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0017DO 11. Miscellaneous Discussions 11.1 Trended Demands Demands in the CRSS,i.e., withdrawals and depletions, may be "untrended" or they may be "trended." Untrended demands are held constant from year to year; trended demands vary over time. In the demand data base, trended demands are specified as either (1) linearly trended, or (2) stepped. Linearly trended demands are those in which the annual amount increases or decreases in a linear manner, i.e., a uniform amount each year, until a specified value is reached in some specified year. An example of such a demand would be a large irrigation project in which the rate of devel- opment is fairly uniform over a number of years until full development is reached. Stepped demands are those in which the amount remains constant for a number of years until it is "stepped" up or down by some specified amount in some specified year. An example of such a demand would be a large thermal powerplant in which each unit would consume a relatively large block of water, and several years would be required to bring addi- tional units on-line. ~j fl .1 I I j Demands can be combinations of these three types. For example, a demand could follow a pattern such as this: Withdrawal Year Demand type amount Change each year 1985 20,000 Li nearly trended +1,000 1990 25,000 Linearly trended +2,000 1995 35,000 Linearly trended +1,000 2000 40,000 Stepped (in year 2010) 0 2010 50,000 Stepped (in year 2020) 0 2020 60,000 Untrended 0 2040 60,000 ~ I, Demands are specified in the demand data base as being either linearly trended or stepped. When the demand data generation program (SMDID) creates the demand data input file to the CRSM, it converts all demands to linearly trended demands. In other words, stepped and untrended demands become linearly trended demands with zero slopes, i.e., a uni- form change from year to year of zero. I , i i 49