Total Mercury v Suspended Sediment (Runoff from Upper and Lower Watershed)
Loads Calculation Methods (WY 2005) USGS 15 minute discharge USGS 15 minute SSC estimates from GCLASS based on rating relationships between flow and about 100 real measurements of SSC Regression between instantaneous SSC and Total Mercury concentrations –All data –Separate regressions for water derived from Lower and Upper watershed
Maximum Daily and Flood Loads Total Mercury Wet Season (Oct 2004 - Apr 2005) (kg)2.5 Maximum Daily (2/15/05) Load (kg)0.23 Load (% wet season)9 Largest Flood (2/15/05 14:30) Load (kg)0.28 Load (% wet season)12
Estimated Average - Methods Average = 41 Mm 3 Measured Estimated
Estimated Average Coyote Loads Using the range in flow experienced from WY 1971 to WY 2006 we estimate the following: Flow (Mm 3 ) Total Mercury (Estimated using separate regressions) (kg) Total Mercury (Estimated using A single regression) (kg) Minimum2.00.001 Maximum173.95544 Average40.676
Coyote Creek versus Guadalupe River Coyote Creek HgT (ng/L) HgT (mg/kg) Load (kg) Export (µg/m 2 /yr) 11-580.17-0.36 7 (0.001 - 55)20 Guadalupe River HgT (ng/L) HgT (mg/kg) Load (kg) Export (µg/m 2 /yr) DL - 18,6730.41 - 95 140 (0.03 - 1,000)600
Particle Concentrations Coyote Ck, Guadalupe R. and Sacramento R.
Applicable Management Questions B. Loads of mercury and methylmercury Are current estimates about loading to San Francisco Bay from watersheds, wastewater treatment facilities, and atmosphere valid? What is the contribution of atmospheric deposition to urban storm water?
Applicable Management Questions C. Processes of mercury methylation What is the relative bioavailability of mercury entering the Bay from various loading sources (e.g., wastewater treatment facilities, atmosphere, urban runoff, tributaries, newly eroded historic sediments, etc)?
Applicable Management Questions D. Given what we currently understand about processes, loads, and impacts (Sections A, B, and C), what are the management implications? Given that rivers, creeks, and storm drains discharge methyl mercury, what can be done to manage production in the watershed and urban environments, and to manage downstream impacts as it passes through wetlands to the Bay margin and Bay?