Impacts of Global Change on the Hydrological Cycle in West and Northwest Africa

Africa is highly vulnerable to the impacts of climate change. In particular shortage of fresh water is expected to be the dominant water problem for West and Northwest Africa of the 21th century. In order to solve present and projected future problems concerning fresh water supply, a highly interdisciplinary approach is used in the book. Strategies are offered for a sustainable and future-oriented water management. Based on different scenarios, a range of management options is suggested with the aid of Information Systems and Spatial Decision Support Systems for two river catchments in Northwest and West Africa: the wadi Drâa in south-eastern Morocco and the Ouémé basin in Benin. The selected catchments are representative in the sense: "what can be learnt from these catchments for other similar catchments? Cover......Page 1 Impacts of Global Change on the Hydrological Cycle in West and Northwest Africa......Page 4 9783642129568......Page 5 Foreword......Page 6 Acknowledgements......Page 8 Preface......Page 10 Content......Page 12 Part I Fundamentals and process understanding......Page 19 1 Introduction......Page 22 P. Speth and A. H. Fink......Page 23 Past and present situation......Page 24 Regionalization of climate projections......Page 25 Choice of catchments......Page 26 Options for a sustainable development......Page 27 Outline of the book......Page 28 2 Impacts of Global Change......Page 30 I-2 Impacts of Global Change......Page 31 References......Page 32 Abstract......Page 33 References......Page 39 Abstract......Page 41 References......Page 45 3. Regional geography of West and Northwest Africa: An introduction......Page 48 I-3 Regional geography of West and Northwest Africa: An introduction......Page 49 I-3.1.1 The Ouémé basin (southeastern edge of WAC)......Page 52 I-3.1.2 The Drâa basin (northwestern edge of WAC)......Page 55 I-3.2.1 Geomorphological provinces of Benin......Page 57 I-3.2.2 Geomorphological provinces of Southern Morocco......Page 59 I-3.3 Soils......Page 63 I-3.3.1 Soils of Benin......Page 66 I-3.3.2 Soils in the Drâa valley of Southern Morocco......Page 67 I-3.4.1 Subtropical climate of Northwest Africa......Page 71 I-3.4.2 Tropical climate of West Africa......Page 73 I-3.5 Hydrology......Page 77 I-3.5.1 Ouémé basin......Page 79 I-3.5.2 Drâa basin......Page 80 I-3.6.1 Upper Guinean rain forest......Page 83 I-3.6.3 Azonal vegetation types......Page 84 I-3.6.4 Mediterranean/Sahara transitional zone in Morocco......Page 85 3.7.1 Colonial period......Page 87 I-3.7.2 Postcolonial era......Page 88 I-3.8.1 West and Northwest Africa......Page 91 I-3.8.2 Benin......Page 93 I-3.8.3 Morocco......Page 96 I-3.9 Economy and infrastructure......Page 99 I-3.9.1 Benin......Page 100 I-3.9.2 Morocco......Page 101 I-3.10.1 Crossing the Tropic of Cancer from the Mediterranean coastal lands to tropical Africa......Page 105 I-3.10.2 Benin......Page 107 I-3.10.3 Morocco......Page 108 I-3.10.4 Agricultural systems as concentrators and dilutors of resources......Page 109 I-3.11.1 West Africa......Page 111 I-3.11.2 Northwest Africa......Page 114 I-3.12 References for chapter I-3......Page 115 4 Measurement concepts......Page 122 I-4 Measurement concepts......Page 123 I-4.1.1 Introduction......Page 125 I-4.1.2 Meteorological measurements......Page 127 I-4.1.3 Hydrological measurements......Page 129 References......Page 130 I-4.2.1 Introduction......Page 131 I-4.2.2 Meteorological observations in Benin used for data products......Page 132 I-4.2.3 Data products and monitoring......Page 135 References......Page 138 I-4.3.1 Introduction......Page 139 I-4.3.2 Meteorological measurements at the test sites......Page 141 I-4.3.3 Hydrological and other measurements......Page 147 References......Page 148 5 Atmosphere......Page 150 I-5 Atmosphere......Page 151 I-5.1.1 Introduction......Page 152 I-5.1.2 Air masses, convergence zones, and wind systems......Page 153 Atmospheric circulation and disturbances......Page 154 Rainfall types......Page 156 I-5.1.4 Interannual-to-decadal rainfall variability......Page 159 I-5.1.5 The role of sea surface temperatures in West African rainfall......Page 161 I-5.1.6 The role of greenhouse gases and aerosols in West African rainfall......Page 163 References......Page 164 I-5.2.1 Introduction......Page 167 Climatic observations in Morocco......Page 168 Rainfall bearing weather situations and global climate variability......Page 169 I-5.2.3 Summer precipitation and convective density currents......Page 176 I-5.2.4 Conclusions......Page 178 References......Page 179 6 Continental hydrosphere......Page 182 I-6 Continental hydrosphere......Page 183 References......Page 184 Abstract......Page 185 I-6.1.2 Hydrological processes at the local scale......Page 186 Runoff generation processes......Page 187 Physically based hydrological modeling......Page 190 Large scale pattern of land use and hydrological processes......Page 193 Regional hydrological modeling......Page 195 Calibration and Validation......Page 196 Simulated water balance and spatial pattern......Page 199 I-6.1.4 Soil degradation and soil erosion......Page 202 Soils in the Upper Ouémé catchment and their susceptibility to soil degradation......Page 203 Modeling soil erosion at the regional scale......Page 204 Model calibration......Page 205 Model validation......Page 208 Discussion of model results......Page 210 References......Page 212 Abstract......Page 215 I-6.2.1 Introduction......Page 216 I-6.2.2 Seasonal predictions of snowmelt in the High Atlas mountains for reservoir management......Page 218 Snow-related processes at the local scale......Page 219 Simulation of snow dynamics at the local scale......Page 220 Remote sensing of snow......Page 222 From the local to the regional scale......Page 224 Hydrological processes at the local scale......Page 227 Quantification of hydrological processes at the regional scale......Page 229 Simulation of water fluxes: model development......Page 232 Model setup......Page 235 Model validation......Page 237 Model results......Page 239 Discussion......Page 240 I-6.2.4 Sub-surface flow in the Middle Drâa basin......Page 241 Aquifer setting......Page 242 Concept of the regional aquifer system......Page 244 Model concept and parameterization......Page 245 Model results......Page 246 I-6.2.5 Soil salinity: Measurements, processes, and simulations......Page 248 I-6.2.6 Soil erosion by water: Processes and simulations......Page 254 I-6.2.7 Conclusions......Page 264 References......Page 266 7 Biosphere......Page 272 I-7 Biosphere......Page 273 Abstract......Page 274 I-7.1.2 Characterizing vegetation cover in Benin using NDVI calculations from remote sensing data......Page 275 Fire regime in Benin......Page 277 Bush fire drivers......Page 279 I-7.1.4 Assessing natural vegetation and land use distribution in Central Benin......Page 282 Data and methods......Page 283 Satellite image classification......Page 285 I-7.1.5 Changing land use: Hot spots of current land use andland cover changes......Page 286 I-7.1.6 Conclusions......Page 288 References......Page 289 I-7.2.1 Introduction......Page 291 I-7.2.3 Plant diversity along gradients......Page 292 I-7.2.4 Resilience of arid and semi-arid ecosystems......Page 294 I-7.2.5 Rehabilitation pace......Page 296 I-7.2.6 Conclusions......Page 297 References......Page 298 8 Anthroposphere......Page 300 I-8 Anthroposphere......Page 301 I-8.1 The societal framework of water management and strategies of livelihood security......Page 302 Abstract......Page 303 The polygynous family......Page 304 Households and residential units......Page 305 I-8.1.1.3 Income and the impact of occultism......Page 307 I-8.1.1.4 Livelihood strategies and land use......Page 308 The risk of cotton production......Page 310 Gift exchange as a risk-minimizing strategy......Page 311 Strategies of Beninese water users to satisfy water demand......Page 312 Limitations and constraints of an optimal water supply in Benin......Page 318 I-8.1.1.7 Conclusions......Page 319 References......Page 320 I-8.1.2.1 Introduction......Page 322 I-8.1.2.2 Ethnic, social, and cultural background......Page 323 Urbanization......Page 324 Labor migration......Page 326 Traditional and state institutions – parallel structures and conflicting decisions......Page 328 I-8.1.2.5 Conclusions......Page 329 References......Page 331 I-8.2 Economics of agriculture and water use......Page 332 I-8.2.1.1 Introduction......Page 333 I-8.2.1.2 Land use, agriculture, and food security......Page 334 I-8.2.1.3 Simulation of cropland use trends in Benin......Page 337 I-8.2.1.4 The role of livestock husbandry in the water cycle......Page 341 I-8.2.1.5 Conclusions......Page 344 References......Page 345 I-8.2.2.1 Introduction......Page 346 I-8.2.2.2 The importance of water use for economic development in Morocco......Page 347 I-8.2.2.3 Traditional water management in the Drâa oases......Page 348 I-8.2.2.4 The push for modernization......Page 349 I-8.2.2.5 The resilience of traditional water institutions......Page 350 I-8.2.2.6 Agricultural production and available water resources......Page 351 I-8.2.2.7 The hydro-economic simulation model MIVAD......Page 353 I-8.2.2.8 Conclusions......Page 356 References (I-8.2.2)......Page 358 9 Summary......Page 360 The Ouémé catchment......Page 361 The Drâa catchment......Page 362 Database......Page 363 Process understanding and modeling approaches......Page 364 Part II Future projections and decision support......Page 367 1 Introduction: The IMPETUS method......Page 370 II-1 Introduction: The IMPETUS method......Page 371 Problem clusters and models......Page 373 Scenarios (for details see chap. II-3)......Page 374 Stakeholder dialogue and capacity building......Page 375 2 The IMPETUS Spatial Decision Support Systems......Page 378 II-2.1 Introduction......Page 379 II-2.2 Spatial Decision Support Systems......Page 380 Information Systems (IS)......Page 381 Compilation of requirements......Page 382 Organizational aspect......Page 383 Societal aspect......Page 384 Scientific aspect......Page 385 II-2.3 The Scientific Model Integration pipeLine Engine Framework......Page 386 Structure of the SMILE framework......Page 387 GUI: Graphical User Interface......Page 388 Configuration XML......Page 389 II-2.4.1 Spatial Decision Support System PEDRO......Page 390 Application......Page 391 Results......Page 394 II-2.4.2 IWEGS......Page 395 Application......Page 396 Application......Page 399 Discussion......Page 402 Application......Page 403 II-2.5 Conclusions......Page 406 References......Page 408 3 Scenarios......Page 412 II-3 Scenarios......Page 413 II-3.1.1 General definition of scenarios......Page 414 II-3.1.2 Definition of alternative scenarios and sub-regions within IMPETUS......Page 415 II-3.1.3 Intervention scenarios......Page 416 References......Page 417 II-3.2.1 Introduction......Page 419 II-3.2.2 The hierarchy of dynamical models......Page 420 II-3.2.3 Construction of alternative climate scenarios......Page 421 II-3.2.4 Characteristic tables and storylines for Benin and Morocco......Page 422 Storyline for scenario (a) in Benin: Climate model projections......Page 423 Storyline for scenario (b) in Benin: Process understanding......Page 424 Storyline for scenario (c) in Benin: Persistence of recently observed trends (business as usual)......Page 425 Storyline for scenario (a) in Morocco: Displacement of the NAO......Page 426 Storyline for scenario (c) in Morocco: Trend extrapolation......Page 427 II-3.2.5 Dynamical downscaling, model bias correction, and the Weather Generator (WEGE): An example for Benin......Page 428 Post-processing of climate model data......Page 429 II-3.2.6 The statistical downscaling approach used in the High Atlas region......Page 433 Identification of Circulation Weather Types (CWTs)......Page 436 II-3.2.8 Summary of the model-based methods of regionalization of climate information for climate scenarios......Page 440 References......Page 441 II-3.3.1 Introduction......Page 443 Storyline for socio-economic scenario B1: Economic growth and consolidationof decentralization......Page 446 Storyline for socio-economic scenario B2: Economic stagnation and institutional insecurity......Page 448 Storyline for socio-economic scenario B3: Business as usual......Page 450 II-3.3.3 IMPETUS socio-economic scenarios for Morocco......Page 451 Storyline for socio-economic scenario M1: Marginalization - non-support of the Drâa region......Page 452 Storyline for socio-economic scenario M2: Rural development in the Drâa region through regional funds......Page 454 Storyline for socio-economic scenario M3: Business as usual......Page 456 References......Page 458 The demographic dimension of environmental change......Page 459 Population projections......Page 460 Methodological approach......Page 461 Conclusions......Page 464 References......Page 465 4 Impacts of Global Change in Benin......Page 468 II-4 Impacts of Global Change in Benin......Page 469 II-4.1.1 Introduction......Page 471 Adaptation of cropping systems......Page 473 Changes in fallow management......Page 474 The productive potential of bas-fonds......Page 476 Conclusions......Page 477 Crop productivity in traditional cropping systems......Page 479 Effects of Climate Change on crop productivity......Page 483 II-4.1.4 Economic scenarios for food markets and land use......Page 486 II-4.1.5 Consequences of deforestation for livestock management......Page 488 II-4.1.6. Increased use of mineral fertilizer: Higher food security?......Page 490 Fertilizer policy in Benin......Page 491 Endogenizing the use of fertilizer in BenIMPACT......Page 493 Scenario design......Page 495 Selected results......Page 496 II-4.1.7 Conclusions......Page 499 References......Page 500 Abstract......Page 501 II-4.2.2 Scenarios of land use change and Climate Change: Impact on hydrology and water availability......Page 502 Land use scenarios......Page 503 Climate scenarios......Page 506 II-4.2.3 Soil erosion by water in the Upper Ouémé catchment considering land use change and Climate Change......Page 511 Results of scenario analysis......Page 512 Applying WEAP to the Ouémé catchment......Page 515 Water demand scenarios......Page 516 Balancing water demand and supply – WEAP modeling results......Page 518 Water supply security of the Ouémé-Bonou catchment: Interpretation of the WEAP modeling results......Page 520 II-4.2.5 Spatial Decision Support Systems for water-related issues: BenHydro and BenEau......Page 522 II-4.2.6 Conclusions......Page 525 References......Page 526 Abstract......Page 529 II-4.3.1 Introduction......Page 530 II-4.3.2 Concepts in land system research......Page 532 Definitions and some methodological aspects......Page 533 Causes and explanations......Page 535 Modeling approaches......Page 536 Remote sensing data......Page 537 Classification of land use and land cover of the Upper Ouémé catchment......Page 538 Parameterization......Page 539 Model results......Page 540 Definition of scenarios and parameters for LUMIS......Page 543 (B1) Economic growth scenario......Page 544 (B2) Economic stagnation scenario......Page 545 (B5) Intervention scenario......Page 546 II-4.3.6 Conclusions......Page 547 References......Page 548 II-4.4.1 Introduction......Page 553 II-4.4.2 Land tenure in the context of national policies......Page 554 II-4.4.3 Water management in times of decentralization......Page 558 II-4.4.4 LISUOC (Livelihood Security in the Upper Ouémé Catchment): An information system for the decentralized communities......Page 561 Module 2: Water management and institutional change......Page 562 II-4.4.5 Conclusions......Page 563 References......Page 564 II-4.5.1 Introduction......Page 567 Malaria modeling......Page 568 Present-day malaria simulations......Page 569 Malaria projections (2001-2050)......Page 570 Water quality monitoring......Page 572 Viral and bacteriological water quality in drinking water sources......Page 574 Information system SIQeau......Page 576 II-4.5.4 Conclusions......Page 577 References......Page 578 5 Impacts of Global Change in Southern Morocco......Page 580 II-5 Impacts of Global Change in Southern Morocco......Page 581 Abstract......Page 583 II-5.1.2 Crop management in oasis agriculture in the Drâa basin......Page 584 Crop management in the desert oases of the Drâa valley......Page 585 Agricultural production in the mountain oases......Page 588 Climate Change scenarios using the MIVAD modeling approach......Page 589 Impact of Climate Change on modeling results......Page 590 II 5.1.4 Pastoralists’ resource management and livelihood securityin the Drâa region......Page 595 Material and Methods......Page 596 Results......Page 597 Traditional and modern management strategies......Page 598 Coping with drought......Page 599 Modern range management strategies: Implications for livelihood security, and resilience......Page 600 Background and Methods......Page 601 Results......Page 602 II 5.1.6 Conclusions......Page 606 References......Page 607 II-5.2.1 Introduction......Page 609 II-5.2.2 Seasonal snowmelt runoff forecast for the management of the Mansour Eddahbi Reservoir......Page 610 Results of scenario modeling with PRO-RES......Page 612 II-5.2.3 Global change effects on hydrological processes in the Upper Drâa catchment......Page 614 Scenario results......Page 615 Hydraa: A Spatial Decision Support System for water-related issues......Page 618 The IWEGS SDSS......Page 619 Climatic scenarios......Page 620 Socio-economic scenarios......Page 621 Results of climatic scenarios......Page 622 Results of the socio-economic scenarios......Page 624 II-5.2.5 Conclusions......Page 626 References......Page 627 II-5.3.1 Introduction......Page 629 II-5.3.2 Too much rain: The case of severe rainfall events......Page 630 The effects of severe rainfall: Floods and erosion......Page 631 Mitigating floods and erosion: The effects of pastoral land management......Page 634 The combined impact of climate and land use change on soil erosion......Page 636 II-5.3.3 Too little rain: The case of meteorological drought......Page 638 Effects of meteorological drought: Natural resource scarcity......Page 639 Mitigating drought: The role of ecological buffers......Page 640 Searching fodder resource reliability......Page 642 Investments into the ecological buffer of the vegetation......Page 644 Functional connections among drought, flood, and erosion......Page 645 II-5.3.4 Agricultural strategies to cope with unpredictable water resources......Page 646 How to mitigate extreme events in the Drâa catchment?......Page 647 References......Page 648 II-5.4.1 International and national migration......Page 651 Migration on a local scale......Page 653 Labor migrant destinations......Page 654 Remittances from national and international migration......Page 656 Pastoral management systems – the practice of transhumance......Page 657 The importance of local knowledge for decision-making processes......Page 659 II-5.4.3 Conclusions......Page 662 References......Page 663 6 Summary and conclusions......Page 666 Summary of some results for Benin......Page 667 Society......Page 668 Livelihood security and society......Page 669 Hydrology......Page 670 Conclusions......Page 671 Authors......Page 673 Acronyms......Page 678 Index......Page 685 How can Africás finite water and land resources be managed sustainably under the influence of Global Change so as to meet the growing needs of humans in ways that avert the looming crisis? The need to find answers to this question has taxed the brains of many scientists who recognize the urgency of these problems. The pressing water problems must clearly be tackled from an integrated perspective, taking into account environmental, human and technological factors and in particular their inter-dependence. This is the approach adopted by the German GLOWA-IMPETUS project and presented in this book. It is based on the wealth of research results gained in two representative African watersheds: the Ouémé catchment in Benin and the Drâa catchment in Morocco. Interdisciplinary, application-oriented tasks were accomplished with the help of a unique mix of scientists from the social sciences, natural sciences, agricultural science and medicine. The book is organized as follows: Part I deals with the fundamentals and process understanding regarding all major aspects of the hydrological cycle. Part I forms the basis of Part II of the book, which focuses on future climate and socio-economic projections and on the decision support for the sustainable management of natural resources How can Africa ́s finite water and land resources be managed sustainably under the influence of Global Change so as to meet the growing needs of humans in ways that avert the looming crisis? The need to find answers to this question has taxed the brains of many scientists who recognize the urgency of these problems. The pressing water problems must clearly be tackled from an integrated perspective, taking into account environmental, human and technological factors and in particular their inter-dependence. This is the approach adopted by the German GLOWA-IMPETUS project and presented in this book. It is based on the wealth of research results gained in two representative African watersheds: the Ouémé catchment in Benin and the Drâa catchment in Morocco. Interdisciplinary, application-oriented tasks were accomplished with the help of a unique mix of scientists from the social sciences, natural sciences, agricultural science and medicine. The book is organized as follows: Part I deals with the fundamentals and process understanding regarding all major aspects of the hydrological cycle. Part I forms the basis of Part II of the book, which focuses on future climate and socio-economic projections and on the decision support for the sustainable management of natural resources Africa is highly vulnerable to the impacts of climate change. In particular shortage of fresh water is expected to be the dominant water problem for West and Northwest Africa of the 21st century. In order to solve present and projected future problems concerning fresh water supply, a highly interdisciplinary approach is used in the book. Strategies are offered for a sustainable and future-oriented water management. Based on different scenarios, a range of management options is suggested with the aid of Information Systems and Spatial Decision Support Systems for two river catchments in Northwest Africa