Thermal study of the Missouri River in North Dakota using infrared imagery

Studies of infrared imagery obtained from aircraft at 305- to 1,524- meter altitudes indicate the feasibility of monitoring thermal changes attributable to the operation of thermal-electric plants and storage reservoirs, as well as natural phenomena such as tributary inflow and ground-water seeps, in large rivers. No identifiable sources of ground-water inflow below t he surface of the river could be found in the imagery. The thermal patterns from the generating plants and the major tri butary inflow are readily apparent in imagery obtained from an altitude of 305 meters. Though the patterns are generally discernible in the imagery from 1,067-meter and 1,524-meter altitudes, there is not sufficient ground resolution to make any but the most general qualitative analyses. The quality of the imagery varied with land-water temperature relations as well as with instrument properties.

Portions of the tape-recorded imagery were processed in a color-coded quantization to enhance the displays and to attach quantitative significance to the data. Apparent radiant temperature computations from the 305-meter imagery were generally within l° Celsius of ground-truth data.

The study indicates a marked decrease in water temperature in the Missouri River prior to early fall and a moderate increase in temperature in late fall because of the Lake Sakakawea impoundment. At the present time, thermal additions generated by the powerplants have little effect on the temperature regimen of the Missouri River at high rates of river discharge.