|
Become a friend of
the Klamath Bucket
Brigade
Send
Donations Here
All donations are tax
deductible
|
|
This Website is Dedicated to
Alvin Alexander Cheyne
January
10, 1921 - June 17, 2005
|
GovTrack.us is an independent tool to help the public
research and track the activities in the U.S. Congress, promoting
government transparency and civic education through novel uses of
technology.
|
|
Scott River: A recent regional fisheries column has
once again dragged out the old myths about the impact of
agricultural irrigation on the
Scott
River. Here are the facts.
http://users.sisqtel.net/armstrng/facts_about_the_scott_river.htm
As a tributary, the Scott River
provides only about 4% of the full natural annual flow
to the Klamath River. According to the Siskiyou Co. Annual Crop
Report, the
Scott
Valley experiences 22
inches of annual precipitation, (30 inches of snowfall.)
This can vary widely with the east side averaging 12-15
inches and the southern mountains receiving as much as
60-80 inches. The Scott River has no dams or reservoirs.
Historically, there was storage of cool water in 28 high
mountain lakes located on the
Klamath
National Forest. As many of
these are now located in Wilderness, they have fallen
into disrepair as functional storage structures. With
292 acres of surface, one foot of additional water
storage in these lakes could provide 5 cfs of instream
flow for a 30 day period in the summer. Storage for
summer flows in the Scott is primarily in the form of
natural snowpack. Snow can hold the water into late
spring when it melts to feed the streams.
Summer and fall
flows in the Scott vary from year to year, but are
largely controlled by the precipitation and snowpack of
the prior 12 months. (Drake, Tate and Carlson) From
1951-1998, there has been a decrease in the water
content of the snowpack in the area, particularly in the
western mountains. There has been a correlating decline
in fall river
flows over time.
The number of irrigated acres in Scott
valley has not changed substantially since 1950. (It was
34,100 acres in 1988 and 31,800 in 2000. The total
watershed is 520,968 acres, so irrigated agriculture
represents only 6% of the land.) Methods of irrigation,
(flood, wheel lines, pivot wheels,) have changed over
the years. In 1968, when water was more commonly
diverted for flood irrigation, 86% of irrigation was
through diversion of surface water, 2% groundwater and
12% mixed. In 2000, 48% was surface water, 45%
groundwater and 7% mixed.
Understanding the affects of
irrigation on flows is complex. Flood irrigation diverts
water directly from the stream, Other methods rely on
water pumped from the wells. Summer in Scott Valley can see ambient air temperatures in
the 90-100 degree F. Different methods of irrigation can
affect the amount of water consumed through evaporation,
plant transpiration and how much is returned to the soil
to feed subsurface flow and to recharge the aquifer. For
instance, pivot wheels are thought by the state of CA to
be the most efficient method of delivering irrigation
water. They can have a high evaporation rate, while less
efficient flood irrigation returns water not directly
consumed in evapotranspiration to the streams as
tailwater. Groundwater use, although not taking water
directly from the stream, can intercept subsurface
flows.
Photos are often cited as
documentation that irrigators are “sucking the river
dry.” In many areas of the valley, heavy gravel
sedimentation has raised the bed of the tributaries
above that of the mainstem Scott. In some areas,
historic mining has caused build up of gravels. In
Kidder Creek, an historic fire upstream cause mass
erosion resulting in gravel deposits. In such cases,
water passing through seeks its own level. The river
will flow through the gravels where it has accumulated
and resurfaces on the other side.
In many areas of the
State “conjunctive use” is the method of water storage.
This is where water is injected or percolated down into
the ground in concentration in order to recharge the
aquifer as a storage receptacle. According to a
presentation by Dr. Thomas Harter, the average annual
discharge in the Scott Valley watershed is 615,000 acre feet of
water. This is more than the groundwater basin can hold
(400,000 acre ft. capacity– U.S. Geological Survey.) Of
this, the Department of Water Resources has estimated
that agriculture uses only 70-90,000 acre ft. annually.
In general, any groundwater loss is recharged within a
year. It is reasonable to expect better system responses
with a more sophisticated understanding of the
groundwater in Scott Valley, renewed use of the historic
mountain lakes, and downstream movement of some of the
gravel build-up.
Scott Valley farmers and ranchers have been
working on salmon “restoration” and conservation
projects for decades. The Northern California Coastal
Coho Salmon is listed both on the federal and the State
level as a “threatened species.” Preliminary Dept. of
Fish and Game Spawning Run Estimates for coho from
2006/07 - 2009/10 illustrate that run counts in Scott Valley are, by far, among the highest in
the State. Our farmers and ranchers are obviously doing
something right.
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
NOTE: In accordance with Title 17 U.S.C. section
107, any copyrighted
material herein is distributed without profit or
payment to those who have
expressed a prior interest in receiving this
information for non-profit
research and educational purposes only. For more
information go to:
http://www.law.cornell.edu/uscode/17/107.shtml
|
