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TABLE I EFFECT OF RESERVOIRS ON THE FLOW OF THE NORTH PLATTE RIVER AT NORTH PLATTE, NEBRASKA Interval 1895-1910 1911-1939 1940-1957 1958-1975 Reservoirs in None Pathfinder Pathfinder Pathfinder place McConaughy McConaughy Seminoe Seminoe Glendo Average flow 3100 2600 610 760 cubic feet per second (ft3/s) Change from previous interval ft3/s -500 -1900 +150 percent -18% -76% +25% Average yearly peak fl ow ft3/s 19 300 9600 2900 3600 Change from previous interval ft3/s -9700 -6700 +700 percent -50% -70% +24% from 4100 feet in 1865 to 150 feet in 1965. One may speculate that these up- stream areas were used by sandhill and whooping cranes in the past, but are no longer suitable. Table II gives the decline in channel widths ~n the critical habitat area. These declines have been especially pronounced in the upstream portion of the critical habitat and have taken place mainly since 1938. Along with channel widths, peak and average flows have decreased substan- tially. Recall Table I, which gives average yearly peak flow and average an- nual flow on the North Platte for a series of intervals following closure of major dams since 1895. Apparently, there were significant drops in peak flows after 1910 and again after 1939. There are only three possible causes: cli- matological change, increased groundwater pumping, and increased surface water consumption. Changes in climate have been ruled out by Williams and others. 37