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I I blue or purple, those areasin which changes in the dissolved solids concentrations, either an increase or decrease, of greater than about 10 percent was observed. Note that highest salinities were observed along the northern boundary of the aquifer and along the county line at the eastern end, and that improvements in water quality, that is, a decrease in dissolved solids, was observed in portions of the central part of this valley. While we cOuld compare the observations now with what was predicted or calculated by the simulation model. First of all, note that the water quality patterns as indicated by these contours calculated by the model, agree quite well with the observed water quality pattern. What really impressed us, was that we got such good agreement between the changes in water quality. That is, both the observed and calculated data agreed in showing increased salinities along the northern boundary of the aquifer and along most of the county line here at the eastern end. The model also predicted improvements in quality in portions of the central part of the study area. Now, there are some discrepancies again between the observed and the computed data, and there is some work left to be done, really, to evaluate whether these discrepancies are due either to deficiencies in the input data or possibly due to refinements which are still needed in the model itself, or actually, it's probably a combination of both. (Slide) We were able to predict the observed dissolved solids con- centrations within about 10 percent of the observed values about 85 to 90 percent of the time. And again, just as with the water table elevations we can look at ahy o~e point in the study area and look at the variations of water quality with respect to time. And again, we see very good agreement between the observed and calculated data. As I mentioned, and as you probably know, (Slide) any stresses placed upon the aquifer itself will ultimately affect the streams. So it's worthwhile to look at the changes in flow, in changes of water quality, in the river ~tself. As far as predicting the actual, or let's say, the mean monthly flow, at the downstream end of the study area, we were quite successful. That is, the calculated observed data agreed quite well. The average gain in streamflow due to (Slide) the flow of ground water into the stream averaged about 5 cubic feet per second within this ten-mile study area. Now, it's this ground water which is of a higher salinity than the water in the stream, in gen- eral, which plays a major role in placing an increase in the dis- solved solids concentration in the river. Note first of all, that during periods of highest flow in the early summer, we observe the -26-