The return of the water - IUCN

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1 1.1 Floodplains Introduction By Paul Loth and Mike Acreman Floodplains (Plate 1.1) are the flat stretches of land adjacent to rivers that are inundated during floods (Nanson and Croke, 1992). Floodplains are created by the deposition of sediment as the river channel migrates laterally (Marriot, 1998). The periodic nature of the floods means that floodplains are composed of a rich mosaic of habitats including backwaters, swamps, ridges and hollows. Lateral connectivity between rivers and their floodplains during inundation is a key driving force for the river ecosystem (Junk et al., 1989). Rivers provide the floodplain with sediments and nutrients, whilst the floodplain provides a breeding ground for river species (Welcomme, 1979). Figure 1.1 shows how fish catches increase with flooded area. Fish catch (kg/yr) 180000 150000 120000 90000 60000 30000 0 0 500 1000 1500 2000 Flooded area (km2) Figure 1.1 Relationship between flooded area and fish catch on African floodplains (after Welcomme, 1996). Floodplains play a key role in regulating river flows: outflows from major floodplains such as the Okavango (Botswana) and Sudd (Sudan) are far less variable (lower floods and higher low flows) than inflows (Sutcliffe and Parks, 1996). Inundated floodplains are also important for replenishing underlying aquifers. Groundwater beyond the wetland has been demonstrated for the floodplains of the River Yamuna, India (Nielsen et al., 1991), the Senegal River in Senegal (Hollis, 1996) and Hadejia-Jamare floodplains, Nigeria (Hollis et al., 1993). In these wetlands generous seasonal water availability is combined with high soil fertility, which supports productive ecosystems of great biodiversity. Floodplains along the Nile, Indus and Tigris and Euphrates supported some of the great civilizations of the world (Mitsch and Gosselink, 1993). Wetlands in low rainfall areas are particularly important. These ecosystems are often the only places where plant growth remains possible throughout the dry season. This is the reason that highly productive floodplains have been chosen as core areas for human settlement (Acreman and Hollis, 1996; Connah, 3
The Return of the Water 1981; Hollis et al., 1993). Floodplains are often not suitable for permanent habitation. Floods force inhabitants of the floodplains away, to higher grounds. Aquatic or water-adapted creatures remain, while others including Palaearctic birds, take advantage of the riches of the floods before migrating. There are many examples of floodplains still fulfilling the same role for human societies today as they have done for many centuries. Nomadic pastoralists in the Sahelian zone take advantage of green fodder, on the floodplains during the dry season (Braukamper, 1996; CTA, 1999). Depressions filled with water after the floods have receded trap fish that are harvested by fishermen and birds. The saturated earth provides water for plant growth to allow cropping into the dry season. Thus, a fine fabric of interwoven ethnic groups exists with various activities succeeding each other during the seasons according to the availability of the resources (Pamo, 1998). Adaptation to the flood cycle is integral to the lives of many communities on the floodplain. Customary laws govern access to resources and festivals celebrate key dates in the calendar. In recent years, a combination of drought, increasing populations of people and livestock and rising poverty has put increasing pressure on the floodplains and has led to over exploitation of the natural resources. In the face of such pressure, the implementation of major river engineering schemes, such as dams, for intensive irrigation and for hydroelectric power generation has often been seen as the key to development (Acreman, 1996a). Consequently throughout West and Central Africa, successive governments built dams in river systems paying little regard to the economic or environmental consequences for those suffering from the loss of the floods. 1.2 Floodplains of the Sahel The Sahelian region of West Africa is defined roughly by average annual rainfall, extending from about 150 mm in the north (at latitude of around 18°N) to 1,000 mm in the south (latitude 10°N). Rainfall is highly seasonal, with a dry season extending from October to May. Average temperatures in January are around 25°C rising to 30°C in July, although daytime temperatures frequently exceed 45°C. Gash et al. (1996) estimated actual evaporation to be, on average, around 2.5 mm per day during the 1992 wet season when rainfall was about 7 mm per day. Thus much of the rainfall evaporates immediately. Further south rainfall is considerably higher, reaching 3,000-5,000 mm per year in, for example, the Fouta Djallon massif of Guinea. Here the wet season can last for seven to nine months. These humid areas are the sources of the major rivers of the region, including the Senegal, Niger, Yobe and Logone. As they run north, the rivers provide vital water resources to the Sahel. Their flow regimes show a distinct peak, controlled by the rainfall patterns in the headwaters. After the peak flows have passed, the extent of the flooded areas decreases rapidly as the dry season progresses. The maximum extent of flooding varies from year to year in response to the amount of rainfall falling in the catchment area. In an average year the total inundated area of the major wetland systems in the Sahel is about 67,000 km 2 (see Table 1.1). Wetland surface area km 2 country 1. Senegal delta 3,000 Senegal, Mauritania 2. Senegal valley 5,000 Senegal, Mauritania 3. Niger inner delta 30,000 Mali 4. Niger fringing floodplains 3,000 Nigeria 5. Sokoto and Rima valleys 1,000 Nigeria 6. Hadejia-Nguru floodplains 4,000 Nigeria 7. Logone floodplain 11,000 Cameroon, Chad 8. Lake Chad floodplain 10,000 Nigeria, Cameroon, Chad 4 Total 67,000 Table 1.1 Major floodplain wetlands of Sahelian West Africa (after Drijver and Van Wetten, 1992).
Page 1 and 2: IUCN - The World Conservation Union
Page 3 and 4: The designation of geographical ent
Page 6 and 7: Table of Contents Foreword vii Cont
Page 8 and 9: Foreword This book tells the story
Page 10 and 11: Contributors Dr. Mike Acreman, Head
Page 12 and 13: from the Atlas de la Province de l
Page 14 and 15: List of Tables 1.1 Major floodplain
Page 16: List of Plates 1.1 Different views
Page 22 and 23: Introduction Rainfall in the Sahel
Page 24 and 25: species of ungulates, such as korri
Page 26 and 27: From its inception, the Waza Logone
Page 28: Part II The Receding Water
Page 31 and 32: The Return of the Water tonnes to 4
Page 33 and 34: The Return of the Water that the re
Page 36 and 37: 3 Consequences of the Dam and the D
Page 38 and 39: eduction in flooding (Drijver and M
Page 40: 3.3 Socio-economic consequences Con
Page 44 and 45: 4 The Wider Context By Sun Yan Evan
Page 46 and 47: Africa. A third migration route to
Page 48 and 49: The Wider Context The geographical
Page 50 and 51: 5 Hydrology of the Waza Logone Area
Page 52 and 53: variable, the extent, depth, durati
Page 54: Hydrology of the Waza Logone Area C
Page 57 and 58: The Return of the Water brought to
Page 59 and 60: The Return of the Water 1997). The
Page 61 and 62: The Return of the Water dam, the pe
Page 63 and 64: The Return of the Water 1948; Ngog
Page 65 and 66: The Return of the Water into the bu
Page 68: Part IV Living with the Seasons
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The Return of the Water While the f
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The Return of the Water Most of the
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The Return of the Water which the f
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The Return of the Water from € 0.
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The Return of the Water The Musgum
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The Return of the Water check their
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Plate 1.2 Kob antelopes at the Mahe
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Plate 7.2 Seasonal movements of pas
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Plate 7.4 Fishing cannals in the Lo
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Plate 7.7 Big fish are only caught
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The Return of the Water staple food
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8 Conflicts and Conflict Management
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Conflicts and Conflict Management i
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Conflicts and Conflict Management i
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Part V The Intervention
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The Return of the Water for the Exi
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The Return of the Water both techni
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The Return of the Water (IUCN 2000a
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The Return of the Water 9.5 The Waz
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The Return of the Water of the part
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10 The Waza Logone Project in Actio
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The Waza Logone Project in Action F
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The Waza Logone Project in Action F
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The Waza Logone Project in Action f
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follow to obtain permits, and also,
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started by painting in red trees or
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The Waza Logone Project in Action
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The project maintained relations wi
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11 11.1 Introduction Economic Justi
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Although it is impossible to effect
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Economic Justification of Additiona
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Figure 11.5 Composition of incremen
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12 Tools and Practices for Floodpla
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of the 1994 and 1997 pilot flood re
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Tools and Practices for Floodplain
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A major output from the study was a
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Step 10. Monitor, evaluate and adap
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5. Assess the impacts of options.
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Introduction 137
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Introduction From this premise the
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Introduction One of the most promis
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Introduction reorganisation of the
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Introduction Improving the effectiv
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Map 6.1 Satellite images showing se
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Map 6.3 Positions of two elephants
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Introduction Beauvilain, A. 1981.
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Introduction Gash, J.H.C., C.A. Nob
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Introduction Moritz, M., P. Scholte
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Introduction communities’ and ind
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