Laserfiche WebLink
<br />. <br /> <br />~ <br /> <br />. <br /> <br />." " .:.~ ...~ <br />.) \J.:..;....l <br /> <br />The operation studies indicated that an average annual project <br />yield of 88,400 acre-feet could be obtained from reservoir regulation, <br />plus the 31,000 acre-foot direct yield from Weldon Valley, or a <br />total project supplemental irrigation supply of 119,400 acre-feet. <br />Table 2 is a \olater budget which summarizes historic and "with" <br />project operations. <br /> <br />ASSOCIATED HYDROLOGY STUDIES <br /> <br />Sediment Control <br /> <br />Sediment analysis of surface suspended samples from the Fort <br />Morgan station show as high as 70 to 80 percent clay-sized particles, <br />the remainder being silt and very fine sand-sized particles. Stream- <br />bed samples are primarily coarse sandy material. The 100-year <br />sediment deposition in Narrows Reservoir is 60,000 acre-feet. <br /> <br />Degradation <br /> <br />The streambed consists of fine sand and medium gravel which is <br />not coarse enough to armor the channel. The average gradient of the <br />South Platte River from the Narrows site to the bridge at Fort Morgan, <br />Colorado, is about 7 feet per mile. There are two controls which <br />would limit the depth of vertical degradation: (1) the sediment <br />deposited at the mouth of Bijou Creek, and (2) the LO\oler Platte <br />and Beaver Diversion Dam. Vertical degradation would occur below <br />the dam to a depth of about 5~ feet until at the end of 49 years <br />the channel would be essentially stable. <br /> <br />Tailwater <br /> <br />Tailwater rating curves were made at Kersey and Sublette above <br />the Narro\ols damsite and at Fort Morgan and Balzac downstream. The <br />Fort Morgan curve was used at Narrows for flows up to 4,000 second-feet. <br />A slope-area method was used for higher flows. <br /> <br />Flood Control <br /> <br />The calculated inflo\ol design flood for Narrows Reservoir has a <br />peak discharge of 344,000 second-feet and a 20-day volume of 1,363,000 <br />acre-feet. This flow results from a design rainstorm on top of a <br />leading snow flood with a runoff of 10,000 cfs. Narrows Reservoir <br />will have a joint use pool of 75,000 acre-feet, a flood control pool <br />of 1175,000 acre-feet and surcharge space of 575,373 acre-feet. <br /> <br />8 <br />