Laserfiche WebLink
<br />weighted discharge. When X=O.O, the equation reduces to S=KO, indicating that storage <br />is only a function of outflow, which is equivalent to level-pool reservoir routing with storage <br />as a linear function of outflow. When X=0.5, equal weight is given to inflow and outflow, <br />and the condition is I~quivalent to a uniformly progressive wave that does not attenuate. <br />Thus, '0.0' and '0.5" are limits on the value of X, and within this range the value of X <br />determines the degme of attenuation of the flood wave as it passes through the routing <br />reach. A value of 'D.O' produces maximum attenuation, and '0.5' produces pure <br />translation with no attenuation. <br /> <br />The Muskingum routing equation is obtained by combing equation 9.15 with the <br />continuity equation (SI.11), and solving for 0 2' <br /> <br />02=G ,12+C 21,+C 30, <br /> <br />(9) <br /> <br />The subscripts 1 and 2 in this equation indicate the beginning and end, <br />respectively, of a timE! interval "I. The routing coefficients C " C 2' and C 3 are defined in <br />terms of "t, K, and X. <br /> <br />C , = "t - 210; <br />2K(1-X)+"t <br /> <br />(10) <br /> <br />C 2 = "t + 21C~ <br />2K(1-X)+.o.t <br /> <br />(11) <br /> <br />C 3 =2K(1-Xl-.~ <br />2K(1-X)+.o.t <br /> <br />(12) <br /> <br />Given8n inflow hydmgraph, 8 selected computation interval "I, and estimates for the <br />parameters K and X,lhe outflow hydrograph can be calculated. <br /> <br />3.2. DETERMINATION OF MUSKlNGUM K AND X. In a gaged situation the <br />Muskingum K and X parameters can be calculated from observed inflow and outflow <br />hydrographs. The travel time, K, can be estimated as the interval between similar points <br />on the inflow and outflow hydrographs. The travel time of the routing reach can be <br />calculated as the elaplled time between centroid of areas of the two hydrographs, between <br />the hydrograph peaks, or between midpoints of the rising limbs. After K has been <br />estimated, a value of X can be obtained through trail and error. Assume a value for X, and <br />then route the inflow hydrograph with these parameters. Compare the routed hydrograph <br />with the observed outflow hydrograph. Make adjustments to X in order to obtain the <br />desired fit. Adjustments to the original estimate of K may also be necessary to obtain the <br />best overall fit between computed and observed hydrographs. <br /> <br />In an ungaged situation a value for K can be estimated as the travel time of the <br />flood wave through the routing reach. The flood wave velocity (Vw) is greater than the <br />average velocity at a ~liven cross section, for a given discharge. The flood wave velocity <br />can be estimated by a number of different techniques: <br /> <br />Colorado Flood <br />Hydrology Manual <br /> <br />78.6 <br /> <br />~ <br />