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<br />21 <br /> <br />has been the second and the volume has vari,ously been reported as cubic <br />feet, cubic centimeters, or cubic meters. In any case the amountll are <br />abiireviated as "cu ft/sec. (cfs)", "cc/s", or "m/s". Therefore, II "second <br />foot" of water refers to a cubic foot of water passing a sinile p()int in <br />onesecond. The amount is often reported all "acre feet" which is the <br />amount of water covering one acre (43,560 square feet) to a depth of one <br />foot deep. A flow of one cfs per day equalll approximately two acre feet. <br /> <br />The United States Geological Survey is responsible for monitelring <br />established stream discharge gauging stations at key locations on <br />watersheds in each of the states (Figure 11). A plot of the discharge rate <br />or flow as a function of time is called a !!y'drograph. Time may be, shown in <br />minutes, hours, days, months, or other units, and discharge is generally <br />shown in cubic feet per second (cfs). The base flow is the discharge <br />during dry periods in summer and winter after surface runoff has ended and <br />bank storage has been depleted. The level of the water table regulates the <br />base flow of streams, except for those in the mountains. The base flow is <br />the minimum flow, and it influences the extent and types of animal <br />communities living in the stream. A hydrograph of the discharge in cubic <br />meters per second for a single stOI1ll event 1.s illustrated in Figure 12. <br />The period between the actual storm event and the peak stream flow' is <br />called the .!.!& !.!.!!. <br /> <br />I'lt'COlQi'._ <br /> <br />'~ <br /> <br />1iI0<kIOO"""I~Y"""I_ <br /> <br />F",..,"'iI,....___ <br /> <br />I <br /> <br /> <br />W.~''''.l,"..._1 <br /> <br />Usuu 11 <br />O'...r.m 01 . '&1'"'1 naUon. ""'WI"" relation of '....IIe!" in .he .,illi.. ~I <br />10 I.M mott_ (U_SG.S.) <br /> <br />Aver.ge daily natural streamflow for the North FOI'k of the South <br />Platte River at the Grant gauge is presented in Table 6.. Average daily <br />cubic feet per second and average monthly acre feet are compared for <br />purposes of monitoring stream flow to meet the needs of downstream <br />municipal, industrial, and irrigation requirements. When data simJllar to <br />that in Table 6 are plotted as discharge in cta venus time in months. it <br />dramatically illustrates the characteristic 8 or 9 months of low fllows and <br />the 3 or 4 1I0nths of high flows for a high elevation lIO'untain stre~lm <br />receivins considerable snowmelt water from near the COll,tinental Divide <br />(Figure 13). Figure 14 is an excellent example of the normal distribution <br />of discharge (runoff) for a number of U.S. r:lvers. The ordinate numbers <br />