The effect on stream flow of the killing of spruce and pine by the Engelmann spruce beetle

An outbreak of the Engelmann spruce beetle on the White River Plateau of western Colorado killed the Engelmann spruce and lodgepole pine on a considerable portion of the 762‐sq mi drainage basin of White River above the town of Meeker, Colorado. Statistical analyses were made to compare stream flow and water content of snow for White River with similar measurements made for the 206‐sq mi drainage basin of Elk River above Clark, Colorado. The analyses show that the flow of White River increased after the beetle outbreak, and this increase is attributed to reduced interception of snow and to reduced transpiration by the beetle‐killed trees. Total annual stream flow of White River was compared for three periods: (1) the 1937–1940 water years before the killing of the spruce and pine: (2) the 1941–1946 water years during which the beetle outbreak was most active; and (3) the 1947–1951 water years after the killing of the mature and over mature spruce and pine had been completed. The average annual stream flow increased by 1.22 inches during 1941–1946 and by 2.28 inches during 1947–1951 as compared to the period 1937–1940 after adjustment was made for climatic fluctuations.