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I I I I I I I I I I I I I I I I I I I On? r:;: '-'J u....v)) APPENDIX E - HISTORICAL AND PROJECTED RESERVOIR OPERATIONS ON THE LOWER COLORADO RIVER Introduction This section provides an analysis of historical and projected reservoir operations on the lower Colorado River from Lake Mead to Mexico. Annually, about 9 maf are released from Lake Mead to meet delivery orders of water entitlement holders in the United States and for Treaty deliveries to the Republic of Mexico. Of this amount 7.5 maf are entitlements for the lower basin states of Nevada, Arizona, and California, while the remaining 1.5 maf is delivered to Mexico. The locations of storage and delivery facilities are illustrated on Figure E-l [Map Number 423-300-59 (Revised April 1993)]. In the following analyses, the historical data are based on normal, non-flood years of 1982 and 1989-95 of the past 15 years. The projected normal, routine reservoir operations for the next 15 years (1996-2010) has been projected using reservoir modeling methods with stochastic hydrology and anticipated uses. Although this data set is for the next 15 years, this section 7 consultation (Endangered Species Act) on lower Colorado River water operations is only for the 5-year period of 1996-2000. Graphs are presented on reservoir releases, elevations, and flow depths. Historical and projected water use data tables are also included in tables EI-EIO. The reader should be aware of the meaning and difference of the terms instantaneous, hourly, mean daily, mean monthly, mean annual, midnight, end of month and end of year as indicated on each graph and should not be used interchangeably. Instantaneous values are values that occur as the viewer stands on the river bank at each moment in time watching the river flow by. A mean daily value is the average for the day of possibly thousands of instantaneous values. When applied to reservoir releases, the mean daily value usually occurs twice a day, once as the flow and power demand is on the increase in the morning and once in the evening as power demands decrease. The same is true of mean monthly values, which correlate even less to instantaneous flows. . The reader should become familiar with the hourly flow patterns presented in the typical seasonal flow graphs Figures 9-13 of Section II before applying the daily and monthly values presented in this appendix as habitat descriptors. The value terms used in this appendix are defined as follows: Instantaneous: Value at a particular moment in time. Hourly: Average of many instantaneous values for 1 hour. (Hourly and instantaneous are close enough to be used interchangeably for use in describing habitat on the lower Colorado River.) Mean Daily: Average of 24 hourly values, may only occur 2 times per day. Appendix E - 1