WATER QUALITY OF THE THOMPSON’S CREEK WATERSHED, CLAREMONT, CA

Water quality is fundamental for healthy riverine ecosystem functions and sustainable human use. To these ends, The Claremont League of Women Voters (CLV) proposed a large-scale project in 2008 to better utilize the Thompson's Creek Dam in Claremont, CA by improving storm water storage and groundwater recharge of the six basins aquifer. The CLV project is also expected to help revitalize and preserve four different biological habitats: Riparian, Chaparral, Wetland and three stages of Riversidean Alluvial Fan Sage Scrub. In addition, drinking water supplies are expected to increase for many local communities throughout the Pomona Valley. An extensive conservation plan, proposed by the CLV, assumed that there is little impact to water quality due to the lack of historical land use and development. However, there was little water quality testing results available for this watershed as verification. To test this assumption, spring water samples were collected throughout the 2012-2013 academic year (seasonal affects). Water samples were analyzed for Chloride and Bromide (salinity); Nitrate (NO₃¯); Fluoride (F¯); Sulfate (SO₄¯); pH; and alkalinity as basic measures of water quality. Oxygen (O¹⁸) and hydrogen (H²) isotopes have been analyzed in the summer of 2013 to understand the source of fluids in the watershed (i.e., meteoric, or deeper groundwater). Tritium isotope values (H³) of select spring samples (higher and lower in the watershed) have been measured to estimate the age of waters in the watershed. Preliminary results indicate that elemental analyses are below Primary and Secondary Environmental Protection Agency (EPA) Standards. Field pH measurements ranged between 6.9 and 8.14, consistent with natural waters. Total alkalinity is consistent with groundwaters from mountain front recharge, ranging between 224 and 352 mg/L. Preliminary tritium results indicate that the lower spring in the watershed may have a longer residence time than the higher spring. These results have some implications for interpreting contaminant migration and watershed management.