Laserfiche WebLink
Irrigation diversions from the river remained relatively constant during <br />this period of diminishing supply because a large number of unregulated <br />wells were installed to obtain water from the South Platte alluvium when <br />surface water became unavailable. That alluvium had previously been filled <br />by deep percolating return flow from surface irrigation under the large <br />irrigation systems developed around the turn of the century. Well <br />development along the South Platte peaked during the severe drought years <br />1954 through 19561 <br />Municipal water demands in the basin also increased significantly during <br />that period with the population of Denver, like that of the basin, having <br />nearly doubled. Imports of Colorado River water began during this period, <br />balancing the effects of the rapid surge in municipal demand. Significant <br />flows through the Moffat tunnel did not occur until 1937 (historic average <br />is 45,000 AF /YR). Although the Adams Tunnel was completed in 1947, flows <br />near the historic average of 203,000 AF /YR did not occur until 1953. <br />1956 -1982 <br />Between 1956 and 1982, there is an increase in the slope of the trend line <br />relative to the slope of the trendline for the 1923 -56 interval. A <br />cumulative mass analysis of the annual flows of the Cache la Poudre River <br />(Figure 4) and a similar analysis by Hurr et. al. on the combined flows of <br />St. Vrain Creek, the Big Thompson River and the Cache la Poudre River show <br />a definite increase in slope of the mass curve. The change in slope occurs <br />Hurr, R.T., P.A. Schneider Jr., and D.R. Minges, Hydrology of the <br />South Platte River Valley, Northeastern Colorado, U.S. Geological Survey, <br />Colorado Water Resources Circular No. 28, 1975). <br />- 7 - <br />