Timely & Adequate Demand Management in Dry Years

Recommendation—that the City establish a policy of timely demand management in response to dry conditions that will enable adequate storage for future dry years.

The timing and adequacy of the City’s response to dry conditions significantly affects the severity of future drought curtailments. In general, early and adequate action to reduce water demand in the first dry year optimizes reservoir levels in case the subsequent years are dry.

To understand the importance of early action, is illuminating to compare the City’s response to dry conditions in 2009 versus in 2013.  In 2009, in response to a second dry year, the City Council declared a Stage 2 response with a target of 15% reduction in demand. Citizens responded and the goal was met. On October 1st, Loch Lomond was at 90% capacity. At that level, even a subsequent dry winter would likely fill the lake and the City would be well prepared for a third dry year.

In April, 2013, in response to the negligible rain since December, the City Council declared a Stage 1 drought response, aiming for a 5% cutback in water demand. The goal was to have 75% capacity in Loch Lomond on October 1st. At year’s end, instead of achieving a 5% reduction in demand, water demand actually rose slightly. The City didn’t achieve its goal for Loch Lomond capacity, and lake levels continued to drop to a low of 63% in December. Had the City initially called for a Stage 2 response, reservoir levels would have been significantly higher, providing more water security for 2014 and beyond.[1] Even invoking a Stage 2 response late in the year could have reduced demand on the reservoir, which dropped significantly between September and December.

This strategy of timely and adequate response to dry conditions can be thought of as a carry-over strategy, until other longer-term strategies, such as banking water in the aquifers, can be implemented. Once the City has more storage, there will be less need to implement demand reduction measures in the first dry year.

[1] The Water Department classifies each year as wet, normal, dry, or critically dry, based on cumulative runoff in San Lorenzo River. Cumulative runoff is a metric that should probably be revised in order to guide decisions about what stage of water shortage response to invoke. For example, 2013 was the driest calendar year on record. However, because of heavy rain in December, 2012, the runoff year was declared “normal”, even though flows in the river and streams were well below normal by April and throughout the dry season.

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