IPUD Board Warns that Third Drought Year Looms

A sobering warning has been issued by the IPUD’s Board of Directors that 2022 appears to be on track to go down as the third consecutive year of a record-setting drought.

This is an updated version of a staff report presented to, and accepted by, the District’s Directors at their meeting on March 23.

Rainfall

While total precipitation so far this rainfall year (as of the end of March) stands at a seemingly healthy 27.42 inches, almost all of that rain fell early in the year, between July 1 and December 31, 2021. An examination of our 91 years of rainfall data leaves little doubt that July-December rainfall typically does not ensure ample supplies the following summer and fall, especially when the amount of rain that falls in the subsequent January-June period is below normal.

 That is exactly the situation we are in this year: Of the total 27.42 inches received so far, 90.3% of it (24.77 inches) fell before January 1. Even more ominous is that total precipitation over the past 83 days (dating back to January 8, historically our most productive time of year for rain) tallies only 1.8 inches. Normally, we would expect to receive a whopping 17.54 inches between January 8 and March 31, so the 1.8 inches we actually received represents a mere 10.3% of the norm.

Streamflows

We also have to factor in the situation with the streamflows, which ultimately constitute the critical metric for our water system because we are dependent year-round solely on the day-to-day flows in the streams that drain our watershed. Streamflows this past December 31 were recorded at a very high 1,404,000 gallons per day. However, by the end of March, the daily flow had plunged by 84%, to just 224,000 gallons per day – an average drop of 13,111 gallons per day.

The significance of these numbers is that we discovered anecdotally a number of years ago that when streamflows measure at least 1,000,000 gallons per day at any time on or after the end of February, the streamflows by the following October will still be adequate to easily satisfy customer demand. Put another way, we never have had a water shortage problem when our streams hit the 1,000,000-gpd mark on or after the last day of February. Conversely, there is little hope for a good outcome in a year like this one, in which we don’t come close to the 1,000,000-gpd benchmark during the critical February through end-of-March period.

Summation

With the passing of each day, the prospect diminishes for a “bailout” series of rainfall events. In Inverness, the 91-year average rainfall from April 1 through the end of the rainfall year on June 30 is only 3.88 inches, so even if a ”normal” rainfall pattern should return suddenly, it’s unlikely it would make much of a difference.

Notwithstanding some models that are showing up to 1.5 inches of rain in the North Bay during April, a long-range prognosis issued by the National Weather Service after last weekend’s small storm (a meagre 0.89 inches recorded in Inverness) concluded that the Bay Area has already seen its last significant rainfall for this year!

Add in the ominous plunge in our streamflows since December 31, and we cannot escape a profound concern that our water shortage situation this coming summer and fall is almost a certainty to be even more challenging than last year.

Under these circumstances, your IPUD Board of Directors and your Water System staff issue this warning to be prepared for even tighter restrictions on water usage this coming summer and fall than were in effect last year – including that this year we may actually have to resort to water rationing. Gardeners especially should think long and hard about attempting to plant this year – and keep in mind that restrictions already in effect limit outdoor watering to what you can do with a handheld hose or a watering can. Please also note that use of System water for power washing of structures and hard surfaces is not permitted.