Below Vasona Park, Los Gatos Creek feeds percolation ponds that are part of the groundwater recharge system built by the Santa Clara Valley Water District. North of Lark Avenue, one can also see a structure resembling a fountain, where imported water from other reservoirs is also added to Los Gatos Creek for recharge. In the 1920s, people discovered that Santa Clara Valley was sinking because of groundwater pumping. San Jose's elevation subsided 13 feet from 1910 to 1970s, correlated with a 250 feet decline in the underground water table. The valley's aquifers were also in danger of being ruined by saltwater infiltration. Local reservoirs were built to provide water for an aggressive groundwater recharge program. While simultaneously dealing with the demands of growing cities, the water district finally managed to stop further sinking by the 1980s. Vasona and Lexington reservoirs were part of the effort.