C153362 Feasibility Study - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I to 8.17 cfs from the North Fork of the Purgatoire River, which provides the basic water supply. In addition, the City has up to 290 cfs in various "junior" water rights from the North Fork and other tributary streams, namely Whiskey, Cherry, and Brown Creeks, plus direct runoff into Monument and North Lakes. Total drainage area above the points of diversion is 33.1 square miles. Actual sustained yields from the streams are difficult to determine, since there are no stream-gauging records available. An analysis was made of stream-gauging records in adjacent basins within the same general area. These records were used to extrapolate water yields from the North Fork Purgatoire River and its tributaries. This analysis indicates the average annual runoff for the North Fork to be 10,200 acre- feet per year, or 14.1 cfs. Runoff from the total drainage area of 33.1 square miles above the points of diversion would be in the magnitude of 25,000 acre-feet per year. The water utilization plan has been developed to meet the following operational criteria: First priority is to meet the municipal water supply demand, which is 3.74 cfs average annual and 13.18 cfs peak demand. Second priority is to maintain the level in Monument Lake at spillway level or at the highest level possible in order to enhance recreational use. Third priority is to maintain the level in North Lake at the highest level possible. In the event the raw water transmission line from North Lake to the treatment plant is out of service, a contin- gency means of getting water to the treatment plant, i.e., via the Monument Lake transmission line, is necessary. Also, limited capacity in the North Lake raw water trans- mission line requires that the Monument Lake transmission line be used during peak demand periods. It appears that sufficient water is available; the system, utilizing both North Lake and Monument Lake storage, would meet peak demand for 488 days, with 8.17 cfs of inflow (the senior water rights), or 203 days without inflow. More realistically, the average annual demand can be met indefinitely with 8.17 cfs of inflow and 623 days without inflow. An analysis of the synthetic hydrology generated for the North Fork indicates that the critical drought period was from September, 1949, to April, 1952, when runoff was 34 percent of the annual average. During this period, iv