Every day, millions of gallons of water flow through pipes across the Coachella Valley and pour out to nourish lawns, artificial lakes, farmlands and a total of 121 golf courses. This lush oasis in the desert owes its existence to groundwater pumped from the aquifer and an imported supply of water from the Colorado River. And during the past decade, public records show the area has made progress in using less water overall and in combating the long-term problem of groundwater overdraft.