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0024D~ C.=C.. 1- 1- Q. 1- n I Qu u=l .E., 1- (5) One special case must be discussed. In several stream segments in the area of analysis, water is lost between the upstream and downstream nodes during certain periods of the year. If the discharge at the upstream node or nodes is greater than the discharge at the next node downstream (that is, if Q <0), then the quantity of dissolved solids is reduced in proportion to the w~ter quantity lost. Reducing the quantity of dissolved solids in this man- ner assumes that water lost in the reach is lost to ground water and, there- fore, the water that is lost takes with it the associated dissolved solids. Unfortunately, some of the dissolved solids assumed lost to ground water may remain on the bed and banks of the stream channel to be removed with the next high flow. In addition, water lost to evapotranspiration leaves the associ- ated dissolved solids in the streamflow. To accommodate these problems, a calibration factor was added to increase the dissolved-solids concentration in this situation. This factor was adjusted during the model calibration. Thus, in a losing reach, C. is reduced to the minimum value and adjusted 1- upward by: where: E.=calibration coefficient >1.0. 1- AVAILABLE DATA Data are necessary for all the input nodes because these nodes initiate streamflow in the network. Streamflow-data collection for several small basins in the area was begun in water year 1976 (October 1975) in a coopera- tive effort with the U.S. Bureau of Land Management. These data (water years 1976 through 1981) provided 6 years of data, which included a mix of dry, wet, and average years, for model calibration. Two different types of station numbers are shown in table 1. If the number has eight digits, continuous streamflow record is obtained at the site as part of the U.S. Geological Survey streamflow-gaging program; in addition, some water-quality information may be available. If the station number has 15 digits, the site only has data on instantaneous discharge with associated water-quality data. One exception to this numbering system--node 19--is noted in table 1. Node numbers associated with the streamflow-gaging stations in the stream network are listed in table 1. Node numbers were assigned consecu- tively in a downstream direction beginning with the input node on Trout Creek. The node numbers associated with streamflow-gaging stations listed in table 1 and shown in figure 1 will be used to identify stations in this report. 8