Updating the Hoover Dam documents, 1978 / Milton N. Nathanson.

page VI-27

APPENDIX VI VI-27 22 COLORADO RIVER STORAGE PROJECT EXPLANATION OF SHEET 1 OF 3 Column (2): Actual flow of Colorado River at Grand Canyon. Flow measured nnd data furnished by Geological Survey. Column (3): Actual total net Lake Mead loss. This is a water budget computation using the measured flow at Grand Canyon as inflow to Lake Mead, the uHual release from Hoover Dam and the actual measured storage change in Lake Mead. It includes unmeasured inflow to the river and lake below the Grand Canyon paging station, evaporation loss from the lake, changes in bank storage, and diversions from the lake to Nevada. Columns (4) and (5): Total Hoover release. Water flowing in river below Hoover Dam is recorded in this column. Column (0): Downstream water requirements. This is the minimum monthly downstream water requirement defined in section 3 of operating principles. This requirement will be estimated by months at the beginning of each year, and adjusted to actual at the end of each month. Column (7): Lake Mead end-of-month content. Surface storage at end of month (changes in bank storage are reflected in column (3)). Column (8): Lake Mead end-of-month elevation. Elevation corresponding with end-of-month content shown in column (7). Column (9): Lake Mead, mean elevation. Computed as average of elevations at end of previous month and end of current month. Column (10): Lake Mohave, mean monthly elevation. Computed as average of elevations at end of previous month and end of current month. This is used in computation of tailwater elevations for Hoover powerplant. Column (11): Hoover powerplant-average tailwater elevation. Values to be taken from Hoover powerplant tailwater curves, drawing 45-300-59, and will be based upon Hoover release (col. 5) and Lake Mohave mean monthly elevation (col. 10). Column (12): Hoover powerplant average 6tatic head. Computed as column (9) minus column (11). Column (13): Total energy at 83 percent efficiency. Values are computed by equation: Kw.-hr. = 1.025Xefficiency (83 percent) Xstatic head (col. 12) Xrelease in acre-feet (col. 4). Column (14): Firm energy. Same as column (13), but not to exceed scheduled firm energy (col. 14, sheet 3). Show annual total only in the event there is no deficiency indicated on basis of total annual generation.