WSP11269 - Laserfiche WebLink

Home Browse Search

. 13Cd the Secretary of the Army. In July 1978 (revised June 1985) the Corps of Engineers published the Water Control Manual for Trinidad Lake on the Purgatoire River. Paragraph 7-05a. of the Corps manual contains the criteria for the nor- mal regulation for flood control. This paragraph states that flood control regulation begins when storage exceeds the irrigOation pool elevation of 6,230 feet. When the water surface elevation is between 6,230 and 6,243 feet, flood control releases will be such as to control flow at the Trinidad gauge to 5,000 cubic feet per second. It further states that when the pool elevation recedes to 6,230 feet, flood control re9ulation wi 11 cease and irrigation regulation wi 11 resume. 46 . . . . . . I . . I I . . - I . I . The Corps of Engineers' water control manual also states that the flood channel through the city of Trinidad was restricted to a flow of 5,000 cubic feet per second or less at the time the manual was written. By the corps of Engineers' letter dated October 11, 1988 to the District, they state that the ori9inal channel capacity has been reestablished, except for the Linden Street low water crossing. Upon removal of that structure, the required 15,000 cubic feet per second channel will be reestablished and the routin9 of the Standard Project Flood (SPF) or any flood of lesser volumne can then be accomplished. ' Flood operations are also addressed in Condition 1 of the State of Kansas' Amendment to the Operatin9 Principles which states that "All inflows over established Colorado Water Ri9hts (l,156.05 cfs) be designated flood flows and released as promptly as down stream conditions permit". The Division 2 Engineer's water accounting records for the 1979-1984 period show that there were five (5) events when water was stored and accumulated in an account 1 abe 1 ed "F lood Contra 1." These events i ndi cate that they were caused by typical summer thunderstorms that produce high peaks and relatively small volume. The absence of dai ly peak flow data at the Trinidad gauge preclude classification of the events as flood control operations in accordance with the Corps' Water Control Manual. The Corps' records do not identify any flood events during the 1979-1984 review period. A review of the pUblished peak flow records at the Madri d gaugi ng stat i on above Tri ni dad Reservoi r suggests that some damaging flows would have passed through the town of Trinidad had the peak flows not been detained in Trinidad Reservoir. As an example, the recorded peak flow at Madrid on August 9, 1981 was 11,600 c.f.s. . Analysis was made of each event to determine if the flood waters released passed through the Project area and were made available for use downstream. A one day 1 ag was assumed between Purgatoi re Ri ver below Tri ni dad Lake and the Thatcher gauge located 63 miles downstream. Three of these events occurred in 1981, and one each in years 1982 and 1984 as shown in Table 14. Duri ng the fi rst event flood water stored accumulated to a maximum of 2,303.78 acre-feet on July 28, 1981. During the following three days 1,416.86 acre-feet were released while the remaining 886.92 acre-feet was retained in storage through the second flood storage event that started on August 4. Flow conditions on the Purgatoire River as recorded at the Trinidad and Thatcher gauges do not justify retention of the 886.92 acre-feet beyond July 31. Review of the Project ditch diversion records indicates that diversions were significantly reduced or terminated during the flood water release period of July 29, 30 and 31. This fact, in combination with the total reservoir release (Purgatoire River below Trinidad Dam) being in excess of the sum of ditch diversions and the amount of flood water released, suggests that the flood water did pass downstream undepleted by project opera- tions.