Laserfiche WebLink
<br />000557 <br /> <br />. <br /> <br />. <br /> <br />i <br /> <br />~ <br /> <br />I. JNTROuucrroN <br /> <br />Timher cutting is ('"l' of the watershed management practices lIsed by the <br />United States and otber n.lt ions of the world, The influence of forest clear- <br />cutt ing or patchcuttill~~ nn water yield has long been recognized. The first <br />catchment experiment was i ni t iated in 1909 ilt Wagon Wheel Gap in Colorado, <br />U.S.A. <br /> <br />The United .statc~; Forest Service (USFS) has developed long range plans <br />for clearcLltting or patchcutting of timber for the San Juan, Grand ~\esa, <br />Unconlpaghre and Gunni son Nat ional Forests in the State of Colorado. These <br />plans for timber cutting, according to the Forest Service, would expand aspen <br />acreage, fight disease, and increase water yield. The Department of Natural <br />Resources has appealed the decision of the Forest Service on these plans and <br />requested the State lng i neer' s Office to conduct a review of literature <br />related to timber cutting. <br /> <br />11. OBJECTIVES <br /> <br />~ <br /> <br />The objectives of this literature review are to study the effect of <br />clearcutting or patchcutting on: (1) water yield and (2) distribution of <br />runoff . <br /> <br />~.~~ <br /> <br />III. FACTORS EFFECTING RUNOFF RFSPONSE TO TIMBER ClJITING <br /> <br />1ne magnitude and timing of runoff in response to clearcutting or patch- <br />cutting depends upon precipitation, soils, elevation, latitude, topography, <br />type of forest cover, density, orientation of slopes (north or south), pre- <br />vailing winds, distribution of precipitation between rain and snow, and other <br />factors. <br /> <br />In Colorado, most of the stream runoff is produced by the SnOh'll1elt. In <br />the high cOLlntry where snowfall is a natural occurrence, some of the snow is <br />intercepted by the trees during the snowstorm. In the case of clearcut areas, <br />all the snow would accumulate on the ground. After the snowstorm, the snow <br />intercepted by the trees in the uncut area may be blown out by the wind to <br />other open areas. The wind forces may \'a ry from area to area. In the area of <br />high winds, the intercepted Sl10\\l may stay on trees for a very short period of <br />time. As the temperature increases, the intercepted snow, if not blown away <br />by the wind, may partly evaporate due to temperature and solar radiation. The <br />temperature and sol"r r,1di"tion rnay vary from area to area based on elevation <br />and orientation of slope (north or south). <br /> <br />Snohmelt is infJllcnced by the elevation, orient3tion of slope "nJ tree <br />cover. Portion~ of the Sl10l>iJllelt is lost to evaporation and the soil moisture <br />deEicit which is affected by the evapotranspiration of the trees. <br /> <br />-1- <br />