Landsat Mss Studies of Chlorophyll in Sediment Dominated Lakes

Landsat MSS can provide valuable data on surface suspended sediments in inland lakes and reservoirs. In this study, chlorophyll in three sediment dominated lakes in agricultural watersheds in the Lower Mississippi Valley was measured and compared with MSS data for 107 dates between December 1976 and August 1988. Chlorophyll-a conc ntrations ranged from 0.3 to 211 mg/?' for 452 measurements. Suspended sediment concentrations ranged from 1 to 867 mg/l for the same samples. Chlorophyll-a concentrations decreased exponentially as suspended sediment concentrations increased. Radiance and reflectance calculated from MSS band 2 and 3 data increased as a function of increasing suspended sediment concentrations. Radiance in all MSS bands decreased as chlorophyll-a concentrations increased, however no significant pattern of decrease related to chlorophyll-a concentration and MSS data could be determined. Thus measurement of chlorophyll-a with broad band (0.1 pm) MSS data in sediment laden waters will not be effective since the detection of the increased absorption of radiation due to increasing chlorophyll is masked by the spectral reflectance due to suspended sediments. Broad band MSS and probably TM data will provide only limited information on chlorophyll in lakes dominated by sediment. Satellite remote sensing of chlorophyll in sediment dominated systems will require high spectral resolution data especially in the chlorophyll absorption areas.