Evaluating the Impact of Conservation Measures on Urban Water Fluxes in Los Angeles, California

Abstract:

California is experiencing one of the most severe droughts on record. In response, the State Water Resources Control Board adopted emergency regulations in May, implementing a mandatory 25% statewide reduction in potable urban water use. Prior to this, the Los Angeles Department of Water and Power had implemented mandatory restrictions and a pricing increase in 2009 and 2010, respectively to encourage reduced consumption. Understanding where conservation measures are having the greatest impact and how it is affecting water fluxes throughout the basin is critical, especially when considering the push for increased reliance on local water resources. Los Angeles is selected as the study area due to its high degree of urbanization, while the Ballona Creek watershed is used for runoff analysis due to the lack of dams and wastewater treatment plants altering flow in the channel. Utilizing a combination of runoff gages, groundwater monitoring well data, consumption data, and hydrologic models, we aim to evaluate how hydrologic processes have been influenced by water conservation measures. The work focuses on how changes in outdoor water use have influenced discharge patterns and groundwater recharge since most of the water conservation efforts have been focused on decreasing landscape irrigation. Previous work has shown that outdoor irrigation rates have decreased after the implementation of conservation measures, causing a decrease in vegetation greenness across the city. Runoff has also significantly decreased, especially dry season discharge. Further work is also being conducted to evaluate changes to evapotranspiration, using a combination of NLDAS model results and CIMIS reference ET data, as well as groundwater and recharge, utilizing a Bayesian Hierarchical model to fill missing groundwater monitoring well data. Results provide improved understanding of response to, and impacts of, conservation measures which ultimately allow for better water resources management for developed areas.