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<br />.\ <br /> <br />. <br /> <br />(5) salt pickup; (6) user function (irrigation, munic'ipal and industrial <br />(MAd), etc.); (7) state; (8) node, sequence point, user number; and (9) <br />node and sequence number for :return Clow location. <br />An important feature of SMDID is the handling of withdrawal and <br />depletion data as a step function or a linear trend function depending on <br />a flag extended by the user. For example. if data are enterc.d '[or 1970 <br />and 1980. the intervening years would use tl).e 1970 va.lue and jump to <br />the 1980 value in J 980 if the step function flag is set. Jf the linear <br />function nag is set, the \970 value would be incremented each year in <br />a linear fashion until it reached the 19&0 value. <br />Another capability of SMDID is summarizing demand information <br />into various report-type forms. Five di({erent report forms can be <br />produced at the option of the user. These are swnmarized as follows: <br />1. Shows information on a biennial basis at the user level with <br />accumulated values shown at the demand sequence point. <br />2. Shows i~formation by function for nine functions, (irrigation. <br />M&I. fish, etc.) for e.ach node. Data are shown for the fiut and last <br />year and each decade' in between. <br />3. Shows information by state, upper and lower subbasins. and' <br />combined basin totals" <br /> <br />4. Shows information by node and function for the first and last <br />year and, intervening decades for each individual state. <br />5. Shows information by state and function for the first and -last <br />year and intervening decades tor the two suhQasins and total basin. <br /> <br />Hydrolo~y Input <br /> <br />Hydrology inputs to the simulation model are of two forms: (l) <br />Flows and salinities at major rim stations around the periphery of the <br />basin: and (2) intervening Hows and salinities between the rim stations <br />and major downstream stations. Duwnstream Hows and salinities are <br />calculated by adding intervening values to rim station valuell. The <br />intervening v,dueti may be either positive or negat.ive. <br /> <br />148 <br /> <br />-.... <br /> <br />Hydrology input data are prepared separately and stored on a <br />disk file in the computer, then read from the disk and used-in the simu- <br />lation model computations. The hydrology base presently used in the <br />model is 'synthetically generated with a separate program (GENHYD). <br />This progr.am uses statistics developed from historic data with appro- <br />priate adjustments to the statisticB to bring them to the 1970 depletion <br />level. The purpose of using synthetic hydrology was to allow model <br />ope,ration on a large number of hydrologic traces. thereby testing a <br />wide range of now conditions. The model v..-ill also accept historic <br />flows or modified historic flows or virgin flows 80 long as rim and <br />intervening flows are prepared on the proper node setup and coordinated <br />with the base level of demand data. <br />The philosophy behind the synthetic hydrology approach used in <br />this applica'tion is to define historical strea'mflow characte rislics as <br />.,1 <br />completely as possible with cyclical and regressive mathematical re- <br />lationships. The remaining unexplained or random part of t.he stream- <br />flow variation is treated with probability concepts. <br />Statistics needed for each rim or intervening flow input to be <br />synthetically generated are as Iollows: (1) Monthly means; (2) monthly <br />standard deviations; (3) coefficient lor Markov model; (4) coefIicients <br />for polynomial fit of frequency distribution oC residuals; and (5) re- <br />gression coefficients between il~ws at this location a.nd flows at other <br />locations. <br /> <br />These statistics are obtained through analysis of historic data. <br />with proper regard to changes in streamflow charact.eristics due to <br />development in the basin. A separate set of computer programs for <br />data analysis are used to analyze the historic data and obtain the nec- <br />essary information for generation of synthetic flows. <br />A detailed discussion 01 the data analysis procedures and synthetic <br />generation procedure is given in the report IIApplication oI Stochastie <br />hydrology to Simulate Streamflow and Salinity in the Colorado RiveI', It <br />by' Willia~ L. Lane and Albert E. Gibbs, May 1975 (2). <br /> <br />149 <br />