erosion and water supplies

EROSION AND WATER SUPPLIESAuthor(s): E. P. StebbingSource: Journal of the Royal Society of Arts, Vol. 93, No. 4691 (MAY 11th, 1945), pp. 290-304Published by: Royal Society for the Encouragement of Arts, Manufactures and CommerceStable URL: http://www.jstor.org/stable/41362039 .

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ZgO JOURNAL OF THE ROYAL SOCIETY OF ARTS May II, 1 945

fact which first gave it world-wide significance was the revelation of the great mischief caused in America by the misuse of land. It is now recognised everywhere as one of our major problems. In passing through Africa I have seen the active steps which are being taken to introduce measures by way of controlled methods of cultivation and the reservation of forest land to repair the mischief caused. Clearly it is difficult to say how much that mischief is due to nature and how much to man ; but the mischief is there. We are also now taking more concerted measures in India,

The problem has to be approached scienti- fically, and I think we could have no better guide to the history of the question, or to the measures which have to be taken to repair the mischief, than Professor Stebbing. He has approached the subject partly in the light of his experience as Professor of Forestry, but he has also approached it from a wider outlook. He has taken particular interest in one question which has disturbed people's minds in Africa, . and which may be shortly described as the 4 4 March downwards of the Sahara."

The following paper was then read : -

EROSION AND WATER SUPPLIES By E. P. Stebbing, m.a., f.l.s., f.z.s., Professor of Forestry y University of Edinburgh

What is the connection between ¿rosion and Water Supplies ?

Probably the first recognition by man of the damage committed by erosion came from the method of farming by shifting cultivation practised for a very long period of time in the afforested parts of the globe, under which a very large area of forests either disappeared entirely or was destroyed so far as its com- mercial value was concerned ; for the area formerly occupied by valuable timbers became overgrown when the shifting cultivator left it, with weeds and worthless soft- wooded trees ; the species depending upon the parts of the world concerned-Temperate or Tropical*

The shifting cultivator, as also the pastoral stock keeper, made use of fire to assist the forest clearance, and, unchecked, these annual fires spread across the countryside. Erosion began to play its. part* at first most noticeable in hilly regions.

It is a mistaken idea that tropical forest will continue almost indefinitely to provide new lahd for colonisation.

This type of forest in fact requires careful

treatment. It is a very delicate organisation and the action of man may now be opposed to that of Nature, who holds the scales. In the past in certain countries considerable areas of this type of forest have been destroyed to grow plantations of coffee, rubber, and so forth ; or opened for purely agricultural purposes, with an almost inevitable result that erosion has taken place, the surface soil has disappeared, and the waters have dried or sunk deep into the lower strata and beyond the economic reach of man. Without stable water supplies agriculture becomes impossible on any sustained basis. Therefore it is of equal interest to the agriculturist and the forester to know where his water supplies come from in the particular part of the world he is working in.

A glance round the world to-day will furnish evidence of how few inhabited countries are unaffected by this question of erosion. Britain has her problems, and in Europe, to mention a few cases, France in the Alps and Pyrenees had to undertake great protective works to stop erosion ; or, in the case of the Landes, the planting up of the inward- moving sands ; Spain, Italy, Greece and Cyprus all show striking illustrations* In the United States and Canada the gigantic so- called dust botols furnish the most modern instances. In the British Empire, the Dominions of Australia, New Zealand, South Aíricà, the Rhodesias and the Sudan are facing problems, some of the first-mentioned of equally recent origin. In India and Ceylon, erosion and its results have been studied for a century or more past, especially in connection with the planting of coffee, tea, and so forth. Palestine with the neighbouring Trans-Jordan, considerable parts of the old Continent of Africa, irrespective of the nations ruling the various peoples - Britain, France, Belgium and Portugal ; in the West Indies, Jamaica, Trinidad, Leeward and Windward Islands - all these countries present complex problems of which the basic cause has been so often man's improvident actions.

It will be of interest to consider for a moment what is meant by the term " Ero- sion." There are several distinguishable types - Sheet Erosiqn, Gully Erosion, Soil Erosion due to over- òu 1 ti vation , Soil Erosion due to excessive pasturage, Soil Deterioration, sur place , due to the removal of heavy tropical forest with a closed canopy to grow arable crops or areas of coffee, cocoa, rubber, etc., Sand Invasion, and Desiccation. The main



May II, 1945 EROSION AND WATER SUPPLIES Zgi

result in each is the disappearance of the top layers of valuable productive soil and the lowering of the water table щ the soil, with the drying-up of springs and the lowering of the water in streams and rivers. Instances are not uncommon when one or more of the types may be operating together, or may succeed one another.

The Influence of Forests on Rainfall is a much debated question, and has been under discussion by foresters, agriculturists and others for well over a century and a half in

humus layer on the forest floor, and slowly percolates and reaches and fills the springs and streams, thus keeping the level of the rivers out in the plains at a fairly uni- form annual amount. In other words, there are but rarely large rises in the levels of the rivers which produce floods and destruction counter-balanced by heavy drops in the water levels in the rivers and drying up the streams in the hot season. These remarks apply also to the level of the water in wells and the artificial reservoirs built by man unless artesian water has been tapped. Öf course, this action

Soil drift and desert after excessive sheep pasture

Europe, over a century in India, and over half a century in the New World. Briefly the question is by no means settled for the temperate parts of the world ; in the tropical and semi-tropical parts for practical purposes the question appears to be no longer open to doubt. The climatic conditions in these regions are (1) great heat in a dry season ; (2) heavy rains following, with a high tem- perature ; (3) a comparatively cool quiescent period for plant growth. Wind plays a part in (1) and (2). Under these conditions the forests should be regarded as Nature's large reservoirs from which the water of the heavy rains period dripping from the leaves (the canopy breaking the heavy fall) and running down the stems of the trees falls on the

of the forest is equally true in temperate regions.

If by inadvertence we leave our large pre-war sponge in the bath when, eventually , it sits on the bottom, the water in it only gradually percolates away down the drainpipe. If after a few hours we return we shall find the sponge nearly dry, but the water it held has only slowly reached the drainpipe. This represents the action of the forest subject to heavy rain-storms whether pro- longed or otherwise, and is,, therefore, one of the functions of the forest vis-a-vis rainfall ; the water reaches the streams and rivers slowly, ̂nd is conserved f<?r a longer period and more evenly distributed throughout that period.

(From an Australian Publication.



2Ç2 JOURNAL OF THE ROYAL SOCIETY OF ART& May II, I945

As to the direct influence of the forest on rainfall, whether the forest actually attracts rain clouds, research which has been carried out to some extent in tropical countries in the interests of agriculture would seem to show that under certain conditions the presence of forests has probably some influence and certainly so on climatic factors. As a result of researches carried *>ut by Nicholson and Walter in Kenya and Uganda, they stated as one of their conclusions that, under favourable circumstances, mountain forests in East

of the troubles which have been experienced in this matter are due to man's often quite unmeaning interference with the equilibrium of Nature. In this small island of ours floods are not unknown. We need go no further than the Thames for an illustration. Did the Thames flood between Windsor and London in Roman times ? I wonder ! Banking up a river with embankments, wharves, and so forth naturally constricts its bed. But this is not, I believe, the whole answer. We have no reason to believe that the rainfall is heavier

Shifting cultivation - cutting the forest to make a farm

Africa can induce occult precipitation up to at least 25 per cent, of the total annual rainfall. It would appear to be beyond dispute that once Nature's balance has been severely upset by the clearance of an excessive amount of the forests on a countryside the water table begins to sink in the soil, the rainfall becomes inconsistent and unstable, periods of drought set in, at first followed by periods of normal rainfall. But as the soil conditions deteriorate, the climate in the absence of the former considerable forest areas becomes drier, rainfall becomes more intermittent and no man can foretell whether he will receive in any one year a sufficient amount to ensure successful crops.

It can be suggested that, the chief causes

now-a-days than it was sixteen or seventeen centuries ago. But there was certainly more forest on the head waters and catchment areas of the river, and of other rivers throughout this island.

In the time of Charles the First, the Forest of Dean stretched down to the shores of the Severn River.

Before the end of the eighteenth century its boundaries nowhere reached the river. In the lower reaches below Gloucester the Severn, once a noble stream, now shows at low tide great stretches of mud banks. Moreover, recorde of the past century -and -a -half show strange changes in the current both inward with the tide and outward, sweeping away areas of valuable agricultural land. How swiftly

(A. H . W. Weir photo.)



May II, 1945 EROSION AND WATER SUPPLIES 293

such a change may result in loss was seen only last year (1944). At a certain point the river runs past a piece of cliff about twenty feet high or so at a slight curve. A short branch line of the neighbouring râilway runs close along the cliff edge and to safeguard this the railway authority had built three stone dykes and this had efficiently protected the cliff, generally of clay, from wash-outs. Early last year the river current changed its course and set dead against the cliff. The water quickly undermined the dykes, washing them away. Within three months, here in temperate England (it would have proved no surprise in a tropical country during the monsoon months), thirty-seven acres of valuable arable

as we all know, has also had its troubles, not for the first time, in connection with its water supplies. Why should this be so in this moist island of ours ? Should we not go to the catchment areas for the answer ?

India furnishes some interesting illustrations. Attempts have been made, perhaps naturally, to classify soil conservation measures into agricultural, forestry and engineering. There are, unfortunately, many areas so destroyed by man's actions that probably only great expenditure will bring about partial restoration. It appears, however, to be often accepted that, in any event, no conservation efforts can be commenced until a considerable programme has been drawn up

Bush still more degraded with thickening covering of sand , coming from Sahara - French Niger

land had been washed into the river. Beyond the railway line a " hush-hush " war factory had been built and was in full operation ; the manager, when the danger became obvious to both the railway and the factory buildings immediately behind it, made representations to London. Within a couple of days cranes and giant shovels, lorries filled with great stones arrived, and they started the work of refacing the rapidly eroding cliff face. The measures taken were effective, even if only of a temporary nature. Heavy fellings had been made in the Dean Forest and elsewhere in the region for war purposes. Water supplies during last spring and summer were extraor- dinarily short on a countryside where one would never have suspected that such a state of affairs could have supervened. London,

and the estimated expenditure involved sanctioned. This is, however, by no means always necessary. In the past it has been often the failure to consult and accept the suggestions of the experienced forest official, or the failure of that officer to recognise the portents, which has so often precluded or retarded the beginning of reclamation attempts. It is often held that the country in which to study soil conservation and reclamation work is the United States. Cer- tainly much research and fine work has been undertaken in this connection and on a grand scale. I am not sure, however, whether for the purpose of parts of the British Empire, e.g., the Colonial parts, India cannot offer some better illustrations ; in the Punjab, to give one example.

[Author's photo.)



294 JOURNAL OF THE ROYAL SOCIETY OF ARTS May II, 1945

From a note of the Inspector General of Forests in India on a visit paid in 1943, it becomes obvious that the general impression that the counter-erosion work in the Punjab, with its relatively small rainfall, but heavy storms, depends upon contour trenching, gully plugging, check damming, and so forth, is incorrect. In other words, that the cheaper and more ordinary methods of closing the area to grazing and firing, and, if necessary, assisting by afforestation are often sufficient. In some parts of one area which have been closed to grazing for forty years, and effec- tively so for the past eight years, only grass- cutting being permitted, the improvement compared with unenclosed areas is obvious

Going from south to north through the Siwaliks into the Jaswan Dun you see the bare Siwaliks again beyond that, separated by the valley of the Beas from the main Himalayas further north. "îhis country is very like the southern part of the Hailey Park in the United Provinces except that there is far more middle Siwalik conglomerate in the northern portion of the Hailey Park and a much heavier rainfall. But while in the Hailey Park there is no serious erosion problem and the whole is covered with moderately dense forest or grass, these Siwaliks south of the Jaswan Dun are a picture of devastation and erosion. Here again, however, areas are being closed to grazing or at any rate it is being regulated,

Farmed-out land now used for pasturage - N. Nigeria

and remarkable and vegetation is far denser than in the unenclosed areas. Again, the catchment area of Dholbaha, 20,000 acres, discharges through a narrow cho (stream bed) which fans out as it leaves the hills into a wide area of sand. In this 20,000 acres one- third has been closed to grazing for forty years ; the rest closed to goats and cattle on a two-year rotation. Both areas are open to grass-cutting. The rotational closure has less effect, though the closure to goats has increased bush growth. The area which has been closed for forty years is improved out of all recognition. It is hardly possible to believe that this now moderately well wooded area with a large percentage of Chir Pine ( Pinus longifolia) had ever been so barren and eroded as the unclosed areas. The run-off must have been largely reduced.

and whenever an area is closed vegetation very definitely improves. Jaswan Dun itself con- tains cultivation but is very largely sandy or swampy land by the excessive run-off from the bare Siwaliks to its south and north. Yet there is no reason whatever why, if these Si- waliks were covered with vegetation, this Dun should not compare with Dehra Dun in fertility and productiveness. On the subject of the work done in the Pabbi Hills, the Inspector General of Forests says : - " This country is very like the ravines of the Jumna and Chambal. A great deal of gully plugging, contour trenching and artificial regeneration has been done at great cost, but, excellent though it is, it is the vegetation, whether as a result of closure or artificial regeneration and not the engineering, which fairly obviously now has had the greatest effect. This would

(A. H. W. Weir photo.)




not be so apparent in the first year or two of closure. " Compared with the total area of closure of one sort or another there is little gully plugging, contour trenching, check damming and the like. The forest department here rightly look upon the natural process of encouraging the spread of vegetation, princi- pally naturally and supplemented artificially as the basis of their work. They use all these minor engineering works òf gully plugging, check damming, contour trenching, etc., to aid them for certain special reasons in certain special places, but they are all used for some special purpose in a special place and are not either the principal or the general method of

Etawah (on the Jumna between Cawnpore and Agra) begun some thirty years ago. Contour trenching and the like is an excellent way of dry farming to get regeneration, if it is necessary and if it is worth the cost, but as a method of erosion and flood control in these areas is of itself both expensive and ineffective. Moreover the making of contour trenches on a grassy slope may break the stability of that slope and actually start erosion."

These are some of the latest opinions from Indian experience in these matters.

It is not proposed to deal here with the crop cultivation methods which have resulted in the formation of the disastrous dust bowls in the United States and Canada. Suffice it to

Disappearing vegetation ending in desert conditions - Sahara

tackling the problem. The Chief Conser- vator in a tour note has written : -

" Trenching is far too expensive to be done on a large scale and dams, though certainly useful, are hardly required at this stage, as the greatest success is being attained by simple closure. Even this very broken ground is producing a crop of grass and bushes which will be of local value in addition to serving as a check to erosion. I do not want to say that trenching and gully plugging are useless but their effect is entirely subordinate to that produced by nature in re-clothing with grass and vegetation barren hill sides. Closure is essential, and engineering works cannot succeed without it or ever ha^e com- parable effect. This agrees entirely with the experience gained in the United Provinces on counter erosion works in the ravines of

say that the over utilisation of the soil in the production of wheat and cotton has resulted in some 900 million acres of land in the north, central and north western states being ruined and threatens even larger areas on their outer perimeter, the Ssame applying to the prairie farms of Saskatchewan and Alberta in Canada. The other example of the results of disaffor- estation of catchment areas on the grand scale is exemplified by the gigantic floods on the Mississippi and Ohio river in 1937-

In 1943, C. A. Connaughton, Director, Rocky Mountain Forest and Range "Experi- mental Station, wrote : - " Service of water- sheds is one of the most important contribu- tions that wild mountain lands m?ke to the semi-arid West. Their utility for watershed purposes is influenced by a number of factors, of which those associated with the

{Author's photo.)



296 JOURNAL OF THE ROYAL SOCIETY OF ARTS May II, I945

kind and density of vegetation may be mani- pulated in co-ordination with other uses to obtain optimum fields of usable water. Since the benefits of land management for water yield may often be less direct than the returns from other resources, land managers are cautioned to guard against subordinating watershed services to other uses at the expense of the public welfare."

In Australia it is admitted that a century- and-a-half ago the first settlers found a land which appeared to be one vast forest in which the nomadic aboriginal was so primitive that he had not acquired the art of tilling the soil. By the end of the century- and -a-half the development had been so rapid that nearly all land capable of growing crops or of raising flocks and herds had been wholly or partially worked. Fortunes were made, but the misuse or over-use of the land upset the balance of Nature, and their greatest national resources, soil and water, have been impaired ; and owing to all failure to plan the formerly fruit- ful soil, has in many cases, ceased to yield a return. Erosion by wind and water, the well- known " soil drift," has taken a great hold over considerable areas which have been turned into deserti. In the mountains over- grazing and fires have attained dimensions which endanger the catchment areas of thè waterways - rivers like the Murray which are not confined to one State, but on which two or three are dependant for water for irrigation. Floods are becoming more serious, and rivers, once secure between their forested banks, are tearing away alluvial soil and bearing it down to the sea. This is a quotation by an Austra- lian - Soil drift in the arid pastoral areas of South Australia is well-known as also the constant " Droughts." Few years pass in which the Press has not some serious reference, such as the report from Canberra of 27th Sep- tember, 1944, on one of the worst droughts in history had befallen Southern and South Western New South Wales. The wheat harvest would be only 50 per cent, and thousands of stock were in peril unless rain fell soon. Horses were selling at 2 s. 6 d. or being shot, and ewes at 4 d. Victoria also needed rain and there was a sudden famine in Melbourne. It is pertinent to our subject to ask, were there any droughts of this type in Australia a century ago ?

In New Zealand in a recent Forestry Department Report, on the subject of " Soil Erosion," it was stated : - " The Forest Service continues to advocate a realistic approach to the problem of soil erosion through Dominion

wide control of land-burning operations. No other measure can give such effective results either as quickly or as economically. So aggressive is the New Zealand vegetation that no ground is too barren to resist its invasion - that is, if burning is controlled instead of repeated and uncontrolled. Even much of the harmful effect attributable to over-grazing is a direct result of indiscriminate burning, and would, therefore, be corrected by control of firing operations. Simple as the premise is it provides the most practicable and economic method of preventing accelerated erosion." This considered expression of opinion could, I think, be usefully studied elsewhere in the Empire.

Space will preclude consideration of the European countries bordering the Mediter- ranean or the islands, such as Cyprus, where the goat has been one of the chief causes of erosion.

Palestine displays one type of the Middle East - covering some 10,000 square miles, approximately half plains, half hills. The hills, once undoubtedly covered with good soil and forests, are now eroded with probably less than one per cent, of agricultural land in good condition. The river valleys are deso- lated by floods and the disposition of infertile detritus ; river beds are choked and railway embankments and bridges frequently damaged. Excessive grazing and uncontrolled cutting are responsible for these conditions of what has been termed artificial desert in Palestine. Perhaps most significant is the fact that there is no fire danger because there is not enough even scrub forest on the countryside to enable fires to spread.

The general management of the West Indian Colonies in the past is an example of concentrating on the production of paying crops which quickly raised the status and wealth of the Colony and its inhabitants while ignoring the inevitable results of upsetting Nature's balance.

The problem, as a result of the great work of Sir Frank Stockdale, is now being handled in a masterly fashion and needs no further comment here ; with the one suggestion of the vital necessity of restoring or rehabili- tating the delapidated forests on the important catchment areas in the interests of an improvement in the water supplies, and to arrest further erosion.

In one way and another Africa presents one or more of these erosion problems, and at times two or more acting in conjunction in a variety of aspects.



May II, 1945 EROSION AND WATER SUPPLIES 2Ç7

In the Dominion of South Africa the main pre-occupations appear to be wood ánd water. The present war has brought up very prominently the known deficiencies in the former. In a country where large arid and semi-arid soils exist and little indigenous forest, a deficiency of wood would be a natural pre-occupation. The Dominion in this respect is in the same position as Great Britain, importing when possible, large amounts of soft woods ; and also envisages an increased afforestation campaign after the war. In the case of water supplies irrigation and large storage tanks have been the chief methods of assisting agriculture. In the extensive wild grazing areas of the veldt,

to be drinking water for the people and their cattle. Improvement of the river beds by the removal of silt, which would necessitate the afforestation of their catchment areas, thereby stopping erosion, the construction of storage dams and the development of underground sources have been suggested. . Swaziland is blessed with numerous streams and rivers ; the question of irrigation on the large scale and the objectives to be aimed at is under consideration. In Basutoland a loan from the Development Fund is, it is believed, to be spent in the construction of small works partly for crop raising but chiefly in anti- erosion measures. A former District Com- missioner in this region gives the following

Degradation of the bush in N. Nigeria - Burnt on right - untouched on left - dry season

where state funds are to be spent, modern opinion appears to favour assisting the stock farmer by the provision of drinking water and irrigation for the growth of fodder reserves in order to stabilise the animal industry. Ir- regularity in thé rainfall occurs, and this intermittency appears to require further study ; since, although underground water has been used through borings by the State, in some parts it is said there is no actual water table, the supplies being maintained by infiltration through pervious strata from annual rainfall.

In Bechuanaland, Swaziland and Basuto- land water and erosion are serious problems. In Bechuanaland boreholes have, in some parts, proved failures owing to brackish water. Apart from erosion, the chief problem appears

eye-picture. In the early days there was land and to spare for the small population and for their cattle and sheep. Internecine warfare ceased, more and more land was opened up, population and stock increased rapidly until all available land had been occupied ; as a result of over-utilisation erosion commenced. Rainfall diminished in the Spring. Round about 1900 thunderstorms occurred in August and onwards. Now it is more usual for little rain to fall before Christmas. Contour furrowing and reservation of water in dams were introduced. The district officer anticipated the Inspector General of Forest in India by remarking that, unless contour furrowing was done carefully, erosion might be started, especially on grassy slopes, while the breaking of the veldt in Africa often gave

{Author's photo.)




rise to a dense weed growth which led to waterlogging.

The Rhodesias - southern and northern, are in rather a different position. No irrigation works of any size have been undertaken. It is too big a subject to deal with here. It may be suggested that, in the interests of the mines and the labour forces employed by them and their requirements in firewood and so forth ; in the interests of the farming and its dependence on the bush ; in the interests of erosion and water supplies in some parts of these countries ; in all these interests reservation of forests is a matter of some importance, if mainly for protective reasons, apart from their capabilities of supplying and maintaining supplies of timber and other products. In Southern Rhodesia the State maintains an engineering and well-boring establishment which carries out drilling for farmers . The following, written to me in 1 9 3 8 , gives a picture of Southern Rhodesia : - " Last year on this farm I had about 21" of rain, which practically all fell in six weeks, from the middle of December, 1937, to end of January, 1938, the worst season for ten years, arid all my streams are consequently lower than I have ever seen them. " Although the natives here have 30 million acres set aside for them as reserves, some 130,000 live in the White Area on Crown land, which, I have no doubt, they are destroying as rapidly as possible. Ten families destroyed on this farm at least 300 cords of wood in a short time, and there are no adequate penalties at law to stop similar destruction in reserves, etc. The increase in the native population in twenty-five years is amazing, as also the increase in their cattle. The destruction of wood by natives and by tobacco growers is enormous and there is no compulsion on anyone to replant. " On the Vumba mountains on which is the boundary between Portuguese East Africa and ourselves, we have a 60" rainfall as a rule, but erosion occurs there due to cattle going to water, roads undrained, and natives making gardens (farms) on the hillside. Few people plant forest trees.' *

The rest of Africa, south of the Sahara from Senegal to the Sudan has many characteristics in common, the regions perhaps of chief importance and most discussed lying from Sierra Leone to the Sudan. Between are situated the Liberian State, the Ivory Coast, Haute Volta, Gold Coast, French Soudan, Togoland, Dahomey, Nigeria, French Niger, the Cameroons, French Equa-

torial Africa, Belgian Congo, the East African Colonies of Nyassaland, Tanganyika, Uganda, Kenya and the Sudan to north. From half to two-thirds of this great area of Africa is covered by the so-called bush or Savannah, variously degraded from a former high forest, becoming more open and of thorn -like character as it goes north on the confines of the Sahara. The method of farming depending upon the bush is the method known as shifting cultivation - but the villages are fixed and the Chief and his people practise this method on a definite area of country in their proprietorship. Population and stock may increase in numbers, but the area of land remains constant. The result is that the fallow period or number of years intervening between cultivating and re-cultivating the same site becomes shorter and the return of crops poorer in amount and value. Added to this the climate becomes drier and the rainfall shows an intermittency. This is no new thing. It has certainly happened in the past centuries and we are only witnessing an often repeated story in the world's history ; but owing to a settled government the rate of the dessication and interference with man's pursuits is becoming more rapid.

The tsetse fly also adds to the difficulties of the land problem in some parts.

It was from the French and from the North Sahara that the first reports came in connection with the Sahara. Duveyrier ( Les Touareg du Nord , 1864), gives records of the existing vegetation and forests, some of which have since entirely disappeared. Between 1898 and 1906 several expeditions were made southwards into the Sahara, with the pro- gressive occupation by the French, and the question of dessication commenced to be discussed in French Circles. Later reports and papers are connected with the Colonies in the south, on the fringe of the South Sahara boundary. Henry Hubert, a chief political officer of long service, and another high political officer in the Haut- Senegal- Niger region both voiced the opinion that dessication was increasing and that wells in their regions had dried up in their own time whilst the rainfall had become very unreliable. Hubert cites Mauretania where there was once a dense population but is now only a great desert. The results of his study of the position were published m 1920. In the following decades several senior French political officers who had passed most of their service in the arid regions situated within the boundaries of the southern Sahara and




immediately to the south, expressed similar ' opinions on the increasing dessication. This strip of country eastwards to Lake Chad lies immediately to the north of the British Colonies.

Quite apart from any investigations made by myself the statement that the Sahara is advancing southwards was recorded by two senior French officers during the last ten years, each having passed thirty-five years of his service in these French colonies. Put in a few words the dessication is attributed to over cultivation by an increased population restricted to their own lands, over-grazing when the latter replaces cultivation, to the custom of annually firing the bush and to unchecked cutting in the bush. One of the outcomes of these operations is a reaction in the annual rainfall supplies previously received. The first reaction appears to be not so much in a decrease in amounts received as in the failure to receive it at the appropriate time. The fall may be delayed at the sowing season necessitating the re-sowing of the seed. The process of dessication is slow and man is slow to recognise that anything is wrong. But the rainfall gradually shows a greater intermittency, sowing becomes more of a lottery and, with the decrease in density of the bush, blown sand increases in thickness over the soil layers.

Several influences are at work - erosion due to drying of the exposed surface of the farms and the blowing away of the upper rich particles of the soil combined with sand pene- rà tion coming from the nearby desert, and the failure of the rainfall at the required time together with the smaller amounts of the fall ; it is the combined results of these influences which are gradually causing the population to move further south. One heard on more than one occasion from the French in the Ivory Coast and Haute Volta that their people (in the colonies bordering on the South Sahara) were moving south into the British colonies. This was not primarily due to the French conscription, but I think, from obser- vations I was able to make, due to the increasing dessication in that strip of French colonies immediately to the south of the Sahara proper.

In their Report a West African Com- mission appointed by the Leverhulme Trust under the heading " The Advance of the Sahara " wrote : - " The dramatic onset of wind erosion in the ' Dust Bowls ' of the United States in the early nineteen-thirties created uneasiness in many other countries.

There was something approaching alarm in certain quarters when after a recent visit to West Africa and a journey across the Sahara Professor Stebbing of Edinburgh suggested that there was more than a possibility within the next fifty years or less that Kano itself might be overwhelmed by the Sahara, should the present methods of agriculture, grazing and firing of the bush to the north continue on an increasing scale. Fortunately, one part of the problem has recently been examined by a competent Anglo-French Forestry Com- mission which failed to find any definite evidence of increasing aridity or any general danger of dessication."

Owing to a misunderstanding or misreading of the remark made in a paper on the subject I read before the Royal Geographical Society it was implied that I envisaged the Sahara as advancing in rolling waves like the sea breaking on the shore under a rising tide. Conse- quently, as was explained to me afterwards, the Commission spent a proportion of its time in searching for moving sand dunes from which Professor Stebbing's " vagues " could emanate ! I remain of the same opinion about Kano and I believe an International Com- mission of countries having jurisdiction in Africa with carefully drawn up Terms of Reference would possibly be the only way to settle upon agreed steps to be taken - soil conservation to use the modern term - if the threat, a very long standing one, is to be laid so far as this may prove possible.

In connection with such a study I would suggest that the determining factor as to how far dessication, to use the word in its widest sense, has gone, depends upon what I call the intermittent rainfall. Lavauden, in his " Les Forets du Sahara " wrote : - " In the middle of the Quaternary period, an epoch which it is impossible to date precisely, the Sahara was a very humid region, the fluvial system was of a particularly powerful type, allied without doubt to very abundant precipitations. To-day all these river beds are dry, and only the largest retain underground water of which the amounts constantly diminish - slowly perhaps but inevitably - owing to the equilibrium existing between precipitation and evaporation . An important question is to determine at what epoch the disequilibrium between the two commenced to make itself felt ; in other words at what period dessication commenced to become seriously apparent."

This represents exactly what I term intermittent rainfall. If in each case we can



300 JOURNAL OF THE ROYAL SOCIETY OF ARTS May II, 1 945

determine the exact stage at which this disequilibrium between precipitations and evaporation has reached, based on the now intermittent character of the rainfall, we shall be in a position to settle upon the measures to take to restore where possible the necessary equilibrium.

During the last decade a very considerable amount of investigation work has been undertaken by officers of the Colonial Services, and this combined with his own investigations has been epitomised in a masterly fashion by Lord Hailey in his work " An African Survey."

In defining the functions of forestry in Africa, Lord Hailey said that the importance which frequently attaches to a forestry regime lies not only in the extent to which timber can be exploited, but also in the direct protection which forests afford to the water supply, or their influence on climatic conditions, both being of vital importance to the methods of livelihood of the African communities. Read the history of the past eighty years in India. The lesson, with backslidings it is true, has been learned there. Read the history of the past forty years in Africa. Forestry was largely governed by the annual revenue obtained from the forests. This may now be regarded as the history of the past.

A new orientation of the point of view has latterly come upon the scene, started to some extent from the inception of the Colonial Development Fund, which, small beginning as it was, led to such quick results in some colonies under the able guidance of Sir Frank Stockdale. 4 .

The new conception of the problem to be faced is being drafted as a result of Soil Con- servation Committees consisting of carefully chosen officers from the administrative, agricultural, forest, veterinary and engineering departments, with the assistance, when required, of the geological, meteorological and medical departments. Some draft reports have been published, and work has been commenced in some colonies. It is evidently of a type which requires careful collaboration before large sums are expended, such sums as will now be available from the far-sighted statemanship of the Secretary of State for the Colonies. His recent epoch-making Bill, the Colonial Development and Welfare Bill, which has been accepted by the House of Commons, sanctions the expenditure over a period of ten years, of a sum of £120,000,000 on colonial development.

As an example of this new attitude the

Sudan has published a Report of their Soil Conservation Committee which gives a very complete exposition of the case. The greater part of the Sudan comes under a zone of instability where natural conditions allow vegetation of a certain type to flourish, but in which zone a slight disturbance of conditions (natural or human) may tip the balance in favour of destruction of vegetation and allow the recession of the zone and the enlarge- ment of the arid or desert zone, where, says the Report, " nothing can be done by man to ameliorate the conditions." Amongst the recommendations for Kordofan are : - " The existing system of attempted fire protection to continue, in view of the nature of the grass vegetation, the grazing situation, and the comparatively advanced state of the public conscience in the matter, fostered as it is by the money value of the gum stocks. The early adoption of ' national ' fire lines either from Du ein westwards or through the latitude of Um Dam." In discussing the Ëquatoria Province the Report says " the immediate effects of fires are : - (1) to kill tree seedlings; (2) to kill some perennial plants and per- manently damage others ; (3) to burn up vegetation debris ; (4) to destroy humus ; (5) to expose and dry the surface of the soil. Other secondary effects are discussed and the causes for the prevalent habits of firing the countryside in Africa " ; and ends up with " it is obvious that the bad effects of fires far out- weigh any good effects that they may have."

It may be suggested that the work of these Soil Conservation Committees would be greatly simplified at the outset if some attempt was made to decide upon the rough boundaries or types of areas which fall to (1) agricultural investigation ; (2) forestry investigation : this might save duplication of work at its initiation ; and (3) a third group occupied with investigations into the intermittency of the rainfall, undertaken district by district ; for this undoubtedly will underlie and form the basis of the whole of the enquiries and investigations.

The objectives of each should not be difficult to prescribe or assimilate ; for instance, perhaps the first objective of the forestry department would be to select within its own area blocks of bush or forests which would be recommended for strict closure to cultivation, grazing, firing and cutting - apart from a careful assessment of catchment areas, in connection with the amount of rainfall being received in the region, and the available



May II, 1945 EROSION AND WATER SUPPLIES 3OI

supplies in the arable land below the catchment area.

There can be little doubt, as has been proved in India, and in a few cases in Africa, that such closure, assisted where necessary on the lines carried out in India with the same object in view, will produce within a comparatively short period of years remarkable results ; and this action has the merit of being cheap whilst ensuring in the future an adequate supply of small timber and other products which will be in demand by an agricultural population, by then settled on a more permanent form of arable production. The grazing areas will have been improved by a rotational cropping. One function of these great forest blocks will be the protection to the countryside they will afford, while assisting to stabilise the water supplies of the region. In the future they will afford further areas of a greatly improved soil for cultivation, required by an increased population. The large clo- sures made in the first instance therefore by no means indicate that the whole of the area will remain permanent forests ; as in effect, has often been witnessed in India where the Civil Department has taken over blocks of Govern- ment Forest later required for agricultural purposes. In Africa, however, in general, many of these great closed blocks of Savannah will have as their chief function for years to come a protective character, while at the same time helping to rebuild the water supplies and bring back a more stable equilibrium in these matters than exists at the present time.

Finally, it may be suggested that this is by no means a matter for individual districts, each working in parochial fashion. As is well known a river in one district, and its catchment area, may be depended upon to furnish a large part of the water supplies for districts situated at a considerable distance. Collaboration on the broadest lines over a whole region having more or less the same characteristics will be required.

It will be inevitable that the problems in some districts will extend outside the British frontier and that districts may be adversely effected by what is taking place on the other side of the frontier. A strong case would appear to exist in Africa that the powers who are chiefly responsible for the improvement of the conditions of life of the people should come to some common agreement upon the general steps to be taken in this grave matter.

In a paper published by the Royal African Society in January, 1941, the suggestion was made that the ideas on the subject of dessica-

tion and erosion in Africa of the Govern- ments concerned might be pooled, since the Administrations of several of these Govern- ments were in London. Under the auspices of the Society a small Commission on Research for Africa was set up and representa- tives from Free France, Belgium and the Netherlands Governments in London were invited to serve, with two British representa- tives. The bulk of the members were administrative (political) officers. The Com- mission came to unanimous conclusions on, the subject of shifting cultivation, bush fires, grazing, reservation of forests, and erosion ; and made practical proposals for dealing with these evils, evils which, it was freely admitted, the various administrations had refrained from touching for so long, being unwilling to interfere with the habits and customs of the people.

My own personal reaction to the work of the Commission came in its early stages, when hearing voiced by the foreign officials, each for the regions in which he had served, problems of erosion 'and water supplies, grazing, firing • of the countryside and unchecked hacking and cutting of the forest areas, problems which I had first commenced to study well over thirty years earlier in India. I do not know why I should have felt this surprise - but listening to problems of the Belgian Congo, French Equatorial Africa, and the Dutch East Indies in these respects, brought the fullest realisation that the problem was, in its main issues, a common one in many parts of the world, with variations for different conditions and peoples ; and that probably the Continent of Africa possesses a greater similarity in conditions, and smaller differences in the main aspects of the causes for erosion and dessication taking place than is the case with other affected parts of the world.

I would make the suggestion that an African International Commission of the four countries chiefly concerned, Britain, France, Belgium and Portugal should be got together - no one better qualified to fill the post of Chair- man could be found than Lord Hailey - to co- ordinate the lines of soil conservation work to be taken. The more one studies the map the more interlocked the zones of influence of the four Powers appear to be in this matter.

There are actions of the people still practised unchecked which, in the opinion of some, spell eventual ruin to the descendants of those still carrying them out. The repre- sentatives of the four Governments




represented on the Royal African Society's Commission all admitted the difficulties in giving effect to their recommendations. That position still remains. It would appear that to tackle it in the only practical fashion to produce results will be for the Governments concerned to come to an unanimous agreement as to the action to be taken through the pronouncements of an authoritative commission whose findings would be accepted outside the confines of Africa or the Govern- ments concerned.

DISCUSSION The Chairman : I draw consolation from

one of Professor Stebbing's conclusions, namely, that the measures needed for repair- ing the mischief done are not necessarily very expensive. Indeed, the most efficacious measure is the closure of pasturage. Engineer- ing work is no doubt required on the upper reaches of streams, but lower down, where sheet erosion is the main danger, closure of pasturage is one of the most effective measures which can be taken. May I add to the facts alreadý given one which I recently learnt about Basutoland ? Some years ago we decided to take active action there and we provided a considerable sum of money for engineering work ; but we went further and succeeded in eliciting the support of the native authorities in a programme of closure of pasturage. They were able to do what we were not able to do ourselves in some of the British Colonies : they put a taboo on the use of land for pasturage for certain periods of the year. A short time ago we asked an American expert in erosion matters to visit Basutoland. He told us : "You need hardly have asked for me ; you have done all I could have advised you to do, and with marked success."

Another conclusion which is obvious is that work of this kind involves co-operative team- work of a comprehensive character. There is the forester ; the botanist (with all that he can tell us of new methods of introducing drought- resisting grasses) ; the meteorologist; the scientist who can tell us about the difficult problem of evaporation from certain trees ; the agriculturist, who is concerned with contour trenching and the extension of methods of mixed farming to take the place of shifting cultivation ; the veterinarian, who, on the one hand, is interested in the preservation of cattle by controlling epidemics and, on the other, is interested in elimination of useless stock by cutting or by upgrading.

And there is, of course, the administrator who must come in to co-ordinate their work and use his own influence to see that the right measures are introduced andi observed.

Professor Stebbing suggests that in Africa we need some co-ordinating committee of the four Colonial Powers chiefly concerned. It is not difficult to get together agencies for joint consultation where research is concerned ; scientific men recognise no nation- alisms. But where joint action is required it is more difficult. I hope, however, that some useful results may follow in this field if practical effect is given to the prçposal for creating Regional Councils or Commissions in various parts of the world to deal with Colonial problems. If there were a Com- mission of that nature in Africa it might be effective in concerting measures which would go far to meet the mischief caused by erosion in its various forms.

Sir Thomas Dunlop : May I offer our grateful thanks to Lord Hailey for taking the Chair this afternoon and for conducting our meeting so ably ?

The vote of thanks was accorded by accla- mation and Lord Hailey then left the meeting.

Dr. H. Ingleson : I should like to know whether the lecturer has any idea of the reason why the presence of trees affects the time and the quantity of rain falling on a particular area and why the removal of those trees gradually affects the time of year at which rain falls and the quantity of the rainfall. Is there any explanation of that ?

Mr. J. M0REW00D Dowsett : Lord Hailey has said that soil erosion is a major problem. It is certainly the most serious problem in the world to-day. I thýik that all who have had the privilege of hearing about it should make it their duty to spread the news of soil erosion far and wide. The more it is talked about the better.

Dr. W. N. Taylor : I should like to ask the lecturer his opinion on the relative merits, in re-afforestation, of planting soft woods, particularly conifers, and hard woods, particularly Australian gums. In South Africa gums are generally used for this purpose and some people think that gums have had a dehydrating effect on the country rather than the reverse.

Mr. W. F. Perree : May I ask whether, so far, there has been anything done, other than the expression of a pious hope that something is going to be done, to arrest soil erosion ? In these various areas in Africa



May II, 1945 EROSION AND WATER SUPPLIES 3О3

what agencies can be made responsible for arresting erosion ? Should not the district officer be made responsible ? After all, he has to deal with the population and he has got to see that the population is provided with sufficient soil and it is not enough just to say that such-and-such an area ought to be protected. There should be somebody to see that it is protected. The administrator is the real person whose business it is to set aside definite areas and who should say which areas are still capable of being comparatively cheaply treated by closure before the more expensive worfe^of re-afforestation is taken in hand.

Professor Stebbing : The first question was what effect the presence of trees had on the quantity of water falling on a particular area. That really is answered by some of the first remarks I made, namely, that whether tropical forests have any effect is still in dispute and as far as temperate climates are concerned is still a matter subject to a considerable diversity of opinion. So far as conserving rainfall is concerned, however, there is no question but that forests do conserve it in that the water runs only gradually into the streams and springs and only gradually gets into the larger rivers. It is known that during past centuries great tracts of land where the population was small did not get the considerable rise and fall which is experienced now in many rivers. My advice is : study the catchment area. If we did that I think we should find the answer to what I understand is the problem to be faced in temperate climates.

One speaker asked about the relative merits of soft woods and blue gums. That is not an easy question to answer because my own view is that in the case of any country which has indigenous species the first duty of the forestry officer is to use them so far as possible before bringing in exotics. There are no large areas of indigenous forests in the Dominion of South Africa, and they do require many soft woods which they have to import and therefore they are planting and growing conifers. One point which came out during the conference of the British Forestry Associa- tion in Africa before the war was that some farmers were planting areas of conifers in the vicinity of their farms in order to improve the water supply ; but the reverse was found to be the case, and as the trees grew they took the water away. I do not think any definite opinion about this was expressed at that conference but it is not really a difficult

problem. When closure was first started in India during the last century steps were taken to close some bare hill areas and as a result of closure this is what was found twenty years later. At first the closure resulted in a sinking of the water table in the tank (reservoir), but gradually, as the trees began to have an effect and humus was built up, the result was a raising again of the water table in the soil and consequently in the tank. That is quite what one would expect to happen. The result was more water and better conditions with increased growth in these enclosed areas. The interesting point, however, is this. When the closure is first started the water may sink, or rather there is less water available, but with the progress in density of the vegetation, i.e., the fruit crop within the closed area, the water table rises in the soil. Therefore it is probable that you will find that the planting of conifers or Australian gums will be equally efficient. More than that I am not prepared to say.

Then there is the last question. I think the general question was who, in Africa, is the officer responsible for advising on the reservation of forest areas. That is the whole point. In India when this question of reservation was first taken up and the Department was small it was not the forestry officer who had to make the decisions ; that was the civil officer's job. The forestry officer was the man who took orders when the decision was made. In Africa the reverse is the case. The Govern- ment does not own the land because ownership of the land by the chiefs is recognised. Therefore it is left to the forestry officer to try to persuade the chief concerned to reserve his forests. The forestry officer has no administrative jurisdiction in the district. If a particular chief happens to like the forestry officer it is all right, and the matter may result in a forest reserve being established in the chief's area. That is, I think, the answer, and a sufficient answer, to the fact that by the end of the last century, thirty years from the time of the formation of the Forestry Depart- ment, all the major reservés of forest had been made in India ; while at the present moment or when the war broke out, only a fraction of the reserves required in West and East Africa had been reserved. There is a different point of view between Africa and India. The matter is left to the forestry officer in Africa and he cannot do anything unless the chief to whom the land belongs agrees.

In his opening remarks the Chairman, Lord Hailey, said he hoped that I should say



304 JOURNAL OF THE ROYAL SOCIETY OF ARTS May II, 1 945

something about the Hoshiar pur Chos. In my original draft of this lecture (which had to be abbreviated) on this subject I wrote : - Perhaps the most notorious example of erosion in the British Empire because one of the most quoted, is the case of the Hoshiar pur Chos. Punjab district reports of the Eighties of last century were already dealing with this example of gully erosion on the grand scale, and much has been written about reclamation attempts in the years which have passed. In 1936 the Chos Act was to be amended to allow closure when two-thirds majority of the owners of the area demanded it. The Forestry Department was preparing a scheme for establishing a demonstration area in which all phases of reclamation and counter-erosion work were to be tried, Officials of the Co- operative Department to be appointed to encourage control of grazing and reclamation of Chos by planting. So monumental is this example of erosion that the Punjab Govern- ment are producing a general manual on counter-erosion work ; and a text book on more popular lines is also to be written.

FOURTEENTH ORDINARY MEETING Wednesday, March 7th, 1945

Sir Thomas Barlow, k.b.e., Chairman of the Council of Industrial Design , in the Chair

The Chairman : I should like to say that I am very glad to be here to-day in this historic building, and I suppose Mr. Wilson has asked me to preside this aftenoon as Chairman of the Council of Industrial Design. As you know, that Council has only recently been formed and has hardly yet had time to formulate its plans and programme, but I can definitely say that one of its functions must be to work with existing organisations, so far as possible, many of which have done such useful and valuable work in the past. The last thing the Council wishes to do isto generate the idea that its existence implies a centrali- sation of energy and functions and the elimination of voluntary effort. I think the latter especially would be a calamity of the first order. Historically it has always been the rôle of this country to depend, to a great extent, upon voluntary effort and I think it a misfortune when a historical background is broken down.

There are a great many interesting points in Mr. Wilson's paper. He stresses the

importance of co-operation and " co-operation " is a blessed word like " co-ordination 9y which we honour so much by word of mouth but practise so little in actual life that some- times one almost despairs. I shall not disguise from you the fact that in my experience as a temporary Civil Servant I often see the dire consequerices which follow lack of co- ordination. At the same time, it is idle to pretend that in the intensity and complexity of modern life it is easy to secure co-operation. It is no use having any illusions about that. It is hardly necessary to stress its importance but what I am wondering myself is what is going to happen when this abominable con- flict is over. Is the reaction from the controls, pains and penalties inflicted upon us going to be so strong that there will be a revulsion against regimentation with every- one struggling to get back as quickly as possible to the conditions of relative freedom experienced in the past ? It will be quite natural if that is so but I think it will be a misfortune in some ways because this war has taught us that mass and simplified production of colour and restriction of design have, to a certain extent, a tremendous advantage and I do not think (I speak only of textiles) that that necessarily involves stan- dardisation and total uniformity. Whether something of these advantages can be salvaged out of this terrible experience of war remains to be seen. I hope I am speaking without illusions when I say that I am not unhopeful that the industries of which I have some knowledge will have found those simplifica- tions and restrictions of such enormous advantage that they will not relinquish them lightly.

Again, I repeat that I am delighted to be here. I know what good work Mr. Wilson and the Colour Council have done during the twelve or fifteen years they have been working. They have established themselves as a vital and essential factor in the general set-up, and I do not doubt that the Council of Indus- trial Design will be able, in the fullest way, to co-operate with them in the future and, if that happens, I think we shall see real changes in many directions after the war.

The following paper was then read : -

COLOUR AS A FACTOR IN INDUSTRIAL DESIGN

By Robert F. Wilson, Art Director of the British Colour Council

When I last spoke in this Hall I dwelt chiefly upon the past. To-day I am going to



erosion and water supplies

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