Laserfiche WebLink
<br /> <br />~ <br />,....) <br /> <br />Starting in the Spring of1938, two years before the plots were cut <br />over, data were obtained on snow s',;orage, melting rates and net <br />summer precipitations under uncut forest conditions. The primary <br />object of these measuremen.ts was to find out whether the measured <br />factors varied markedly with natural variation in stand density, so as <br />to obtain a preliminary estim'lte of the probable effect of timber cut~ <br />ting. <br /> <br />fJl <br />lo- <br />W <br /> <br />In the study of snow storage and melting rates. twenty-five sampling <br />points were established in 1938 on each of the twenty plots selected <br />for the study. The details of these experiments are found in Technical <br />Bulletin No. 968 U. S. D. A. <br /> <br />They have stated their results and conclusions as follows: <br /> <br />"When the various components of net snow storage and rainfall were <br />combined with estimate of snow evaporation and the data on soil moisture <br />deficits, quantitative figures on the amount of water available for stream <br />flow under each timber outting treatment were obtained. On the uncut <br />plots this:amount was 10.34 inches, or about 42 per cent of the precipi- <br />tation. In contrast. the heavily cut over plots yielded 13. 52 inches so <br />that the treatment actually caused an increase of 31 per oent in the <br />quantity of water available in the stream" <br /> <br />Am>r est Service man reported at the December 10th, 1958 Missouri <br />Basin Interagency Co ;~:,mittee meeting that their experiments in the. <br />Fraser area to date showed that timber cutting increased run-off but <br />that the results were still not conolusive. <br /> <br />The U, S. Forest Service and the U. S. Weather Bureau oarried on an <br />experiment jointly from 1910-1926 to determine the effect on stream flow <br />of' changes of forest and brush cover, They selected two contiguous tracts <br />of land in southern Colorado near Wagon Wheel Gap in the Rio Grande <br />River drainage. The areas of the two tracts, designated A and B, were <br />22.4 acres, respectively, and the elevation varied from 9,000 to 11,000 ft. <br /> <br />In 1919 and 1920 area B was entirely deforested and the following table <br />shows the measured run-off from the two areas: <br /> <br />Precipitation Runoff A <br />Inches Inches <br /> <br />Year <br /> <br />Runoff B <br />Cut Over <br /> <br /> 1919-1920 22.14 7.865 8.55 <br /> 1920-1921 22, 59 6.898 8.328 <br /> 1921-1922 20.98 6. 830 8. 769 <br /> 1922-1923 24. 08 6, 091 7.168 <br /> 1923-1924 1 6. 86 7.104 8.016 <br />. .. 1924-1925 22.15 4.269 4.948 <br />.',...'. ' <br /> 1925-1926 18,16 4. 379 5.050 <br /> ..5- <br />