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Given that steelhead were the impetus for the interdisciplinary investigation that led to Rainfall to Groundwater, I haven’t written a lot about them on this site to date. There’s the Ecohydrological Economics page, What’s in it for steelhead & salmon? They were the fish mentioned in blog post 9. Rational Way to Recharge & Cold Flows for Fish. And there’s not an abundance of existing data to draw from, perhaps surprisingly if we really care about these salmonids.

One landscape scale study that indirectly hints at the applicability of the Rainfall to Groundwater (R2G) catchment uplands/ rangelands restoration approach for improving steelhead habitats is “Impact of environmental factors on fish distribution assessed in rangeland streams” (Thompson and colleagues 2006), published in California Agriculture, so freely available online. They summarize:

We sampled fish in pools located on tributaries of Cow Creek in the northern Sacramento Valley [Shasta County], and related fish distribution and habitat use to environmental factors across the 2003 agricultural growing season. This rangeland watershed experiences extensive livestock use, and many landowners divert stream water for pasture irrigation. Our goal was to provide landowners and managers with current baseline information about the conditions in which fish were found. Our results provide a basis for the development and comparison of irrigation best management practices that may improve conditions for native fish in rangeland streams.
(Thompson and colleagues 2006)

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They also note, “There is little specific information on the responses of fish in California rangeland streams to land-use practices.” My own recent literature searches suggest that remains the case more than a decade later.

Among Thompson and colleagues’ (2006) findings, most striking was the midsummer association of rainbow trout/ steelhead (Oncorhynchus mykiss) with the coolest pools, with pool depth being a secondary correlate.

. . . [T]he maximum daily temperature of pools occupied by trout was 12.86°F cooler than pools not occupied by trout. . . .

The cooler “trout refugia” pools also occurred at higher elevations. Some excerpts:

The increase in trout density in higher elevation pools may indicate that trout are moving upstream toward cooler waters, or out of riffles and into pools in search of depth (cover) or food. . . .


Pools that contained trout in midsummer contained only native fish species. Other pools contained a higher proportion of native species in spring and fall, when water temperatures were cooler.


Flows declined across the summer months, then began to increase in October (fig. 4). Flows were higher in pools with no midsummer trout, because these pools were farther downstream in the system where more tributaries, surface runoff and groundwater flow had joined the stream. This suggests that flow volume alone is not a good predictor of the presence of trout, and that other factors such as water temperature and dissolved oxygen should also be considered. In general, it is important to determine whether increased flows in lower pools reflects the return of potentially warm tailwater from irrigated pastures, a determination critical to BMP development and implementation. . . .


. . . If irrigation practices tend to cause stream water temperatures to increase, it may be possible to adjust agricultural water-use practices so that tailwater is no warmer than the stream water to which it is returned. It would then be possible to extend the length of the stream that is cool enough to be habitable for trout throughout the summer, and increase the minimum habitat area available.
(Thompson and colleagues 2006, emphases added)

Regrettably, the researchers apparently didn’t have comparative data on associated specific rangeland irrigation practices, nor on what percentage of summer irrigation waters may have ended up as runoff, i.e., the potentially warm tailwater.

Depending on the specific geology and soil types there, even excess irrigation water that infiltrates and percolates through the substrata as interflow (see below diagram) may have been warmed by high summer air temperatures. One might guess volcanic rock and soils in the vicinity might confer some relatively rapid preferential interflows to stream baseflows.

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Spatially correlating such factors with the fish data and soil/geological conditions should lend greater insight.

In any case, I appreciate their attention to such rangeland streams. Part of my own interest in rangeland streams from a fish standpoint has been because they tend to be less impacted by dams. If we can restore such sub-catchments/ watersheds on tributaries not obstructed by the dams, those rangeland tributaries may support the salmonid populations whose historical territories in more forested zones now lie behind dams.

My own last visit to that part of northern California was more than two decades ago so I don’t have a clear sense of the Cow Creek landscape. But the above panorama offers an overview and CalFire thankfully offered up the below images from the mid-August 2019 Cottage Fire to Wikimedia Commons.

CalFire notes the Cottage Fire location as “northeast of Anderson”, which puts it in the near vicinity (< 10 miles) of Thompson and colleagues’ (2006) nearest of sampling sites. So we get a sense of the late summer appearance of the unirrigated landscape in that region from the CalFrire photos.

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While I knew dairy cows and certain specialty livestock (alpacas, for one) in the Central Valley benefit from irrigated pasture, I was unaccustomed to seeing irrigated rangelands on the Central Coast uplands. So, after moving to the central Sierra, my eyes popped out when I first noticed some irrigated uplands cattle pastures outside Sonora, in Tuolumne County, on my regular route there for groceries. Since then I’ve seen them in some other parts of the Gold Country region and I marvel over it.

I knew nothing about the economics and/or water rights issues that support the practice, but considering this post piqued my curiosity. I’ve observed Canada Geese enjoying it, and would guess other wild species do as well, though one of the pastures I see regularly lies adjacent a large storage pond and the combination is doubtless what attracts the geese.

Despite the ever-green fodder, I’ve noticed the cattle nevertheless like to beat the heat in the shade of the remnant dispersed oak trees and just last week (pre-storm) I observed a group grazing the dry unirrigated hillocks adjacent the green zones within the same pasture. The green zones did appear rather mown down.

I did a quick search to learn a bit more about irrigated pastures in California. According to the UC Davis Rangelands Irrigated Pastureland Enhancement Program,

California’s irrigated pasturelands—including valley, foothill, and mountain meadow pastures— account for nearly 500,000 acres across the state, and ranks third among agricultural water users.

I learned that in Nevada and Yuba Counties irrigated pastures can support habitat for the California Black Rail (Laterallus jamaicensis coturniculus) (Richmond and colleagues 2010, 2012), while Shapero and colleagues (2017) cite other literature correlating irrigated pastures elsewhere with other wetland dependent wildlife species.

But Shapero and colleagues (2017) found that irrigated pastures had declined in Nevada County between 2005 and 2014 and state that “its economic returns are low”. More detail on the economics is apparently not readily available and is beyond the scope of this current post anyway.

If the practice of irrigated pastures is so widespread in Shasta County, we must guess it’s working economically for the ranchers. But it’s apparently not working so well for native fishes.

Consider a rough Rainfall to Groundwater scenario applied to the Cow Creek catchment.   The premise:

!.) Those with rights to Sacramento River water conclude their long-term interests will be best served by restoring detention functions on the Cow Creek catchment/ watershed.  [They come to realize that restoring detention functions cost-effectively prolongs the flow of winter runoff, making more water available later in the season when it’s most needed.]

2.) Those interests pay Cow Creek catchment ranchers to restore woody and other perennial native plants suited to the existing rangelands, especially oaks, according to a strategic plan they have collaboratively worked out to prioritize their efforts.

3.) Initially the existing irrigation systems could be adapted to support restoration plantings – a boon not available on many other California rangelands. But they would be used only to supplement seasonal precipitation (i.e., not in summer) and be phased out as the native vegetation becomes reestablished. Omitting summer irrigation ensures no potential for warm tailwaters to impact rsummer refugia for native fishes. Restored native plant root systems and their soil ecosystems facilitate detention of winter precipitation longer into summer and fall than did the functionally degraded nonnative annual grasslands.

4.) Ultimately, some of those water rights formerly used for summer irrigation might be sold via water markets, while some might be used for watering stock away from natural riparian zones and/or vernal pools.

5.) Sacramento River water interests continue to offer ongoing incentives for catchment management/ maintenance because it pays for itself in more timely water supply, along with providing for ecosystem needs.

6.) Ranchers employ perhaps novel livestock to help manage the restored catchments, switching from the large-framed grass-dependent cattle of northern European heritage to variants of “Criollo” cattle – adapted to North American environments through five hundred years of natural selection in Mexico. Such browsers help keep flammable vegetation in check and help maintain openings in the scrub and other perennial viegetation.

7.) The smaller-framed Criollo cattle cause less soil compaction and tend not to congregate in riparian zones, so their impacts on catchment functions are reduced relative to the former stock. The perennial vegetation and its litter helps decompose and filter animal wastes before they can impact water quality.

8.) Because they can browse the native vegetation throughout the season, the Criollo cattle need not be shipped out to midwest feedlots for fattening and can be marketed as specialty range-fed beef, in demand by locavores and other gourmets/ “foodies”.

9.) Because the native vegetation adapted to the Cow Creek catchment is regionally unique, the cattle raised start to finish on those lands adopt a regionally unique flavor – terroir. Ranchers on the Cow Creek catchment formalize a “livestock appellation” under which to market its beef and perhaps other livestock adapted to the restored native vegetation.

10.) Meanwhile, the rainbow trout/ steelhead and other native fishes find a much greater abundance of summer refugia, allowing for population expansion. More woody debris is increasingly provided by the restored catchments, as are abundant natural nutrients to feed aquatic ecosystems.

I could go on – perhaps restoration of catchment detention functions becomes such a widespread practice that dams (retention storage) become obsolete? Doesn’t hurt to envision, eh?

The acutely observant reader may have noticed my use of the plural “fishes” in the title and text of this post. That is intentional, inspired by Jonathon Balcombe, in his (2016) What a Fish Knows: The Inner Lives of Our Underwater Cousins. Amazingly, especially now that I’m wholly into it, that book had languished on my shelves since soon after its publication.

Balcombe makes the distinction regarding “fishes” right from the get-go, in the following footnoted statement from his Prologue.

We traditionally refer to anything from two to a trillion fish by the singular term “fish,” which lumps them together like rows of corn. I have come to favor the plural “fishes,” in recognition of the fact that these animals are individuals with personalities and relationships.
(Balcombe 2016)

Well, I’m down with that – so “fishes” it is from now on.



Balcombe, J. 2016. What a Fish Knows: The Inner Lives of Our Underwater Cousins. Scientific American/ Farrar, Straus and Giroux, New York.

Richmond, O. M. W., S. K. Chen, B. B. Risk, J. Tecklin, and S. R. Beissinger. 2010. California black rails depend on irrigation-fed wetlands in the Sierra Nevada foothills. California Agriculture 64:85-93.

Richmond, O. M. W., J. Tecklin, and S. R. Bessinger. 2012. Impact of cattle grazing on the occupancy of a cryptic, threatened rail. Ecological Applications 22:1655-1664.

Shapero, M., I. Dronova, and L. Macaulay. 2017. Implications of changing spatial dynamics of irrigated pasture, California’s third largest agricultural water use. Science of The Total Environment 605-606:445-453.

Thompson, L. C., L. Forero, Y. Sado, and K. W. Tate. 2006. Impact of environmental factors on fish distribution assessed in rangeland streams. California Agriculture 60:200-206.