Final Environmental Impact Statement Volume II Appendix K, Part 2

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Fk 00 N COMMENTS OF U.S. ENVIRONMENTAL PROTECTION AGENCY EPA -36 Any such proposed plan also needs to include a recognition of the exigencies of the "real world" with respect to both the practicalities of compliance and enforceable alternative options which will be implemented in those instances when the flows or other critical variables monitored do not provide the desired results in terms of protection of those identified resource values of concern. In this regard, EPA concurs with FERC's recommendation to adopt the Staff's Recommendations for flow measurements at Overton and Grand Island and the Nebraska Game and Parks Commission's compliance criteria as discussed on pages 4 -23 and 4 -24 of the RDEIS. EPA -37 As stated above, the monitoring plan should also be used as a mechanism to appropriately validate the hydrologic modeling used as the basis for the flow analysis discussed in the RDEIS. Specifically, the evaluation of the various alternatives and the anticipated effective operation of such alternatives are largely dependent on the output of the hydrological model presented in the RDEIS. Although not subjected to an extensive, detailed analysis in the RDEIS, the model appears to be subject to minimal calibration, at least with respect to the calibration presented in the supporting documentation (no calibration was presented for the reach between Overton and Grand Island). The model also evidenced some error at certain times of year and under certain conditions of flow. In particular, the model appeared to overestimate water in storage, which would result in the potential for less water to be available for release than anticipated. Specific Comments Hydrologic Modeling Major decisions are based on the output of the computer model used to simulate the system of diversions, hydropower stations, and reservoirs. It follows, therefore, that demonstrating the applicability of the model will increase confidence in the model results, and hence, the comparison of alternatives. The model review indicated that it includes relevant variables and parameters, the model documentation is substantial, and obviously a great deal of work was done to modify the model to meet the project requirements. There are, however, some aspects of the report that may need to be improved or clarified. EPA -38 1. Page A -23, A -24. A calibration is presented for the Lake McConaughy storage volumes. Measured and simulated values were compared. The results of the comparison show that the r was 0.90. What is the value of the slope and intercept? The r value can be high if two variables are related but not necessarily the same magnitude (e.g., if one variable is always 21 RESPONSES TO U.S. ENVIRONMENTAL PROTECTION AGENCY EPA -36 Agreement noted. EPA -37 Additional calibration was performed for the SDEIS. The OPSTUDY model is not designed to be a real time predictive tool. We believe the monitoring effort should be directed at the affected species and their habitat, and at how available water supplies can be most efficiently conserved, released, and transported to improve that habitat. Validation of the hydrologic modeling is of lesser importance. EPA -38 These parameters were presented in the SDEIS.