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<br />lowest dissolved solids concentration in the river due to the dilution <br />effects of the higher flows. <br /> <br />(Slide) During this study period the actual increase in dissolved <br />solids within the study area averaged about 400 milligrams per liter. <br />That is, the dissolved solids concentration at the downstream end <br />was about on the average 35 percent higher than that observed at. the <br />upstream end of the study reach. Again the increases or the changes <br />in quality themselves are affected by dilution during periods of higher <br />flows. Now you see that the calculated data agrees fairly well in <br />trend at least with that which was observed. However. it is obvious <br />that the calculated data is consistently lower than the observed data. <br />This indicates to me that as the model was handled up to now it was <br />some factor which significantly affects the quality of water in the <br />river within this study reach which was not considered in the model. <br />And right now we are fairly sure that this factor would be the salt <br />load contributed by tributary inflow. This would include. say the. <br />sewage treatment plant at La Junta which discharges effluent into the <br />river within the study reach. When we account for the salt load <br />contributed by tributaries the calculated and observed data come into <br />excellent agreement again. This indicates one thing that the entire <br />increase in water in dissolved solids concentration in the river can- <br />not be attributed entirely to irrigation practices. <br /> <br />I <br /> <br />Well. let me just (Slide) summarize again and I will just flash this <br />slide up here once more as I summarize the results. First of all. <br />there are many factors which affect the movement of water and changes <br />in water qu~11ty in a stream-aquifer system. Because of this. there <br />are ~a1rly complex data requirements for running this type of simula- <br />tion model. However. as we gain experience in working with the <br />model and interpreting these complex relationships. some of these <br />data requirements will undoubtedly become relaxed. We will learn <br />which of the data do not require such detailed measurements in the <br />field. <br /> <br />There is little doubt that this technique can be applied to other <br />areas in which similar problems are occurring. In fact the technique. <br />the computer program, is actually general enough that with a few I <br />programming mOdiftcations. it can be used in almost any case where <br />it is desired to predict the rates and directions of movements or <br />migration of contaminants for dissolved solids through a saturated <br />porous media. Well. I think we began. at ieast within the study area. <br />running this ~odel has greatly aided us in interpreting the water <br />quality pattern which existed there. and the model has proved itself <br /> <br />-27- <br />