Rio Grande - Rio Grande Reservoir Multi-Use Enlargement_Application Addendum

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ML Travis Smith, Superintendent October 16, 2003 Page 7 The first area would be to temporarily store some compact water early in the irrigation season to use as a ucushionu against fluctuations in curtailments that might be 'caused during the course of the irrigation season by. the-inability to accurately predict the volumes of the runoff and the necessary curtailments. Fluctuations in curtailments during the course of the irrigation season could affect certain groups of water users disproportionately. For example, if it was necessary to increase the curtailment during the peak af the runoff, the more junior water rights would suffer a larger curtailment. If it turns out the Compact water so impounded during the early part of the irrigation season is needed to avoid an increase in the curtailment, it can be released and delivered to' the State Line. If the Compact water so impounded is not needed, it can be released during the recession of the runoff so as to reduce the curtailments to all the water rights - juniors, mid-range, and seniors. This operation would not affect Colorado's or the Rio Grande's separate accounting under the Rio Grande Compact We have not attempted to quantify the storage that could have been made for this purpose during water years 1946-20,02, but we believe that it would have been helpful in many years when curtailments are necessary~ The second area would involve some temporary storage of water that needs to be delivered to New Mexico and Texas but is occurring when the Rio Grande flow is at a hig'h rate so as to suffer high conveyance losses. The water could be held in storage until the flow in the river has diminished and then released for delivery to the State Line. This would involve only water that is not available to Colorado water users under the Compact Administration. We have not yet attempted to quantify the storage that could be made for this purpose) but we believe that type of Compact storage would have had some benefit in as many as 20 years in the analysis period~ The third area would be storage of Colorado Credit water. As you know, an over-delivery under the Compact in a year produces an annual credit in the Rio Grande Compact Commission accounting that is carried forward into the next year and considered as being contained in Project Storage. Having a credit carried forward into the next year mayor may not make additional water available to the Colorado water users depending on whether curtailment is or would otherwise be necessary. If curtailment is necessary in the next year, the credit water will reduce the curtailment and will make additional water available to the Colorado water users~ If curtailment is not necessary in tile next year) the credit would be carried forward again, but reduced for evaporation and subject to spill under Article VI of the Compact~ The evaporation charges in Project Storage are significant, amounting to about 4 percent of credits brought into the accounting year. Thus, the advantages of storing credit water in an enlargement of Rio