Reservoir Topography by Shoreline Plotting

Irrigation development in the 35,000 sq mile Upper Snake River Basin, above Bliss, Idaho, requires coordinated use of uncommitted ground and surface water. To use the surface water, new storage is needed; enlargement of American Falls Reservoir is a possibility. To appraise enlargement, the present (1963) capacity of the reservoir has to be known. Reservoir remapping was based on plotting the shoreline, the contact between water-line and ground-line, at selected reservoir water-surface elevations. A triangulation network of shore points extending into dewatered zones provided horizontal control. Multiple flights for aerial photography of the shoreline were used in obtaining vertical ground control. Where banks were steep, successive flights gave infinite image point elevations for vertical control, allowing conventional stereoplotting.