Man-Made Mountains and Earthquakes

Water is heavy.  Groundwater actually weighs down the Earth's crust as it floats on the mantle.

When you remove the water, the crust gets lighter, and floats higher.

Research by the University of California - Berkeley shows that the weight of water pumped from California's agricultural heartland, the Central Valley, over the past 150 years is enough to allow Earth's crust to rebound upward, raising surrounding mountain ranges, the Sierra Nevada and Coast Ranges, some six inches.

The rising seems to be causing more small earthquakes along the San Andreas fault.  

In addition, even a 6 inch rise in the mountains can affect winds and rain.  Tall mountains create deserts.

In other words, by pumping vast amounts of water from the ground, we are decreasing the amount of water that falls from the sky over California.