Laserfiche WebLink
<br />. <br /> <br />" ,-',' ~ 11 <br />;G.U.... , <br /> <br />Hydrology <br /> <br />Flood Control <br /> <br />The calculated inflow design flood for the Narrows Reservoir will <br />have a peak discharge of 344,000 second-feet and a 20-day volume of <br />1,363,000 acre-feet. This flow results from a design rainstorm <br />superimposed on a leading snow flood with a runoff of lO,OOO c.f.s. <br />The drainage area above the damsite is about 13,450 square miles. <br /> <br />To provide regulation of floods of the usual size, the reservoir <br />would have a joint use capacity of 75,000 acre-feet, and an exclusive <br />flood control capacity of 475,000 acre-feet. The maximum reservoir <br />release while these capacities are being filled or evacuated would be <br />5,000 c.f.s. <br /> <br />. <br /> <br />Surcharge capacity, the spillway, and outlet would provide protection <br />against overtopping of the dam. The surcharge, which is over and above <br />the flood control capacity, would be 575,373 acre-feet. The maximum <br />discharge of the spillway would be 27,600 c.f.s. and that of the outlet <br />8,600 c.f.s. These capacities were established for protection against <br />the calculated inflow design flood, and are more than adequate to handle <br />the largest observed flood which occurred in June 1921. If Narrows <br />Reservoir had been in place at that time, this flood could have been <br />contained with a maximum discharge of 5,000 c.f.s. <br /> <br />Quality of Water <br /> <br />Quality of water analyses were conducted on streamflows within <br />the unit area during the 1947-l963 period. Samples for testing were <br />taken at the gaging stations near Kersey, Balzac, Crook and Julesburg <br />during most months of the year and at various stages of streamflow. <br />The tests were made in order to forecast the nature and severity of <br />problems which might be encountered from using the water for future <br />irrigation. The factors taken into account in the analyses were the <br />boron content, the ratio of sodium ions to the combined calcium and <br />magnesium ions, and the total salinity of the water. <br /> <br />The results indicate that the boron content is low and a <br />favorable ratio exists between the sodium ions and the combined <br />calcium and magnesium ions. With respect to total salinity, the <br />analyses show that during high stages of flow the quality is <br />entirely satisfactory in all reaches of the project area. During <br />low stages, however, the salinity increases appreciably, but not to <br />the point where use of the water is hazardous for irrigating the <br />porous types of soils which are characteristic of the Narrows service <br />area. <br /> <br />. <br /> <br />69 <br />