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.. '" ....: - _t~ Memorandum Page 2 of 3 J anual)' 7, 1994 The PRWCD believes it will be able to exchange transmountain water purchased on the Arkansas mainstem in the Pueblo area down to JMR and back up the Purgatoire to Trinidad, a distance of over 200 miles. Numerous intervening rights between Pueblo and JMR would have to be protected. Possible use of JMR as a temporary depository for exchange water will have to be negotiated with Kansas. A major impediment to obtaining approval from the Courts and the Arkansas River Compact Administration (ARCA) of such an exchange is the uncertainty concerning transit losses on the Purgatoire River below Trinidad. It is known that at times the losses can be enormous and occasionally a call from the Arkansas mainstem can not be placed up the Purgatoire to Trinidad because of the futile call doctrine. To reduce this uncertainty and to better determine the true feasibility of an exchange up the Purgatoire, the PRWCD has requested the U. S. Geologic.:!! SI1TVPY (11<::r.<::) tn mnnnrt.... ansit loss stud on the Purgatoire River. The USGS is well suited to do this task having . done similar studies on e River, but requires 50% cost-sharing on these efforts:.. The PRWCD is prepared to pay a part of the necessary cost share, but will need additional cooperators on the project. The Board is now being asked to consider at what level it may wish to participate. Discussion The USGS presented a very preliminary draft proposal for various levels of a'transit loss study to ARCA at its annual meeting on December 14, 1993. Colorado supported moving ahead with efforts to refine the scope and cost of such a study. Kansas expressed moderate interest, but subject to prioritization with requests for other studies which it probably deems more important. Colorado volunteered to take the lead in coordinating a scoping effort and bringing a more definite proposal back to ARCA The current USGS pre-proposal considers a range of methods and cost ($50,000 to $250,000) for the study. The main difference in cost is the degree to which new data is needed and the amount of field work required to obtain the data. A bare bones look at the historical record may not provide much useful information about current channel characteristics and may not allow statistically valid separation of flow components. A more elaborate study would require test releases from Trinidad Reservoir and require extensive monitoring of flows along the channel undervarying conditions. The type of study performed will ultimately depend on'the types of uses to made of the -results, the precision required for those uses and participants willingness to pay a share of the costs,