But to produce instant Paradise you have to add water - and keep on adding it. Once the scant local sources had been tapped, wasted, and spoiled, the politics of hydrology became a pressing concern, even a deciding factor in fixing the political boundaries of Los Angeles. The City annexed the San Fernando Valley, murdered 'the Owens Valley in its first great raid on hinterland waters under William Mulholland, and its hydrological frontier is now on the Colorado River. Yet fertile watered soil is no use if it is inaccessible; transportation was to be the next great shaper of Los Angeles after land and water.