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New Melones modeling & mega-droughts: Setting stage for state’s water Armageddon
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Dennis Wyatt

New Melones Reservoir is the proverbial canary in the mine when it comes to where state water policy wedded with the return of mega-droughts is taking California.

Using historical hydrology data on the Stanislaus River basin between 1922 and 2019:

• Based on current regulatory rules New Melones Reservoir would fall below 250,000 acre-feet of storage in three out of the 98 years.

• Based on the pending State Water Quality Control Plan and the 40 percent unimpaired flow requirement that will help boost the combined numbers of Chinook salmon on the Stanislaus, Merced, and Tuolumne rivers by 1,500 annually, New Melones Reservoir would fall below 250,000 acre-feet in 20 out of 98 years.

A few things to add to the mix:

• When New Melones drops to 10 percent of capacity, it is in the dead storage zone. That means the 250,000 acre-feet of water is trapped behind the dam.

• Hydrologists point to data that indicates the period between the mid-1700s and the mid-1900s was abnormally wet in the area we refer today as California and the Southwest.

• The return to the natural mega-drought cycle punctured with a year or several strung together with normal or above average precipitation is not taken into account on models using hydrology data gleaned between 1922 and 2019 on the Stanislaus River Basin.

• New Melones did not start filling until 1978. It generated its first power in 1979.

• New Melones is the most overcommitted component of the Central Valley project in terms of water deliveries. The water promised in federal contacts in the 1970s was far more than the hydrology of the basin historically could deliver.

• When water levels at New Melones drops below 1.2 million acre-feet during critical fish flow periods on the Stanislaus River, the risk of higher water temperatures comes into play. Not only is there less surface area in the reservoir but the remaining water at the bottom that is released into the river is colder is subject to being “heated up.” That can raise temperatures in the Stanislaus River and reduce oxygen which in turn can “fry” fish by suffocating them.

• The same issue arises when releases from New Melones drop below existing operational guidelines for fish during specific times of the year.

As sobering as this may seem to folks who – much like the rest of California – go through water as if they are sailors on a 48-hour shore leave hitting the bars between year-long deployments at sea, it is just a small part of the problematic Rubik’s Cube that is California water policy.

Experts believe mega-droughts will manifest the following changes in California precipitation patterns:

• There will be less snow and rain.

• Warmer temperatures mean higher in elevation snow levels.

• It also means higher elevations in winter will receive warm rains.

• Warm rains on snowpacks trigger earlier runoffs.

• Smaller snowpacks can lead to a higher percentage of evaporation loss.

• Drier conditions in the Sierra means more of what snowpack there is will be absorbed into the ground and vegetation.

• There will likely be more precipitation in the form of rain at lower elevations.

• The spread of impervious surfaces – rooftops, roads, sidewalks, etc. – over the past century or so will reduce groundwater absorption in the lower parts of water basins such as the Valley. This is turn will work to further reduce groundwater replenishing on the levels that occurred in previous mega-drought periods.

Because of all of that and more, the last thing California needs when it comes to investing scarce water infrastructure dollars is more dams like New Melones.

You might be able to argue to a smaller degree raising Shasta and Friant makes sense.

Such a move somewhat will expand 100 percent useable storage capacity as the acre-feet in dead storage won’t increase.

But here’s the rub: Less snowpack as well as changes in the timing of snowpacks runoffs occur and where the most precipitation falls may make investing in such dam expansions of traditional reservoirs the less effective way to stretch the state’s water supplies.

Two much more effective ways are more off-stream reservoirs at lower elevation levels and addressing recharging of ground water during periods when there is higher runoff.

The pending Sites Reservoir project in Colusa County — the Sacramento Valley version of the San Luis Reservoir in the San Joaquin Valley — will be much more effective at snaring runoff in mega-drought conditions than more reservoirs such as New Melones.

To maximize “local” storm runoff to prevent it from going into storm drains, into rivers, and into the ocean, the creation of local recharge basins and simply delivery flooding orchards as is being studied by the University of California at Davis in Stanislaus County are needed.

Local recharge basins for the diversion of excessive runoff will help enhance groundwater replenishment.

We already have a dropping water table in most places even without drought conditions.

It is almost a given we will be turning more to underground sources when surface supplies are stressed.

Yes, there is a state mandate looking that by 2040 users within specific water basins need to return as much water in a given 12-month water year as they take out to stabilize aquifers.

Reaching that equilibrium needs to be done much sooner and on a much more muscular basis than currently envisioned.

None of this is going to happen overnight.

That is why we all need to come to grips with not the new norm but what has always been the norm — we live in an area of the planet that for thousands upon thousands of years has been in a mega-drought cycle.

It means we must address our water use for nonessentials — landscaping and such — to reflect where we live and what Mother Nature sends our way in terms of water.

It also means becoming hyper water efficient is essential.

All the other crisis situations and problems facing the state are superfluous if we can’t figure a way to go forward with less water.

Pandemics, immigration, gun violence, greenhouse gases and more become moot issues if we lack water to grow food, sustain the environment and to simply live.

We can find a way to live with $7 a gallon gasoline. We can’t live, though, without water.


This column is the opinion of Dennis Wyatt, and does not necessarily represent the opinions of The Courier or 209 Multimedia.