Processes Controlling Riverbank Filtration of Pathogens in the Russian River Basin, Sonoma County, California
The Sonoma County Water Agency (SCWA) supplies drinking water to municipalities and water districts in Sonoma and Marin Counties by diverting water from the alluvial aquifer underlying and adjacent to the Russian River. The U.S. Geological Survey, in cooperation with SCWA, is conducting an ongoing research program on water quality conditions in the Russian River and the physical and geochemical conditions in riverbank deposits through which surface water is drawn into wells supplying drinking water.
Preliminary evaluation of the water-quality data collected from the 7 surface-water sites within the lower segment of the Russian River and Mark West Creek between 2003 and 2005, as well as from 10 tributaries during early, middle, and late summer, 2004 indicated that there is considerable variability in bacterial concentrations from reach to reach and from year to year (Anders and others, 2006). Furthermore, tributaries that maintained continuous surface flow throughout the summer were characterized by lower specific conductance measurements and higher dissolved oxygen and bacteria concentrations typically, than the mainstem Russian River. One set of ongoing research activities is aimed at better understanding how tributary discharges influence the water quality of the Russian River during late spring to early summer and identifying the sources of bacteria concentrations in the Russian River.
Preliminary evaluation of these data collected from surface and ground water in the vicinity where Russian River water is treated by natural filtration processes suggest the water can be separated into at least two distinct sources of recharge and the chemical composition of the ground-water is dominated by cation exchange, dissolution of Na/Ca-feldspars and mineralization of dissolved organic carbon. However, it is not clear to what extent these primary reactions contribute to the ground-water chemistry adjacent to the river. Recently completed injection and recovery microsphere field experiments at the SCWA’s water supply facilities suggest that the shallow sediments at the bottom of the Russian River and adjacent infiltration ponds are highly efficient in removing weakly-charged, oocyst-sized colloids. However, more experiments are needed to ascertain the contribution of metal oxide surface coatings, the poorly sorted nature of the sediments, and the character of the dissolved organic matter to the removal of oocysts along individual pathways from the river to points of withdrawal. In addition, the efficiency of deeper alluvial material in removing oocyst-sized colloids is needed. The overall objective of this set of studies is to better understand the predominant geochemical reactions that contribute to the ground-water chemistry associated with natural filtration processes and to gain more detailed information about the C. parvum oocyst-removal potential of the Russian River/infiltration pond bottom sediments and alluvial materials.
The Sonoma County Water Agency (SCWA) supplies drinking water to municipalities and water districts in Sonoma and Marin Counties by diverting water from the alluvial aquifer underlying and adjacent to the Russian River. The U.S. Geological Survey, in cooperation with SCWA, is conducting an ongoing research program on water quality conditions in the Russian River and the physical and geochemical conditions in riverbank deposits through which surface water is drawn into wells supplying drinking water.
Preliminary evaluation of the water-quality data collected from the 7 surface-water sites within the lower segment of the Russian River and Mark West Creek between 2003 and 2005, as well as from 10 tributaries during early, middle, and late summer, 2004 indicated that there is considerable variability in bacterial concentrations from reach to reach and from year to year (Anders and others, 2006). Furthermore, tributaries that maintained continuous surface flow throughout the summer were characterized by lower specific conductance measurements and higher dissolved oxygen and bacteria concentrations typically, than the mainstem Russian River. One set of ongoing research activities is aimed at better understanding how tributary discharges influence the water quality of the Russian River during late spring to early summer and identifying the sources of bacteria concentrations in the Russian River.
Preliminary evaluation of these data collected from surface and ground water in the vicinity where Russian River water is treated by natural filtration processes suggest the water can be separated into at least two distinct sources of recharge and the chemical composition of the ground-water is dominated by cation exchange, dissolution of Na/Ca-feldspars and mineralization of dissolved organic carbon. However, it is not clear to what extent these primary reactions contribute to the ground-water chemistry adjacent to the river. Recently completed injection and recovery microsphere field experiments at the SCWA’s water supply facilities suggest that the shallow sediments at the bottom of the Russian River and adjacent infiltration ponds are highly efficient in removing weakly-charged, oocyst-sized colloids. However, more experiments are needed to ascertain the contribution of metal oxide surface coatings, the poorly sorted nature of the sediments, and the character of the dissolved organic matter to the removal of oocysts along individual pathways from the river to points of withdrawal. In addition, the efficiency of deeper alluvial material in removing oocyst-sized colloids is needed. The overall objective of this set of studies is to better understand the predominant geochemical reactions that contribute to the ground-water chemistry associated with natural filtration processes and to gain more detailed information about the C. parvum oocyst-removal potential of the Russian River/infiltration pond bottom sediments and alluvial materials.