Remote-sensing data were evaluated as to their usefulness in Minnesota water-resource studies. Data are available from several private as well as governmental agencies, the chief supplier being the EROS Data Center. Landsat-1 multispectral imagery was selected as the standard against which other types of imagery were compared. Landsat-1 imagery is available from July 1972, and Landsat-2 from January 1975. The kinds of remote-sensing data available for Minnesota are tabulated and the coverage of each is mapped.
Direct-visual analyses and image-enhancement techniques were used on Landsat-1, SKYLAB, and aerial photographic transparencies. Examples of remote-sensing applications in both surface and ground-water studies are presented.
Applications in surface-water studies are largely direct and are documented by examples: surface-water extent (flooded versus nonflooded), autographic theme extraction of surface-water features, open-water areas in winter, and remote-sensing data as indicators of water quality. Applications in ground-water studies are thus far only. indirect. Remote-sensing data are helpful in defining the geology, which controls the occurrence of ground water. Most successful was the use of late spring Landsat-1 imagery to map surficial outwash, a readily available source of large quantities of ground water. A single color-composite scene was used to map nearly 3,900 Square kilometres (1,500 square miles) of surficial outwash in less than 1 hour with an accuracy close to that achieved by methods usually used in regional studies. It was concluded that remote sensing would be valuable in the planning phase of nearly every water-resource study, so that maximum benefits might be obtained from its use. Essential ground truth would have to be collected in support of the remotely sensed data.
