Mertes, L. A. University of California,
Warrick, J. A. University of California, jwarrick@icess.ucsb.edu

 
MEASURING THE IMPACT OF COASTAL WATERSHEDS ON NEARSHORE WATERS OF CALIFORNIA WITH SEAWIFS DATA
 
Resource management of coastal environments requires an interdisciplinary consideration of both marine and terrestrial influences in order to take account of the entire range of processes influencing the functioning of nearshore waters. We have met this challenge by combining field data, modeling, and digital technologies for the coastal waters and watersheds of California. A synoptic, nearly cloud-free view of the entire California coast was captured by the SeaWiFS instrument on February 9, 1998. This image was acquired after intense, El Nino driven storms had blanketed the coast for approximately one week, with rainfall totals for the week ranging from 12 cm in northern California to over 32 cm in southern California. The impact of these storms was to produce extensive coastal river plumes emanating from 110 coastal watersheds that comprise approximately 200,000 square kilometers. We based a calibration of the SeaWiFS signal to total suspended matter (TSM) on measured concentrations from samples collected in the Santa Barbara Channel on February 11. The spectral signatures of the most turbid, least turbid, and algal-rich waters were separated, assigned as endmembers, and used in an application of spectral mixture analysis (Mertes et al., 1993) to define the components of each 1 square kilometer pixel. The derived concentrations of TSM ranged from <2 mg/L to approximately 100 mg/L. An error analysis of the calibration curve and the success of spectral mixture analysis to separate the spectral endmembers produced a potential error for TSM of +/- 10 mg/L. The combined impact of these 40 discrete surface plumes was that approximately 300,000 metric tonnes of suspended matter covered nearly 8000 square kilometers of coastal waters, with the largest plumes extending 10's of kilometers out from river mouths. For comparison, the 3.5 million square kilometer Mississippi River watershed produces river plumes that may cover up to 20,000 square kilometers of the Gulf of Mexico (Walker, 1996).
 
Day: Tuesday, Feb. 2
Time: 12:00 - 12:15pm
Location: Sweeney Center
 
Code: SS43TU1200S