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I I I I I I I I I I I I I I I I I I I suitable as a point in time from which to evaluate the year. In any case, a date can be chosen and storage at the time can then "automatically" trigger a response. At least some sort of plan can be in place which would identify levels of appropriate response. It is easier to do this planning when the severe influences of drought are not already upon us. Table 4 shows the author's attempt to draft a threshold for triggers and responses to varying drought events under the Lake Canal system. Drought stage 0 is associated with normal or wet years when there is plenty of water available for urban landscapes. With only 90% or 80% of normal storage in reservoirs at July 15\ drought stage 1 or 2, respectively, are assumed and this stage suggests that voluntary restrictions would be instituted and customers would be advised to generally monitor their irrigation and avoid waste. Drought stage 3 and 4 institute mandatory restrictions on landscape irrigation and drought stage 5 and 6 limit in varying levels irrigation to only trees and shrubs (the most valuable and likely non-replaceable plants in the landscape) and to high priority public places such as sports fields and golf courses. Drought stage 7 or 8 might be implemented with specific Lake Canal Board input to tailor the response to the situation but, whatever the response detail, drought stage 7 or 8 are quite significant and fortunately infrequent. In fact, an analysis of past drought events and again giving consideration to a future Lake Canal build out as urban projects, no past drought would have dictated more than a drought stage level 4 trigger. In the analysis, past droughts are used as an indicator of future drought events. Future water requirements are estimated based on a build out of the Lake Canal service area into urban landscapes. So, a look at the future is gained by fast forwarding in time to think of a complete build out of the Lake Canal system and the water requirements of the future are compared to the water availability of past drought years. It is hoped that something can be learned from these extrapolations and comparisons. The historic stream flow data for the Poudre River shows years of low stream flow which are known to be significant and memorable droughts. Drought years of 1937,1954, 1977,1987, and 2002 have been picked from the record for study. These years are noted in Table 5 along with the Lake Canal diversions for those years. In 1937, the Poudre stream flow data is available but the Lake Canal diversion for that year is unknown so this drought event cannot be fully understood except to say that it was similar to the droughts of 1954 and 1987. So, after some research into the data availability and the deficit of water under Lake Canal, four years of historical drought for 1954,1977,1987, and 2002 were considered and are thought to be indicative of or predicting of future drought under the Lake Canal system. Some adjustments of the Lake Canal data are warranted as related to C-BT water. Specifically, an adjustment is made to subtract C-BT deliveries during some years because C-BT would not contribute to the late season needs under the urbanization scenario of the future. This analysis is intended to assist future planners and Board members of the Lake Canal system in formulating a drought strategy to include thresholds and triggers. Experience with real future droughts will be the best guide in making adjustments to the process. Aqua Engineering, Inc. June 7, 2004 Canal Modernization Feasibility Study - 8-