REMOTE-SENSING OF WATER-QUALITY IN ACTIVE TO INACTIVE COOLING WATER RESERVOIRS

Airborne Daedalus DS-1260 MSS data were acquired over three water cooling reservoirs (active to inactive, large (1068 ha) to small (68.6 ha)) concurrent with field data collection to map the distribution of the water quality as related to the trophic state within each reservoir. Water characteristics, including algal pigments, total suspended particles, as well as dissolved and particulate organic matter, were obtained at 31 sites. These water quality measurements were evaluated in terms of their importance in explaining water phenomena observed by using remote sensing reflectance images. Measurements that exhibited unique variances were related to remote sensing data using a statistical methodology to identify relations explaining the greatest amount of variance for each water variable. This approach resulted in predictor equations explaining 91 per cent of the chlorophyll-a variance, 91 per cent of the total suspended particles variance, and 98 per cent of a Trophic State Index variance based on the depth of light penetration. Further, remotely-sensed thermal data explained 88 per cent of the measured surface water temperature variance. These relations were used to produce maps depicting the quantitative distribution of these water quality variables and the bulk near-surface water temperature distribution within the active water cooling reservoir. The two-water cooling reservoirs not affected by thermal inflows were characterized by water containing very low and uniform concentrations of all water property measures. Conversely, the thermally active reservoir was characterized by higher and more variable water property concentrations; there was a spatial covariation between decreases in the bulk near-surface water temperature and increases in almost all water quality indicators.