indigenous soil and water conservation by teras in eastern sudan

INDIGENOUS SOIL AND WATER CONSERVATION BY TERASIN EASTERN SUDAN

J. A. VAN DIJK

Department of Geography, University College Dublin, Bel®eld, Dublin 4, Ireland

Received 9 April 1996; Accepted 16 May 1996

ABSTRACT

Recent remotely sensed and socio-economic data of the Border Area in eastern Sudan indicate that indigenous soil andwater conservation (ISWC) is expanding. The most elaborate technique is (bunded landholding) which uses earthbunds to harvest rainwater from small catchments. Most factors suggested in the literature to account for ISWCexpansion do not apply to the Border Area. On the contrary, the region is characterised by precisely those factors whichare commonly held to be responsible for a declining incidence of ISWC. Given the low level of ISWC returns whencompared with incomes from other economic sectors and crop production techniques in the Border Area, the importanceof ISWC must be understood from other merits. These include its role in livelihood diversi®cation and risk-reductionstrategies at household level. # 1997 by John Wiley & Sons, Ltd.

Land Degrad. Develop. 8, 17±26 (1997)No. of Figures: 2 No. of Tables: 3 No. of Refs: 19

KEY WORDS: Sudan; arid lands; indigenous techniques; soil and water conservation; water harvesting

INTRODUCTION

African drylands are vulnerable to food insecurity. Their populations grow rapidly, while most of the bestsoils for crop production are already being used. The resulting forced expansion into more marginal areas forcultivation results in land degradation, which further increases the hazard of food insecurity (Engelman andLeroy, 1995). In an attempt to halt this downward spiral, several new crop production systems have beenintroduced in recent decades. Those relying on large-scale irrigation and fertilizer use ®nanced withinternational donor funds have proved to be a costly strategy in Africa. These systems are also di�cult tosustain for technical and socio-economic reasons (Adams, 1992). Similar smaller-scale projects introducingsoil and water conservation were frequently abandoned because users were not consulted beforehand, andthe techniques used were not adapted to local circumstances (Hudson, 1991). Therefore, more attention isnow being given to building on indigenous knowledge (Warren, 1991). When indigenous techniques areimproved, dissemination is usually faster, more widespread and cheaper because it ®ts better into localenvironmental and socio-economic niches (Reijntjes, et al., 1994).

Pioneer insights into applications of indigenous soil and water conservation (ISWC) in sub-SaharanAfrica were given in Pacey and Cullis (1986) and IFAD (1986). These were followed by discussions in Reijet al. (1988), Reij (1992), Critchley et al. (1992) and IFAD (1992). More recent experiences with ISWC werepresented in Critchley et al. (1994). This state-of-the-art overview, drawing upon a 140-source bibliography,also discusses general conditions under which the application of ISWC is likely to expand or decline.Favourable environments for expansion are noted as those where (i) moisture availability limits cropproduction, (ii) cultivation takes place on hillsides, (iii) population numbers exert pressure on scarceresources, and (iv) land tenure systems are relatively secure. The postulated main causes of ISWC decline, onthe other hand, are (i) local labour exodus, (ii) declining rainfall, (iii) introduction of new tillage methodsincompatible with ISWC, and (iv) implementation of projects ignoring local ISWC traditions (Critchleyet al., 1994: 304±306).

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LAND DEGRADATION & DEVELOPMENT, VOL. 8, 17±26 (1997)

CCC 1085±3278/97/010017±10$17.50 # 1997 by John Wiley & Sons, Ltd.

Field research carried out in the programmes of Water Spreading Research Kassala (WARK; NationalCouncil for Research, The Ford Foundation) and Livelihood and Environment (L&E; University ofAmsterdam) in eastern Sudan recently yielded a range of data on ISWC and other crop productiontechniques. Data were also collected on the environmental and societal conditions under which thesetechniques are used. Findings di�er from the observations presented in Critchley et al. (1994). Indigenoustechniques for SWC are expanding in eastern Sudan, but the majority of the favourable conditionsmentioned above do not apply. On the contrary, the region is predominantly characterised by developmentsrelated to the postulated main causes of ISWC decline.

IN THE BORDER AREA

The Border Area in eastern Sudan covers some 8600 km2 northeast of the town of Kassala (1990 population217 000) along the international border line with Eritrea (Figure 1). This semi-arid to arid zone receivesabout 300 mm annual rainfall, unimodally distributed throughout May to November. The region is ¯ankedby the Ethiopian Highlands, whose foothills are drained by some 30 large ephemeral water courses, or

. Numerous smaller streams seasonally spring from outcropping inselbergs (island mountains) on thesparsely vegetated plain.

Geomorphologically, the area consists of a series of northwest-sloping valley-bottoms and inter¯uveswhich steepen in gradient at regular intervals in the direction of the slope. The resulting terraced-shapedlandscape has a braided and highly dynamic drainage system. Major soil types are Fluvisols, Regosols,Cambisols and Luvisols. These are predominantly loamy textured and typi®ed by high surface-sealing and

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Figure 1. The Border Area and research villages.

18 J. A. VAN DIJK

# 1997 by John Wiley & Sons, Ltd. LAND DEGRADATION & DEVELOPMENT, VOL. 8, 17±26 (1997)

crusting capacities. Such properties enhance run-o� generation of rainwater at the inter¯uves and ¯oodwaterat the valley-bottoms.

The Beja tribe inhabiting the region was largely nomadic until the 1950s. Government sedentarisationpolicies in the 1960s, restrictions on livestock movement as a result of civil war in Eritrea, together with large-scale agricultural development in eastern Sudan since the 1970s, and droughts in the 1980s and 1990sincreasingly forced the Beja people to settle. Religious movements were an important organising force in thisprocess of livelihood transition, enhancing the Beja's negotiating power vis-aÁ-vis the government regardingthe provision of basic services. Nowadays, Beja livelihoods depend on a combination of incomes fromsubsistence crop production, livestock husbandry, labour migration, o�-farm employment and informaltransfers of wealth through social networks or relief aid. Various techniques are used for crop production,such as valley-bottom and ¯ood-recession cultivation, gravity irrigation and SWC. Some of these SWCtechniques have been introduced by the government, such as earth dams and contour embankments for¯oodwater harvesting. Others are indigenous, such as the application of brushwood panels and earth bundsfor rainwater harvesting.

(bunded landholding) is the most elaborate indigenous technique for SWC applied in the BorderArea (Van Dijk and Ahmed, 1993). It presumably originated as a means of irrigation in the Nile region andwas adjusted by settling Beja to meet local conditions in the Border Area from the 1950s onwards. isthe name given to a landholding which is bunded on three sides. The fourth is left open to capture run-o�from an adjacent, slightly elevated catchment. Characteristic of the technique is the base bund built on theapproximate terrain contour which serves to catch run-o�. Two outer collection arms constructed perpen-dicular to this base act as conveyors. Sometimes, shorter inner arms are added to improve the distribution ofcollected run-o� over the cultivated area. The height of bunds is between 0.5 and 2 m. The length ofbase bunds and outer arms is usually 50±300 m and 20±100 m, respectively. The cultivated area of a typical

in the Border Area is between 0.2 and 3 ha, excluding the catchment. When the size of this catchment istwo to three times that of the cultivated area, su�cient rainwater can be harvested to sustain cultivationunder local conditions. Another bene®cial e�ect is that bunds also harvest sediment and organic material,such as animal droppings and crop residues, from upslope locations. There are indications that this enhancesthe soil nutrient status of land under (Figure 2).

bunds are built by hand and are made of local alluvial and colluvial material. In the dryer northernparts of the Border Area, land users also erect brushwood to capture sand and dust in order to let bunds riseby wind action. The labour demands of use are relatively low, with 6±16 man-days per hectare for

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Figure 2. in the Border Area landscape.Teraseeeee

CONSERVATION BY TERAS IN SUDAN 19


construction and 3±18 man-days per hectare for annual maintenance (excluding cultivation). The Bejaincreasingly rent tractors for construction and maintenance purposes. However, cultivation remainspredominantly for subsistence. The main crop is sorghum, with okra, rosella and watermelon occasionallybeing intercropped. The average sorghum production in the 1980s was 400 kg haÿ1 (Van Dijk, 1995).

Developments in use in the Border Area in the late 1970s and 1980s have been assessed from remotesensing and socio-economic data. Black and white vertical aerial photographs (1 : 75 000 February 1979;1 :80 000 May 1979; 1 :20 000 December 1986) and digital information of SPOT XS satellite imagery (fullscene, August 1988) provide absolute data for this purpose. Farming zones where is the dominant typeof land use ( zones) were delimited, and measured by mechanical polar planimeter and grid overlay. Thesatellite imagery was used for a part of the Border Area which lacks recent photo-coverage. The imagery wasprocessed and interpreted in the GIS package Geographic Resources Analysis Support System (GRASS).GRASS provides standard procedures for the measurement of polygons which on the ground have beenidenti®ed as representing zones.

Questionnaire surveys were made in the Border Area villages of Um Safaree, Hafarat, Ilat Ayot andTelkook (1990 population 2000±4500, see Figure 1). These data provide socio-economic information on therelative importance of the technique in Beja livelihoods. A total of 244 households was studied for thereference years 1983 and 1988 using a sample of approximately 20 per cent. The growing seasons of theseyears were relatively dry and wet, respectively. The data were partly modelled to allow a comparative analysisfor the Border Area as a whole (Van Dijk, 1995). The relative importance of ISWC was assessed, amongother parameters, by calculating its shares of income generated in crop production and in the total of allhousehold economic sectors together (livelihood).

INCREASING IMPORTANCE OF OVER TIME

Table I shows the 1979±1986/88 changes in size of zones for the four research villages. is morelabour-intensive than other techniques such as ¯ood-recession cultivation. Usually, a negative relationshipexists between intensity of application and distance to the village. Developments in zones near the village aretherefore listed separately.

zones were found to have increased in size in Telkook and Ilat Ayot. Nearby zones hadexpanded locally by 14 and 32 per cent, respectively, which is more than double the rates of 6 and 11 per cent,respectively, found for all zones together. The size of zones had declined in Um Safaree by 5 per centfor all zones, and 17 per cent for those closest to the village. In Hafarat, a small decline of only 2 per cent wasfound for all zones, while nearby zones had expanded by 14 per cent. Sample data for all villages togethershow that the total size of zones has increased from 2700 ha in 1979 to 2795 ha in 1986/88: an increaseof 4 per cent. When only the group of zones closest to the village is considered, this increase amounted to15 per cent (from 585 to 670 ha).

Table II shows the changes in the composition of household economic sectors and the relative importanceof in household livelihoods in 1983±1988. These data should be interpreted with caution, since theywere collected for another purpose. First, the growing season in 1983 was dryer than that in 1988. Thisin¯uenced the number of land users cultivating under ISWC, as well as their production levels. Second,households in the Border Area su�ered signi®cant losses of livestock during a major drought in 1984±1985.This caused additional changes in Beja livelihoods, which also in¯uenced the relative importance of ISWC.Third, the proportion of households applying di�ers. This variation is not over years but betweenvillages, and ranges from 11 of the 61 respondents (18 per cent) in Telkook, to 59 of the 64 respondents (92per cent) in Um Safaree (see Table II). In all three situations, variation was found to be related to a clearnorth±south gradient in the level of aridity, and also to small tribal cultural di�erences between Beja sub-groups (Van Dijk, 1995).

Taking account of these restrictions to interpretation, Table II indicates a general increase in theimportance of in the Border Area. The technique's contribution to livelihood declined only in Telkook

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(26 per cent). At the same time, its contribution to crop production in this village remained at the maximum100 per cent. This indicates that households did not rely on other techniques to generate income in thissector. Sample data for all villages together show that the 1983±1988 increase in the contribution of tocrop production and livelihood amounted to 6 and 11 per cent, respectively.

The combined data of Tables I and II illustrate two more developments. Decreasing areas under inUm Safaree and Hafarat are associated with increasing contributions of this technique to crop productionincome and livelihood. This suggests that land-use intensi®cation can be understood from the proximity ofthese villages to Kassala town. Proximity not only results in higher urban-to-rural income transfers, but alsoin better access to urban services which raise productivity, such as tractors for tillage and constructionand maintenance (Van Dijk, 1995). The reverse is found in the more remote Telkook; here, the samecontributions remained constant or declined despite an increase in the size of zones. This, andthe relatively small number of households applying , suggests that the margins of crop productionunder ISWC have been reached in this most northern and arid of the four villages researched in the BorderArea.

SUGGESTED PROCESSES FOR EXPANSION

Data referred to in this and the following sections are taken from Van Dijk (1995: passim) unless statedotherwise. Critchley et al. (1994) mention four main factors which favour the expansion of ISWC worldwide.Of these, only moisture scarcity applies to the Border Area. Hillside cultivation, population pressure onscarce resources and secure land tenure are not relevant phenomena in this context.

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Table I. Developments in use. Changes in the area of farming zones where is the dominant land use (ha) inselected villages in the Border Area and all farming zones closest to the village area, 1979 and 1986/1988

1979 1986/1988 (% change)

Ilat AyotAll zones: Ilat Ayot, Youdrut, Tebiai, 860 950 �11%Tendelai, Eragot, Hemiai, Hag Adam

Closest to village: Ilat Ayot 170 225 �32%

Telkooka

All zones: Kadabot, Gadaweet, Gadamai, 765 810 �6%Telkook, Mindoweet

Closest to village: Telkook 290 330 �14%

Um SafareeAll zones: Wad Kaduj, Ja'ahbir, Kawateib, Sherifei, 620 590 ÿ5%

Idi Kideb, Silkiai, Fil NatarClosest to village: Idi Kideb 90 75 ÿ17%

HafaratAll zonesb: Wad Kaduj, Hedadeib, Sherifei, Bernoop, Orun 455 445 ÿ2%Closest to village: Sherifei 35 40 �14%

Border Area four villagesAll zones 2700 2795 �4%Zones closest to village 585 670 �15%

Source: L&E research and ®eld checks.aArea based on 1988 data.bExcluding Aftila and Baha Bina zones for which no data are available.The 1979 data are taken from aerial photographs V17 109±121, 159±169; V31 089±091, 095±096; V32 001±007, 173±175, 178±180 and ®eld checks. The 1986 data are taken from aerial photographs SD 86 04 001±005, 071±075, SD 86 05076±078, 139±155, 211±214. The 1988 data are taken from SPOT XS full-scene 130±318.

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Table II. Developments in livelihood. Changes in total household income shares in livelihood by sector (%) and totalincome shares in crop production and livelihood (%) for selected villages in the Border Area, 1983 and 1988

1983 1988 (% change)

Ilat Ayot (N � 58)% crop production 50 52 �4% livestock-related 20 6 ÿ70% labour migration 11 13 �18% local o�-farm 14 25 �79% networking 5 4 ÿ20Total livelihood 100 100

% in crop production (N � 26)a 45 49 �9% in livelihood (N � 26)a 19 24 �26

Telkook (N � 61)% crop production 12 20 �67% livestock-related 23 6 ÿ74% labour migration 15 23 �53% local o�-farm 41 49 �20% networking 9 2 ÿ78Total livelihood 100 100

% in crop production (N � 11)a 100 100 0% in livelihood (N � 11)a 31 23 ÿ26

Um Safaree (N � 64)% crop production 35 34 ÿ3% livestock-related 9 9 0% labour migration 42 48 �14% local o�-farm 12 8 ÿ33% networking 2 1 ÿ50Total livelihood 100 100


Hafarat (N � 61)% crop production 55 69 �26% livestock-related 5 3 ÿ40% labour migration 14 6 ÿ57% local o�-farm 26 22 ÿ15% networking na 0 naTotal livelihood 100 100


Border Area (N � 244)% crop production 38 44 �16% livestock-related 14 6 ÿ57% labour migration 21 22 �5% local o�-farm 22 26 �18% networking 5 2 ÿ60Total livelihood 100 100


Source: L&E research.aBased on the sub-group of households using indigenous SWC; na means not applicable.

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Moisture Scarcity

The Border Area receives on average between 150 and 400 mm rainfall per annum at its northern andsouthern margins, respectively. The water requirement of the main crop, sorghum, is some 600 mm underlocal climatic conditions. Hence, moisture limits crop production and induces the application of waterconservation measures, such as , as expected.

Hillside Cultivation

The foothills of the Ethiopian Highlands rise to 600 m above mean sea level. Geologically, this BasementComplex formation mainly consists of granitic and hornblendic gneisses. Soil formation is largely absent.Direct cultivation of hillsides, with or without SWC, is not feasible. Locally, weathered rocks provide loosestones, but these are not used on any signi®cant scale for SWC or other purposes. The Beja consider workwhich involves the collection and transportation of stones as physically too demanding.

Population Pressure on Resources

The 1944 population density was 2±20 persons per km2 in the rural areas around Kassala, and less than2 persons per km2 in more remote areas. Reports indicate increasing ®gures over subsequent decades,reaching an average of 14 persons per km2 around Kassala and 22 people per km2 in the remainder of theBorder Area for the situation covered by the last census in 1983. These low densities are found in areas withequally low carrying capacities of natural resources. However, DHV/IES (1989) classi®ed the region as onewhere these resources still have su�cient capacity to allow expansion of crop production without compellingland users to apply SWC as a necessary measure to cope with negative environmental e�ects.

Secure Land Tenure

Still only a minor portion of all rural land in the Sudan is o�cially registered. The remainder, includingnearly all land in the Border Area, is considered government property under the 1970 Unregistered LandAct. This land may be cultivated under customary rights of usufruct, for which purpose the Beja havedeveloped an elaborate system of de facto access to land. However, de jure land tenure essentially remainsinsecure, and deters land users from making signi®cant conservation investments.

SUGGESTED PROCESSES FOR DECLINE

The importance of ISWC is increasing in the Border Area. Therefore the ®ndings that the region ischaracterised by another four factors which Critchley et al. (1994) identify as causing ISWC decline wasunexpected.

Labour Exodus

Households in the Border Area depend on non-farming activities because the returns from ISWC and othercultivation techniques are seasonal and insecure. As far as income is concerned, o�-farm employment andseasonal labour migration are the most important non-farming activities (see Table II). Although there areno ®gures available on numbers of migrants leaving the region, these must be substantial since the o�cialgovernment policy is to discourage the in¯ux of rural migrants into urban areas such as Kassala (KADA,1988). The Border Area has a partly permanent and partly seasonal shortage of labour during the growingseason.

Declining Rainfall

Rainfall has tended to decline since the 1960s, as is found in most sub-Saharan regions. The long-term meanrecorded in Kassala is 299 mm (1901±1990), but the average is only 250 mm when measured over the lastthree decades (1961±1990).

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Incompatible Tillage Methods

Ploughing by tractor-mounted equipment is the only agricultural innovation introduced in the Border Areasince the 1970s. The Beja do not own any machinery, but rent it from contractors. Although the use oftractors is not incompatible with the technique, the costs involved in renting usually prohibit tractoruse together with indigenous techniques.

Projects Ignoring ISWC

Earth diversion banks and stone-pitched dams were ®rst built in the Border Area under the Anglo-EgyptianAdministration (1898±1956). New SWC techniques were introduced in the region on a larger scale from1983 onwards. The same year, the Ministry of Agriculture in Kassala launched a comprehensive programmefor rural development. During a period of 8 years, no less than 123 earth dams were constructed. Anothertechnique based on broad-based earth embankments was introduced by an international project in 1987. Itwas therefore possible to control and harvest ¯oodwater in an estimated 125 000 ha in total by 1990. Themerits of ISWC were largely ignored in these projects. Land users applying ISWC have only received modestsupport from 1988 onwards, for example, in the form of subsidised tractor rent for construction andmaintenance.

DISCUSSION

The interpretation of socio-economic data on the relative importance of in the Border Area remainsambiguous. Data are available for only two reference years, which di�er in climatic conditions andhousehold livelihood pro®les. However, interpretation in combination with absolute data from remote-sensing techniques on the size of zones leads to only one possible conclusion. Indigenous SWC byhas generally increased in importance over recent decades. Factors mentioned in the literature as favouringISWC expansion, such as hillside cultivation, population pressure on resources and land tenure security,cannot be said to apply to the Border Area. Moisture shortage for cultivation, which is the fourth typicalfactor for ISWC expansion, is common, but this is merely a general trait of dry lands. However, factorsmentioned in the literature as resulting in declining ISWC are found in the study area. These factors arelabour exodus, declining rainfall, incompatible tillage methods and projects ignoring ISWC.These ®ndings show that regional developments in ISWC can only be understood when the historical

processes are known and appreciated. A list of these processes favouring ISWC development in the BorderArea was presented in Van Dijk and Reij (1994). These include: (i) the demonstration e�ect of earlygovernment interventions in ¯oodwater harvesting; (ii) the relatively wet decade of the 1950s in the BorderArea; (iii) Beja familiarity with rudimentary irrigation techniques which supposedly had already beenadapted to perform as dryland water harvesting techniques in the 19th century; (iv) the emergence of aclosely knit organisational structure based on religion; this has both induced and facilitated the sedentar-isation of nomadic Beja and their adoption of crop production as part of their livelihood. More compellingfactors behind the adoption of ISWC were: (v) losses of livestock as a result of drought. The intensity ofdrought seems to have increased since the late 1940s, reaching levels of 70 per cent loss of stock perhousehold in the Border Area during 1984±1985; (vi) Beja expulsion from traditional grazing grounds as aresult of the havoc of civil war in Eritrea and large-scale agricultural development in eastern Sudan.The Beja now ®nd themselves in a process of adjustment to rapidly changing outside conditions. Crop

production is still an important economic factor in their subsistence; in terms of income, this sectorcontributed an average 38 per cent to their livelihood in 1983 and 44 per cent in 1988. was a majortechnique in local cultivation with contributions of 68±72 per cent of the part of the household incomewhich is derived from crop production. However, contributed only 28±31 per cent, if these ®gures areexpressed as shares in the total of all household economic sectors together (livelihood).When additional data are considered to obtain income per unit of labour time invested, the level of income

generated by use compares unfavourably with other sectors, notably labour migration and o�-farm

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24 J. A. VAN DIJK


employment (Van Dijk, 1995: 262±263). For example, in 1988 the daily income in the Border Area earned inISWC was about £s 2 (£s1 � US$0�26 in 1988), in di�erent urban jobs in the private sector this was £s 5±19,and in a typical o�-farm activity such as wood-cutting it was £s 1±19. It is therefore necessary to ask why theBeja pursue the application of a technique which is rainfall dependent, and hence insecure, and provesrelatively unattractive in terms of opportunity costs to labour.

Table III presents daily incomes from crop production for various techniques and climatologicallydi�erent years. The ®gures are based on calculations of labour investments for the selected tillage andcultivation activities of maintenance, weeding, thinning and gap-®lling. Although incomes from ISWC werereported to compare unfavourably with non-farming incomes, ISWC returns are occasionally higher thancan be reached by means of any of the other crop production techniques in the Border Area. When thesituation is assessed over the 4 years for which data are available, use tends to show comparativeadvantages in the form of higher returns to labour in the dryer years.

ISWC by is therefore likely to be continued because it helps to diversify income sources in normalyears, and becomes an outright advantage during dry years. Apparently, the Beja are willing to incur costs interms of labour opportunities and income lost during wet years, in order to buy the greater overallsubsistence security which is vital during dry years. This type of risk-spreading strategy is well documentedfor hazardous drylands. In this respect, and ISWC do not di�er from traditional irrigation in Africa(Horst and Ubels, 1993).

AACCKKNNOOWWLLEEDDGGEEMMEENNTTSS

This research was funded by The Ford Foundation, The Netherlands Organisation of Scienti®c ResearchNWO, and the University of Amsterdam, Department of Human Geography. I thank Dr Gerry O'Reilly forhis comments on the draft version and correction of the English.

RREEFFEERREENNCCEESS

Adams, W. M. 1992. Wasting the Rain. Rivers, People and Planning in Africa. Earthscan, London.Critchley, W., Reij, C. and Seznec, A. 1992. Water harvesting for plant production. Part II. Case studies and conclusions for sub-Saharan

Africa. World Bank Technical Paper 157, Washington, DC.Critchley, W. R. S., Reij, C. and Willcocks, T. J. 1994. `Indigenous soil and water conservation: A review of the state of knowledge and

prospects for building on traditions', Land Degradation & Rehabilitation, 5, 293±314.DHV/IES 1989. Environmental Pro®le Kassala Province, Eastern Region, Sudan. DHV Consultants, The Netherlands' Institute of

Environmental Studies, Sudan. DHV Consultants Repro, Amersfoort.Engelman, R. and Leroy, P. 1995. Conserving Land: Population and Sustainable Food Production. Population and Environment Program.

Population Action International, Washington, DC.Horst, L. and Ubels, J. 1993. Designing sustainable farmer-managed irrigation in Africa, pp. 93±105 in J. Ubels and L. Horst (eds)

Irrigation Design in Africa. Towards an Interactive Method. Wageningen Agricultural University, Wageningen, and CTA, Ede.Hudson, N. W. 1991. A Study of the Reasons for Success or Failure of Soil Conservation Projects. FAO Soils Bulletin 64, FAO, Rome.

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Table III. Crop production returns. Income per man-hour invested in selected tillage activities (1983 £s) by growingseason characteristic and applied technique in four Border Area villages in 1983 and 1988±1990

Year Total rainfall and growing ISWC Government- Non-SWCseason characteristic techniques introduced SWC techniques

1983 249 mm, normal-to-dry 56 No data 351988 396 mm, wet 70 97 871989 218 mm, normal-to-dry 65 47 741990 76 mm, very dry 110 98 82

Source: L&E research (N � 244); Van Dijk (1995: 240, Figure 7.4, adjusted).Note: ISWC includes and brushwood panels; government-introduced SWC includes earth dams and embank-ments; non-SWC techniques include valley-bottom and ¯ood-recession cultivation.

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IFAD 1986. Soil and Water Conservation in Sub-Saharan Africa. Issues and Options. CDCS Free University Amsterdam, Amsterdam,and IFAD, Rome.

IFAD 1992. Soil and Water Conservation in Sub-Saharan Africa. Towards Sustainable Production by the Rural Poor. A report preparedfor the IFAD by the CDCS Free University Amsterdam, Amsterdam, and IFAD, Rome.

KADA 1988. Workplan 1989±1990. Kassala Area Development Activities, Kassala.Pacey, A. and Cullis, A. 1986. Rainwater Harvesting. The Collection of Rainfall and Run-o� in Rural Areas. Intermediate Technology

Publications, London.Reij, C. 1992. Indigenous Soil and Water Conservation in Africa. IIED Gatekeeper Series SA27, International Institute for Environment

and Development, London.Reij, C., Mulder, P. and Begemann, L. 1988. Water Harvesting for Plant Production. World Bank Technical Paper 91, World Bank,

Washington, DC.Reijntjes, C., Haverkort, B. and Waters-Bayer, A. 1992. Farming for the Future. An Introduction to Low-External-Input and Sustainable

Agriculture. Macmillan and ILEIA, London.Van Dijk, J. A. 1995. Taking the Waters. Soil and Water Conservation among Settling Beja Nomads in Eastern Sudan. African Studies

Centre Research Series No. 4, Avebury, Aldershot.Van Dijk, J. A. and Ahmed, M. H. 1993. Opportunities for Expanding Water Harvesting in Sub-Saharan Africa. The Case of the Teras of

Kassala. IIED Gatekeeper Series SA40, International Institute for Environment and Development, London.Van Dijk, J. A. and Reij, C. 1994. Indigenous water harvesting techniques in sub-Saharan Africa: Examples from Sudan and the

West African Sahel. pp. 101±112 in FAO Water Harvesting for Improved Agricultural Production. Proceedings of the FAO ExpertConsultation, Water Reports No. 3, FAO, Rome.

Warren, D. 1991. Using Indigenous Knowledge in Agricultural Development. Discussion Paper 127, World Bank, Washington, DC.

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indigenous soil and water conservation by teras in eastern sudan

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