Pressures on Marina's Water Supply Over the Years

By David W. Brown

Because our water supply now depends primarily on the deepwater aquifer about which we know very little, and because of the history of seawater intrusion, we must encourage conservation and be mindful that our water supply is limited.

Historically, Marina groundwater has come from wells drilled into the 180-foot and 400-foot aquifers. However, since the 1940's, urbanization has resulted in enough groundwater being drawn so that groundwater no longer flows to the sea so as to keep out seawater. Instead, some seawater intrudes into at least the 180-foot and 400-foot aquifers. If the chloride level exceeds 500 parts per million, the water does not meet drinking-water standards. As a result, Marina's water now comes primarily from wells drilled 1500 to 2000 feet deep. (So deep, in fact, that this water, being geothermally heated, is often warm to the touch when first pumped out of the ground.)

While there are no signs of seawater intruding into the deepwater aquifer, very little is known about the deepwater aquifer capacity or its susceptibility to seawater intrusion in the future. Because we know so little about the deepwater aquifer's capacity, we cannot assume the water supply is limitless. If we do, we ultimately face a requirement for desalinated water at two to three times, at least, the current cost of water.

As your MCWD Board director, I will continue to urge conservation and wise use of our limited water resources.