Maintaining Sustainability While Meeting Growing Water Demand in a Southern California Ground Water Basin

The Santa Clarita Valley is a rapidly urbanizing semi-arid valley in northern metropolitan Los Angeles, California. The local groundwater resources have remained a viable supply during the valley’s 40-year urban history because of management strategies conceived and implemented by the local water purveyors. These strategies and their implementation have been conceived, funded, and coordinated by the local public and private water providers working cooperatively among themselves, and with overlying agricultural landowners and adjacent basin managers. Groundwater sustainability in this basin is defined and maintained through an “operating plan” that specifies time-varying pumping from a surficial alluvial aquifer according to local hydrologic conditions, and time-varying pumping from a deeper aquifer according to the availability of imported surface water and groundwater that is banked in other basins. The purveyors have developed the operating plan by examining over 60 years of pumping history and hydrologic data as the valley evolved from entirely agricultural to predominantly suburban, and by balancing local water demands with the need to maintain sustainability of local water resources. Additionally, the sustainability of the operating plan has been evaluated quantitatively using a detailed numerical groundwater model of the basin. The purveyors developed the model for this purpose and to evaluate more targeted questions and problems, such as the potential effects of climate change on aquifer recharge, the potential role of artificial recharge programs in enhancing groundwater sustainability, and how best to implement mitigation activities in response to localized groundwater contamination. In summary, groundwater management in the Santa Clarita Valley is conducted primarily at the local level. Because of local initiative and cooperation, this groundwater basin has retained its sustainability despite continued urbanization, and it has remained one of the few basins in southern California that has not had to pursue a legislative solution or legal remedy to groundwater resource management.