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How the MMWD exacerbated the 2020 - 2021 water crisis

From October 2020 to September 2021 we experienced our worst water crisis since 1976 - 1977.


As shown on the graph above, the 2020 - 2021 period came in much below average. In October 2020, the MMWD reservoir level was about 53,000 acre feet (AF) close to average. But, by September 2021, the reservoir level was only 27,000 AF, half of the average.

How we got there is interesting. There are causal factors outside the MMWD's control (low rainfall). There is a causal factor that was under the MMWD's control (excess water release). And, this is what this analysis is about.

Before jumping into this issue, let me share with you a bit of background. The MMWD is mandated by environmental regulations to release a huge amount of water to sustain the small local salmon population. The table below from the MMWD describes the water release requirements. The latter is measured in cubic feet per second.

Picture-1-A.pngThe above table is challenging to decipher. However, it translates into 10,604 AF during normal years and 8,961 AF during dry years. That is a ton of water. And, the MMWD can't do anything about it but follow this regulatory mandate.

Next, let's look at the actual record of such water releases. The dry years are highlighted in red. The water releases are in column B called Fisheries.


As shown above, water releases to maintain the fisheries are huge and typically amount to around 45% of human consumption. Next, let's look at a more complete data set to better understand how the MMWD did not manage its water releases precisely enough.


The above data indicates that the MMWD released a lot more water above mandates during dry years than during normal years. The data below focusing on average water releases during dry years vs. normal years is informative.


The above data tells us that, on average, the MMWD released just about the proper amount of water during normal years. But, during dry years the MMWD released over 3,100 AF above the water release mandates.

Next, looking at the relationship between the MMWD water release and either rain or runoff, we observe very strong negative correlations. This means that the dryer our climate the more water the MMWD releases to sustain salmon fisheries.


The historical data suggests that the MMWD has prioritized the lives of about 600 adult salmons over the lives of its 192,500 human water customers.

Below, I review how the excessive water releases (much above mandates) exacerbated the 2020 - 2021 water crisis.


Above, I am making the conservative assumption that in October 2020, the MMWD may not have known yet that they were facing a prospective dry period. Given that, I use a mandate of 10,604 AF which results in an excess water release of only 2,652 AF at the time instead of 4,295 AF if we assume the lower release mandate during dry years of 8,961. However, going forward there was no doubt we were in a dry period. And, I incrementally phased in the additional 2.773 AF of excess water release during the remainder of the water crisis period.

Below I focus on how much extra water the MMWD would have obtained at no cost during the 2020 - 2021 water crisis if only MMWD had managed its water release more precisely, especially during dry periods.


The 5,425 AF represented about 3 extra months of human water consumption. They also would have represented a cost saving of $9 million in purchased water from Sonoma at an all-in cost close to $1,700 per AF.

Financially, the MMWD can't afford to mismanage water releases. And, we can't afford it either if we care to live till the next rainy season.

We got lucky. The MMWD was bailed out by a series of record-breaking atmospheric rivers in the Fall of 2021 that filled up the reservoirs to full capacity. You can see this phenomenon in the graph below when focusing on the green line that jumps from 27,000 AF in October of 2021 (way below average) to near 80,000 AF by the end of 2021 (way above average).


During the water crisis, while the MMWD forced us to implement fairly drastic water conservation, it simultaneously wasted a ton of water.

Since then, we have replaced three MMWD Board members. Also, Jacobs Engineering (JE), consultants hired by the MMWD, have recommended improving the precision of water releases. That is a low-cost and low-hanging fruit to shore up our water supply security.


MMWD, water crisis, environment, water conservation, salmon