User Manual: Google earth engine script for semi-automated mapping of small reservoirs using sentinel-2 satellite imagery

This user manual describes the methodology to be followed to use the Google Earth engine script for semi-automated mapping of small reservoirs using Sentinel-2 satellite imagery. It is developed to support suitability analysis for multiple uses (including fisheries) of reservoirs in Ghana

Assessing climate model accuracy and future climate change in Ghana's Savannah regions

This study aimed to compare the performance of six regional climate models (RCMs) in simulating observed and projecting future climate in the Savannah zone of Ghana, in order to find suitable methods to improve the accuracy of climate models in the region. The study found that the accuracy of both individual RCMs and their ensemble mean improved with bias correction, but the performance of individual RCMs was dependent on location. The projected change in annual precipitation indicated a general decline in rainfall with variations based on the RCM and location. Projections under representative concentration pathway (RCP) 8.5 were larger than those under RCP 4.5. The mean temperature changes recorded were 1 °C for the 2020s for both RCPs, 1–4 °C for the 2050s under both RCPs, and 1– 4 °C under RCP 4.5, and from 2 to 8 °C for the 2080s. These findings will aid farmers and governments in the West African subregion in making informed decisions and planning cost-effective climate adaptation strategies to reduce the impact of climate change on the ecosystem. The study highlights the importance of accurate climate projections to reduce vulnerability to climate change and the need to improve climate models in projecting climate in the West African subregion

Google earth engine script for semi-automated mapping of small reservoirs using sentinel-2 satellite imagery

Google Earth engine script for semi-automated mapping of small reservoirs using Sentinel-2 satellite imagery. It is developed to support suitability analysis for multiple uses (including fisheries) of reservoirs in Ghana

A decision support tool for targeting inland valleys with high potential for agricultural development and biodiversity and ecosystem services preservation

Inland valleys are defined as the upper parts of river drainage systems with a complete toposequence from the interfluves to the valley bottom with its seasonally waterlogged depression. Due to their specific hydrological conditions, where the bottom of the valley has predominant water seasonally or throughout the year, inland valleys have a favorable agricultural production, especially for the rice crop. Thus, the inland valleys are considered Africa's future food baskets. While Africa Rice Centre has deployed considerable efforts in characterizing inland valleys ecology in West Africa in recent years, there is still a need to develop actionable maps of inland valleys in terms of the geodatabase and their suitability for rice production in the region. These outputs (geodatabase and suitability) are needed to support project development and implementation for NGOs, and research institutions and to orient government policies aiming at expanding cropland in inland valleys with limited impact on biodiversity and ecosystem services. International Water Management Institute and AfricaRice developed a decision support system to map inland valleys and their potential for agricultural development in Mali using integrated fuzzy-based morphometry multi-scale and ecological niche modeling approach. The integrated approach developed was validated with an accuracy over 90% for both the testing and training datasets. In total, 6,815,205 ha of inland valleys were located, mapped, and characterized using both biophysical and socio-economic variables. Of the total inland valleys area, 802761 ha were mapped as suitable for rice-based systems development, while the remaining 6012444 ha were mapped as suitable for biodiversity and ecosystem services preservation. The tool can be used by the national government, investors, agronomists, and potential land users to identify inland valleys where cropland expansion, sustainable intensification, and ecosystem services preservations could all be feasible

Suitability Analysis of Rice Cropping in Burkina Faso: Assessing the Gap between Current and Potential Rice Cropping Area

The challenges of climate change in West Africa are closely linked to food security in the region. Rising temperatures and increasingly variable rainfall threaten traditional rain-fed agriculture based on the rainy season. Climate change is affecting the rainy season in West Africa by shifting the onset, shortening the growing period and the rainy season are increasingly interrupted by dry spells. An increase of extreme weather events such as heavy precipitation or storms add another risk to agriculture. The risk of crop failures hits an already vulnerable food system since a large portion of food is imported what makes the West African countries vulnerable against external economic shocks. Furthermore, West Africa has one of the highest population growths and will be triple by 2050 to 1.5 billion people. For a sufficient food supply and to achieve the Sustainable Development Goals an intensification of the agricultural area is needed and adaption strategies against the negative effects of climate change are in demand. Especially in the growing cities in West Africa a change in dietary leads to a swift from traditional staples crops like yam or sorghum to e.g. rice. To decrease the dependency from rice imports West African countries are expanding the domestic production of rice. A West African geomorphological specificity allows rice cropping in inland valleys and flood plains, characterized by soils with a high water capacity, highly suitable for rice cropping. These inland valleys are partially used for agricultural practices but there is still an unexploited potential. To quantify the potentially suitable area in for rice cropping and to map the already used area for rice cropping Burkina Faso, this study is combining different dataset. On the one hand SRTM data are used to derive inland valleys and on the other hand Sentinel-1 and Sentinel-2 time series are used to map the already used area for rice cropping. Since agriculture practices always depend on climatic conditions ERA5 data are analyzed regarding the suitability for rice cropping in Burkina Faso depending on the need of rice in different growing stages. The combination of the rice mapping and the potential suitability for rice cropping can be used as decision support for local stakeholders to improve the planning of future expansion of rice area

Impacts of Rainfall Variability, Land Use and Land Cover Change on Stream Flow of the Black Volta Basin, West Africa

Potential implications of rainfall variability along with Land Use and Land Cover Change (LULC) on stream flow have been assessed in the Black Volta basin using the SWAT model. The spatio-temporal variability of rainfall over the Black Volta was assessed using the Mann-Kendall monotonic trend test and the Sen’s slope for the period 1976–2011. The statistics of the trend test showed that 61.4% of the rain gauges presented an increased precipitation trend whereas the rest of the stations showed a decreased trend. However, the test performed at the 95% confidence interval level showed that the detected trends in the rainfall data were not statistically significant. Land use trends between the year 2000 and 2013 show that within thirteen years, land use classes like bare land, urban areas, water bodies, agricultural lands, deciduous forests and evergreen forests have increased respectively by 67.06%, 33.22%, 7.62%, 29.66%, 60.18%, and 38.38%. Only grass land has decreased by 44.54% within this period. Changes in seasonal stream flow due to LULC were assessed by defining dry and wet seasons. The results showed that from year 2000 to year 2013, the dry season discharge has increased by 6% whereas the discharge of wet season has increased by 1%. The changes in stream flows components such us surface run-off (SURF_Q), lateral flow (LAT_Q) and ground water contribution to stream flow (GW_Q) and also on evapotranspiration (ET) changes due to LULC was evaluated. The results showed that between the year 2000 and 2013, SURF_Q and LAT_Q have respectively increased by 27% and 19% while GW_Q has decreased by 6% while ET has increased by 4.59%. The resultant effects are that the water yield to stream flow has increased by 4%

Land Use and Land Cover Changes under Climate Uncertainty: Modelling the Impacts on Hydropower Production in Western Africa

The Bui hydropower plant plays a vital role in the socio-economic development of Ghana. This paper attempt to explore the combined effects of climate-land use land cover change on power production using the (WEAP) model: Water Evaluation and Planning system. The historical analysis of rainfall and stream flow variability showed that the annual coefficient of variation of rainfall and stream flow are, respectively, 8.6% and 60.85%. The stream flow varied greatly than the rainfall, due to land use land cover changes (LULC). In fact, the LULC analysis revealed important changes in vegetative areas and water bodies. The WEAP model evaluation showed that combined effects of LULC and climate change reduce water availability for all of demand sectors, including hydropower generation at the Bui hydropower plant. However, it was projected that Bui power production will increase by 40.7% and 24.93%, respectively, under wet and adaptation conditions, and decrease by 46% and 2.5%, respectively, under dry and current conditions. The wet condition is defined as an increase in rainfall by 14%, the dry condition as the decrease in rainfall by 15%; current account is business as usual, and the adaptation is as the efficient use of water for the period 2012–2040

Mapping suitability for rice production in inland valley landscapes in Benin and Togo using environmental niche modeling

Inland valleys (IVs) in Africa are important landscapes for rice cultivation and are targeted by national governments to attain self-sufficiency. Yet, there is limited information on the spatial distribution of IVs suitability at the national scale. In the present study, we developed an ensemble model approach to characterize the IVs suitability for rainfed lowland rice using 4 machine learning algorithms based on environmental niche modeling (ENM) with presence-only data and background sample, namely Boosted Regression Tree (BRT), Generalized Linear Model (GLM), Maximum Entropy (MAXNT) and Random Forest (RF). We used a set of predictors that were grouped under climatic variables, agricultural water productivity and soil water content, soil chemical properties, soil physical properties, vegetation cover, and socio-economic variables. The Area Under the Curves (AUC) evaluation metrics for both training and testing were respectively 0.999 and 0.873 for BRT, 0.866 and 0.816 for GLM, 0.948 and 0.861 for MAXENT and 0.911 and 0.878 for RF. Results showed that proximity of inland valleys to roads and urban centers, elevation, soil water holding capacity, bulk density, vegetation index, gross biomass water productivity, precipitation of the wettest quarter, isothermality, annual precipitation, and total phosphorus among others were major predictors of IVs suitability for rainfed lowland rice. Suitable IVs areas were estimated at 155,000–225,000 Ha in Togo and 351,000–406,000 Ha in Benin. We estimated that 53.8% of the suitable IVs area is needed in Togo to attain self-sufficiency in rice while 60.1% of the suitable IVs area is needed in Benin to attain self-sufficiency in rice. These results demonstrated the effectiveness of an ensemble environmental niche modeling approach that combines the strengths of several models

A review of sewerage and drainage systems typologies with case study in Abidjan, Côte d'Ivoire: failures, policy and management techniques perspectives

The failure of sewage and drainage systems in SubSaharan African cities is frequent and can be considered as a critical issue, both from an environmental standpoint and in terms of associated maintenance costs. This study analyzes the state of the sanitation systems, the elements behind the failures, the environmental concepts used to classify the problems, and the tools and methodological alternatives for ranking the various management solutions. This research illustrates the causes that contribute to the dysfunctions in the sewage systems of Abidjan as a typical example of sewerage systems management challenges in SubSaharan Africa’s large cities. Poor solid waste and wastewater management practices by residents, e.g., illegal dumping of solid waste into the sewers, unauthorized and defective connections to the network, structural dysfunctions related to the age of the network (cracked, denuded, or broken), urban agriculture in the vicinity of the channels, natural phenomena such as erosion, landslides in the undeveloped parts, and the high concentration of vegetation in the network, wholly contribute to the degradation of the network. A variety of decision support systems for the management of the assets of the urban sewage network were presented. The instruments have been categorized based on their capacity and functionality. The operating concept of each of these tools has been outlined, as well as their respective data needs. In addition, the study analyzes challenges related to the usage of existing decision support systems and provides an outlook on future research requirements in this area. This study offers a detailed analysis of the issues of sanitation management and could serve as a reference for other emerging nations in SubSaharan Africa