HomeMy WebLinkAbout5.4 Release Water From Del Valle Reservoir r
CITY OF DUBLIN
AGENDA STATEMENT
City Council Meeting Date: May 28, 1991
SUBJECT: Written Communication from Zone 7 Board of Directors
Regarding Release of Water from Del Valle Reservoir
Report by: Public Works Director, Lee Thompson
EXHIBITS ATTACHED: Letter from August M. Hagemann, Jr. , Chairman, Zone 7
Board of Directors, dated May 15, 1991
RECOMMENDATION: �� Receive written communication and oral presentation
FINANCIAL STATEMENT: None
DESCRIPTION: At the April 22, 1991 meeting, the City Council
received an update on the status of drought restrictions and discussed the
release of water by the Alameda County Flood Control and Water Conservation
District (Zone 7) from Del Valle Reservoir. The City Council then sent a
letter to the Zone 7 Board of Directors requesting a status report regarding
alternatives to the present system for releasing water from the reservoir. At
the present time, the State requires that the water level be kept at or below
a specific point for flood control purposes.
The letter from Mr. Hagemann explains that Del Valle Reservoir has a flood
pool elevation of about 40,000 acre feet. Normal operation is to fill the
lake to the 40,000 acre foot level by the end of May and maintain that level
until after Labor Day when the State Department of Water Resources (DWR)
typically draws the lake down to about 25,000 acre feet. This past winter,
however, the reservoir was left at about 30,000 acre feet. Additionally, the
DWR added another 7,000 acre feet to the reservoir prior to March 4, 1991.
Therefore, the lake was nearly full, and it was not possible to capture local
runoff without going over the 40,000 acre foot level. A total of 3,653 acre
feet were released between March 25 and 27, 1991.
Mr. Hagemann's letter continues that Zone 7 and two other water agencies have
met with DWR to discuss the operation of Del Valle and the aqueduct. Zone 7
has also requested additional water from DWR to make up for the water that was
released. -
In addition to the water release. item, the City Council had requested
information on Zone 7's plans to increase well and pumping capacity so that
the Valley would not be so dependent upon receiving water allotments from DWR.
Mr. Jim Dixon, General Manager of Zone 7, has agreed to make a brief
presentation at the City Council meeting in conjunction with these items.
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ITEM NO. COPIES TO: Jim Dixon, Zone 7
Zone 7 Board of Directors
/COa- Z/o
RE S OU ��
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ALAMEDA COUNTY FLOOD CONTROL AND WATER CONSERVATION DISTRICT
5997 PARKSIDE DRIVE 4 PLEASANTON, CALIFORNIA 94588 A (415) 484-2600
GEM May 15, 1991 R E C E_ ) V E fl.
1991
City Council
City of Dublin CITY OF DUBLIN
P.O. Box 2340
Dublin, CA 94568
Dear Councilmembers:
Lake Del Valle was completed in 1968 by the Department of Water
Resources (DWR) as part of the South Bay Aqueduct. The Lake is
operated by DWR as a multi-benefit facility providing for flood
control, recreation and water supply.
Zone 7 and Alameda County Water District hold water rights
permits on Arroyo del Valle and have a contract with DWR for the
storage of local runoff.
Water operations and reservoir space are divided into two major
classes. The upper roughly one-half of the reservoir is for
flood control purposes and is operated in accordance with the
requirement of the U.S. Corps of Engineers. The lower roughly
one-half of the reservoir is used for water supply purposes and
is operated in accordance with the local water contract between
Zone 7, Alameda County Water District and the Department of Water
Resources. .
For the past 20 years the lake has been operated to maximize
water supply and recreation. Normal operation, if there is no
runoff, is to fill the lake to its flood pool elevation of 40, 000
acre-feet by the end of May and to hold the lake at that
elevation until after the Labor Day weekend. Releases are then
made to the South Bay Aqueduct that draw the lake down to 25, 000
acre-feet. This leaves a water supply storage space of 15, 000
acre-feet, which as noted is shared by the Alameda County Water
District and Zone 7 .
This water year DWR did not draw the lake down to the normal fall
level of 25, 000 acre-feet, but left the reservoir about 5, 000
acre-feet above the normal level.
Zone 7 questioned the operation by letter to the Department in
December 1990. We received a reply from Director Kennedy in late
January identifying the continuing drought combined with the need
to fill the lake by the end of May as their reason for not
drawing down the lake.
Additionally, DWR began to fill the lake from the aqueduct about
three months earlier than normal. By March 4 , when the pumping
Dublin City Council
May 15, 1991
Page 2
from the aqueduct was stopped, over 7, 000 acre-feet had been
pumped into the lake and the water conservation pool was nearly
full.
These two actions--failure to draw the lake down and filling it
too soon--greatly reduced our ability to capture local runoff
into the lake. If either of the actions had not taken place,
there would have been no flood control releases.
These releases began shortly after midnight on March 25, 1991,
and were continued until about 10 a.m. , March 27 . A total of
3 , 653 acre-feet were released during the three days of releases
to channel.
As a water supply agency, we regret the loss of water at any
time, but particularly during the continuing drought. But, as a
flood control agency, we understand the need to follow carefully
developed flood control procedures to protect against flooding
when the lake level enters the flood pool of the reservoir.
We believe the Department had no choice but to initiate flood
control releases into Arroyo Valle on March 25. The judgmental
error was filling the lake too soon. We have expressed to the
Department, both orally and in writing, our concern regarding the
two extraordinary actions they took this water year with respect
to water operations at Lake Del Valle.
On April 5 staffs of the three South Bay Contractors met with DWR
personnel to discuss the Lake Del Valle flood control releases
and aqueduct operations. There was agreement to improve
communications between the local water agencies and the
Department--particularly when changes in long-standing lake
operational practices are being considered.
On April 16, 1991 Alameda County Water District and Zone 7
requested additional water to replace the water lost by the March
flood control releases. We are hopeful that our request will be
given careful consideration and are looking forward to a
favorable response from the De rtment.
Very ruly our ,
Au ust f-Pa mann, Jr.
Chairman, Board of Directors
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