Laserfiche WebLink
<br />Comments to SWSI, November 3t 2003t by John Wiener <br /> <br />28 <br /> <br />Does this exampfe define the problem? If notr can it be corrected or repaired? If it doest then <br />the approach which seems most useful right now is a meeting of the right people, to work on how <br />and under what circumstances the kind of Uc10se enough-- estimations described can be <br />produced~ For examprst are there georogical [imitations:; such that Plains aHuvial river valJeys <br />could use an approach that would not work weU enough in montane environments~ or vice versa? <br />Are soil conditions criticaf, or simpfy a factor that has to be taken into account? And can NRCS <br />maps suffice, or should there be some program for competent engineers to make measures <br />which would suffice? And so on.~4 f envision this, if it can be done) to be a sort of very <br />transparent expert system applying the necessary terms and information to make useable <br />estimations to begin experiments with new management techniques. <br /> <br />Additional features of the problem: What are the variables? <br /> <br />FortunatelYt there are a small number of changes in technology that may be sufficiently common <br />to warrant consideration. Butt are there a relatively small number of other important features to <br />make this feasibre? Can the slope, soUt depth of horjzons] and other factors be treated in simple <br />enough form to make adequate estimations achievable with the needed speed and low cost? Orf <br />are there some conditions in which these estimations can be made~ and others in which they <br />should not be used? <br /> <br />From a different perspeotive, there are various conditions identified in materials such as those <br />from the Cooperative Extension Service, on how to identify best management practices (BMPs) <br />for irrigation for a given field (e.g4 Waskom 1994)r These variables may be important for the <br />problem at hand. <br /> <br />They include: <br /> <br />Soil and crop properties: <br />1. Water hording capacity of different soil textures (sometimes called field capacity; measure <br />usuaUy by inches of water per foot of soil); additionally~ depth to different soil horizons may be <br />important. <br /> <br />2~ Maximum rooting depths of different crops. <br /> <br />3. Approximate efficiency of the various irrigation application methods (for BMP considerationst <br />mean percentages of technologies have been described as: <br />· furrow -- 40% <br />· surge - 60% <br />· sprin kler - 75% <br />· drip - 900/0 <br /> <br />These are means for rough guidance, subject to site and particular technology features. <br /> <br />4. The total seasonal crop water use is also important for selection of irrigation technoJogYt and <br />should be relevant to estimation of the consumptive use from a given combination of choices and <br />place4 <br /> <br />There are aJso relatively few changes in irrigation technology that make sense and increase water <br />delivery efficiency (Smith at a11996; CPlA, various). They include: <br /> <br />Structural changes to irrigation technology: <br />1 4 ditch to pipe <br />1. ditch to Ijned pipe (significantly different from pipe?) <br />