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The Hadejia-Nguru Wetlands [170] concern a part of the flood plain of the Komadougou-Yobe river basin in the Lake Chad basin in the north-east of Nigeria (Map 3) and are home to probably about a million people. The wetlands have formed where the waters of the Hadejia and Jama'are rivers meet the lines of ancient sand dunes aligned northeast-southwest. An area of confused drainage has formed here, with multiple river channels and a complex pattern of permanently and seasonally flooded land and dryland. The wetlands are nationally and internationally important for migratory waterfowl. The wetlands support extensive wet-season rice farming, flood-recession agriculture and dry-season irrigation. The flood plain also supports large numbers of fishing people, most of whom also farm, and is grazed by very substantial numbers of Fulani livestock, particularly cattle, which are brought in from both north and south in the dry season. There is also an important dispatch from the wetlands of fuelwood and fodder for horses. In the past, much of the rice, as well as fish and birds, was traded out of the area. This has changed, but there is now a strong export of other agricultural products, for example peppers, wheat and fuelwood. The economic value of production from the wetlands is very large, many times greater than that of all the irrigation schemes for which the inflowing rivers are dammed, diverted and their waters used.
There are natural changes, for example the impacts of drought, that have serious implications for the future of the wetlands and the sustainability of their production systems. There are also major economic changes within the wetlands themselves. The extent of irrigation has greatly increased over the 1980s, largely as a result of the advent of small petrol-powered pumps and the ban on the importation of wheat in 1988. As the use of small pumps spreads, conflicts are beginning to emerge between farmers and pastoralists, and between small and large farmers for access to land.
The wetlands have also been affected by developments elsewhere in the river basin. The construction of the Tiga Dam on a tributary of the Hadejia river in the early years of the 1970s has exacerbated the effects of the low rainfall of the last two decades. The result has been a reduction in the extent of flooding in the wetland. Construction of a dam on the Hadejia river just above Hadejia town to provide short-term storage of water to irrigate the Hadejia Valley Project Phase 1 began, in the early 1980s, but was stopped for several years because of financial problems. The main dam was completed in 1992, soon after work restarted on the project. The dam has created a large shallow lake upstream and it will probably have a major effect on the timing and extent of flooding in the wetlands.
Most of the dams, irrigation schemes and water resources plans for the Yobe basin were prepared in the 1970s and early 1980s, using data for the relatively wet period up to 1973. The post-1972 drought has reduced the proportion of rainfall which runs off to the rivers. The 1988 flood at Hadejia was probably one of the largest for some years and it was augmented by the failure of the dam at Bagauda.
The Hadejia-Nguru wetlands have long been known as a centre of fish production. Upstream hydrological developments induced by irrigation projects threaten to degrade this important resource. Studies of flood plain fisheries have shown that fish production is closely related to flood extent. The existing and planned dams upstream of the Hadejia-Nguru wetlands are likely to have a serious impact on fisheries. Despite the lack of information specific to the Hadejia-Nguru wetlands, there are enough studies from other flood plains affected by hydraulic works to show that the effects of dams on fish communities are likely to be serious. The dams are likely to bring changes in river flow, loss of habitat, blocking of channels, changes in silt loading, plankton abundance and temperature which are likely to affect fish communities.
The economic value of fish production from the flood plains adds weight to the argument in favour of maintaining the annual flooding of the wetlands. Moreover, the significance of fishing goes beyond its value in monetary terms. Fishing plays an important role in the flexibility and adaptability of the rural economy in the flood plains. A reduction in this flexibility through degradation of the fishery resource may have serious repercussions on the ability of communities to adapt to fluctuations in their environment. Many people are involved in the fisheries and so the social consequences of any appreciable reduction in productivity will be felt throughout the area. Degradation of the fisheries may also affect other sectors of the rural economy. Most people who fish also pursue other activities - such as farming, livestock rearing, manufacturing of crafts or trading - and the loss of, or reduction in one component of the household economy is likely to affect activities in other sectors. There will also be 'downline' effects on fish processors, fish dealers, customers and consumers.
In addition to producing fuelwood, the forest reserves and bushland of the flood plains yield important non-timber forest products that are significant to the livelihoods and subsistence of local communities. Some, including leaves, are important marketed commodities that generate substantial income. Doum palm leaves are either processed into mats and other products or sold as raw material. The harvesting and processing of doum palm leaves is a dry season activity, and many people migrate to the wetlands to harvest the palm. Mat-making from doum is also a specialized activity of many flood plain villages. Mats and other doum products, for example rope and baskets, are sold locally or exported to other regions. Baobab leaves are used widely as an ingredient for soups and stews and are especially important as a 'drought food'. Honey, produced by local beekeepers, is a highly valued commodity.
Since 1985, the area has been the focus of the Hadejia-Nguru Wetlands Conservation Project. This project has been run jointly by the Nigerian Conservation Foundation, IUCN (International Union for the Conservation of Nature), the Royal Society for the Protection of Birds and the International Council for Bird Preservation (now renamed Birdlife International). In 1990 a major development project was started by the European Community that included the eastern part of the area. The North East Arid Zone Development Project (NEAZDP) has a very substantial budget to generate village-based development initiatives. Attention has tended to be directed in particular to the potential resources of the wetlands.
Wise use of the wetlands of the Hadejia-Nguru wetlands demands a proper understanding of the environmental and socio-economic changes that are occurring and of those that may be predicted. Understanding of the impacts of changes inside and outside the flood plain is far from easy, and prediction of future impacts is even harder. However, without such understanding and prediction, effective planning and management is impossible.
The economic importance of the flood plains suggests that benefits it provides cannot be excluded as an opportunity cost of any scheme that diverts water away from the flood plain system. Policy makers should be aware of this problem when designing water development projects in the river system. Further analysis is also required of the type of 'regulated flood projects' regime, which could maintain much of the flood plain system intact while still allowing some upstream water developments. Further investigation of all the economic benefits provided by the wetlands is also needed, and the sustainability of production within a flood plain area should be more thoroughly examined.
Effects of the Jonglei canal on the Sudd swamps
In the southern of Sudan, the Nile discharges its water into the great wetlands of the Sudd, a network of channels, lakes and swamps in which as much as half of the inflowing water is disappears through evaporation (see also Chapter 6: the Nile basin section). The Jonglei Canal was designed to bypass the Sudd and direct downstream a proportion of the water that is 'lost' from the Nile each year by spill and evaporation in the swamps. The projected dimensions of the canal are as follows: a width from bank to bank of about 75 metres, a channel bed-width averaging 38 metres, a depth varying from 4 to 8 meters, and a length of 360 km, over twice the length of the Suez canal. Jonglei is a small Dinka village close to the Atem channel at a point where the canal alignment was planned to begin. Although the offtake will now be further south at Bor, the canal is still so named and Jonglei has given its name to a province as well.
The canal has not been completed, but detailed surveys were undertaken to determine a whole range of effects, many of which will be shown to be disadvantageous to the inhabitants of the Jonglei Area. Some of the effects are described below.
The river-flooded grasslands are an essential seasonal resource during the driest months of the year. Not only is there drinking water available in the rivers, but the process of seasonal inundation itself produces species of grasses which sustain the herds from about January until April. There are no other alternatives as the grasses of the high land are exhausted or reserved for the livestock (mainly smaller stock), held by the few people who elect to remain behind, and the rain-flooded grasslands have become woody and unpalatable and produce little or no regrowth after burning. It follows that the river-flooded grasslands are crucial to the pastoral economy at this time of the year. It is, however, just these grasslands that may be reduced by the operation of the canal.
The water benefit of the canal downstream will be around 4 km³/year and according to some estimates even an extra water flow of up to 10 km³/year may be reached. These quantities are a substantial percentage of the average 'losses' by the evapotranspiration, the natural production of river-flooded grasses being a function of the annual fluctuation in river discharge and thus of the annual variation in area flooded. In other words, to the local inhabitants these are not losses in water at all, though the waters are excessive and the cause of damaging floods, as in 1964.
The floods of the 1960s, reaching a peak in 1964, caused great damage to human interests. On the Zeraf island alone it was reckoned that 130000 cattle were lost owing to exposure and lack of grazing since practically the whole area remained under water for a long period. Similar disastrous effects occurred west of the Bahr el Jebel in the vicinity of Adok. It follows that any reduction in peak flows could be protective and beneficial. The same model can be applied to give some indication of the effect of the canal on areas of flooding. The figure of 25 million m³/day for a canal diversion may reduce the area of flooding by about 19% at a 1964 peak discharge [41].
The established fisheries of some large lakes in the Sudd are said to have been adversely affected by increased water depth, but, overall, the flooding of the 1960s has multiplied the number of perennial lakes in the system and, thereby, the fishing potential. A severe decrease in the discharge into the Sudd resulting from the Jonglei canal would bring about the total disappearance of many lakes in the papyrus zone and reduce others to the status of seasonal lagoons, with a serious loss of year-round fish and fishing potential.
The Jonglei Canal brings the obvious advantage of shorter river communications between Khartoum and the main urban centre of the southern Sudan at Juba, in effect reducing the length of the journey by 300 km. The canal will also bring communications, as well as water, to a particularly remote part of Sudan, which is inaccessible during the rains and largely abandoned in the dry season. Passing points and berthing places are part of the design and will lead to the creation of small ports which are likely to develop and open up contact with the hinterland in much the same way as those along the natural channels of the river have done. There is, however, likely to be considerable disadvantage to the people of the Zeraf Island and those living west of the Bahr el Jebel, in that mainstream traffic will follow the canal and the old western landing places will be ill-served. In the past, moreover, river traffic has been a major factor in keeping the channels open. Oil prospecting is likely to restart once peace has been restored and this may mean that the companies concerned will wish to keep channels clear. However, if discharges drop to the low figures prior to 1961, the canal could become too shallow for commercial traffic and for the movement of fisheries barges.
The canal will in many areas drive a barrier between wet season villages and dry season grazing grounds along the river channels and therefore dislocate the pastoral cycle. Many people living east of the canal will have to cross it with their livestock when regrowth from rain-flooded grasslands is exhausted and they have to move westwards to the river-flooded grasslands of the Nile. Reinforced structures at various points along the canal are needed to facilitate the crossing of livestock without damage to the embankments and to provide suitably designed boats more efficient than the usual 'dug-out' canoe. Crossing the canal will present a massive logistical problem and besides, raises questions of land ownership among those who may need to cross the canal and cross each others' territory in order to do so.
There exists a kind of 'Jonglei Controversy'. The criticism of the environmentalists are many but can be segregated into charges that the Jonglei Canal will drastically affect climate, groundwater recharges, silt and water quality, the destruction of fish and changes in the lifestyle of the Nilotic people. However, other studies claim that the positive effects will counterbalance by far the negative effects. As is the case with the Hadejia-Nguru wetlands understanding and prediction of the impacts is very difficult. However, without such understanding and prediction, effective planning and management is impossible.
Regional aspects of environmental impacts and 'hot spots'
The arid North African sub-region
The Sudano-sahelian Belt
Humid West Africa
The Congo/Zaire basin
East Africa
Southern Africa
This section summarizes the regional outlook for the main African sub-regions with regard to the impact of irrigation on the environment. For each of the sub-regions, environmentally salient features, particularly in relation to irrigation development issues, are presented. Wherever possible, environmental 'hot spots' are identified and described.
The arid North African sub-region
The North African sub-region lies in arid or semi-arid zones where the water resources are minimal and where evaporation and seepage losses are very large. The sub-region includes two main zones: the Nile Basin in the east and the western part (Morocco, Algeria and Tunisia). This ecological zone is fragile and agricultural production is regulated by alternating periods of water surpluses and deficiencies. Irrigation is the main alternative to cover the food requirements of the increasing population per unit of agricultural land.
The 'hot spots' of the sub-region are the main rivers located in the arid zones threatened by the irrigation-induced salinization of the soils and more generally the degradation of irrigated lands resulting from poor irrigation management and practices. Field drainage and removal of drained water from the irrigated zone is necessary to limit the risk of soil degradation and salinization.
Establishing field drainage is costly, as is the provision of a main drainage network. Moreover, disposal of drainage water represents a major problem. The concentration of salt increases gradually from upstream to downstream as a result of the drainage water inflows.
In the Mediterranean coastal zone, reduction of flow systematically induces sea water intrusion problems.
The natural capital of this ecological zone is the most fragile, evincing most of the negative effects of irrigation projects on the environment due to the poor soils, extremely variable rainfall and high risk of drought.
Soil degradation has substantially increased the risk of desertification because of mutually reinforcing factors including: loss of organic matter and nutrients, soil structure deterioration and surface crusting, which in turn decreases water infiltration and retention, aggravated by the irrigation-induced salinization.
The environmental degradation has been both a cause and a consequence of poverty, with the Sudano-Sahelian belt comprising some of the poorest countries of the world.
Sudano-Sahelian societies face a formidable challenge which makes the whole belt an environmental 'hot spot'. Pressure is likely to be high on the river valleys and major wetlands such as the Niger Inner Delta in Mali, the wetland and flood plains in the Lake Chad basin (Hadejia-Nguru, Yaere and the Sudd swamps in the Nile basin in southern Sudan.
The natural capital of this ecological zone is relatively favourable in terms of climatic conditions: high and regular rainfall, soils of reasonable quality. However, the high population growth during the last decades has placed the environment under serious stress. About half of the total land area is cultivated under reasonably good conditions with a much lower climatic risk than in the Sahel. Forest land has shrunk to less than a third of the total area, and what remains is decreasing at an alarming rate of 1%, the fastest rate in tropical Africa.
The environment of the fragile coastal ecosystems is also threatened by industrial and urban development with increasing pollution levels particularly in the Niger delta of Nigeria. A major part of the biodiversity capital of the sub-region is at risk. Any upstream irrigation project requires special care in order to avoid negative impacts on the wetlands, mangroves and lagoons located in the coastal zone in the Guinea Gulf, from Guinea Bissau to the Niger delta in Nigeria. This zone is likely to become a continuous urban megalopolis with a population of over 50 million people on 500 km of coastal line. The current development of private small-scale irrigation projects, using groundwater for horticultural crops, could contribute to increase the intrusion of saline waters due to overexploitation of coastal aquifers.
About three-quarters of the total surface area of the sub-region would theoretically be cultivable but a major part of it is under tropical rainforest. Overall pressure to clear the rainforest is still relatively low, except at the periphery of the sub-region where it interfaces with areas of high population density.
Land currently cultivated represents about 15% of the total area. Agricultural activities are relatively less important in the sub-region compared to the rest of the continent. They are focused on supplying a growing urban market and on permanent plantations.
Irrigated areas are marginal compared to the huge potential of land and surface waters. The irrigation development will have a minimal impact on the environment. Global environmental problems faced by the Congo/Zaire basin are less severe than those of the other sub-regions, although its future development will present a serious challenge. In particular, countries need to preserve the primary rainforest for global biodiversity and climatic reasons.
The good soils in the eastern African highlands have favoured the development of intensive agriculture, although soils require conservation measures because of steep slopes. Less favourable lands are cultivated under arid and semi-arid conditions. Forests cover less than 20% of the total area of the sub-region. Due to land scarcity, the primary rainforests with their unique biodiversity are at risk.
Due to the pressure of population on arable lands, the environment is at risk particularly in Kenya with a ratio of 0.2 ha per person. To cover the food deficits, areas under irrigation are increasing. Permanent intensive cropping is the current pattern in favourable highlands, but degradation is high under low-input technology and without adequate erosion control measures.
In Tanzania, the central area and the Lake Victoria region represent areas of high population density and areas with a reported high degree of land degradation.
Ethiopia has a very large water resources potential. The development of this resource has been impeded for decades, first by agreements made by colonial powers and shell by political instability. The Ethiopian Blue Nile and other tributaries contribute over 80 % of the water in Sudan and Egypt (see Chapter 6, section: the Nile basin). The mobilization of this potential would have to take into account environmental and basin issues to mitigate the impact on downstream users.
The natural capital of the sub-region is very rich in terms of biodiversity and production potential, although large areas are under semi-arid and arid conditions with moderate to high risk of drought.
In some countries, particularly South Africa, past policies have had a negative impact on the environment by encouraging agricultural development through high subsidies on farm inputs and irrigation development without stimulating enough soil and water conservation.
Almost half of the total areas of the sub-region is cultivated with reasonably good soils but climatic conditions are highly variable with a risk of recurrent droughts. To mitigate this risk and to cover the food deficit, areas under irrigation are increasing without significant impact on the environment.