Hot Spring Monitoring at Lassen Volcanic National Park, California 1983-1985

Data collected on several occasions between 1983 and 1985 as part of a hydrologic monitoring program by the U.S. Geological Survey permit. preliminary estimation of the natural varability in the discharge characteristics of hydrothermal features in Lassen Volcanic National Park and the Lassen XGRA in northern California. The total rate of discharge of highchloride hot springs along Mill Creek and Canyon Creek in the Lassen XGRA has averaged 20.9 2 1.7 L/s , based on seven measurements of the flux of chloride in these streams. Measured chloride flux does not appear to increase with streamflow during the spring-summer snowmelt period, as observed at Ye1 lowstone and Long Val ley Caldera. The corresponding fluxes of arsenic in Mill Creek and Canyon Creek decrease within distances of about 2 km downstream from the hot springs by approximately 30%, most likely due to chemical absorption on streambed sediments. Within Lassen Volcanic National Park, measurements of sulfate flux in streams draining steam-heated thermal features at Sulphur Works and Bumpass Hell have averaged 7.5 +, 1.0 and 4.0 5 1.5 g/sl respectively. Calculated rates of steam upf low containing, dissolved H S to supply these sulfate fluxes arek.8 kg/s at Sulphur Works and 1.0 kg/s at Bumpass Hell.