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<br />-.-l <br />t.O <br />L. ") <br />o <br /> <br />.- <br /> <br />. <br /> <br />. <br /> <br />---; <br /> <br />,'--, <br /> <br />CHAPTER II <br /> <br />GRAND VALLEY RIVER BUDGET <br /> <br />Unaccounted Flow <br /> <br />The salt inputs and outputs can be adjusted in light of the water <br /> <br />budget's unaccounted flow. The unaccounted flow is defined as the amount <br /> <br />that the inflows exceed the out flows. Due to measurement and IDOdeling <br /> <br />errors, the total water inflow does not balance the total water outflows. <br /> <br />The unaccounted flow significant 1y affects the salt pickup e,stimates, because <br /> <br />the flow discrepancy essentially adds or subtracts water without any associ- <br /> <br />ated salt, implicitly assuming that all the measurement and !mode1 error lies <br /> <br />in precipitation or consumptive use, but not in streamflow m,e.asurement nor <br /> <br />ground water inflows and outflows. <br /> <br />Observing the annual unaccounted flow for the State Lin" budget (see <br /> <br />Tables 4 and 5, and Figure 3), it can be seen that the unaccounted flow is <br /> <br />significantly large, varies greatly from one year to the next, and is usually <br /> <br />positive (i.e., inflows exceeding outflows). For the period of study, the <br /> <br />unaccounted flow averaged a positive 51,700 acre-feet per ye,ar, which is a <br /> <br />little more than 1% of the mean annual flow of 4,202,000 acr,,-feet per year <br /> <br />at the State Line gage. The annual 'lOaccounted flow varied from a positive <br /> <br />5.3% to a negative 2.9% of the mean annual flow at the State Line~ <br /> <br />The largest source of error in the budget undoubtly lie,s in the stream- <br /> <br />flow measurememts. The three major gaging stations, the Colorado River near <br /> <br />Cameo and near the State Line, and the Gunnison River near Grand Junction, <br /> <br />are all rated as "good" by the USGS, which means that about 95 percent of the <br /> <br />daily discharge measurements are within 10 percent of the actual flow. This <br /> <br />does not, however, necessarily imply a 10 percent error in the annual flow <br /> <br />because the daily errors should average out somewhat over a year. <br /> <br />II-10 <br />