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~. ", '2.ZQ;;" 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 ~he irrig_tion pool elevation of 6,230 feet. When the water surface e 1 evat i on 1 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 statbs that when the pool elevation recedes to 6,230 feet, flood control regulation will cease and irrigation regulation wi 11 resume. . The Corps of Engineers' water control manual also states that the flood channel thrOU9h 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 Oistrict, they state that the original channe 1 capac i ty has been reestab 1 i shed ,j except for the Linden Street low water crossing. Upon removal of that structlJre, the required 15,000 cubic feet per second channel wi 11 be reestab 1 i shed and the rout i ng 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 Operating Principles which states that "All inflows over established Colorado Water Rights <1,156.05 cfs) be designated flood flows and released as promptly as down stream cond,itions permit". The Division 2 Engineer's water accourjting 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 Contro 1." These events i ncli 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 durin9 the 1979_1984 review periQd. A review of the publ ished peak flow records at the Madrid gauging station i above Trinidad Reservoir suggests that some damaging flows would have passed through the town of Trinidad had the peak flows not been detained in Trinidad Res~rvoir. 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 la9 was assumed between Purgatoire River below Trinidad 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 n9 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 day~ 1,416.86 acre-feet were released while the remaining 886.92 acre-feet was reta~ned 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 (PurgOjtoire River below Trinidad Dam) being in excess of the sum of ditch diversions land the amount of flood water released, suggests that the flood water di d pass! downstream undep 1 eted by project opera- tions. ' 46 I I I I I I I I I I I I I I I I I I I