Monday, December 3, 2012

Coho Reprieve – Scott Valley streams finally flow!

In recent days heavy, sustained rain has been falling across Northern California. At 11 AM on December 2nd, forty-eight hour rainfall totals in the Scott River Valley were 2.38” at Fort Jones and 2.79” at Callahan. As a result of the heavy rain, streams draining into the Scott River Valley – including the East and South Forks of Scott River - finally connected to the main Scott River on December 1.

This means that most Coho seeking to spawn in streams draining into Scott River will be able to reach prime spawning ground. KlamBlog has previously reported that Chinook Salmon were denied access to these spawning grounds as a result of a relatively dry fall combined with stream dewatering by some irrigators, including those using the Farmers Ditch in the Upper Scott Valley below Callahan.

Judging from USGS streamflow data  Scott Valley tributaries to Scott River probably briefly connected to the main river on November 22nd at the end of the last sustained rainfall period. However, streamflow dropped quickly at the end of those storms to well below the long-term average and the streams once again disconnected from the main river. 

Scott River Flows - USGS Gage - Nov. 26 - Dec. 3, 2012

Much of the relatively large run of Chinook salmon which ascended the Scott River in October was not able to access the highest quality spawning grounds in streams entering Scott Valley including (from the lower end of Scott Valley to the top at Callahan) Shakleford Creek, Kidder Creek, Patterson Creek, Etna Creek, French Creek, Sugar Creek, Wildcat Creek, East Fork and South Fork.

This year the Scott River in Scott Valley below Etna Creek did not go completely dry although flows below Etna became very low. As KlamBlog reported, however, the River did go dry below the Farmers Ditch in what is known as the "tailings section" of Scott Valley below Callahan. In dryer years, however, Scott River often goes dry below Fort Jones. When the rains do not return early enough, Chinook salmon can not even access spawning grounds in the main part of Scott Valley – much less in the tributaries.

Why the disconnect?

Irrigation interest in the Scott River Valley – and their supporters on the Siskiyou County Board of Supervisors – are fond of claiming that these streams disconnected from the River even before the coming of white Europeans and the onset of irrigation diversions.

There is some truth in that. The main streams enter Scott Valley from the western mountains. Past storms and floods have carried much sand, soil and gravel from these mountains and deposited the load in broad alluvial fans where the streams leave the mountains. It is probable that some of these streams went underground toward the end of the dry season in late summer and early fall when flows were lowest. However, it is clear from old journals and reports that the major streams – including Shakleford, Kidder, Etna and French Creeks as well as the East and South Forks - connected to Scott River year around. Even the smaller tributaries flowed for much longer periods during spring and early summer and returned sooner in the Fall.

So what factors account for the fact that Chinook salmon – which once spawned in all Scott River tributaries – now only make it to prime spawning grounds in the tributary creeks in wetter years?

Fortunately, there is high quality, peer reviewed science which has illuminated the factors influencing the dewatering of Scott River and its tributaries. Relative effects of climate and water use on base-flow trends in the lower Klamath Basin 
by Robert W. Van Kirk and Seth W. Naman looked at precipitation, snow pack and stream flow for the six Klamath River Basin streams – including the Scott and Salmon Rivers - for which long term precipitation, snow pack and stream flow data is available. Here is what they found:
  • Precipitation, snowpack and streamflow in all six streams has declined; regression analysis indicates that the climate became dryer beginning in 1977 – the year of the Great California Drought.
  • The dryer climate explains decreases in stream flow in five of the six streams. In the Scott River, however, changes in precipitation and snowpack explain less than 39% of the decrease in streamflow. Van Kirk and Naman attribute the rest of the decline in Scott River and flows primarily to a massive increase in groundwater pumping for irrigation.
  • Ground water made up less than 3% of total (irrigation) withdrawals in 1953 and more than 80% in 2001. Total annual withdrawal increased from 48 Mm3 in 1953 to an average of 103 Mm3 over the period 1988-2001, in close proportion to increase in irrigated area (62 Mm3 in 1953, average of 117 Mm2 over 1988-2001).”
Another reason Scott Valley streams go underground for so much of the year now is that they have been locked into fixed channels. Prior to the coming of white Europeans, the channel location of streams coming into Scott Valley from the west regularly changed within the broad alluvial fan area. Now, however, the channels are locked in place between diked banks. New gravel and rocks coming down the streams during major storms now collect in the channels – a process known as aggradation. Soon the channels are elevated above the surrounding lands making it much easier for the stream to go underground.

What about the uplands?

There has been much speculation that changes in the uplands surrounding Scott Valley may also play a role in the decrease in Scott River and tributary “base flows” - that is, in reduced late summer and early fall flows at the end of the dry period. Some locals advocate removing brush and juniper trees from the east (dryer) side of Scott Valley and aggressive logging on the west (wetter) side as a means to increase base flow.

While some models have been used to suggest that base flows can be increased through removing vegetation including “thinning” forests, the preponderance of available science indicates that any gain in baseflow resulting from logging will be short lived. Clearcutting, for example, will increase baseflow yield in the short term. Within 3-5 years, however, baseflow is reduced to below pre-logging levels as small trees and brush sprout, grow and consume more water.

Managing vegetation intensely enough to increase water yield, moreover, is likely to also vastly increased erosion and sediment delivery to streams. With many streams – including the Scott River – already suffering from excessive sediment (primarily resulting from logging roads and clearcuts) – managing vegetation intensely enough to increase water yield is a non-starter.

Long-term paired watershed studies on the HJ Andrews experimental forest in Oregon, suggest that logging and road building increase flood flows and decrease base flows. Logging typically involves exposing and compacting soil which reduces rainfall infiltration and the amount of water that can be stored in the soil. This suggests that protection of forests in wilderness is the best way to maximize base flows in streams. 

That is exactly what can be seen in the Klamath Mountains. During late summer-early fall base flow periods the Wooley Creek drainage - which is almost entirely within the Marble Mountain Wilderness sustains flows which are roughly equal to the more developed South Fork of the Salmon River. The South Fork Salmon River watershed contains almost twice the drainage area as compared to Wooley Creek.

Wooley Creek enters the Salmon River 

Van Kirk and Naman suggest testing this conclusion in the Klamath Mountains by gaging flows on those watersheds which are largely roadless and unmanaged. They suggest Wooley Creek (which forms the heart of the Marble Mountain Wilderness) and the North Fork of the Trinity River (in the Trinity Alps Wilderness) as the best streams to gage in order to confirm that wilderness protection also maximizes stream baseflow. So far, however, neither the Forest Service nor local restoration councils have implemented that recommendation. Because of the agency's pro-logging bias, Forest Service managers may not be eager to collect data which are likely to confirm that wilderness is the best management if the objective is to maximize stream baseflow.

Climate change

Climate models suggest that – while precipitation may increase in the Klamath Mountains as a result of human induced climate change – temperature will also increase. As a result, while snow pack may increase at higher elevations (e.g. above 10,000 feet on Mt. Shasta), at lower elevations - like those in the Klamath Mountains - snow pack will likely decrease as a result of Climate Change. As Van Kirk and Naman have pointed out, that change may already be underway.

In the Scott River Valley it has long been observed by locals that streamflow drops dramatically when snowpack in the mountains above the Valley is gone. This typically occurs between early July and early August depending on the accumulated depth of the snowpack. This suggests that Scott River and tributary flows may already be suffering from the double whammy of increased irrigation water use and decreased snowpack. If climate change continues to reduce Klamath Mountain snowpack the extirpation of Chinook and Coho salmon from the Scott River Valley and above becomes more and more likely.

Human change

As snowpack and streamflow decline the fate of Scott River Salmon will be increasingly in the hands of those humans who manage Scott River Basin land and water. Will the state agencies responsible for enforcing California water and fish protection laws begin enforcing provisions of those laws designed to protect streamflow? Will private outfits like the Scott River Water Trust receive the massive increase in funding needed to lease the water fish need year after year? Will management of uplands change sufficiently to make a dent – one way or the other – on Scott River base flows? Will irrigators voluntarily reduce water use and will livestock operators stop diverting full ditches to supply stockwater and instead rely on small, more efficient wells? Will environmental and fishing groups be successful in challenging ground water pumping and excessive irrigation diversions?

A “yes” answers to any of those questions appears unlikely; continued dewatering of the Scott River appears most likely. That can only mean the likely extirpation of Salmon from most of the Scott River.

As Jim Denny pointed out in the mid-1970s, the decline of Scott River Salmon has been going on for a long time. Early white Europeans observed that there were so many rotting salmon in the rivers that in the fall they stunk and rendered the rivers unfit to drink. The Gold Rush had a big impact on salmon but after the miners left salmon runs recovered. Then came logging and agriculture. First Spring Chinook were extirpated; then Coho became scarce. Now Chinook are not making it to prime spawning grounds in and above Scott Valley during dry years and Coho are also sometimes denied access to spawning grounds when fall rains are delayed.

In modern times the decline has not been dramatic but it is continual and appears inexorable. What we now call a “good run” of salmon would have been seen as a disastrous run failure in the old days. Total extirpation becomes more likely each year.

Jim Denny called it “The death of a lady”. Poet T.S. Elliot had another way of saying it:
           This is the way the world ends
           This is the way the world ends
           This is the way the world ends
           Not with a bang but a whimper.

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