Miranda Fram, Ph.D. (Northern California)Geochemist
Program Chief, Groundwater Ambient Monitoring and Assessment Priority Basin Project United States Geological Survey
Quality of Groundwater Used for Public Drinking Water Supplies in California
Dr. Fram’s presentation provides an overview of the GAMA Program Priority Basin Project (GAMA-PBP), and draws on results from more than 10 years of GAMA-PBP studies to illustrate the primary factors affecting groundwater quality in California. GAMA-PBP is a SWRCB program implemented by the USGS and designed to assess the quality of groundwater in aquifers used for drinking water supplies statewide, to help better understand the risks to groundwater resources, and to increase availability of information about groundwater quality to the public. Groundwater provides approximately half of the water used for public and domestic drinking water supplies in California. Assessment of nearly all of the groundwater used for public supply statewide indicated that about 20% has high concentrations for one or more constituents of concern. High concentrations are defined as greater than state and federal maximum contaminant levels set for drinking water standards, or for constituents without MCLs, other human-health based benchmarks. On a statewide basis, trace elements, such as arsenic, manganese, and uranium, were found to be more prevalent at high concentrations than either nitrate or organic compounds. However, different areas of the state had different combinations of constituents prevalent at high concentrations, reflecting three primary factors controlling groundwater quality. (1) Time: Wells may tap mixtures of groundwater with ages ranging from just a few years to several tens of thousands of years, and groundwater of different ages commonly has different chemical compositions. (2) Hydrogeologic conditions: The geochemistry of sediments and rocks through which groundwater percolates determines which constituents are available to dissolve into the water, and groundwater flow patterns affect how these constituents move in the aquifers. (3) Human activities: Anthropogenic contaminants, such as nitrate and organic compounds, may be intentionally or unintentionally introduced to groundwater in agricultural, urban, and industrial environments. Furthermore, groundwater pumping and irrigation may cause changes to hydrogeologic conditions that result in changes in groundwater quality.
Miranda Fram has been a geochemist with the U.S. Geological Survey California Water Science Center since 1997. She received her Ph.D. from Columbia University in Geological Sciences. While with USGS, she has worked and published on a variety of water quality issues, ranging from characterizing natural organic matter from Sacramento-San Joaquin Delta environments, to tracking the fate of trihalomethanes in aquifer storage and recovery operations, to assessing water quality in aquifers used for drinking water supplies statewide. Since 2012 she has been lead scientist and program chief for the USGS implementation of the California State Water Resources Control Board’s (SWRCB) California Groundwater Ambient Monitoring and Assessment (GAMA) Priority Basin Project.