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<br />period will plot as a straight line so long as the data are <br /> <br /> <br />proportional; the slope of the line will represent the <br /> <br /> <br />constant of proportionally between quantities.~ A break in <br /> <br />,,' <br /> <br />slope of a doublemass diagram indicates a change in the <br /> <br /> <br />relat~onship of the two quantities and the difference in the <br /> <br /> <br />slopes before and after the break indicate the magnitude of <br /> <br /> <br />the change. As previously noted QY Colorado in its first <br /> <br />report, mass analyses do not provide any causative informa- <br /> <br />tion: <br /> <br />.. (I)t should be emphasized that while single <br />and double mass curves are useful in detecting <br />trends and,checking the consistency of streamflow <br />data, they do not explain the reasons for trends <br />or changes in the relationship between two sets of <br />streamflow data. Such changes may be due to the <br />inherent variability of hydrologic data, changes <br />in record-keeping methods, or many other factors. <br />Likewise, the mere fact that there is no change in <br />the relationship between two sets of streamflow <br />data, does not necessarily mean that no real <br />change in the relationship has occurred or that <br />there is a causal connection between the two sets <br />of data. Id., p. 1. <br /> <br />The mass diagrams prepared for the VIII (H) investi- <br /> <br />gation included several single and double mass diagrams of <br /> <br />streamflow data for the Arkansas River Basin. Streamflow <br /> <br />records at several upstream and downstream ~ocations were <br /> <br />compared by use of double mass diagrams. By comparing <br /> <br />'inflow and outflow of a river basin, a determination can be <br /> <br />:made if net streamflow accretions or depletions have changed <br /> <br />, , h t' <br />jWJ.t J.me. <br />I <br />I <br />.', ,I the outflow <br /> <br />",~ .' 'I ' ' <br />iwill bear a <br /> <br />Providing that the uses of water do not change, <br />as measured at the downstream gaging station <br />fixed relationship with the measured inflow. <br /> <br />Generally, it is not possible to measure all inflows so an <br /> <br />"12- <br /> <br />. <br /> <br />'" .,.,;;, <br />