Application of multispectral digital imagery to the assessment of primary productivity in flaming gorge reservoir

Abstract

In support of the Bureau of Reclamation effort to manage eutrophication trends in Flaming Gorge Reservoir, Utah and Wyoming, remote sensing studies employing multispectral digital imagery were undertaken. Specifically, the imagery was used to extrapolate point measurements of chlorophyll concentration and light penetration to characterize conditions throughout the reservoir. In 1981 and 1982, aircraft and satellites acquired digital imagery of the reservoir concurrent with surface sampling. Sampling stations were identified within the imagery and the digital values at these points recorded. The surface measurements of chlorophyll and light penetration were regressed against the digital image values to obtain predictor equations for these indicators of primary productivity. The equations were then applied to the images of the whole reservoir to obtain maps of the distribution of chlorophyll and light penetration. A unique set of equations was defined for each data-gathering date. The favorable results obtained in the date-specific studies prompted a search of data archives for other dates for which surface sampling and satellite imagery were both available. An atmospheric radiative-transfer model was also obtained to allow for correction of imagery for sun angle and atmospheric effects. This effort served two purposes: (1) to permit development of chlorophyll and light penetration predictor models from as many surface observations as possible, regardless of date of collection, and (2) to permit estimation of reservoir conditions from imagery for which no concurrent surface sampling was available. Seven satellite scenes were processed to estimate and map chlorophyll and light penetration, although concurrent surface sampling data were available for only four of them. The maps produced were used by reservoir managers to follow year-to-year trends in primary productivity. © 1984 Taylor & Francis Group, LLC.