Press "Enter" to skip to content

Research & The River (Part 2)

These articles were begun in early February this year in an atmosphere of deep anxiety from the driest thirteen months this reporter had ever seen in 43 years in Anderson Valley. Since then, at least at my station, the gods have smiled, over seventeen and a half inches of rain at our end of the Valley after early February have revived grasslands, plants and trees and hopefully local wells, springs and ponds enough I hope to get through the summer. The River last week looked alive though not vibrant as it should be in April, at the mouth barely open through Navarro-by-the-Sea beach, the flow a meander at River Rest bridge.

The Survey's Research Methods & Credibility

This writer is a confessed data addict, enjoys gathering and analyzing quantitative information about his farm and its performance, makes overly obsessive business plans and budgets for it, keeps temperature, rainfall and bear sightings records. He often spends evenings at the dinner table poring over weather and crop, business financial and football and baseball numbers, among other things, and thinks there is value in thoroughly assembled and carefully analyzed quantitative information, particularly when it comes to understanding something as complex as the Navarro River watershed, its resources and their use.

In general I consider the design and findings of the MEETING AGRICULTURAL WATER NEEDS IN THE NAVARRO RIVER WATERSHED report (http://ce,endocino.ucanr.edu/files/166809.pdf) of very high quality and integrity and of great value to my agenda, understanding the present usage and future health and security of the river's resources and its ability to support the way I want to live in Anderson Valley. But there is an analytic element of the Report which I want each interested reader to be aware of as you consider its observations and findings and their use for you.

As you look at the numerical data my previous article highlighted in the 9 introductory bullets describing the Survey's important findings, notice they are generally based on a complete count or census of these features. That is, items like acreage of planted vines and trees, number of storage ponds, annual rainfall or waterflow at the Hop Flat gauging station are almost fully accounted for, either using aerial photography or actual measuring instruments.

Other findings, however, are based on methods of deduction and computation which are generally less accurate than a complete count of a particular feature of interest. This writer's estimation of watershed pond storage capacity reported in Bullet #7 last week, for example, I deduced by combining the surface acreage count with an assumption that each pond is in maximum compliance with state regulation about its total size including depth. This deductive apparatus yields what I want to be a highest likely storage figure, 1200-1400 af. This calculation I assume contains some degree of error. I don't know the actual depth of any of the ponds counted, but I want my depth error number to be on the side of over- rather than underestimating the stored water capacity in the watershed. Data gatherers and researchers call this approach a "conservative" one.

Earlier under Bullet #6 I reported on a third approach the Report uses to gather important data about resource uses: the Watershed Survey sampling a portion of the whole population of the watershed's irrigation dependent farmers . This approach researchers use when a complete count or census of all "subjects of interest" is not possible or too expensive. It also needs to be recognized as less accurate than the full count of the information being sought. But when it is employed with care by the researcher and with cautious understanding by the interested reader, a sampled survey can be an extremely valuable tool for estimating information data points not otherwise findable using a complete count.

An example of the sampling approach this article reports on earlier describes local farmer annual water usage employing information from only 14 respondents out of, say, 120 actual commercial irrigated farms in the watershed, a small proportion of the whole grower community. But the good news, for me at any rate, is that those fourteen who completed the questionnaire the Report describes ranged in size from 1 to 600 acres and represent almost half of the irrigated acreage in the Valley, a large enough proportion of the total irrigating farmer population to represent, with some degree of inaccuracy or error, the usage pattern for the whole valley.

The reader will hear more about sampling and research reliability in a later article. What's important at the moment is to think that, if a full tabulation of the activity of interest isn't possible, I claim this sampling technique is a very valuable substitute data gathering and analysis tool. And, to repeat, it must be used with care by the researcher and with understanding and caution by the interested consumer of any information created this way. In the case of the water usage data based on the 14 respondent, 1339 acre sample, we must understand that whatever usage numbers it generates, they are simply estimates, almost never the actual number, and the important part of the exercise of generating or using the number includes estimating the extent of inaccuracy in the calculation.*

I also want to mention a valuable and missing activity datapoint the Report was unable to uncover because of limitations to the survey sampling research method it employs. This farmer/writer would like to know what proportion of the 2009 total irrigating farmer water usage, the 1848 af, was drawn from exclusively from the Navarro River and tributaries, how much was taken from storage ponds filled only from sheeting storm run-off, drainage tile buried in vineyards and orchards, and from wells.

Conclusion

This reporter trusts the integrity of the Navarro Watershed Report and has found it of enormous value, in ways I'll discuss later, for his understanding of how this fragile ecosystem, so daily and influentially shaping the texture of his life here in the Valley, works. I also invite all of us to get a copy of the Report and see if it is as useful as I claim it is for what I think we all need to understand about the present and future of the resources it provides us all and their contribution to Anderson Valley's ecohealth.

Apology: I wanted make this article dedicated to endorsing the Watershed Usage Survey simpler and more to the point and came up short. Consider though my conviction that the design and quality of the research behind it stands as a valuable model for pursuing the topic of my next piece, I hope a more entertaining reporting effort on Research and the Navarro. There is more, I propose much more about water usage in Anderson Valley we need to be informed about than just the agricultural areas the Survey covers, and to pursue that agenda is likely going to take the interest, concern and action of the local community as a whole to get to that next level of informedness (deliberately coined word) I think we need to achieve. Next article will describe what I believe to be the usages and availability information we need to search for to get there.

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

Acknowledgement: I asked some interested friends and neighbors to review an article draft for the accuracy and interpretive credibility of my reporting on the Watershed Survey. Their comments have improved both elements of my article, but I am solely responsible for the way I describe and analyze the Survey.

Footnote 

* To illustrate the technique, let's suppose the 2009 total ag irrigation consumption figure, 1848 acre feet, is based on sampling techniques and is in error by 20%, plus or minus, I believe a very high "margin of error" for the sample. Does that error in any environmentally significant way change our understanding of what proportion of water available that year is actually being used, even in a river low flow year like '09? A 20% water usage estimation error range based on sampling computes to either 1500 or 2,200 af of ag usage that year. These sampled estimates would describe 2009 usage as either 1.4 or 2.1% of the annual "discharge" or flow at the Hop Flat Gauging Station. At this analytic instant the credibility question becomes "does the difference in any of the estimated usage proportions, 1.4, 1.7 or 2.1% influence in any significant way our concern for the impact of any of these usage amounts would have on the Watershed's condition as a supportive ecosystem for human and for other habitats? What if the estimation were 100% error, or 50%? Or 10%, what I am guessing the "error" likely is using the Survey's sampling procedures.

The point I am making, and I regret not being able to do it more simply, is that the information the Watershed Needs Report is not entirely precise in all of its specific features or datapoints, particularly when sampling techniques are used, but close enough to be of great value to its readers wanting to understand more usefully the Watershed and its condition. And as I said earlier, it takes care by both the creator and the consumer of the document to get the most value from it, a challenging proposition when trying to understand something as important, complex and controversial as this critical resource motivating our Valley.

Be First to Comment

Leave a Reply

Your email address will not be published.

-