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e'J (.0 I.") Cl -:"1 ~., -- . . CHAPTER II GRAND VALLEY RIVER BUDGET Nevertheless, note that a 10 percent error in the mean annual flow one way at the Cameo gage, and the other way at the State Line gage, would cause an annual unaccounted flow of 685,000 acre-feet, which is an order of magnitude larger than that in the State Line budget. Another factor that could cause significant unaccountec, flow is ground water storage. The variation in ground water storagE! from year to year could result in significant unaccounted flow in the annual budgeting process. For this reason, and because of the possibility of relatively large streamflow estimation errors, precise estimates of salt pickup for any given year cannot be expected. The estimate of the average annua:, salt pickup, on the other hand, should be accurate (see Discussion of Confidence in Results) . Given the large variability in annual unaccounted flow" and again the possibility of relatively large streamflow estimation error,;, the source of the relatively small positive tendency in unaccounted flow ,:ould not be identified. It could result in part from unidentified groulld water losses, an underestimation of consumptive use; or an overestimation of precipitation ungaged inflows, or municipal imports. But, for the reason,; noted above, most of the positive tendency is probably caused by a sligh:: systematic error in streamflow measurement. If this is the case, or if ther.. is some unidentified ground water outflow, then the unaccounted flo'. has salt associ- ated with it, and therefore, a straight forward accounting process neglecting the consistently positive unaccounted flow (i.e., inflows eKceeding outflows) will underestimate the salt pickup. In other words, ignoring a consistently lit positive unaccounted flow is the same as ignoring an outflow. Now, if the II-ll