INCREASED STREAM DISCHARGE IN URBANIZED SOUTHERN CALIFORNIA WATERSHEDS

Since the onset of widespread urbanization in the 1950s and 1960s, fresh water runoff has increased in southern California during the three driest months of the year: August, September and October. Analysis of discharge data from stream gauges with a minimum of forty years of record from urbanized and non-urbanized watersheds finds streams that were completely dry in the summer months prior to urbanization have subsequently become perennial. In addition, stream discharge in summer has also increased with increasing urban land cover. Land-cover data from the USDA is used to estimate whether agricultural, urban, or undisturbed land contributes most to increased freshwater runoff. Increased stream runoff in urbanized watersheds suggests over watering of landscaping which, if controlled, could provide appreciable water savings. Water waste in Southern California has serious ecological impacts and also contributes to greenhouse gas emissions and energy expenditures. Understanding the dynamics of increased stream discharge from urbanized watersheds in Southern California helps promote public awareness and support for policies to reduce long-distance water importation.