As California's drought enters its fourth year, policy makers here mostly argue over two alternatives - stepping up conservation and water-use enforcement or building new dams and other water-storage facilities. But the solution to the water crisis is more likely to be found on an application that can be downloaded onto our cellphones. A growing state can't assure abundant water supplies by fining businesses and residents who use too much water -- any more than it can expect new reservoirs to do much to bolster supplies in the near future given the many years it takes to build (and fill) them. However, it's been shown -- most recently in Australia -- that making it easier for water owners and users to buy and sell their water supplies and water rights will assure that water will flow to its highest and best uses. In other words, California needs a more active water market, with more decisions made by businesses and consumers -- and fewer made by agencies responding to groups (farmers, environmentalists, big-city water users) that wield political power.