Water Level Control and Tidal Flows

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Current Operation of the Flood Control Structure: In the 90’s, the County adopted a policy of leaving the tide gates open to natural flow more often, and this resulted in an improvement in water quality. With both gates open at the flood control structure, the Lake water has an average residence time of about four days (Abbe and Haltiner, 1992). “The return of regular tidal flushing undoubtedly was a major factor in improving the Lake’s ecological health” (Travis, 1995).

Under current policy, natural flows are allowed except for the following:

• Flood control Tidal flows into the Lake are limited and the Lake is kept at about 1.0 feet when rain is in the forecast based on twice weekly weather forecasts. This is effective in reducing floods, but may result in restricted tidal flows for extended periods of time; e.g. several days or weeks. If the weather forecast changes, it may be several days before the incoming tides are allowed into the Lake.

Dates of Limited Tidal Circulation in 1998-99: During the winter of 1998 - 1999, high tides were kept out of the Lake on the following dates:

November 2 - 12
November 21 - December 6
January 16 - 19
February 4 - 7
March 16 - 24
April 5 - 7

• Keeping the Lake level high (2 feet above MSL) during boating races and special events such as Festival at the Lake
  
• Keeping the Lake level high or low for unusual circumstances such as dock inspections, construction, emergency spills etc. and
  
• Keeping the Lake high for several days per week so that the harvester boat can navigate closer to shore to pick up nuisance growths of algae and drifting pieces of widgeon grass. In 2001, the Lake was kept at about 2.0 feet for two days per week from June - August.

To implement one of the above listed scenarios, instructions are given to County staff from one or more of several City of Oakland departments, including the Boating Center, the Public Works Agency or the Parks and Recreation Department. Next >>

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