By Scott Hamilton, President, Hamilton Resource Economics
Delta smelt has cost valley farmers, rural communities, and residents in Southern California significant quantities of water. Since water supplies have been restricted to protect delta smelt starting in 2008, no estimate of the water cost has been produced, but it is very likely that the total number exceeds 10-million-acre feet. The cost to replace that water is in the order of $5 billion.
Delta smelt are a small, native fish, found only in the Sacramento-San Joaquin Delta and westwards to the Napa River in salinity that ranges from slightly salty to one third that of sea water. They were listed as threatened in 1993 and the status was later changed to endangered. Since 2017, they have no longer been found in long-running fish surveys in which they were once abundant. Their protection under the Endangered Species Act is warranted.
Their Delta habitat has changed from a massive number of dead-end channels surrounded by tidal marshland to a series of rivers and channels that are primarily lined with ripraps. Most of the marshlands have disappeared. Delta smelt face predation from non-native species that have been deliberately or accidentally introduced into the Delta. And due to reservoir and water exports operations, the hydrology in which they evolved has changed substantially.
Delta smelt have attracted attention recently because one of the management actions intended to improve their habitat was recently suspended. This action, referred to as Fall X2, has been reported in the last two issues of Valley Voice. As noted previously, this action, which requires a reduction in water exports from the Delta, was intended to increase the volume of water in suitable salinity ranges available to delta smelt in September and October in years of above normal hydrology. In 2023, this action was estimated by DWR to cost 600,000-acre feet. If implemented in 2024, the cost would have been lower – perhaps around 250,000-acre feet.
The suspension of the action-initiated outrage among some environmental groups. According to the LA Times (10/2/24) the justification for their concern was simple – the additional outflow created by the action is “vital for delta smelt, and that the decision by state and federal officials to suspend the measure this year poses an additional threat to the fish”. They said the additional water in some years has played an important role in preventing the extinction of delta smelt, and that not making the water available would be irresponsible and indefensible and “a wealth of scientific research shows that larger flows in the delta during the fall continue to be important in preventing the extinction of delta smelt”.
Since 2007, there have been at least 20 studies analyzing the effectiveness of the fall X2 action. Seven of those studies allege to be a benefit of the Fall X2 action. Two studies did not even consider flow in the fall to be a covariate worthy of including in studies to explain the changes in abundance of delta smelt, while 11 studies found no benefit, or the study results were inconclusive.
The quality of the science of the studies supporting the Fall X2 action deserves some attention. A few of those studies included some basic statistical flaws leading to incorrect conclusions. But some studies seemed particularly misleading. For example, one study by Lee and others in 2023 titled “Flow augmentations modify an estuarine prey field” concluded that “(t)his study is management- relevant because it shows that important Delta Smelt prey items increase in downstream regions when X2 is lower.” That is, when the outflow is higher, there is a suggested food benefit to delta smelt from the action. There were several problems with the study: 1) that study considered only four years. Four years is too few to draw statistically significant results. 2) Rather than consider two wet years where flows were augmented and two wet years where flow was not augmented, the study considered two wet years where flows were augmented (2017, 2019) and two dry years (2018, 2020). The comparison of wet years to dry years was not appropriate for the study purpose. 3) No consideration was given to the amount of food needed to sustain delta smelt. Areas upstream had sufficient and much better food availability and even with an increase, the food availability downstream was insufficient to sustain delta smelt, and therefore would provide no benefit to delta smelt. 4) Lastly, the conclusion of the study only reported on the number of food organisms, not their weight, while the study results showed that total weight of prey items (prey biomass) was less in wet years, and so the overall food supply for delta smelt was lower in wet years, in direct contrast to the reported conclusion. The science in the study was not rigorous and the conclusions were mis-stated.
The details of scientific studies, the methods they use, and the conclusions they draw are interrelated and can be complex. As a result, most readers look at the title and the abstract and have neither the willingness nor the time to assess the rigor of the science. This provides an opportunity for some groups to misrepresent science. In this case, it damages the credibility of certain environmental organizations, potentially affecting the credibility of all environmental organizations.
The wealth of scientific evidence, including the scientists in the US Fish and Wildlife Service, and findings from four quantitative models representing the best available science, found no benefit for the Fall X2 action. Thus, there is no threat to the fish by suspending the action. There is no evidence to suggest the additional water in some years has provided important benefits for the fish. Suspending the action was both responsible and defensible. The claims of the environmental organizations were baseless.
The wealth of scientific research now shows that the focus over the last 30 years on more flows for delta smelt has been misplaced. As a result, attention has been diverted away from what delta smelt needed most – more food. Had attention been on the real cause of decline during the last three decades, modeling suggests that delta smelt’s abundance might have increased. That misdirection, perhaps more than any other factor, has led to the near extinction of delta smelt.
There is a need for rigorous, unbiased science to advance good policy. Anything less can have severe consequences. The plight of delta smelt is one example.
