Evolution of small reservoirs in Burkina Faso

Small reservoirs (SRs) are important infrastructures for providing water for a wide range of activities in Burkina Faso and other semiarid environments. In recent years, SRs have become even more important, considering the effects of climate change and variability such as erratic rainfall patterns, recurrent droughts and floods, delays in the onset of the rains (Laux et al. 2008), increased incidence of in-season dry spells (Lacombe et al. 2012), and high evapotranspiration rates. SRs provide vulnerable rural communities with water for multiple purposes, including domestic and agricultural uses (McCartney et al. 2012; Venot et al. 2012). However, a number of external factors are negatively influencing the sustainable uses of SRs. Rapid population growth (Zuberi and Thomas 2012) and its attendant human-induced activities are a threat to the quality of water in SRs, as are agricultural extensification and intensification around SRs, including the increased use of inorganic fertilizers

Contribution of informal shallow groundwater irrigation to livelihoods security and poverty reduction in the White Volta Basin (WVB): Current status and future sustainability

Shallow groundwater irrigation (SGI) using hand-dug shallow wells and dugouts is expanding, in the WVB, and is becoming attractive to farmers throughout. SGI is farmer-driven and has developed without any government or donor involvement. The production of vegetables and cash crops during the dry season utilizing SGI has provided farmers with a supplemental source of income and an alternative to seasonal urban migration. Although SGI has been increasing substantially, the extent of this practice is not documented.This project has help assess, the impacts of intensive SGI on sub-basin hydrology, net groundwater recharge farmers' livelihoods and on rural poverty reduction in the Atankuidi catchment a tributary of the WVB with the highest per capita groundwater use

Characterization of small reservoirs in Burkina Faso

Small reservoirs (SRs) are used for multiple purposes in Burkina Faso and West African agroecological landscapes (Venot et al. 2012). These SRs are used for domestic (drinking, bathing and washing) and agricultural (crop, livestock and fishery) purposes, among others (McCartney et al. 2012). However, natural processes and human-induced activities in the surrounding landscapes can be a threat to the water quality and sustainable use of SRs. In order to reduce negative effects, several projects have been designed to study different aspects of how SRs are used and impacted by natural and human-induced activities. But the number of SRs in Burkina Faso (about 1,450) (Cecchi et al. 2009) makes it practically impossible to study every single one of them. A possible solution to this is to categorize the SRs into groups in terms of their responses to the aforementioned natural and anthropogenic influences. Such categorization can provide the basis for site selection in subsequent research programs and further permit generalization (upscaling) of results obtained for selected SRs (at local scale) to many other SRs (at national scale)

Land and people

Our relationship with the landscape has developed through time and more and more the environment is responding to human-driven changes. Now is the time to steer this relationship towards a sustainable future, suggest our Editorial Board Members. Our relationship with the landscape has developed through time and more and more the environment is responding to human-driven changes. Now is the time to steer this relationship towards a sustainable future, suggest our Editorial Board Members

The water resource implications of changing climate in the Volta River Basin

The Volta River is one of the major rivers in Africa. A transboundary basin, which is the principal water source for approximately 24 million people in six riparian states, it is likely to experience increasing stress in the near future as a consequence of both greater water demand and climate change. In a study to ascertain the joint impacts of changes in demand and supply within the basin, a dynamic regional climate model (CCLM), a hydrological model (SWAT) and a water resource model (WEAP) were used to provide an assessment of the possible implications of one downscaled ‘middle impact’ (i.e., lying between extremes) climate change scenario on the performance of existing and planned irrigation and hydropower schemes. The models were used to simulate the climate change in tandem with four scenarios, each reflecting different levels of water resources development as indicated in the plans of the riparian states. It is not possible to quantify the error arising from the models in combination and the results should be considered indicative rather than absolute. Nonetheless, they provide a useful indicator of possible future change and have important implications for water resource planning. The results indicate that, by the middle of the twenty-first century, basin-wide average annual rainfall, mean annual runoff and mean groundwater recharge, will all decline. These changes significantly undermine the technical performance of existing and planned reservoirs, which, in turn, affects development outcomes. In the ‘intermediate development’ scenario, climate change is anticipated to reduce average annual hydropower generation by approximately 30% and increase average annual unmet irrigation demand four-fold by the middle of the century. By the end of the century and in the ‘full development’ scenario, the reduction in technical performance of reservoirs is even greater. Therefore, even though investment in reservoirs brings benefits, these benefits are significantly reduced in comparison to those that would accrue in the absence of climate change. The changes are likely to have dire consequences for economic development, food security and poverty in the region. Against this background, water resources development in the basin requires interventions that bolster resilience and water security. This necessitates much more systematic planning of water storage, greater cooperation between the riparian states and consideration of innovative approaches to water storage, such as managed aquifer recharge

Smallholder shallow groundwater irrigation development in the upper east region of Ghana

In sub-Saharan Africa, there is paucity of information on the potential of groundwater resources. The limited available information paints a pessimistic view about groundwater resources. Due to its perceived inadequate availability, groundwater is associated with domestic use but the potential for using it for agriculture is not well reflected in the national irrigation policies. Contrary to official pessimism, farmers do use groundwater for agriculture in many countries of sub-Saharan Africa including Ghana. This paper analyzes the current extent of use, economics, socioeconomic impacts, and constraints and opportunities of shallow groundwater irrigation based on the experiences of smallholders in the three micro-watersheds of the White Volta Basin in the Upper East Region of Ghana

Kartierung landwirtschaftlicher Landnutzung unter Verwendung multi-sensoraler Satellitendaten

Rapid population growth in West Africa has led to expansion in croplands due to the need to grow more food to meet the rising food demand of the burgeoning population. These expansions negatively impact the sub-region's ecosystem, with implications for water and soil quality, biodiversity and climate. In order to appropriately monitor the changes in croplands and assess its impact on the ecosystem and other environmental processes, accurate and up-to-date information on agricultural land use is required. But agricultural land use mapping (i.e. mapping the spatial distribution of crops and croplands) in West Africa has been challenging due to the unavailability of adequate satellite images (as a result of excessive cloud cover), small agricultural fields and a heterogeneous landscape. This study, therefore, investigated the possibilities of improving agricultural land use mapping by utilizing optical satellite images with higher spatial and temporal resolution as well as images from Synthetic Aperture Radar (SAR) systems which are near-independent of weather conditions. The study was conducted at both watershed and regional scales. At watershed scale, classification of different crop types in three watersheds in Ghana, Burkina Faso and Benin was conducted using multi-temporal: (1) only optical images (RapidEye) and (2) optical plus dual polarimetric (VV/VH) SAR images (TerraSAR-X). In addition, inter-annual or short term (2-3 years) changes in cropland area in the past ten years were investigated using historical Landsat images. Results obtained indicate that the use of only optical images to map different crop types in West Africa can achieve moderate classification accuracies (57% to 71%). Overlaps between the cropping calendars of most crops types and certain inter-croppings pose a challenge to optical images in achieving an adequate separation between those crop classes. Integration of SAR images, however, can improve classification accuracies by between 8 and 15%, depending on the number of available images and their acquisition dates. The sensitivity of SAR systems to different crop canopy architectures and land surface characteristics improved the separation between certain crop types. The VV polarization of TerraSAR-X was found to better discrimination between crop types than the VH. Images acquired between August and October were found to be very useful for crop mapping in the sub-region due to structural differences in some crop types during this period. At the regional scale, inter-annual or short term changes in cropland area in the Sudanian Savanna agro-ecological zone in West Africa were assessed by upscaling historical cropland information derived at the watershed scale (using Landsat imagery) unto a coarse spatial resolution, but geographically large, satellite imagery (MODIS) using regression based modeling. The possibility of using such regional scale cropland information to improve government-derived agricultural statistics was investigated by comparing extracted cropland area from the fractional cover maps with district-level agricultural statistics from Ghana The accuracy of the fractional cover maps (MAE between 14.2% and 19.1%) indicate that the heterogeneous agricultural landscape of West Africa can be suitably represented at the regional or continental scales by estimating fractional cropland cover on low resolution Analysis of the results revealed that cropland area in the Sudanian Savanna zone has experienced inter-annual or short term fluctuations in the past ten years due to a variety of factors including climate factors (e.g. floods and droughts), declining soil fertility, population increases and agricultural policies such as fertilizer subsidies. Comparison of extracted cropland area from the fractional cover maps with government's agricultural statistics (MoFA) for seventeen districts (second administrative units) in Ghana revealed high inconsistencies in the government statistics, and highlighted the potential of satellite derived cropland information at regional scales to improve national/sub-national agricultural statistics in West Africa. The results obtained in this study is promising for West Africa, considering the recent launch of optical (Landsat 8) and SAR sensors (Sentinel-1) that will provide free data for crop mapping in the sub-region. This will improve chances of obtaining adequate satellite images acquired during the cropping season for agricultural land use mapping and bolster opportunities of operationalizing agricultural land use mapping in West Africa. This can benefit a wide range of biophysical and economic models and improve decision making based on their results.Das schnelle Bevölkerungswachstum im Westen Afrikas hat, durch das erhöhte Bedürfnis nach Lebensmittel der expandierenden Bevölkerung, zu einer steigenden Lebensmittelnachfrage und damit zur Ausweitung von Ackerland geführt. Diese Expansionen haben negative Einflüsse auf das Ökosystem der Subregion, die Konsequenzen für Wasser- und Bodenqualität, sowie für Biodiversität und das Klima nach sich ziehen. Um die Veränderungen der Ackerflächen überwachen und die Folgen für das Ökosystem und anderer Umweltprozesse richtig abschätzen zu können, werden genaue und aktuelle Informationen über die landwirtschaftliche Nutzung benötigt. Das kartographieren landwirtschaftlicher Flächennutzung (z.B. das Abbilden der räumlichen Verteilung von Feldfrüchten und Ackerflächen) in Westafrika wurde durch die mangelhafte Verfügbarkeit geeigneter Satellitendaten (durch das Auftreten massiver Wolkenbedeckung), der geringen Größe der landwirtschaftlichen Flächen, sowie der heterogenen Landschaft, erschwert. Aus diesen Gründen untersucht diese Studie das Potential landwirtschaftlich genutzte Flächen, durch die Nutzung von optischen Satellitensystemen mit höherer geometrischer und temporaler Auflösung und Aufnahmen des Synthetic Aperture Radar (SAR) als ein nahezu wetterunabhängiges System, aufzunehmen. Diese Studie wurde sowohl auf der Skala von Wassereinzugsgebieten als auch von Regionen erstellt (Agrarökologische Zone in der sudanesischen Savanne). Auf der Skala der Wassereinzugsgebiete wurden Klassifikationen verschiedener Feldfrüchte in drei Einzugsgebieten in Ghana, Burkina Faso und Benin, mithilfe multitemporaler Abbildungen, bestehend aus entweder (1) nur optischer Abbildungen (Rapideye) oder (2) optischer und dual polarimetric (VV/VH) SAR Aufnahmen (TerraSAR-X), durchgeführt. Zusätzlich wurden interannuelle oder kurzzeitige (2-3 Jahre) Veränderungen in der Ausdehnung von Ackerflächen über die vergangenen zehn Jahre hinweg mittels historischer Landsataufnahmen untersucht. Die Ergebnisse zeigen, dass das Kartographieren verschiedener Feldfrüchte in Westafrika durch nur optische Abbildungen eine moderate Klassifikationsgenauigkeit von 57% bis 71% widergibt. Überlappungen zwischen dem Anbauplan der meisten Feldfrüchte und dem Zwischenfruchtanbau stellen eine Herausforderung für optische Abbildungen dar, um eine angemessene Unterscheidung der Feldfrüchte zu erreichen. Die Hinzunahme von SAR Aufnahmen kann die Klassifikationsgenauigkeit, abhängig von der Anzahl verfügbarer Szenen und deren Aufnahmedatum, jedoch um 8% bis 15% erhöhen. Die Empfindlichkeit der SAR Systeme gegenüber unterschiedlichem Aufbau der Fläche von Feldfrüchten und der Charakteristika der Landoberfläche verbesserten die Trennbarkeit unterschiedlicher Feldfrüchte. Wie sich herausstellte hat die VV Polarisation von TerraSAR-X eine bessere Trennung der Feldfrüchte bewirkt als die VH Polarisation. Außerdem zeigt sich, dass Aufnahmen zwischen August und Oktober sehr nützlich zur Abbildung von Feldfrüchten in der Subregion sind, da in dieser Zeit strukturelle Unterschiede einiger Feldfrüchte beobachtet werden können. Auf regionalem Maßstab wurden interanuelle oder kurzzeitige Veränderungen der Ackerflächen in der agrarökologischen Zone der sudanesischen Savanne in Westafrika durch das hochskalieren historischer Informationen zu den Ackerflächen auf der Skala der Wassereinzugsgebiete (aus Landsat Aufnahmen) auf eine gröbere Auflösung, aber geographisch weite Satellitenszene (MODIS), unter Zuhilfenahme eines auf Regression basierenden Modells, berechnet. Die Möglichkeit regionalskalierte Informationen zu Ackerflächen zu nutzen um staatlich erstellte landwirtschaftliche Statistiken zu verbessern wurde untersucht, indem die extrahierte Fläche der Äcker aus fraktionierten Karten zur Landbedeckung mit landwirtschaftlichen Statistiken auf Distrikt-Level miteinander verglichen werden. Die Genauigkeit der fraktionierten Landbedeckungskarten (Mean Absolute Error zwischen 14,2% und 19,1%) weist darauf hin, dass die heterogene Agrarlandschaft Westafrikas auf einem regionalen oder kontinentalen Maßstab, durch die Abschätzung fraktionierter Ackerflächen aus gering aufgelösten Satellitendaten, angemessen repräsentiert werden kann. Die Analyse der Ergebnisse zeigt, dass die Ackerflächen der Agrarökologischen Zone der sudanesischen Savanne interannuelle oder kurzzeitige Schwankungen in den vergangenen zehn Jahren unterlegen waren. Diese Schwankungen ergeben sich durch bestimmte Faktoren wie: klimatische Faktoren (z.B. Überschwemmungen oder Dürren), sinkende Bodenfruchtbarkeit, Bevölkerungswachstum und landwirtschaftliche Politik wie der Subvention von Düngemitteln. Der Vergleich von fraktionierter Landbedeckungskarten mit staatlich erstellten landwirtschaftlichen Statistiken (MoFA) in 17 Distrikten in Ghana ergaben große Unregelmäßigkeiten in den staatlichen Statistiken und zeigten das Potential von aus Satellitendaten abgeleiteten Informationen zu Ackerflächen auf regionalem Maßstab um nationale oder subnationale landwirtschaftliche Statistiken in Westafrika zu verbessern. Angesichts der baldigen Starts der optischen (Landsat 8) und SAR (Sentinel-1) Sensoren, die frei zugängliche Daten für die Kartierung von Feldfrüchten in der Subregion liefern werden, sind die Ergebnisse, die in dieser Studie gewonnen wurden, vielversprechend für Westafrika. Dadurch steigen die Chancen, dass adäquate Satellitenszenen für das Abbilden landwirtschaftlicher Landnutzung während der Anbauzeitraums bezogen und operationalisiert werden können. Dies hat zur Folge, dass ein breites Spektrum biophysikalischer und ökonomischer Modelle davon profitieren und die Entscheidungsfindung durch die Ergebnisse optimiert wird

Agricultural Land Use Mapping in West Africa Using Multi-Sensor Satellite Imagery

Rapid population growth in West Africa has led to expansion in croplands due to the need to grow more food to meet the rising food demand of the burgeoning population. These expansions negatively impact the sub-region's ecosystem, with implications for water and soil quality, biodiversity and climate. In order to appropriately monitor the changes in croplands and assess its impact on the ecosystem and other environmental processes, accurate and up-to-date information on agricultural land use is required. But agricultural land use mapping (i.e. mapping the spatial distribution of crops and croplands) in West Africa has been challenging due to the unavailability of adequate satellite images (as a result of excessive cloud cover), small agricultural fields and a heterogeneous landscape. This study, therefore, investigated the possibilities of improving agricultural land use mapping by utilizing optical satellite images with higher spatial and temporal resolution as well as images from Synthetic Aperture Radar (SAR) systems which are near-independent of weather conditions. The study was conducted at both watershed and regional scales. At watershed scale, classification of different crop types in three watersheds in Ghana, Burkina Faso and Benin was conducted using multi-temporal: (1) only optical images (RapidEye) and (2) optical plus dual polarimetric (VV/VH) SAR images (TerraSAR-X). In addition, inter-annual or short term (2-3 years) changes in cropland area in the past ten years were investigated using historical Landsat images. Results obtained indicate that the use of only optical images to map different crop types in West Africa can achieve moderate classification accuracies (57% to 71%). Overlaps between the cropping calendars of most crops types and certain inter-croppings pose a challenge to optical images in achieving an adequate separation between those crop classes. Integration of SAR images, however, can improve classification accuracies by between 8 and 15%, depending on the number of available images and their acquisition dates. The sensitivity of SAR systems to different crop canopy architectures and land surface characteristics improved the separation between certain crop types. The VV polarization of TerraSAR-X was found to better discrimination between crop types than the VH. Images acquired between August and October were found to be very useful for crop mapping in the sub-region due to structural differences in some crop types during this period. At the regional scale, inter-annual or short term changes in cropland area in the Sudanian Savanna agro-ecological zone in West Africa were assessed by upscaling historical cropland information derived at the watershed scale (using Landsat imagery) unto a coarse spatial resolution, but geographically large, satellite imagery (MODIS) using regression based modeling. The possibility of using such regional scale cropland information to improve government-derived agricultural statistics was investigated by comparing extracted cropland area from the fractional cover maps with district-level agricultural statistics from Ghana The accuracy of the fractional cover maps (MAE between 14.2% and 19.1%) indicate that the heterogeneous agricultural landscape of West Africa can be suitably represented at the regional or continental scales by estimating fractional cropland cover on low resolution Analysis of the results revealed that cropland area in the Sudanian Savanna zone has experienced inter-annual or short term fluctuations in the past ten years due to a variety of factors including climate factors (e.g. floods and droughts), declining soil fertility, population increases and agricultural policies such as fertilizer subsidies. Comparison of extracted cropland area from the fractional cover maps with government's agricultural statistics (MoFA) for seventeen districts (second administrative units) in Ghana revealed high inconsistencies in the government statistics, and highlighted the potential of satellite derived cropland information at regional scales to improve national/sub-national agricultural statistics in West Africa. The results obtained in this study is promising for West Africa, considering the recent launch of optical (Landsat 8) and SAR sensors (Sentinel-1) that will provide free data for crop mapping in the sub-region. This will improve chances of obtaining adequate satellite images acquired during the cropping season for agricultural land use mapping and bolster opportunities of operationalizing agricultural land use mapping in West Africa. This can benefit a wide range of biophysical and economic models and improve decision making based on their results

Dynamics of land-use and land-cover change in Freetown, Sierra Leone and its effects on urban and peri-urban agriculture: a remote sensing approach

This paper presents findings of a land-use and land-cover (LULC) change mapping exercise conducted in Freetown, Sierra Leone. Nine LULC classes were mapped from multi-temporal Landsat data of 1974, 1986 and 2000. Special attention was given to the growth or otherwise of agricultural land in relation to other LULC classes. Conversion of one land-use/-cover type to the other was identified, and its effects discussed. Major conversions occurred between agricultural lands, grasslands, evergreen forest, built-up areas and barren land. Built-up areas increased by at least 140% between 1974 and 2000, suggesting a high urbanization rate. About 882 ha (27%) of agricultural lands in 1986 were converted to residential purposes in 2000, especially at the urban fringes, in response to an increase in population. Some 14% of evergreen forest was found to have been converted to agricultural land. These major conversions suggest a strong linkage between urbanization, agriculture and deforestation

Monitoring Agricultural Expansion in Burkina Faso over 14 Years with 30 m Resolution Time Series: The Role of Population Growth and Implications for the Environment

Burkina Faso ranges amongst the fastest growing countries in the world with an annual population growth rate of more than three percent. This trend has consequences for food security since agricultural productivity is still on a comparatively low level in Burkina Faso. In order to compensate for the low productivity, the agricultural areas are expanding quickly. The mapping and monitoring of this expansion is difficult, even on the basis of remote sensing imagery, since the extensive farming practices and frequent cloud coverage in the area make the delineation of cultivated land from other land cover and land use types a challenging task. However, as the rapidly increasing population could have considerable effects on the natural resources and on the regional development of the country, methods for improved mapping of LULCC (land use and land cover change) are needed. For this study, we applied the newly developed ESTARFM (Enhanced Spatial and Temporal Adaptive Reflectance Fusion Model) framework to generate high temporal (8-day) and high spatial (30 m) resolution NDVI time series for all of Burkina Faso for the years 2001, 2007, and 2014. For this purpose, more than 500 Landsat scenes and 3000 MODIS scenes were processed with this automated framework. The generated ESTARFM NDVI time series enabled extraction of per-pixel phenological features that all together served as input for the delineation of agricultural areas via random forest classification at 30 m spatial resolution for entire Burkina Faso and the three years. For training and validation, a randomly sampled reference dataset was generated from Google Earth images and based on expert knowledge. The overall accuracies of 92% (2001), 91% (2007), and 91% (2014) indicate the well-functioning of the applied methodology. The results show an expansion of agricultural area of 91% between 2001 and 2014 to a total of 116,900 km². While rainfed agricultural areas account for the major part of this trend, irrigated areas and plantations also increased considerably, primarily promoted by specific development projects. This expansion goes in line with the rapid population growth in most provinces of Burkina Faso where land was still available for an expansion of agricultural area. The analysis of agricultural encroachment into protected areas and their surroundings highlights the increased human pressure on these areas and the challenges of environmental protection for the future