HERBERT C. STOREY
Director of Watershed Management Research, Forest Service, United States Department of Agriculture, Washington
IT is only during the past ton years that the term " watershed management " has become much used throughout the world, although concern about some aspects of watershed management dates back at least one hundred years.
During those early years, activities were aimed at control of torrents in steep unstable mountain areas, the control of floods through the construction of dams, levies, and similar structures, and in reforestation for the purpose of regulating streamflow, ameliorating the climate, and reducing erosion.
About the end of the nineteenth century, interest increased considerably, particularly in the form of arguments as to the magnitude and character of the effect of forests on water yields, floods, local and regional climate. At this time, in Western Europe, several international meetings were held to discuss the state of knowledge pertaining to the influence of forests on their environment, the need for more reliable information in this regard, and improved methods and instrumentation to obtain such information.
Since the second world war, watershed management has become a subject of great international interest. An examination of recent world literature reveals much material on watershed management problems, research programs and results, and action programs in many parts of the world.
There are a number of reasons for this widespread and rapid increase in concern about watershed problems and interest in methods of meeting them. Concern over repeated destructive floods, their attendant loss of life and property has brought about numerous programs intended to prevent or reduce flood damages. Excessive siltation of streams with consequent impairment of navigation, deterioration of fish habitat, reduction of water quality, and aggradation of river channels and water logging of fertile valley bottoms have all resulted in a widespread interest in measures to correct these situations and prevent their occurrence in the future. Great concern has developed over accelerated erosion in practically all regions of the earth with the serious loss of soil and consequent loss of productive capacity while production needs are increasing rapidly. Although, in the past, problems associated with water shortages may not have been given as much attention as that extended to the more striking destructive elements, there is a rapidly growing concern over the alarming increase in water shortages with their present and potential impacts on industrial and agricultural economies as well as the serious hazards to domestic supplies for human consumption. All of these concerns and interests are closely associated with skyrocketing populations and increasing efforts to improve the wellbeing of present and future generations.
Water problems of varying types and intensities are nearly worldwide in the populated parts of the earth but are generally most crucial where pressures on the land are greatest. In areas of dense human populations, there has developed a tremendous pressure for water, food, fuel, fibre and living space. These elements are necessary to some degree in order to sustain life, and must be available in much larger quantities if more than a bare existence standard of living is maintained. The result is that land is exploited in an effort to supply all needs and degradation begins - vegetation is depleted, soil is eroded and productivity reduced, stable streamflow is changed to sequences of floods alternated with little or no flow. Degradation is a vicious cycle and self-perpetuating. As land becomes unproductive and useless, pressure on that remaining is increased and degradation is hastened. If this process is not stopped and reversed, a once fertile and productive landscape eventually becomes virtually a biological desert.
Watershed management, though a widely used term, may mean different things to different people. In this discussion, watershed is used synonymously for catchment and is considered as all that surface area drained by a specific stream, large or small, or draining into a lake. Watershed management is the carrying out of planned practices and operations to attain desired objectives in terms of the functioning of the watershed. The two key words of this definition are planned and objectives. Watershed management does not just happen, things are done or deliberately not done for a specific purpose.
The objectives are generally determined on the basis of the present and future economic and social requirements of the population of a large basin, of a region or even of the nation as a whole. But planning of practices and operations in order to reach these objectives efficiently and effectively can be applied only to relatively homogeneous physical, economic and social units, that is to say in the framework of a watershed, the determination of which is, in fact, the first phase of watershed management.
Some people think of watershed management as solely a protective process. " Good timber management is good watershed management " is a commonly used expression. This is not necessarily correct. Good timber management is usually aimed at attaining the maximum sustained yield of desired commercially valuable timber crops. This says nothing about watershed objectives, nor desired characteristics of water yield, It is true that operations intended to attain continued high yields of timber must include practices that will protect the growing sites, prevent erosion of soil, and consequent reduction of productive capacity. Prevention of erosion is also desirable from the watershed standpoint but this general line of reasoning implies that watershed management is a passive thing whereas its very name shows that it is a positive action. Management means the " judicious use of means to accomplish an end " and thus requires both plans and objectives.
Watershed management may have one of three broad objectives, or in some areas combinations of modified forms of these three. The first objective is rehabilitation. This consists of practices intended to repair watersheds that have deteriorated because of past misuse or unwise use, accidental or intentional, such as repeated fire, overgrazing, repeated overcutting of timber, improper tillage practices, and use of land for purposes to which it is not suited.
This objective of watershed management has received much earlier and more widespread consideration than either of the other two. Centuries of destructive use have resulted in deterioration of vast areas of the earth, with resultant serious effects on water yields, increase in frequency and severity of floods, and loss of productive capacity of the land. A large proportion of this land is located in semiarid climates where conditions are such that rehabilitation is extremely difficult and costly. The need for more land to meet the needs of increasing populations requires the rehabilitation and rebuilding of these damaged areas. This is of prime importance in much of the land around the Mediterranean and through the Middle East. The future wellbeing of the people of this region and the establishment and maintenance of stable economies will hinge to a major degree upon the rehabilitation of these ravaged lands.
One of the first steps in a rehabilitation program is to remove or discontinue the cause of damage if this has not already been done. If repeated fires are a major cause, an adequate program of fire prevention and control is indicated. If overgrazing is the culprit, grazing should be materially reduced and carefully managed or discontinued until such time that the area is again able to provide this use. If unwise use has caused damage, a change in use should be made. For example, an area currently devoted to agricultural crop production might be converted to grass or timber production.
The next step is to re-establish an adequate protective covering of vegetation by seeding of grasses or tree planting (Figure 1). This must be supplemented in many cases by structural measures such as gulley-plugs, small dams, contour terraces and furrows, grassed drainage ways, water spreaders, and similar devices.
The second objective of watershed management is protection. This consists of practices aimed at maintaining good watershed conditions that already exist while carrying on other uses of the land, such as for timber growing and harvesting, grazing of domestic livestock and big game, recreation, or crop production. This objective is extremely important although it has not had as long or widespread attention as rehabilitation. Protection of watershed land that is already in good condition is vital because it maintains productive capacity at a time when needs are growing at a rapidly increasing rate; secondly, it prevents the development of destructive processes; and third, it is much less costly than rehabilitation of land following serious depletion (Figure 2). We need to maintain the productive capacity of our soils, forests, and watersheds if the needs of present and future generations are to be met.
FIGURE 1. - Rehabilitation of this formerly gullied area has been brought about by reforestation and gulley-control structures. A wasteland is now producing again and will soon have harvestable timber products.
FIGURE 2. - This was once a logging road, but poor location, inadequate drainage, and a heavy rain resulted in this boulder-strewn channel. Another road will be needed for removal of additional timber cut and large quantities of sand, silt, and gravel have been deposited in streams below.
The need for this objective of watershed management is illustrated by conditions in the northwestern United States. In this area harvesting of virgin timber stands is rapidly pushing back into formerly inaccessible regions in the higher parts of the Cascade mountains. These areas constitute the head waters of important rivers. It is imperative that timber harvesting operations be carried on in such a manner that growing sites are protected, and soil and water values are not impaired. In some cases, this may require the development of entirely new concepts and methods of timber harvesting and removal. In certain instances, timber harvesting will be deferred until such time that techniques are available that will insure full protection of the soil and water.
Protection of soil and water values of maintenance of presently good watershed conditions requires all uses of the land to be so planned and carried out as to insure it minimum of soil disturbance or alteration of existing hydrologic conditions. Logging roads should be located and constructed so as to avoid unstable soils, prevent concentration of storm run-off and discharge of erodible material with grades maintained at a minimum, and no encroachment upon stream channels (Figure 3). System, timing, and intensity of grazing use should be designed to avoid excessive soil compaction and to maintain a good protective covering of vegetation. The particular method used will depend upon the characteristics of the land involved and will vary with soil types, topography, climate, vegetation, and availability of water. Adequate protection from wildfire is a primary need, as uncontrolled destruction of vegetation by fire is fundamentally incompatible with the basic concept of management.
FIGURE 3. - A logging road properly located with adequate drainage and gentle grades will cause little increased sedimentation of streams.
The third and final objective of watershed management is the improvement of water yields. This includes practices aimed at either increasing total water yields or changing timing of yields better to suit man's needs. This objective has received, in general, less attention through the years than either rehabilitation or protection. - This is recognizable because rehabilitation and protection represent the bare minimum necessary if we are just to survive even without materially improving worldwide standards of living. Improvement of water yields on a major scale represents a look into the future and probably may be considered as the ultimate in watershed management, because here we are improving on nature. Through our efforts we will tailor the functioning of a watershed to best meet our needs, of course, within limitations imposed by things over which we have no control.
The developing importance associated with this aspect of watershed management may be illustrated by situations in the United States, United Kingdom, and South Africa. In the western United States, a rapidly growing concern as to the adequacy of water supplies for increasing domestic, industrial, and agricultural needs is resulting in a demand for management of watersheds so as to increase water Yields or extend the period of yield further into the dry summer months of the year. Intensive studies are under way to determine whether water yields may be materially influenced by changes of vegetation, the magnitude of such changes and what are the conditions under which practices may be successful. In addition, studies above timberline are aimed at determining methods of accumulating snow at greater depths in selected locations and retarding the melt rate so that water will be available to extend streamflow into the summer months when needs are highest.
In the United Kingdom, much question is being raised as to the effect of reforestation on water yields. Some measurements indicate that water yields may be reduced when grass-covered watersheds are reforested. Proposals have been made that reforestation be ceased in certain areas or allowed to continue if the income from forest products is used in part to finance the development of additional water supplies to replace the quantities used by the forest.
In the Union of South Africa, the problem developed as a result of the establishment of artificial forests where there were none before. Since the end of the 19th century extensive " man-made forests " have been developed by the plantations of exotic timber trees in areas which had for many years, if not always, been covered with grass or shrubs. After considerable study it was recommended that extensive afforestation should not be undertaken without careful thought being given to the possible consequences to water yields. It was even established as a forestry department policy in 1932 that where discharge of streams is used for irrigation, industrial or municipal purposes, moist areas along streams would not be planted.
The general subject of increasing water yields or materially changing the timing of yield presents many unknown relations and will require much intensive research to unravel the complex processes involved and explain some of the apparently contradictory results of various studies. In general, results of research to date indicate that water yields may be increased to a varying degree by reducing the density of woody vegetation, although extreme removal of vegetation may result in increased evaporation from the exposed soil surface and no increased water yield. Research has also indicated that conversion from deep-rooted plants to a cover of shallow-rooted species may increase water yields under some circumstances. In an area of deep winter snow-pack water yields from an experimental watershed have been increased by special patterns of cutting the coniferous forest (Figure 4). Water yields have also been increased by cutting of woody vegetation along stream channels. These results and others lend strength to the hypothesis that water yields may be increased if evapo-transpiration losses can be reduced.
FIGURE 4. - Annual water yields from this 290-hectare (714-acre) watershed -were increased an average of 25 percent during the first two years following removal of about 50 percent of the coniferous timber in a pattern of clear-cut strips.
The three main objectives which have just been described cannot be reached without taking into consideration the needs and the possibilities of the populations concerned and without obtaining their actual co-operation. Even high watersheds to be managed are frequently inhabited, and the welfare of their inhabitants must be fully recognized and provided for. Watershed management must find the necessary compromise between sometimes conflicting but legitimate interests.
A number of international organizations are carrying on various activities that assist in the advancement of watershed management. Some of these organizations are made up of scientists from a number of different countries. In some cases, they are made up largely of ordinary citizens who are interested in conservation, and in others they are created through the joint action of national governments. The contributions of these different organizations vary widely in importance and value and include general educational activities, development and dissemination of technical knowledge, and efforts toward policy development. Collectively they assist materially in advancing watershed management.
The International Association of Scientific Hydrology recently held a meeting in Germany and devoted an entire symposium to the subject of the effect of water on woodlands. This provided a valuable exchange of information between scientists of different countries on a subject of prime importance to watershed management.
The International Union for Conservation of Nature and Natural Resources devoted a major portion of its last annual meeting to discussions of soil and water conservation problems and programs. This organization has been giving more and more consideration to the conservative use of natural resources as contrasted with its former concern solely for straight protection.
The International Union of Forest Research Organizations has a special section on forest influences and includes this subject as an important topic for discussions in their regular meetings. A knowledge of forest influences constitutes an important basis for development of watershed management practices.
The World Meteorological Organization has assisted in the standardization of presentation of meteorological information, hag helped disseminate information about techniques and equipment, and will now expand its activities to provide similar services in the field of hydrology. Both of these activities are highly important to watershed management.
The Food and Agriculture Organization has been quite active in promoting a better knowledge of watershed problems, techniques for meeting these problems, and providing assistance in planning necessary action programs. FAO sponsored jointly with the Government of India a watershed management development center for Asia and the Far East, where representatives from nine different countries in that part of the world received training in the principles of watershed management and methods of developing and carrying out watershed programs. A similar development center is being planned for the Near East area. FAO has also sponsored the organization of various working parties and subcommittees to consider various phases of watershed management; these include a working party on watershed management of the Asia-Pacific Forestry Commission, a working party on avalanche and torrent control of the European Forestry Commission, and a subcommittee on soil and water conservation of the European Committee on Agriculture. FAO also organized jointly with the Government of the United States an eight-week seminar and study tour on watershed management that was held during the summer of 1959. FAO has also provided assignments of technical personnel to assist various governments in delineating their watershed management problems and preparing plans for programs to meet these problems.
The Fifth World Forestry Congress, to be held in the autumn of 1960 in the United States, will have a separate section of the program on forest and range watersheds. Three half-day sessions will be devoted to this general subject.
Although progress in watershed management has been increasing rapidly during recent years, the rate of increase must be still further quickened if needs are to be met adequately and expeditiously. There are a number of things that international agencies as well as national governments might do to step up the level of accomplishment. International agencies could materially increase their efforts towards obtaining a better exchange of knowledge between technicians of different countries. Technicians in some countries are hampered by the lack of access to literature of other countries. Where the need exists such agencies might assist countries in developing good technical libraries on the subject of watershed management and the disciplines providing the scientific basis for such management. International agencies might also assist in the interchange of translations of technical material and possibly in the development of multilingual glossaries of terms used in watershed management.
International agencies might also work with countries concerned in delineating problems involved and in development of action plans for watersheds of streams that cross international borders.
National governments can do a number of things to increase the rate of accomplishment in the field of watershed management. One of the primary steps needed is to educate the general public as to watershed problems and actions needed to meet these problems. A very urgent need is a considerable increase in the training of technical personnel in watershed management as this is basic to success in this field. Research programs in various aspects of watershed management should be materially increased. Governments should work towards improving opportunities for exchange of information between their watershed management personnel and those of other countries. Watershed management plans should be developed for programs that are sound technically, economically, and socially. Then the final and the most important thing is to provide the necessary financing for carrying out the needed programs and to carry the programs through to fulfilment. This is most important as plans, even good ones, accomplish little if not put into practice.
Thus, through concerted action, using all available resources of national governments and international organizations it may be possible to meet the challenge and opportunity encompassed in watershed management throughout the world -one of the most important elements towards building a better and more stable life for this and future generations.