WSP13021 ‎(2)‎

• File Number: 8430.500
• Description: Denver Water
• State: CO
• Basin: Statewide
• Date: 1/16/2004
• Author: USDOI?BOR
• Title: City of Denver's Water Use of Colorado River Water - Water Year 2003
• Water Supply Pro - Doc Type: Data

Mf:. Maryanne C. Bach
December 30, 2003
Page 2

TABLE II - Blue River Water Diversions and Utilization
This table shows monthly totals, in acre-feet, for Denver's deliveries of Blue River water
through the Roberts Tunnel. These figures include water withdrawn from storage in
Dillon Reservoir and water diverted directly from the Blue River. Also shown are
monthly totals for: 1) carrying charges assessed by the State Engineer on deliveries, 2) the
portion of the Roberts Tunnel discharge delivered or exchanged into South Platte storage,
3) the portion used directly, and 4) the amount of Blue River water previously stored in
South Platte reservoirs and subsequently released for municipal use in the Denver area. A
modification was made this year that enables more precise quantification of the amounts
of Blue River water used directly or stored.

TABLE III - Return Flow of Colorado River Water
This table presents the calculations to determine the percentage and amount of Colorado
River water used by Denver that returns to the South Platte River through wastewater
treatment plants. The table presents total monthly amount of water delivered by Denver
to its treated water and raw water customers. Also shown are monthly amounts of Moffat
Tunnel water used from Column 8 of Table I and Blue River water used from Column 6 of
Table II. The sum of these two gives the total Colorado River water delivered by Denver
to its treated and raw water customers. The percentage of Denver's water use that is
Colorado River water is calculated by dividing the amount of Colorado River water used
by the total water use and appears in Column 5 of the table.

Column 6 shows the monthly amounts of wastewater effluent base flow from Denver's
customers. Base flow is the quantity of effluent determined to be available during the
months of December, January, and February. Because water usage is principally limited
to inside uses during the winter months and is lowest during this period, the resulting
wastewater flows can be assumed to be available throughout the year. The base flow is
reduced by 5% to account for potential infiltration and inflow to the wastewater system
pursuant to the settlement of litigation in Case No. 96CW145 with the City of Thornton.
The base flow amounts in Table III include the quantities used in Denver's daily water
rights accounting and additional amounts of effluent not included in the daily accounting.
The monthly totals of effluent base flow were then multiplied by the corresponding
monthly percentage of Colorado River water usage to estimate the quantity of Colorado
River water returned to the South Platte River through the metropolitan area's wastewater
systems.

TABLE IV - Successive Use Operations Involving Colorado River Water
This table shows monthly totals, in acre-feet, for the 2003 water year of the successive use
Denver made of its Colorado River return flows. The figures reflect the successive use of
a portion of the return flow shown in Column (7) of Table III. Reported in Column (1) of
this table is the amount of transmountain effluent exchanged to South Platte Reservoirs
attributable to Colorado River water imported through the Roberts Tunnel and Cabin-
Meadow Creek water imported through the Moffat Tunnel and used under contract by
Denver. Column (2) shows the amount of water stored in Antero, Eleven Mile, and
Cheesman Reservoirs equivalent to the out-of-priority evaporation losses from those