OCR Text |
Show Foreword Early in my activities as Senior Specialist in Natural Resources in the Legislative Reference Service of the Library of Congress, a program of special studies was undertaken to determine the physical and economic results of water use. I found that water was generally considered as an adjunct of the soil and available data were mainly in terms of products per acre of land rather than in terms of yields per acre foot of water. Since Federal agencies are almost completely in charge of the Public Domain and resources under examination and appraisal, it would seem to be especially important that the scientific basic data foundation of these programs be adequate and sound. Reports by both the Forest Service and the Bureau of Land Management were secured for all areas used for grazing. From these reports the number of animal unit years was calculated. [ Enough fodder for a mature cow or five sheep for a full year.] The grazing requirements of all wild life animals were also included in these reports. These studies with their extensive tables show dramatically the large quantities of water consumed on these public grazing districts to produce the folder used in grazing. The first tables were compiled in 1950 while the third set, the ones used in this report, were based on official reports for 1958. The basis for judgment of the relative efficiency of the number of acre feet of water shown in the tables to produce the fodder for an animal unit year, is provided by the basic information that an animal- unit- year of fodder is currently produced by the normal use of one acre foot of water on an irrigated pasture or from a crop of alfalfa under irrigation. In dramatic contrast water used in producing an animal unit year of fodder on the public domain averages near eighty times the amount used under effective irrigation, varying from a low of 40 to a high of over 300. An average of near 100 acre feet is shown in all these studies. It was these surprising results which caused me to delay their publication after the first study in 1950. When they were completely verified by later studies I became involved in a wide range of other studies and activities which have delayed their publication. Other reports show the variable productivity of water consumed in the yield of timber, 200 board feet per acre- foot of water consumed on some forested areas in contrast to only 20 board feet for each acre foot on other forest areas. For a few the spread is even greater. A high yield of approximately 250 board- feet per acre foot is secured on four forests in Washington and Oregon with a combined total of three million acres. By way of contrast ten National Forests, two from each of Colorado, Nevada, Utah, New Mexico and Wyoming with a total in excess of four million acres show a yield of only four to 17 board feet per acre foot of water consumed. These areas of low timber production are predominantly in the mountain areas of the more arid parts of the Public Domain that have been placed under the administration of the United States Forest Service. Usually the basic water shed programs are ( most intensively) applied to hold the water falling for use in the production of trees and other vegetation and to prevent soil erosion. The meager physical and value products on these watersheds are in marked contrast to the scarcity of water and the high cost of water management projects in these same areas. |