Rwanda country paper
The agricultural characterization and the classification of wetlands of Eastern and Southern Africa

Introduction

Rwanda is situated in Central Africa, bordered by Burundi in the South, the Democratic Republic of Congo in the West, Uganda in the North and Tanzania in the East. Its surface area is 26 338 km² with a population of about 7.5 million inhabitants in 1998. The population density is with more than 300 inhabitants/km² one of highest in Africa. The topography is very irregular, offering a landscape of hills and valleys with a backbone made of the Zaire-Nile Ridge and rising to more than 3 000 m in the North and 2 000 m in the South. Only the Imbo region in the southwest goes down to 900 m.

Rwanda has a moderate climate with an annual average temperature is of 19⁰C and an annual cycle of four seasons: two rainy seasons and two dry seasons:

• a short rainy season (October - November); only the month of November is characterized by heavy precipitation
• a short dry season (December - January)
• a long rainy season (February - May) bringing 14 to 61% of the annual precipitation
• a long dry season (June - September)

The agricultural sector employs about 90% of the active population and contributes 40% of the GDP, which gives this sector a predominant role in the economy of Rwanda. The cultivable area is estimated at 1 385 000 ha, which is 52% of the total surface area of the country. The cultivated area is about 825 000 ha, that is 52% of the total surface area of the country. The arable area is about 825 000 ha, hillside slopes (about 660 000 ha) are not exploited in the dry season and marshlands (about 165 000 ha) are partially exploited in the rainy seasons depending on their degree of flooding. About 94 000 ha of marshlands are currently exploited, mostly the ones called mineral, the remaining being large marshlands made up of peaty or organic soils covered by papyrus, are not cultivated.

Sam G. Kanyarukiga 
Advisor in the President's Office 
Vincent Ngarambe 
Director of Land Use and Soil Conservation 

The high demographic growth rate resulted in strong land pressure on the available uplands. It also caused a modification of the fundamental land structure. The land available for a household for agricultural exploitation is below 1 ha. Consequently, the demographic growth cannot be sustained by farming on hill slopes alone. The development of marshlands and valleys remains one of the sustainable alternatives in response to population pressure on the fragile soils of hillsides. Marshlands contain large water reserves, have lower erosion risks, a natural fertility and offer possibilities to populations to work together in these marshlands, which is considered to be a factor that can contribute to national reconciliation.

Characterization and classification of marshlands of Rwanda

In Rwanda semi-detailed classification studies have been carried. Within this framework, there are the following types of classification:

• Classification according to Cambrezy
• Classification according to their surface area
• Classification according to the natural vegetation
• Classification based on the utilization and stages of development
• Hierarchical classification according to hydrology

Classification according to Cambrezy

Cambrezy (1981) recognizes three types and one subtype of marshland in Rwanda (Table 1). His classification is based on a deep analytical survey of physico-climatic conditions.

TABLE 1
Typology of marhlands according to Cambrezy (Source: Cambrezy, 1981)

Classification of marshlands according to their surface area

Based on the surface area, five categories of marshlands are distinguished, as shown in Table 2.

TABLE 2
Classification of marshlands according to their surface area

Classification of marshlands according to the natural vegetation

According to this classification one can distinguish four types of marshland:

1. The papyraie This type of marshland is essentially swampy, with stagnant water on the surface. It is characterized by an abundant and nearly exclusive vegetation of Cyperus Papyrus, indicating that the valley contains an excess of water throughout the year.

2. The marshland with Cyperus Latifolius Water is less abundant than in the type, the level fluctuates by some centimeters below the soil surface. Contrary to the marshland with papyrus, it is almost completely cultivated in the dry season.

3. The spongy valley Free water never covers the surface of the soil, its level fluctuates below the surface according to the abundance of rains. Vegetation is shrub-like under which one finds ferns and tall grass. The river flows slowly out and is covered by thick grass.

4. The valley for grazing (pastures) Rivers meander through narrow valleys with small plains serving as pastures in the dry season. Water does not cover the whole valley which therefore doesn't become flooded.

Classification of marshlands based on the utilization and stages of development

The classification based on the utilization and stages of development takes into account the historical development of a marshland from its natural state to intensive utilization for agricultural production. In Rwanda, intensification of the agricultural utilization of marshlands coincides with the growth of the population; indeed, it had been noted that marshlands are put completely under cultivation when all the upland is cultivated. Therefore in the classification based on the utilization, the basic criterion is the food self-sufficiency of families. In this context one can distinguish four stages of the development of a marshland:

First Stage No development. The marshland is covered by a vegetation of papyrus and other herbaceous plants, which is the case for the big peaty marshlands in the East and the North of Rwanda. In spite of the high demographic pressure, the utilization of these marshlands remains limited due to extremely difficult drainage conditions.

Second Stage There is a partial utilization of the marshland. The population only resorts to the marshlands during years of acute rain shortage, most farming being carried out on hillsides.

Third Stage The marshland is exploited intensively, both for pastures and crop production.

Fourth Stage Intensive utilization of the marshland for agricultural production. At this stage the management of arable lands on the hills becomes a limiting factor. It is therefore necessary to invest in marshland development activities through construction of irrigation/drainage infrastructure as well as introduction of the application of mineral fertilizers.

Hierarchical classification

This classification is made according to streams/rivers in the marshland, as shown in Table 3.

TABLE 3
Classification of marshlands according to their hydrological system

Aspects of marshland characterization

Soils and geomorphology

The surface area of each of the small marshlands of Rwanda varies widely, ranging from 20 ha to hundreds of ha. The configuration of these marshlands is one of the most important factors for their classification. This varies depending upon their length and width and is often limited by the presence of a rocky sill or by any other factor that deters or favours the rivers speed of flow.

The small marshlands are generally separated from hills by small strips of land called transition soils. The importance of their surface area depends on the marshland configuration. These transition soils have properties that are intermediary between upland soils and marshland soils, due to a low concentration of alluvial material, high concentration of colluvial material and better drainage than in the marshlands.

Climate and soils

Water and temperature play a primary role in the genesis and utilization of soils. The vegetation of papyrus and typha, for instance, favours water retention and regulates the temperature, thus creating a micro-climate favourable to the formation of organic soils. Table 4 shows the different soils of marshlands in Rwanda.

In the East of the country and in the West in Bugarama, where there is a hot, ustic climate, mineral soils (of alluvial/colluvial origin) of marshland are generally rich in exchangeable bases and are often vertisolic. Their PH is at least 5 or more, and their colour is dark. The salts can, after water evaporation, accumulate on the surface in the dry season. In general, the agricultural potential of these soils is very high but the vertic character found in some areas makes their development difficult. Also, the excess of sodium in some limited places can be harmful.

In the area of plateaus and hills (1400m to 2,00 m altitude), where one finds the highest density of small marshlands (Jones and Egil, 1984) and where the climate is udic isothermic, many marshlands have organic soils which are fairly to very acid and relatively poor in exchangeable bases. Mineral soils are less dark. The agricultural potential of these marshlands is variable. Physical properties are more suitable, but the risks of extreme and sometime irreversible dryness exists for organic soils and clayey soils, rich in iron.

TABLE 4
Orders, sub-orders and groups of soils of the small marshlands of Rwanda

Parent material	Order	Sub-order	Group
Mineral matter	Oxisol	Aquuos	Plinthaquox Ochraquox Umbraquox
	Vertisol	Ustert	Chromustert Pellestert
	Utisol	Aquult	Plinthaquult Paleaquult Tropaquult
		Humult	Plinthaquult Paleaquult Tropohumult
	Alfisol	Aqualf	Plinthaqualt Natraqualf Tropohumult
		Ustalf	Durustalf Plinthustalf Natrustalf Paleustalf Rhodustalf Haplustalf
	Inceptisol	Aquept	Haplaquept Plinthaquept Tropaquept
		Tropet	Humitropept Ustropept
		Aquent	Hydraquent Ruvaquent Tropaquent
Organic matter	Histosol	Fibrist	Borofibrist Tropofibrist
		Hemist	Sulfihemist Luvihemist Borohemist Tropohemist
		Saprist	Borofiprist Tropofiprist

In the high altitude areas (more than 2 000 m), where the climate is isomeric, peat predominates over mineral soils. All the soils are in general acid and very poor in exchangeable bases. The agricultural potential is low to average and the altitude limits the variety of crops. Physical properties are good and the risk of acute dryness is limited by the climate.

Agricultural potential of marshlands

The potential of a soil for agriculture is determined by inherent soil properties which may be limiting to production within an environment and for a given crop. For the wetlands soils of Rwanda, this potential varies from marshland to marshland.

The large pedo-agronomic variability of marshlands renders the type of crop cultivated as well as the yields very variable. The high diversification of areas, depending upon the altitude and the climate, results in the existence of a wide variety of crops, like tubers, legumes and cereals (Table 5). One salient point to note is, however, the predominance of sweet potatoes especially in the dry season. Many reasons can explain this phenomenon. Sweet potato is resistant to drought, requires very little inputs and has a vegetative cycle of 4 to 6 months (Acland, 1981). As soil degradation and poor water regimes characterize many marshlands, farmers prefer to grow the sweet potatoes, which at least guarantees them a harvest, however meager it may be.

TABLE 5
Ecological zones, soils and crops,

Hydrology of the marshlands of Rwanda

Marshlands and their surrounding hills form delicate ecological systems with diverse water regimes. The data presented in Tables 6, 7 and 8 below represent an area covering half of the country.

TABLE 6
Rainfall and evaporation data for the Mwogo River basin (data from Nyabisindu station)

TABLE 7
Mwogo basin water flow

TABLE 8
Average annual water flow for four stations

Socio-economic situation

To improve the socio-economic situation of farmers utilizing marshlands in Rwanda, at least two aspects must be taken into consideration:

1. A deep knowledge of the sociological consideration of a Rwandan farmer as not only the utilizer of marshlands, but also of land on hillsides.
2. The economic importance of small marshlands with regards to the potential of the resources they contain and the role they play in the agricultural production as a whole.

Faced with the need to supply the society with necessary foodstuffs, a producer sometime controls production according to the demand conditions anticipated. The money value, and therefore the income that the farmer gets, becomes very low during abundant harvests. The production plan of the peasant depends on the market structure. Take for example a traditional farmer who is forced to sell his whole rice harvest to the factory or project which maintains the drainage or irrigation works of the area from which he cultivates one or more plots. This case is very frequent in Rwanda. If the price paid to the producer by the factory is lower than that on the free market, the normal inclination, which responds rationally to the principal of the maximization of benefit to the peasant, would be to retain part of his production to sell it to highest bidder on the free market.

Legislation

The necessity to develop a legislation on marshlands was perceived very early by the Government, due to the acuteness of land shortage which characterizes the country. That situation makes marshlands the only alternative to alleviate pressure on the fragile slopes as well as increase production in order to ensure food security for the population.

In 1988, the Rwandan Government began to work out legislation for the exploitation of marshlands with assistance from the FAO. Within the framework of this assistance, legal texts were prepared but they have not yet been submitted to the Government. In those legal texts, are defined: the status and definition of marshlands, their delimitation, classification, rules of exploitation, institutions in charge, modalities of management, maintenance and production, contracts of the utilization of the marshlands, etc. These legal texts, which date back to the pre-ware period, now have to be updated following the preparation of a new land law currently under study. We can however say that in Rwanda marshlands belong to the State and can be given to associations or private people according to defined modalities.

Responsible institutions

The Ministry of Agriculture, Livestock, Environment and Rural Development is the institution in charge of the management and the exploitation of marshlands as well as other rural lands without any title deeds. The Directorate of Land Use and Soil Conservation within this ministry is in charge of the implementation of the Government policy in the sector of marshlands development.

Areas of Research-Development

The main constraints in the characterization and classification of wetlands in Rwanda can be summarized as follows:

• Lack of financial resources for research activities, as well as for other studies.
• Lack of competent staff as well as material resources.

Presently, no research activities exist in the field of characterization and classification of marshlands. This could be detrimental in the long term to the fragile eco-system, which has become a political and economic stake for the country. It is important to undertake research activities of detailed characterization for the main large basins (Nyabarongo, Akanyaru, Akagera, etc.), within the perspective of sustainable development.

Inventory and mapping: database on marshlands

Despite many localized surveys and attempts of classification of marshlands, no official document exists registering in a complete and reliable manner all the marshlands of Rwanda. For this, the Government had requested FAO and UNDP to provide assistance to set up a project capable of filling that gap. The objectives of this project PNUD/FAO/RWA/89/006 "Inventaire des marais du Rwanda" were:

• To gain an understanding of marshlands larger than 15 ha which are likely to be developed later for agriculture, through collecting, classifying and computerizing all useful data on these marshlands and valleys in the country
• To train national personnel to be capable to manage and utilize the data.

The Project adopted the "catchment" approach. First, a primary hydrographic network was determined. Then, starting from that network, the national territory was divided into catchments. Each of the catchments was given a technical card containing data on geography, climate, hydrology, pedology and administrative division, etc. These cards were fed into the computer and constitute the catchment database. Each catchment contains a complex of marshlands which have also been divided into sections. Each of the sections of the marshlands has been given a technical card containing most specific data regarding the location, surface area, agro-ecology, pedology, etc. The cards of the sections were also fed into the computer and constitute the marshland database.

Results obtained

The project collected, classified and exploit the following existing maps:

• Administrative map and the map of the hydrological network map of Rwanda
• The map of pedological zones of Rwanda
• The map of the lithological zones of Rwanda
• The reference topographic map of Rwanda
• The maps of the hydrological network by Prefecture
• The maps of land use by Commune,
• The map of agricultural regions of Rwanda

The project produced the following maps and plans:

• 10 maps of catchments by Prefecture indicating the localisation (1 : 100 000 scale), the delimitation, and the code number of the catchments listed by the Project
• 39 maps of the Catchments and complexes of wetlands (1 : 50 000)
• 39 maps of sections of marshlands listed by the Project for the whole country (1 : 50 000)
• A complete set of the soil map of Rwanda at 1/50,000 scale especially coloured for the zones of wetlands
• The map of distribution of specific water flow and total evaporation in Rwanda
• Detailed topographic survey of Bishya wetlands in Gitarama and Butare Prefectures. Permanent boundary marking of the site. Production of plans at 1 : 1 000 for 300 ha

The project produced the following cards, that have been fed into the computer and consitute the database:

• 3017 cards of sections of marshlands have been fed in the computer, which implies a representation of 11,817 ha
• 352 cards of smaller catchments fed in the data base
• 283 cards of catchments + sections of large marshlands have been compiled in the data base.

The following persons received training within the framework of the project:

• One technician in the survey attended a training programme on photo-interpretation and teledetection
• One surveyor underwent training in photo-interpretation
• Five senior staff of the Division of Hydro-Agricultural Marshland Development had training in the management of data based on wetlands

The Directorate of Land Use and Soil Conservation is the department in charge of that computerized database on the wetlands of Rwanda. Table 9 summarizes the areas of the wetlands of the primary and smaller networks by prefecture.

Table 9
Distribution of surface areas (ha) of wetlands by Prefecture

Sustainable development of wetlands

According to Table 9, the total area of marshlands of Rwanda is estimated at about 165 000 ha which are partially exploited depending on their degree of flooding. However, only 4 000 ha of wetland are fully equipped with irrigation and drainage systems and 1 200 ha are partially equipped.

Faced with the increasing pressure on hillside lands, the optimization of the utilization of the marshlands in order to ensure food security for the population constitutes a priority in Government's policy. The strategy adopted by the Government is the participation of the beneficiaries in the development and the utilization of the wetlands. In this regard the Government, with the assistance of UNDP and FAO, has recently launched the implementation of a pilot project of development and utilization of marshlands. The pilot project aims at developing according to the participatory approach 450 ha of marshlands that will be used for the purpose of demonstration and training of groups of producers. It also aims at the institutional reinforcement of the services of the Ministry of Agriculture and other ministries involved in the management and the exploitation of marshlands. Parallel to this project, the Ministry of Agriculture has requested and obtained aid from the African Development Bank (ADB) for the realization of a National Master Plan for the development of marshlands and for soil conservation.

Other accompanying measures indispensable for the sustainability of the development and utilization of marshlands have been identified:

• Research - Development
• Development and transfer of technology
• Specific technical surveys
• Revision of policies and strategies

Concerning Research - Development, it is necessary to develop themes on: characterization of wetlands and GIS methods, inventory, adapted techniques of hydro-agricultural development (irrigation and drainage), improvement of physical and morphological properties of wetlands (mineral, organic fertilization), farming techniques and the vegetable material, as well as the diversification of crops in the wetlands.

Concerning the development and transfer of technology, the introduction of adapted new techniques relating to soil preparation (animal traction, small and intermediate motorization, low cost irrigation, etc.) is desirable.

Concerning specific studies, the hydrological studies must be deepened and the surveys on the main marshlands of the country should be completed.

Rwanda's water resources cover a surface area estimated at about 212 000 ha, made of rivers and wetlands; the water of wetlands cover some 77 000 ha, that is 37% of the total surface, which explains the importance of taking into account the environment impact of hydro-agricultural developments in that fragile ecosystem of wetlands. Consequently, it is necessary to carry out studies on the environmental impact so as to preserve that resource.

It is necessary to promote and reinforce farmers' organizations and to encourage the involvement of the private sector in the development of marshlands for their sustainable exploitation. The popularization of new techniques, easing access to loans for the small holders of marshlands are the main trends to be fostered.

Finally, the implementation of the sectoral policy of land development and conservation is an imperative necessity to ensure the sustainable development of the wetland of Rwanda.