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<br />..l-VV-:l; <br /> <br />, <br /> <br />, <br /> <br />and the normal kinds of phenomena that are <br />recorded at a weather bureau station. You <br />might say that it is perfectly obvious that <br />when there is heavy rainfall, there will be <br />a large amount of water flowing in the <br />streams. But actually the relationship is <br />not a simple one. If the water falls, for <br />example, in a large number of relatively <br />small storms and the storms are separated by <br />very dry periods, then the amount of avail- <br />able water that turns up as stream flow is <br />very different from that if the water is <br />made available-in concentrated periods when <br />the storms are rather substantial in extent. <br />Also it makes a great deal of difference <br />what season of the year the peaks in preci- <br />pitation occur, and it also makes a great <br />deal of difference what the strength of the <br />wind is following period of precipitation - <br />how much of this water is lost in evapora- <br />tion in the atmosphe~e and so on. <br /> <br />So that the second portion of the study <br />which will be done principally here at C. S. <br />U., the objective of this will be to study <br />the long period of historic records for the <br />great number of stations that are available <br />to try to relate these well observed and <br />well known meteorological measurements to <br />stream flow. It is certain that this will <br />allow us to carry our period of observation <br />beyond the period for which there are accu- <br />rate stream flow data themselves and it will <br />also permit us to relate the flow of water <br />in the particular basin that we are talking <br />about, to relate that to the broader trends <br />of weather over United States at large. Just <br />to give you an example,of how drastic some <br />of these trends can be, I had Mr. McDonald <br />of our staff prepare a couple of things. I <br />didn't realize there were going to be so many <br />of you here, it may be hard for you to see <br />these, but I had him prepare two graphs show- <br />ing, for two periods, the extreme differences <br />that are known to occur in temperature over <br />United States at large. These are average <br />temperatures for the month of January and <br />the one in ~y left hand deals with the period <br />1947, '48 and '49. In the red part of the <br />graph is a region where the temperatures are <br />warmer than normal so that you see in the <br />eastern part of the United States, for those <br />three years, temperatures were generally rang- <br />ing about three degrees warmer than normal; <br /> <br />I <br /> <br />I <br />