough even with regular pumping, but with 45,000,000 acre feet of over-pumping, the normal harm done was magnified to the point where the whipsawing of river flows back and forth wore down and further degraded the levees. The natural migratory paths of Delta fish species were so upset that the total fish population declined dramatically. It took a court order from a federal judge to cut back pumping in 2006 so the fish population could recover–which it did–proof of the damage of over-pumping!

As if all this were not enough, the MWD recently said that when (not “if”) the Peripheral Canal is built in the Delta, it would like its allotment to be set at the 2006 level–twice what it has received in the past!