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<br />ro <br />oi-"" <br />.'.. <br />""-..J ;, <br /> <br />reduction in the yields of cotton, sugar beets, and Wheat When drainwater of <br />3000 mg/L salt has been substituted for 50 to 75 percent of the irrigation <br />water. The lysimeter study described in the 1983 Annual Report is underway at <br />Riverside to simulate conditions at the Imperial Valley test site. Another <br />lysimeter study has been initiated in the San'Joaqui~ Valley for testing a <br />computer DlO,del for making r;eneral' predictions of long term effects of \Ising <br />brackish waters 'for irrigation on soil' and water properties. This study is in <br />the data collection and computer programming stages. Computer mapping <br />progrBms and strategies have been developed for both mini and microcomputer' <br />graphic systemiltoarialyzeandt1lustrat.e complex interrelated geographic <br />information system data bases so as,to'delineate a~eas of potentially <br />, . excessive salinity development' in 'irrigation .projects. . Overlay'maps were <br />prepared for a 350 square mile' section of the Wellton-Hohawk Irrigation <br />District using data taken from 1968't~1973. The predicted salination <br />potentials for the area agreed wel~ with ,salinity traverse data Collected in <br />1973. Development of an expert system ("artificial intelligence") for <br />'salinity management is being ~onsidered subject to obtaining the neCessary <br />cOmputer equipment at the U.S. Salinity Laboratory. The system will'identify <br />the type and cause of the salinity problem under consideration, identify <br />appropriate actions or management practices to improve' the situation and <br />project and evaluate consequences and long term effects' of alternative <br />management practices. ' <br /> <br />Preliminary results of the'ongoirig stable isotope study'in the Grand Valley <br />indicate that the relative quantities of local groundwater Which originate <br />from Colorado River water, local precipitation and lateral flow from <br />'nonirrigated areas cari be' determined. About 1/3 of t.he wells sampled were <br />concluded to contain water of non~Colorado Riv,er origin. Estimates of the <br />'relative contribution of these two,lJources of water to, Colorado River ,return <br />flow will be made; Separation of deep perColation and canal seepage losses <br />using stable isotopes is still understudy and requires further research. <br /> <br />U.S. Water Conservation Laboratory <br /> <br />, , <br />Bngineers at phoElni,c',Arizonil initiilt~d cooperative studies: with the ImPerial <br />and Wellton-Hohawk Irrigation and Drainage Districts 'In ,the Lowei' Colorado <br />River Basin to intensively monitor canal responses to district operations. <br />The monitoring programs will provide a data base for iltudyingopen chatinel <br />water delivery 'responses and the interactions between various hydraulic and <br />management inputs. Several canals in each district 'will be included in' the <br />study. He!,-suring structure construction and instrument installation will <br />begin in 1985. <br /> <br />The flow monitoring equipment employed as part of the irrigation'water <br />delivery research'project must be' accurate, easily installed and maintained, <br />' and inexpensive (less than $1,000 per measuring site). Engineers at Phoenix <br />surveyed a large portion of the commercially available flow monitoring <br />equipment and found it far too costly. They were not simple to install, <br /> <br />-20- <br /> <br />