California Water Reservoirs Part 2: Let's Talk about Drought and Aridification

This is a first in a series of blog posts on California’s water supply and aridification due to climate change.

1976-77 Drought

A warning message from the past:

Now that the two dry years are past, we must not allow the abundant water supplies of 1978 to lull us into a false sense of security. Droughts do not recur in precise historical sequence or in equal severity. These years 1976 and 1977, together, far exceeded the dryness in our historic prior two-year dry period of record. The experience of the worst earlier drought, covering the seven years from 1928-1934, should be reason enough for Californians not to let up in their water conservation efforts. In the 1928-34 drought, at least one year within the cycle provided near-normal rainfall. The year 1978 may turn out to be a temporary respite, also. Ronald B. Robie, Director of Department of Water Resources for the State of California, 1978

Ronald gives us a stern warning to not take pressures on our water resources lightly. He’s correct because the ramifications are great. The most dire situation could look like food not growing in the Central Valley - where 25% of the United States agricultural output comes from; people leaving metropilii as refugees because life simply becomes inhospitable. I’m trying to describe a situation that not only looks worse that the shutdowns we saw in the United States at onset of the coronavirus pandemic. The most dire situation is would be ghost towns with no people living in cities that once had population in the millions.

We don’t have to go far back in history to recount a time where such a shutdown could have happened.

Above is an interactive chart to view the total water supply. Change the dates on the chart and take a look at the 70s and 80s. You can see the dip in our water reservoir's water supply during the drought. Bear in mind that from 1978 to 1990, 22 new reservoirs were filled whose total potential capacity of water was 41,677 acrefeet.

year by year chart of acrefeet and reservoirs added by year

Note in the chart above, it does not list every year from 1925 to 2023. It just lists the years that at least one new reservoir was "filled". The left axis is the count of reservoirs added that year, and the axis on the right is the capacity of acrefeet added.

Alright enough of that. Let's get into a little bit of recent history and droughts and aridification.

What could happen before the most dire situation?

The most immediate tool a water management agency has is to ration water. From 2015 to 2018 Cape Town, South Africa experienced a drought where water rationing for urban and agricultural use ramped up. Cape Town was on the verge of having its entire population stand in lines with buckets to get water; that is to say: their plumbing and water supply would have been so low that it would not be reasonable to have the water flow to homes and elsewhere as it would normally. Leading up to that point Cape Town had put in place several “levels” of water rationing, from limiting how one waters lawns, recommendations of flushing toilets with grey water, and providing guidelines of how much water a person or household can use in a day.

Let’s imagine for a second how might Californians manage water rationing:

  • Do you see the greater Los Angeles Basin, or the San Francisco Bay Area following water rationing guidelines of daily water use? What about other major metropilii or rural areas of the state?
  • Are municipalities capable of reasonably enforcing water rationing?
  • Does the state begin to ban the watering of water intense crops such as alfalfa and almonds? Would California try to exhaust the ground water as much as possible to try to “fish itself out” of water shortage?
  • If things go sour, how would cities manage distribution of water when it is not adequate to distribute water through plumbing normally? Would it like people standing in line with buckets at designated sites?

Aridification Versus Droughts

The lexicon for how we describe climate change should change. Note in the Google Word Trends pictured below, aridification is woefully underused relatively to drought. Droughts are temporary effects whereas aridification are a permanent (i.e. in the human timescale) effects to a region. So I ask the reader, is what we are seeing a temporary or permanent affect? I would answer aridification is the word we should as I believe what we’re seeing is aridification due to climate change.

Aridification versus Drought Google Word Trends

Perhaps the over-utilization of droughts is problematic in the perception of the public. Most people in the western world have not been impacted in any significant way when they’ve experienced a drought due to an abundance of water supply. Everyone on the planet now is experiencing aridification en masse simultaneously and perhaps misidentifying this aridification as a drought and may expect the same outcome as any other drought they have encountered before.

You might ask, “Clinton, are you serious about that extremely dire situation of ghost towns?” Yes! Droughts come and go. It’s extremely unusual for a drought to cause people to relocate from their metropolis (I’m not saying it doesn’t happen. It does). With aridification permanence, you have to consider that the water levels cannot be reliably be restored to what we’re familiar with.

What Policies Could Help Mitigate the Worst of Aridification?

Addressing the largest

Water Use Efficient GMO Plants

Agriculture is responsible for 40% of California's water use [3]. If genetically modify plants to need less water, this could help save a great deal of water. Let's illustrate this point on two crops that are notoriously thirsty for water: alfalfa and almonds (disclaimer: this is just to illustrate the point and not in any way realistic here) under the following hypothetical scenario:

  1. Let's assume we can make our GMO'ed alfalfa and almonds use 25% less water. That does sound like a lot but let's be ambitious and we've been able to produce tobacco crop that is 25% more water use efficient [4].
  2. The fine folks at UC Davis' Agricultural and Resource Economics has a cost studies site that reviews costs to growing crops in various regions in California. It's fascinating to learn that for the same crop, the amount of water needed can vary by region and methodology for growing. We'll use one number that's within the cost studies for almonds and alfalfa.
  3. Lastly we'll use the California Agricultural Production Statics [1] to get some idea of how much land is used across california to grow almonds and alfalfa.
  4. We'll ignore the water used to establish an orchard of almonds or a field of alfalfa. We'll only focus on the water used to produce almonds alfalfa for a harvest.

GMO Almond Scenario

photo of almonds on tree

  1. For 2021, 1,250,000 acres of almond trees were harvest.
  2. Using the cost studies, we can assume 42 acre-inches (3.5 acrefeet) per acre for a harvest.

In total, this scenario shows 4,375,000 acrefeet of water used in California to grow almonds. You could fill the largest water reservoir within California, Lake Shasta, with that much water! If we grew GMO almonds that allows 25% less water use, that would translate to a savings of 1,093,750 acrefeet of water a year. That's a sizeable amount of water!

GMO Alfalfa Scenario

photo of alfalfa field

  1. For 2021, 515,000 acres of almond trees were harvest.
  2. Using the cost studies, we can assume 42 acre-inches (3.5 acrefeet) per acre for a harvest. Note that the cost studies indicate that watering can very greatly from as little 18 acre inches to even over 60 acre-inches depending on region that it is grown.

In total, this scenario shows 1,802,500 acrefeet of water used in California to grow alfalfa. With GMO alfalfa that allows 25% less water use, we'd save 450,625 acrefeet of water.

From the water conservation perspective there is some good news! From the 2021 California Agricultural Production Statics [1], we've nearly halved the acreage grown which translates to a tremendous amount of water conserved.

How realistic of a solution is GMO to water conservation?

Annual crops like alfalfa make sense. They're quick to grow and can have a great change right away. I think this is something that should be an area of investment that California and the world can benefit from just from a food security perspective alone.

Almonds are a different story as they come from trees and that may take quite some time to realize a GMO almond worthwhile using; then more time getting an orchard to replace their existing trees which could be productive for up to 25 years or more. GMO almonds is not realistic at all but used merely as demonstration from a water thirsty crop.

Improved Water Reclamation in California

I will write about this in Part 3.