Marin Reservoir to Buffer Winter Floods

As Marin County anticipates potentially severe flooding this winter, a strategic plan is in place to leverage Phoenix Lake as a crucial flood buffer. The Marin Municipal Water District intends to lower the water level in this smallest of its seven reservoirs, creating significant capacity to absorb excess runoff from future storm events. This proactive measure is designed to mitigate increased flooding downstream, particularly in areas around Mt. Tamalpais.

The concept gained traction following a prolonged drought in 2021, when Phoenix Lake reached critically low levels. Subsequent heavy rainstorms in late October of that year demonstrated the reservoir's substantial ability to capture storm water, preventing it from overwhelming downstream areas and preventing ground saturation. Officials recognized this inherent capacity as a valuable tool for future flood preparedness.

While Phoenix Lake was not originally designed for flood control, its new role represents an innovative adaptation. The reservoir currently holds water at 120 percent of its normal level for this time of year. By utilizing it as a primary source for the district's water delivery system, its level is expected to decrease sufficiently to serve its flood mitigation purpose. The water will not be released but rather managed within the district's system. The drawdown will bring the lake to a level comparable to that seen in 2021, ensuring its water quality is maintained. This initiative highlights a fresh collaborative effort within the county for enhanced flood control.

This planning comes in the wake of recent high tides that already brought water into coastal streets, such as in Larkspur, serving as a potent reminder of potential weather impacts. Although Monday's event was not caused by a king tide, it was notably higher than expected, demonstrating the ongoing need for such preparedness measures.