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<br />-$- <br /> <br />of a headgate to be recorded at the gage~ natural losses in the stream channels~ <br /> <br />and whether the river stage is rising or falling. It is thus very difficult <br /> <br />to make an exact segregation as to the portion of the rise in stream flow due <br /> <br />to closing the trans mountain diversions as compared with that resulting from <br /> <br />shutting off the meadowland ditches. A.'1 analysis of the charts for 1939 and <br /> <br />1940 roughly indicates, however, that the innnediate increase in stream now at <br /> <br />the Jelm gaging station due to the closing of the meadowland gates was about 25 <br /> <br />to 30 per cent of the total diversions being made by those ditches at the time <br /> <br />of the shutoff. Thus under those diversion conditions some 70 to 75 per cent <br /> <br />of the water being diverted to the meadowlands was being practically continuously <br /> <br />returned to the streams. <br /> <br />This does not necessarily mean that 25 to 30 per cent of the diverted water <br /> <br />was being cons~~ed through the irrigation of the meadowlands, since undoubtedly <br /> <br />there were some returns to the stream for several days after the ditches were <br /> <br />shut down. In fact~ it is not a valid assumption that stream depletions due to <br /> <br />irrigation can be expressed in terms of percentage of total diversion. Studies <br /> <br />of stream depletions indicate that. with a full water supply, and under the same <br /> <br />conditions of tennperature and precipitation~ there will be a relatively constant <br />J <br /> <br />amount of irrigation water consumed annually due to evaporation and transpiration <br /> <br />incident to the growth of any particular crop. If diversions are made in excess <br /> <br />of those necessary to assure a full supply to the crop~ the resulting stream <br /> <br />depletion will not be materially increased, since the plants will still use the <br /> <br />same. amount of water and the only additional consumption v/hich could result <br /> <br />would be that due to some increase in evaporation opportunity. <br />