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<br />onf!c63 <br /> <br />. <br /> <br />. <br /> <br /> <br />Long Term Water Flows in the Platte River System <br />A Preliminary Analysis <br /> <br />Michael Duever <br />National Audubon Society <br />May 1991 <br /> <br />I NTRODUCTI ON <br /> <br />As I became involved in Platte River water issues, one <br />aspect that particularly interested me was trying to identify <br />long term patterns of water flow in the Platte River system. As <br />a result, I have been on the lookout since 1987 for data that <br />might shed some light on the topic. This search has included <br />information on precipitation and drought indices as well as on <br />river flows. I have not had the time to conduct an exhaustive <br />search for information or to do detailed analyses of the data I <br />have found. However. there do seem to be some interesting <br />patterns in the available information. In this report I will <br />present the information as a series of cases with figures <br />illustrating the long term patterns and some comments on the most <br />relevant information on the figures. <br /> <br />CASES <br /> <br />FIGURE 1. <br />While working at the Tree Ring Lab at the University of <br />Arizona. I first encountered a study by Chuck Stockton which <br />reported a pattern of annual water flows in the COlorado River at <br />Lee's Ferry near the Arizona-Utah border. This study indicated <br />that the longest period with the highest flows since 1500 <br />occurred during the. first three decades of this century. The <br />1930s drought was apparent in the data. as were higher flows in <br />the early 1940s. and "average" flows in the late 1940s and 1950s. <br />The data were reconstructed from.tree ring widths and annual <br />river flow relationships. which were then extended for the period <br />from 1500-1960. <br /> <br />FIGURE 2. <br />Tom Pitts prepared a report which included a figure showing <br />very high flows on the North Platte at Saratoga (above Seminoe <br />Reservoir) from the beginning of the record in 1913 until 1930 <br />followed by very low flows from 1931-1942, and relatively low <br />flows from 1952-1968. The data in the figure were based on a 5 <br />year moving average for the period 1913-1968. <br /> <br />FIGURE 3. <br />A study by Resource Consultants on. the Cache La Poudre River <br />which drains into the South Platte downstream of Denver also <br />showed generally high flows from 1895-1928, followed by very low <br />flows 1929-1942. There were additional low flow periods in 1952- <br />1956 and 1961-1968. Flows have showed an increasing trend since <br />1932, and had attained the range of pre-1900 flows by 1970. I <br />plotted data from tables in their repor,t. which I presented as <br /> <br />-- <br />