Evaluation of the groundwater resources of the Petaluma Valley

Science Center Objects

The city of Petaluma, located in the Petaluma Valley and home to about 12 percent of the population of Sonoma County, faces growth in population and demand for water. Water supply is provided primarily by water delivered via aqueduct from the Russian River; however, groundwater is a vital supplemental source of water for the city of Petaluma and is the primary source of supply for domestic and agricultural use by rural property owners.

Water managers face the challenge of meeting the increasing water demand with a combination of Russian River water, which has uncertainties in its future availability, and local groundwater resources. Water managers need to determine the likely effects of future groundwater development in the Petaluma Valley and to identify efficient strategies for surface-water/groundwater management that will assure the long-term viability of water supply.

The primary objective of this study is to develop an updated assessment of the geohydrology and geochemistry of the Petaluma Valley. This new information will establish the framework for the future development of a coupled watershed/multi-aquifer groundwater-flow model for the Petaluma Valley, for the purpose of evaluating the hydrologic impacts of alternative groundwater management strategies for the basin.

The proposed study will provide hydrologic information needed by Sonoma County Water Agency, the city of Petaluma, and other management and regulatory agencies to better understand the potential impacts of increasing groundwater use on groundwater levels, stream-aquifer interaction, and water quality. The proposed study addresses USGS strategic science directions “A Water Census of the United States”. The study will consider several priority U.S. Geological Survey (USGS) water-resource issues including surface- and groundwater interactions, effects of urbanization on water resources, and hydrologic-system management.

Specific tasks will be: (1) data compilation, utilizing a Geographic Information System (GIS); (2) new data collection, focusing on water-quality sampling; (3) data interpretation and geohydrologic characterization – including refining hydrologic budgets and updating conceptual models of the groundwater-flow system based on the new data and the results of ongoing USGS geologic studies in the basin.

A USGS scientific investigation report (SIR) will describe the updated geohydrologic characterization of the Petaluma Valley.