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<br />001803 <br /> <br />. <br /> <br />INTROroCTION <br /> <br />The Drouth Period <br /> <br /> <br />Greatly reduced runoff of Western Colorado streams started in <br /> <br /> <br />1931. It has been interrupted only in 1932 and in 1938 by runoff ap- <br /> <br /> <br />proachiIl@: fonner volume. In all other years runoff was much less than <br /> <br /> <br />formerly accepted values and in 1931, 1934, 1939 and 1940 runoff reached <br /> <br /> <br />low values that seriously handicapped waterusers on most of the smaller <br /> <br /> <br />streams. <br /> <br />. <br /> <br />The effect of this long continued drouth has been greater than <br /> <br /> <br />at first appears. Not only is the total runoff reduced, but due to <br /> <br /> <br />gradual drainage of underground supplies, the base flow, that water <br /> <br /> <br />which supplies the streams during late SUlluner, fall and winter, has <br /> <br /> <br />decreased even more than the total runoff decreased. The movement of <br /> <br /> <br />underground water is much slower th'm that of surface supplies, so that <br /> <br /> <br />it is only within the last few years of the period that this most serious <br /> <br /> <br />cumulative effect has begun to be rccoenized. <br /> <br /> <br />Restoration of groundwater is a vory slow process, but will come <br /> <br /> <br />sbout, all othor conditions being favorable, as total annual precipitation <br /> <br /> <br />rises to higher veluos. Unfortune.tely a p.,riod of comparative drouth is <br /> <br /> <br />usually one in which the other conditions do not seem to be favorable to <br /> <br /> <br />groundwater restoration. <br /> <br /> <br />Areas can be cited where the total annual precipitation has not <br /> <br /> <br />been mntericlly less during the dry period. Some areas have apparently <br /> <br /> <br />had greater yenrly precipitation during each of the present dry years. <br /> <br /> <br />However, distribution of that precipitation, average temperature and all <br /> <br />. <br /> <br />-1- <br />