It wasn’t that long ago that increasingly arid California seemed as watery as a wet sponge. At the time the state became part of the U.S., Tulare Lake was the largest body of freshwater west of the Great Lakes, and winter flooding made it even larger. In particularly wet years, when it overflowed its banks and joined with Kern Lake and Buena Vista Lake, it would have been possible to sail a boat from what is now Interstate 5 eastward to the Sierra foothills, and from Bakersfield to Fresno.
The change isn’t only because of warmer weather. Agricultural growth drained the lakes and dammed the rivers that fed them. Tulare Lake was gone by the 20th century, except for some occasional wet winter reappearances.
The land underneath the dry lake beds, as well as much of the rest of the Central Valley, remained a sort of damp sponge or, rather, a collection of sponges, containing groundwater that had been there for millennia, constantly replenished by Sierra snowmelt.
