About 1/3 of Santa Clara county's water comes from underground aquifers. Most of the reservoirs in Santa Clara county are recharge reservoirs - simply to allow

About 1/3 of Santa Clara county's water comes from underground aquifers. Most of the reservoirs in Santa Clara county are recharge reservoirs - simply to allow water to percolate down to refill the underwater aquifers, there are many small ponds scattered around the county to assist in this effort. There are parts of the other states (Texas,Kansas off top of my head) that rely on underground aquifers for a much higher percentage of their water.