Mrs. Prost. The gentleman from Alaska, Mr. Rivers. Mrs. ProST. The gentleman from Minnesota, Mr. Langen. Mr. LANGEN. No questions. Mrs. Prost. Thank you very much, gentlemen. We appreciate your contribution. Our next witness is Mr. H. R. Glascock, Jr. forest counsel, Western Forestry & Conservation Association. You may proceed, Mr. Glascock. STATEMENT OF H. R. GLASCOCK, JR., FOREST COUNSEL, WESTERN FORESTRY & CONSERVATION ASSOCIATION Mr. GLASCOCK. Thank you. Madam Chairman, first I want to ask your permission to insert into the record an article from the Fifth World Forestry Congress entitled "Increasing Water Yields by Effective Cutting Methods," by Mr. Herbert C. Storey, Director, Division of Watershed Management Research, Forest Service, U.S. Department of Agriculture. In the introduction to this paper he makes this concise statement: In some localities and at certain times of year, water supplies become insufficient to fully meet the demands of agriculture, industry, and municipalities. Therefore, in such areas consideration should be given to designs of timber cutting that might be expected to increase water yields either in total amount or at those times of the year when water uses are greatest. And I would direct your attention to the concluding section of this learned paper entitled "Cutting Can Increase Water Yields." The statement is made: Measurements made on small watersheds give fairly reliable and conclusive evidence that cutting of timber can result in increased water yields. I would ask this paper be included in the record of the hearing on the subject that was discussed yesterday, Madam Chairman. There was a discussion yesterday of the effect of cutting on the snow patch in the upper watershed and the relevance of the future possibilities of increasing water yield in the high mountain areas by such treatment. Mrs. ProST. Without objection, the article wil be placed in the [Fifth World Forestry Congress, Seattle, Wash., Aug. 29-Sept. 10, 1960] (By Herbert C. Storey, Director, Division of Watershed Management Research, Forest Service, U.S. Department of Agriculture, Washington, D.C.) INTRODUCTION Commercial forest areas in the United States generally occur only in those regions having at least an average annual precipitation of 20 inches. With average annual precipitation of this much or more, forested areas constitute major sources of water for farmlands, industries, and communities. As these forest lands in general occur in mountainous topography with relatively steep stream channels, the water yielded therefrom is also important for hydroelectric power. In some localities and at certain times of year, water supplies become insufficient to fully meet the demands of agriculture, industry, and municipalities. Therefore, in such areas consideration should be given to designs of timber cutting that might be expected to increase water yields either in total amount or at those times of the year when water uses are greatest. INCREASING YIELDS BY REDUCING LOSSES Water yields may be increased in total amount by reducing losses due to any one or all of the following processes: interception of precipitation, transpiration by plants, and evaporation from soil or snow surfaces. Water yields during the drier seasons of the year may be increased by reducing transpiration or evaporation during that season or by retarding snowmelt and thereby extending the availability of water later in the spring and early summer. INTERCEPTION Interception of rainfall by tree crowns can constitute an appreciable percentage of the annual precipitation. In the north-central part of the United States, Mitchell (7)1 determined interception in a jack pine (Pinus banksiana) stand was about 21 percent of the total precipitation and in a mixed hardwood-hemlock stand, about 18 percent. In the State of California, Kittredge (4) found that in a young plantation of Canary Island pine (Pinus canariensis) interception varied from 17 to 28 percent of the precipitation. In South Africa, Wicht (12) found that a stand of poplar (Populus sp.) in full leaf intercepted 15 percent of the precipitation while only 3 percent was intercepted during the leafless season. Niederhof and Wilm (9) determine in the State of Colorado that interception by a mature lodgepole pine (Pinus contorta) stand amounted to about 30 percent of the rainfall during the summer. In England, Law (6) showed interception by a dense Sitka spruce (Picea sitchensis) plantation to be about 38 percent of the annual precipitation. And in California, an 80-year-old stand of ponderosa pine (Pinus ponderosa) intercepted about 12 percent of the average annual precipitation, according to Rowe and Colman (10). Thus it appears reasonable to assume that if interception is reduced, there should be an increase in the amount of water available for streamflow. Although it does not necessarily follow that the increase in streamflow would be equal to the reduction in interception, an appreciable portion of the 5 to 10 inches (13-25 centimeters) of water that might be saved should be realized in increased water yields. Studies have shown that cutting trees will reduce interception. For example, Niederhof and Wilm (9) found that the reduction in interception of rainfall was proportional to the intensity of the cut in a mature lodgepole pine (Pinus contorta) stand. Their figures show that a virgin stand of lodgepole pine intercepted 30 percent of the summer rainfall, whereas a stand that had been treated by removing half the commercial stand and thereby reducing the residual stand to 6,000 board feet per acre (35.5 cubic meters per hectare) intercepted only 18 percent of the summer rainfall, and an area that had received a commercial clear cut leaving only small scattered trees intercepted only 10 percent of the rainfall. Wilm and Dunford (13) in another study in Colorado found that 30 percent more snow and rain reached the ground on a commercial clear-cut area than under a virgin stand of lodgepole pine, and 15 percent more reached the ground where half the commercial stand had been cut. EVAPOTRANSPIRATION Evapotranspiration (excluding interception) from forested areas can also constitute a considerable percentage of the annual precipitation. In Colorado, Wilm and Dunford (13) determined these losses from a mature lodgepole pine stand to be nearly 6.5 inches (16.5 centimeters) annually or about 25 percent of the annual precipitation. In California, Anderson and Gleason (2) estimated evapotranspiration losses plus interception in dense old-growth red and white fir (Abies magnifica and A. concolor) and mixed stands of red fir and lodgepole pine (Pinus contorta) 1 Numbers in parentheses refer to literature cited. amounted to a little over 21 inches (54 centimeters) annually. If interception makes up about 7 inches (18 centimeters) of these losses, evapotranspiration would be about 14 inches (36 centimeters) or approximately 30 percent of the total annual precipation. In the State of North Carolina, Kovner (5) estimated total evapotranspiration. and interception by an oak-hickory stand to be about 39 inches (98 centimeters) annually with an average annual precipitation of about 70 inches (178 centimeters). If interception makes up about 15 inches (38 centimeters) of the total loss, evapotranspiration would be about 24 inches (61 centimeters) or approximately 32 percent of the annual precipitation. In Thus, the quantities involved in evapotranspiration losses of such magnitudethat it is reasonable to assume that reduction in these losses through cutting of timber would provide a significant amount of increased water available for streamflow. Studies have shown that the opportunity for realizing gains through manipulation of the vegetative cover would be greatest in areas of deep soils. areas with shallow soils (12–18 inches (30-45 centimeters) deep or less), although removal of the vegetation or reduction in its density would tend to reduce or eliminate transpiration losses, evaporation from the soil would undoubtedly increase and could effectively remove moisture throughout the depth of shallow soil. In deeper soils a gain would be realized as evaporation is generally effective only in the top 12 to 18 inches (30-45 centimeters) of soil, whereas trees will remove water throughout the depth of root penetration. Several studies indicate that timber cutting will have an effect on evapotranspiration losses. In most cases the cutting resulted in a reduction in losses, but this may not be the case in all instances. For example, in Colorado, Wilm and Dunford (13) showed that cutting a mature lodgepole pine stand so that the original stand of 12,000 board feet per acre (71 cubic meters per hectare) was reduced to 4,000 board feet per acre (24 cubic meters per hectare) resulted in an increase of evapotranspiration from an original quantity of 6.43 inches to 7.57 inches (16 to 19 centimeters) from the lighter stand. But, 0.80 inch (2 centimeters) of this increased loss was due to an increase in evaporation from the snow surface due to opening up of the stand. Thus moisture losses from the soil differed little (about 0.3 of an inch (0.8 centimeters) more from the 4,000board-foot-per-acre stand (24 cubic meters per hectare)) in this area where soil depths are only from 12 to 24 inches (30-60 centimeters). In South Carolina, thinning a 17-year-old loblolly pine (Pinus taeda) stand, thereby reducing basal area from 150 square feet per acre (35 square meters per hectare) to 75 square feet per acre (17.5 square meters per hectare), caused an appreciable reduction in soil moisture depletion (11). Starting both areas at field capacity with about 5.25 inches (13 centimeters) of available moisture (field capacity less wilting point) in the upper 48 inches (122 centimeters) of soil, 30 days of drying left only 1.5 inches (4 centimeters) of moisture in the unthinned area while 2.5 inches (6 centimeters) remained in the thinned. During the dormant season following thinning, winter rains recharged soil moisture to a depth of 8 feet (244 centimeters) under the thinned stand, whereas complete recharge did not occur below the 4-foot (122 centimeters) level in the unthinned stand. Anderson and Gleason (2), in California, found that strip clear cutting in a dense old-growth fir stand reduced summer soil moisture losses 3.2 inches (8. centimeters) from 48 inches (122 centimeters) of soil and 4.6 inches (12 centimeters) from soils of 90-inch (229 centimeters) depth. They further found that a commercial cut in a mixed conifer stand (Abies concolor and A. magnifica, Pinus jeffreyi) removing all trees over 18 inches (45 centimeters) in diameter, totaling 35,000 board feet per acre (204 cubic meters per hectare), and leaving 2,000 board feet per acre (12 cubic meters per hectare), resulted in a decrease in summer soil moisture losses of about 1 inch (2.5 centimeters). In this area soil depths varied from 2 to 6 feet (61 to 183 centimeters). Clear cutting a dense hardwood stand on a small watershed in the Coweeta Hydrologic Laboratory but leaving all the cut material in place, increased the. water yield about 65 percent or approximately 17 inches (43 centimeters) the first year following cutting. As the cut material was well distributed over the ground surface, it is thought the evaporation from the soil was not increased and interception was only slightly decreased; therefore most of the increased water yield can be ascribed to a reduction in transpiration. SNOW ACCUMULATION AND MELT Some of the most striking effects of timber density and timber cutting have been noted in connection with snow accumulation and melt. This has particular significance in the United States because timber areas that receive an appreciable proportion of their annual precipitation in the form of snow constitute important sources of water and supply a significant part of streamflow during the summer months when water needs for irrigation, domestic and other uses are highest. The effects of forests on snow and water yield from snow are complicated. being the resultants of a number of processes which may be conflicting or complementary. For example, Anderson, Rice, and West (3) have pointed out that— 1. Forests intercept snow; therefore they must reduce the snowpack. 2. Forests shade the snow; therefore they prevent melting and reduce evaporation, causing the snowpack to increase. 3. Forest trees radiate heat and use water; therefore they decrease the snowpack. From this it is obvious that the relationships are complex and a practice aimed at increasing the total water yield from snow may not serve equally well to reduce melt rates and thereby prolong the water yield. A number of studies show that openings in a coniferous stand result in greater accumulations of snow than occur under the forest canopy, and that this increase reaches a maximum for openings about equal in width to the average height of the surrounding trees. For example, Niederhof and Dunford (8) in Colorado, showed that the maximum accumulation of snow in a young lodgepole pine stand was found in openings with a diameter of 20 feet (6 meters) or more with the surrounding trees averaging from 17 to 23 feet (5 to 7 meters) in height. Anderson (1), in California, found the maximum accumulation, as represented by the depth on April 1, to be in a cleared strip of a width equal to about 90 percent of the tree height. On this date such a clear-cut strip would have about 60 inches (152 centimeters) of snow water equivalent when a dense forest would have about 46 inches (117 centimeters). Studies also show that the melt rate increases with size of openings; therefore, to obtain the optimum combination of accumulation and prolonged melting, openings in the range of one-half to three-fourths of the surrounding tree height are indicated. For example, Niederhof and Dunford (8) showed the maximum storage-duration index occurred with openings of about 16 feet (5 meters) in diameter in a young lodgepole pine stand. Anderson (1) showed the best relationship to occur on cleared strips about one-half tree height in width. Studies in the Sierra Nevada of California have shown some of the relationships between increments and depletion of the snowpack and several variables of the forest canopy. Anderson, Rice, and West (3) through a multiple-regression analysis of a large number of snow measurements under a wide variation of forest cover, showed that three forest variables had significant effects upon snow accumulation: Snow was increased 6 to 10 percent by the interception of solar energy as indexed by the cover density and depth in the path of solar energy, and snow was decreased 7 percent by the general hemispherical canopy cover. which served as an index to radiation melting and interception of snowfall. These results indicate that to the extent forests can be cut so as to leave the trees to the south and remove the trees to the north of or over a point, snow can be increased. Their conclusions concerning the design of a forest managed for water production and how such a design might be attained are: "Judging from these analyses, the 'ideal forest' would result from strip cutting. The strips would be oriented across slopes perpendicular to the hour angles with maximum solar energy; generally the strips would be east-west on north and south slopes, northeast-southwest on east slopes, and northwest-southeast on west slopes. Successive cuttings would proceed generally southward; that is, toward the maximum radiation. Once through a cutting rotation we would have established a wall-and-step forest. This forest would provide the maximum shade with the minimum interception and back radiation. The width of the cutting would be governed by the aim in water production-wider strips for maximum total water yield, narrower strips for maximum delay of melt. For the same delay in melt, wider strips would be cut on north slopes than on the south." Although this pattern is recognized as being oversimplified and only a first approximation, it does constitute the first orderly integration of a number of complicated factors into terms of possible management direction. CUTTING CAN INCREASE WATER YIELDS Measurements made on small watersheds give fairly reliable and conclusive evidence that cutting of timber can result in increased water yields. One such study was carried out on the Fraser Experimental Forest in Colorado where an appreciable portion of the annual precipitation occurs in the form of snow. Here the 714-acre (289 hectares) Fool Creek watershed contained 550 acres (223 hectares) of merchantable forest consisting of lodgepole pine (Pinus contorta) and spruce-fir (Picea-Abies) type. Following calibration of the watershed by comparison with an adjacent controlled watershed, 11.9 miles (19 kilometers) of logging roads were constructed and the timber then harvested in a pattern of alternate clear-cut and uncut strips. Altogether, 278 acres (113 hectares) of the watershed were cleared; this consisted of 35 acres (14 hectares) covered by the road system and 243 acres (99 hectares) within the clear-cut strips. During the first 2 years following cutting, water yields were increased an average of about 25 percent. Most of this increase came with the spring freshet, but slightly increased flows were measured in summer and autumn when water needs are highest. It should be pointed out that the clear-cut strips were not so oriented as to obtain the maximum benefits from reduction in solar energy reaching the snow surface, therefore this study does not give a measure of the full effect of best strip orientation on rate of snowmelt and consequent delay in runoff. At the Coweeta Hydrologic Laboratory a 40-acre (16 hectares) watershed with a dense oak-hickory (Quercus-Carya) cover was clear-cut, all woody vegetation being mowed off at the ground surface. All the cut material was left where it fell. Here the average annual precipitation of about 70 inches (178 centimeters) occurs mainly in the form of rainfall. The first year following cutting, the water yield was increased 14.5 inches (37 centimeters) or some 65 percent. Vegetation was allowed to regrow and 13 years following cutting an even-age coppice stand had been established with a basal area of about 50 square feet per acre (12 square meters per hectare). This is about one-half the basal area of the stand before cutting. At this time the water yield was still 5 inches (12 centimeters) greater than would be expected under the uncut condition. Although this particular method of cutting is not presented as a recommended watershed-management practice, it does show that cutting a hardwood forest where precipitation occurs largely as rain in an area of deep soils will produce increases in water yield. It also shows that the increase in yield will drop off in proportion to the rate of regrowth of the vegetation. In the study cited it is estimated that increased yields will be reduced to zero approximately 40 to 50 years after the original cut. Mr. GLASCOCK. Madam Chairman, as an American citizen first of all, I would like to congratulate you and this committee on the manner in which you are conducting this hearing. I have had the privilege of sitting in on a few hearings previously, both conducted by the Congress and hearings conducted by the executive branch, and I believe that the exemplary manner in which this hearing is being conducted could not help but strengthen one's faith in the three branches of our Government, and the two Houses of our Legislature, as being a democratic and very constructive way to administer our public affairs. Mrs. Prost. Thank you, Mr. Glascock. I am sure members of the committee appreciate your remarks very much. Mr. GLASCOCK. I mean them sincerely. I am quite impressed. Position: The position of the association on wilderness legislation, arrived at by mail ballot of its trustees is quite brief and is as follows: We feel strongly that additional wilderness legislation is unnecessary to accomplish the desirable purpose of delineating and maintaining defensible areas of wilderness. If Congress, however, deems additional wilderness legislation necessary, we urge that it be confined. to the existing wild and wilderness areas and such other Federal areas as Congress shall designate as predominantly valuable as wilderness by positive congressional action. 77350-62-pt. 4- -37 |