HR: 0830h
AN: H41A-03    [Abstracts]
TI: Modeling Water Clarity Using Aster Multispectral Remote Sensing Data, Lake Tahoe
AU: * Prescott, T G
EM: prescot4@unr.nevada.edu
AF: University of Nevada Reno, Department of Geological Sciences MS/172, Reno, NV 89557 United States
AB: The decline in water clarity has been an important issue affecting Lake Tahoe since water clarity measurements began in the late 1950's. Traditional estimates of water clarity rely on secchi depth; however turbidity as a proxy for water clarity is gaining popularity with the nephelometer. Both methods rely on point data and unless sufficient measurements are taken the spatial dimensionality of lake water clarity may be grossly underestimated. Previous investigations throughout North America and Europe have successfully correlated satellite data with water clarity. This project explores the utility of remote sensing as an alternative to traditional water clarity measurements at Lake Tahoe. A series of Aster images (Ast 07, reflectance) spanning four years were calibrated to one image (September 2000) using static ground targets. A mask was then applied to each calibrated data set to isolate the lake from the surrounding basin. Aster band 1 and band 3 (520nm - 600nm and 780nm - 860nm respectively) calibrated data sets were classified independently based on absolute reflectance values. Processed image data was then used to create a series of maps depicting lake water reflectance over the entire four year period. Preliminary comparisons of reflectance data with empirical secchi depth and turbidity data indicate a positive correlation. Additional analysis will be performed with the ultimate goal of deriving a numerical correlation between data sets. Reflectance values are seasonally dependent with the highest values consistently occurring in the late spring and early summer months. Variance within the lake is also elevated during this time of year. Seasonal trends and relationships to in situ measurements will be presented at the meeting.
DE: 1845 Limnology
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2005 Joint Assembly