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Research & The River

Almost a year ago an important document about a primary resource sustaining the Anderson Valley community was published with little local notice or comment. A report called Meeting Agricultural Water Needs In The Navarro River Watershed is the work of the University of California Cooperative Extension Service Mendocino County office research team of seven under the direction of Extension Advisor Glenn McCourty. It is 38 pages of densely packed information on water availability and watershed agricultural interests' usage and is accessible at

http://cemendocino.ucanr.edu/files/166809.pdf

Beginning in 2009, the Extension Service research team spent over three years in the field and back in their Mendocino County offices gathering and analyzing the data and creating the report summarizing what all of us living here in Anderson Valley need to understand about what the watershed contributes to our daily lives, domestic and commercial. Their findings identify and analyze and summarize with charts and tables virtually all irrigated farming uses of watershed provided water relative to its annual availability.

The article you are reading, written by a Deepend grapegrower of some 40 years experience, is a summary of what this reporter thought were the important highlights of the Survey's findings. It also claims to be the first in a series of four. A following report will include a description of how the research supporting it was carried out, along with my interpretation of what the findings tell us about the watershed's ability to support irrigation based agriculture now and another generation or so into the century. Two other articles will attempt to describe what further information the Watershed community should seek to construct a complete picture of its supply capability and usage today and for the foreseeable future; and to explore ways to engage Anderson Valley, ag and non ag residents, in identifying and gathering the information enabling us all to practice a sustainable and conservational use of the principle source of water for all of us living between Yorkville and Navarro.

 

Project Funding

The UC Agricultural Extension Services project was funded principally from the Mendocino County budget through the now defunct County Water Agency, with some financial and research support coming, I have heard, from a local chapter of Nature Conservancy. The Nature Conservancy continues to show interest in further work contributing to improving wild fish habitat and populations.

 

Key Findings:

• In 2009 Irrigated Agricultural Acreage in Anderson Valley totaled 3,124 acres. 89% of this acreage was winegrapes, 7% orchard crops (mostly apples), the rest was irrigated pasture or other horticultural crops, olives, etc.

• The study estimates that in 2009 total irrigated agricultural water CONSUMPTION was 1,825 acre feet (af). An acre foot of water is about 325,000 gallons. 678 af, 37% of total water usage was for vineyard frost protection, 558 af or 30% was for grapevine irrigation, 25% for orchard irrigation, 8% for irrigated pasture and other permanent crops.

• The Survey reports that as of 2012, there are 264 licensed and permitted water rights in the watershed with a “cumulative annual... maximum possible diversion amount” per year of 9635 acre feet, or about five times the 2009 irrigated agriculture consumption. “Water Rights” activity includes pumping water from the Navarro and its tributaries directly into irrigation systems, storing water in ponds drawn from the Navarro and its tributaries, and pond-stored water taken from the river and/or from winter rain runoff.

• The Study estimates “non-forested...suitable” land in the watershed available for “potential irrigated agricultural development” as approximately 2650 acres with a slope of 10% or less, another 2000 acres with a slope of less than 20%. If all of the additional potentially plantable acreage were in fact developed in the future, it would increase the irrigated agricultural acreage in Anderson Valley by two and a half times the currently farmed size, or to around 7,800 acres.

• The Survey's estimate of 2009 irrigation total usage in the watershed was 1,825 acre feet, 1.7% of the total 'discharge” calculated at the Navarro River Gauging Station on Hop Flat, 9 miles northwest of Navarro, five miles from the river mouth, the discharge being 106,971 af.

 

Usage Information Sources. 

Results of a direct grower “assessment” show 84% of the survey respondents' acreage was irrigated from offstream ponds, 13% from direct diversion of surface water, 3% was from wells. This part of the survey was based on responses from 14 irrigation using farmers of the more than 100 this writer thinks Anderson Valley's watershed supports. These fourteen represent 1,339 acres or 43% of the 2009 irrigated acreage. A later article will address in more detail both usage sources and “assessment” estimations and their accuracy and credibility.

 

Storage

The Survey reports 165 ponds and reservoirs in the Watershed with a combined surface area of approximately 140 acres. Not all the ponds identified are used for agriculture. This writer estimates the total storage capacity of identified ponds as 1,200 to 1,400 acre feet, or between two thirds and three quarters of the 2009 estimated agricultural usage. Storage capacity can be different from total usage/year from the pond source. A grower may, for example, refill from another source, a well or stream, during the course of the usage year, or may not use all of a pond's stored water.

• The whole Navarro River watershed comprises about 200,000 acres. Total average rainfall onto the watershed is about 700,000 acre feet, or 42"/year. As I noted earlier, in 2009, a very dry year, more or less 106,000 af, about 15% of the average annual rainfall, flowed out of the watershed to the Gauging Station volume measuring site at Hop Flat northwest of Navarro. Survey data shows that 2009 rainfall provided the fourth least “discharge” amount in the 61 years of recorded flows. The Survey doesn't address this issue, but your reporter estimates that the median annual flow at the Gauging Station is approximately 350,000 af or about half of annual watershed rainfall.

 

Other Features

The Survey also includes detailed, though not necessarily complete (next article will address) discussion with data tables on the following topics of importance to anyone wanting to understand what the watershed's capabilities and actual usage in fact are:

There is useful discussion of both the recorded Navarro River waterflow history dating back to 1950 when, I believe, the Gauging Station was installed and on the annual growth of “modern” irrigated agriculture in Anderson Valley since 1970.

There is also a very thorough complex, and hard for the layperson to follow discussion with tables showing for 2009 the acreage and estimated water usage/acre (p. 27) for various crop types. This part of the Survey also includes the seasonality of annual irrigation usage periods and demonstrates a division of major consumption between spring frost protection, when the river is near annual full flow, and fruit development irrigation in the July-October period, when the visible river flow declines dramatically.

A very important feature of the Report is an estimation of the sources of 2009 irrigation water usage between storage ponds fed by wells, drainage tile and rainfall run-off, ponds fed by direct pumping from the Navarro and its tributaries, and by direct pumping from the latter to irrigation systems. The data appears to report that about 16% is estimated as pumped directly from flowing streams, the rest being served by storage ponds. During the 2009 frost season The Survey reports estimating 90% of water used was taken from holding ponds. This writer discusses the term “estimation” in the next article.

The Survey also reports on field work done by the Extension Service research team in 2009 to study the “efficiency” of the irrigation systems of growers willing to participate in this project. This reporter was one of the 26 respondents supporting the research effort. My description of the work is partially based on recollection of a day in the field with the team. The efficiency measurement of my drip irrigated system, no frost protection, was done by actually measuring in sample blocs scattered throughout the vineyard the amount precise to the ounce of water applied relative to the best needs of the plant being irrigated: whether it got too little, stressing vines, trees or pasture, or too much, creating run off out of the planted area, possibly erosion, and whether the equipment was well maintained, no broken and leaking equipment or unequal applications of water to the plants in question.

This part of the Report also addresses in a general way the matter of evapotranspiration as a source of water loss from the watershed's. Your journalist won't describe the analytic details for this topic and will only remind us all that any surface water flowing or stored in the Navarro Watershed endures a degree of natural evaporation and loss of availability most dramatically during the course of Anderson Valley's summertime temperatures.

Finally the Report provides a fascinating set of tables describing by individual local watershed from Rancheria out Yorkville to Navarro village the non-forested land potentially available for agricultural development along with a discussion of estimated water consumption under various regimes of irrigated agricultural development in the future.

 

Conclusion

In my view the Navarro River Watershed Usage Survey couldn't have arrived on our doorstep at a more timely moment. The drought of the last couple of years, particularly since January, 2013, has been for this resident the most dramatic natural event in my 43 years here in the Valley, more intimidating than even the last record dry cycle in 1976-7. This current drought episode has been deeper than then, and with the growth in population AND consumption since the earlier times all of us living in and caring about the watershed, whether farmers or not, are increasingly aware of the importance of its role in our lives as well as the limits of its ability to perform it. Get the Survey and read it.

And as they used to say at the livestock auction: from this reporter “there's more to come.”

Navarro River Watershed Usage Survey: http://cemendocino.ucanr.edu/files/166809.pdf

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Acknowledgement: I asked some interested friends and neighbors and a member of the Report Research Team to review a working draft of the article for my Watershed Survey reporting's accuracy and interpretive credibility. Their comments have improved both elements of the article, but I am solely responsible for the way I describe and analyze the Survey.

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