Search

Abstract This research aimed to assess changes in mean and extreme rainfall within the Kaduna River Basin (KRB), specifically examining the implications of two Representative Concentration Pathways (RCPs)—4.5 and 8.5 scenarios. Employing a quantile mapping technique, this study corrected inherent biases in four Regional Climate Models, enabling the examination of mean precipitation and six indices capturing extreme precipitation events for the 2050s. These findings were compared against a historical reference period spanning from 1981 to 2010, considering the basin's upstream and downstream segments. Results revealed an average annual rainfall reduction under scenarios 4.5 (21.39%) and 8.5 (20.51%) across the basin. This decline exhibited a more pronounced impact on monthly rainfall during the wet season (April to October) compared to the dry season (November to March). Notably, a substantial decrement in wet indices, excluding consecutive wet days (CWD), was foreseen in both seasons for the upstream and downstream areas, signalling an impending drier climate. The anticipated rise in consecutive dry days (CDD) is poised to manifest prominently downstream attributed to global warming-induced climate change brought on by increased anthropogenic emissions of greenhouse gases. These findings accentuate a heterogeneous distribution of extreme rainfall, potentially leading to water scarcity issues throughout the KRB, especially impacting upstream users. Moreover, the projections hint at an increased risk of flash floods during intense wet periods. Consequently, this study advocates the implementation of targeted disaster risk management strategies within the KRB to address these foreseeable challenges.

The study focuses on assessing the individual and combined impacts of climate variability and land use change on hydrological responses. The results indicate that the basin, urban area, cropland, degraded forest, and open forest shows an increasing trend, while gallery forest shows a decreasing trend over the period 1992–2015. Climatic variability is marked by two climatic periods (a wet one from 1980 to 1996 and a dry one from 1997 to 2016) with a 35% decrease in rainfall. Regardless of the state of the landcover used, the simulated mean annual runoff decreases by 67.92% between the wet and dry climate periods. Changes in land use between 1992 and 2015 reduce mean annual runoff by 4.71%. Analysis of the joint effect of climatic and LU variation shows a 68.96% reduction in runoff. In this catchment. The joint impact has a clearly greater effect on runoff than the climatic impact, which is greater than that of human activities. There is a need for policymakers to prioritise sustainable land use practices and integrated water resource management strategies in the area to mitigate the combined effects of climate variability and anthropogenic activities, ensuring the long-term resilience of the ecosystem and water availability for local communities. HIGHLIGHTS The SWAT model was used to isolate the climate and land use change impacts on streamflow.; Impact of autocorrelation in the study of time series trends using modified Mann–Kendall test.; Hydrologic responses follow the direction of joint effects of climate and land use change.; Individual and combined impacts of climate and land use changes on hydrologic responses were evaluated.;

The purpose of this study is to analyse trends in annual rainfall extremes over five watersheds within Côte d'Ivoire using observed (1976–2017) and projected (2020–2050) rainfall data from the fourth version of the Rossby Centre regional atmospheric model, RCA4, for the representative concentration pathways RCP 4.5 and RCP 8.5. Four rainfall extreme indices, namely, the consecutive dry days (CDD), maximum annual rainfall (Pmaxan), very wet day (R95p), and maximum 5-day rainfall (Rx5days), were considered for trend analysis by using the non-parametric modified Mann–Kendall test and the distribution mapping bias-correction technique to adjust the simulated regional climate model of the simulated daily precipitation. As a result, it is found that during the period 1976–2017, there was a significant downward trend in the drought-related index (CDD) at the Bagoue, Baya, Agneby, and Lobo watersheds. The Baya and N'zo watersheds also experienced a significant downward trend under the RCP 4.5 and RCP 8.5 scenarios. The flood-related indices (Pmaxan, R95p, and Rx5days) show a clear downward trend in the recorded data for almost all the considered watersheds and generally a significant upward trend for both cases. These findings indicate that the watersheds are vulnerable to climate-induced disasters. HIGHLIGHTS This article is an original work.; This article analyses the past and projected changes in extreme precipitation indices.; This article allows us to see the past and projected changes in extreme precipitation indices under different climate zones in Cote d'Ivoire.; This article allows us to see a great change in extreme precipitation indices under different climate zones in Cote d'Ivoire in the near future.;

This study examined the temperature variations in West Africa's Volta River Basin (VRB) from 2021 to 2050 in comparison to the historical period (1985–2014) under two Shared Socioeconomic Pathway Scenarios (SSP2-4.5 and SSP5-8.5). Datasets from three Global Climate Models (GCMs) of the sixth Coupled Model Intercomparison Project (CMIP6) were used. The GCMs and their ensemble were evaluated on a monthly scale. The study used the ensemble mean to analyse the changes in annual and monthly temperature over the Sahel, Savannah, Guinea Coast, and the entire Volta basin. The results demonstrate the individual GCMs reproduced the observed temperature pattern at the VRB, though with some overestimations, but the ensemble mean indicated a better representation of the observed temperature. A warming trend in the basin is projected under both climate scenarios, with higher temperatures projected under SSP5-8.5 compared to SSP2-4.5 in all three zones. The mean annual temperature is projected to increase by 0.8 and 1.0 °C, with a statistically increasing trend under SSP2-4.5 and SSP5-8.5, respectively. Without a doubt, high temperatures, if unchecked, can erupt into resource conflict among the competing interest groups, thereby affecting the achievement of economic development at the VRB. HIGHLIGHTS The study contributes to understanding climate change impacts on economic development.; Temperature in VRB to rise up to 1 °C by 2050.; Temperature rise will lead to water shortages, extinction of fish species, and livelihood loss.; Temperature rise could lead to droughts, pest invasion, reduced crop yields, food security, and economic growth.; VRB is home to large hydropower dams, which could be affected by temperature rise.;

Small private irrigation (SPI) is a farmer-initiated irrigation which has the potential to increase the contribution of the overall irrigation sector to global food security. However, there is no much information about these systems for effective policies for regulation. This study compared the resource use productivities and environmental impacts of SPI systems to those of a government-led irrigation scheme (GIS) in Northern Ghana. The results showed that land productivity was higher in the SPI than in the GIS. Productivity per unit cultivated area was 2571.00 US$/ha under SPI while that of the GIS was 676.00 US$/ha. Output per unit command area was also two times higher in the SPI than in the GIS; that is 2571.00 US$/ha and 1113.00 US$/ha for SPI and GIS respectively. For water productivity, output per unit irrigation supply was 0.33 US$/m3 and 0.08US$/m3 for SPI and GIS respectively while output per unit water consumed by ET was 0.60 US$/m3 for SPI and 0.06 US$/m3 for the GIS. The results implied that the SPI schemes performed better in land and water productivities compared with the GIS which is attributed to higher yields and the selection of high valued crops by farmers under SPI. However, both irrigation system types at the time of this study did not cause significant deterioration to the water bodies and surrounding environment as the biochemical oxygen demand (BOD) values of nearby water bodies were less than 3.0–5.0 mg/l, which is considered as acceptable levels for drinking water by World Health Organisation (WHO) while salinity levels were also within acceptable limits (

As part of measures to promote good hygiene, the United Nations International Children's Emergency Fund adopted affordable handwashing with soap facility (Tippy-Tap), and implemented sensitisation training for residents in the Binduri District of Ghana. In the context of good hygiene technology adoption, this study examines how poor communities have adopted and used Tippy-Tap over a period of 1 year. The study further identifies the associated post-sensitisation drivers of the Tippy-Tap. In addition to descriptive analysis, this study relies on post-sensitisation cross-sectional data and a logit regression with its marginal effects for the analysis. The results show that after the sensitisation programme, the adoption and use rate now stand at 90%, up from the baseline of 4%. The study provides evidence that female household-heads are more likely to adopt and use the Tippy-Tap relative to male household-heads. The study further reveals that being educated increases the probability of accessing the Tippy-Tap facility by about 23%. Subsequently, this study finds that personal, household, and community-level characteristics are the key drivers of the high adoption and use rate. In conclusion, the study finds evidence of a high adoption and use rate of the Tippy-Tap initiative after its sensitisation. The study recommends extensive sensitisation of hand hygiene using community-level social norms and practices. HIGHLIGHTS Developing country study that examines post-sensitisation drivers of household (HH) adoption of handwashing with soap (HWWS).; Relevance of sensitisation to rural poor HHs is shown as about 90% HHs adopted HWWS after sensitisation.; Personal, HH, and community-level characteristics are found as key drivers of HWWS.; At cut-off age of 52, respondents are more likely to adopt HWWS.; Smaller HHs are more likely to adopt HWWS.;

Global hydro-climatic trends are ambiguous, challenging the management of water resources. This challenge is addressed in the current study by investigating the impacts of hydro-climatic trends and upstream water management on hydropower generation at the Bagré dam. Modified Mann–Kendall trend test, Standard Normal Homogeneity Test and Pettit test were applied to some selected hydro-climatic variables for the trend and the change year detection, whereas the relationship between upstream dam management, hydro-climatic variables and hydropower were assessed through the Spearman correlation. The results revealed an annual positive trend for all hydro-climatic variables except for water level, lake evaporation and outflow. The break years observed in hydropower generation (2002) and inflow (2006) were mainly due to the construction of the Ziga dam in 2000 and its management change in 2005, respectively. The study also showed that hydropower generation declines each May (−30.36 MWh) and June (−16.82 MWh) due to the significant increase in irrigation withdrawals (1.94 hm3 in May and 0.67 hm3 in June). The results of this study highlighted the non-linearity in the relationship between hydropower generation and hydro-climatic variables as none of the correlation coefficients (apart from turbine) are very strong (>0.8). As many human activities occurred in the basin, further research should be focused on the use of semi-distributed models to assess the impacts of water-use and land-use change on hydropower generation. HIGHLIGHTS All hydro-climatic variables increased significantly except water level, lake evaporation and outflow.; The construction of the Ziga dam in 2000 led to a significant increase in annual hydropower generation at Bagré dam from 2002.; The change in management of the Ziga dam in 2005 led to a significant increase in annual inflow at Bagré dam from 2006.; All the months of the year experienced an increasing trend of hydropower generation except May and June.; The decline of hydropower generation in May and June is the consequence of the increase of water withdrawals for irrigation.;

Understanding rainwater dispersion in a spatiotemporal context is invaluable toward resourceful water management and a food-secure society. This study, therefore, assessed the variations in rainfall at a spatiotemporal scale in the Oti River Basin of West Africa for observed (1981–2010) and future periods (2021–2050) under the representative concentration pathways (RCPs) 4.5 and 8.5 emission scenarios. Rainfall data from meteorological stations and Climate Hazards Group Infrared Precipitation with Stations (CHIRPS) were used. The percentage changes in rainfall for the peak month as well as for rainy and dry seasons under the two climate scenarios were determined. The coefficient of variation (CV) and the standardized anomaly index (SAI) were used to assess annual variations in rainfall. In general, under both emission scenarios, rainfall is projected to decrease over the study area. However, the amount of rainfall during the peak month (August) for RCP4.5 and RCP8.5 could increase by 0.26 and 9.3%, respectively. The highest SAIs for the observed period were +1.58 (2009) and −2.29 (1983) with the latter showing a relationship with historic drought in the basin. The projected SAI under RCP4.5 and RCP8.5 indicated extremely wet (+2.12) and very wet (+1.91) periods for the years 2037 and 2028, respectively. The study provides relevant information and a chance to aid the design of innovative adaptation measures toward efficient water management and agricultural planning for the basin. HIGHLIGHTS Spatiotemporal rainfall analysis was conducted over the Oti River Basin.; The performance of climate models is improved when bias-corrected.; Rainfall is projected to decrease in the basin.; The decline in rainfall poses a threat to the livelihood of fringed communities.; The Mann–Kendall test fostered knowledge of rainfall trends in the basin.;

Considering the high vulnerability of Northern Tanzania to climate change, an in-depth assessment at the local scale is required urgently to formulate sustainable adaptations measures. Therefore, this study analyzed the future (2021-2050) changes in rainfall and temperature under the representative concentration pathways (RCP4.5 and RCP8.5) for the watersheds surrounding the Ngorongoro Conservation Area (NCA) at a spatio-temporal scale relative to the observed historical (1982-2011) period. The climate change analysis was performed at monthly and annual scale using outputs from a multi-model ensemble of Regional Climate Models (RCMs) and statistically downscaled Global Climate Models (GCMs). The performance of the RCMs were evaluated, and the downscaling of the GCMs were performed using Statistical Downscaling System Model (SDSM) and LARS-WG, with all the models indicating a higher accuracy at monthly scale when evaluated using statistical indicators such as correlation (r), Nash-Sutcliff Efficiency (NSE) and percentage bias (PBIAS). The results show an increase in the mean annual rainfall and temperature in both RCPs. The percentage change in rainfall indicated an increase relative to historical data for all seasons under both RCPs, except for the June, July, August and September (JJAS) season, which showed a decrease in rainfall. Spatially, rainfall would increase over the entire basin under both RCPs with higher increase under RCP4.5. Similar spatial increase results are also projected for temperature under both RCPs. The results of this study provide vital information for the planning and management of the studied watershed under changing climatic conditions.

Climate change is projected to negatively affect water security which is already a challenge in many areas of Ghana including the Tano river basin (TRB). This study assessed the projections of rainfall and temperature and its impact on streamflow and actual evapotranspiration (ET) in the TRB of Ghana for 2021-2050 relative to the period 1986-2015. The impact assessment focused on how climate change under Representative Concentration Pathways (RCP 4.5 and RCP8.5) based on an ensemble mean of two regional climate models (RCMs) would affect streamflow and ET using the Soil and Water Assessment Tool (SWAT) model. Trend analysis and quantification for the streamflow and ET were analyzed using the Mann-Kendall's and Sen's slope estimators. The results show that the mean annual rainfall of 1401.9 mm would increase slightly by 0.5 % with a decreasing trend (1.22mm/yr) under the RCP4.5 scenario, but would decrease by 3.2% with a decreasing trend (0.3m mm/yr) under the RCP8.5 scenario. The mean annual temperature showed an increase (2.1 °C and 2.6 °C) with a statistically significant increasing trend of 0.07 and 0.09 °C/yr under RCP 4.5 and RCP8.5 respectively. An increase in ET with a non-significant increasing trend at a rate of 0.74 and 1.07 mm/year under RCP4.5 and RCP8.5 scenarios respectively is also projected. The mean annual streamflow is projected to decrease, with the decrease been more pronounced under the RCP8.5 (37.5%) scenario compared to the RCP4.5 scenario (19.9%). In general, the outcome of this study presents a useful perspective on the vulnerability of water resources to climate change and the need for better planning and management of the water resources in the basin.

Groundwater account for about 60 to 80% of water supply to the population of Tanzania's semi-arid regions for domestic and agriculture uses. Despite the importance of groundwater resource in semi-arid areas, limited information exists on the recharge amount and potential recharge zones in Tanzania in the context of climate change which could result in unsustainable withdrawals. This study aimed to estimate the potential impact of climate change on groundwater recharge and identify potential recharge zones in the Lake Manyara catchment using Water and Energy Transfer between Soil, Plants and Atmosphere under the quasi-steady State (WetSpass) model. The WetSpass model was setup and calibrated using hydro-meteorological data (rainfall, temperature, wind speed, potential evapotranspiration, and groundwater depth) and biophysical data (soil, land use, topography, and slope). Simulated rainfall, temperature and potential evapotranspiration from an ensemble of four CORDEX-Africa regional climate models for the period 2021–2050 under the Representative Concentration Pathway (RCP 8.5) scenario (hereafter referred as business-as-usual scenario) were used as input in the WetSpass model for the climate change impact assessment. WetSpass model calibration using the water balance equation showed a coefficient of determination (R2) value of 0.9 and Root-Mean-Square Error (RMSE) of 0.49 mm/yr between the simulated and calculated recharge. It was determined that the mean annual recharge of 53.9 mm/year (149 MCM/year) for the period 1989–2018 would increase by 7.9% in the future (2021–2050) under the business-as-usual climate scenario, due to the increase in rainfall. Seasonality and spatial differences in recharge amount were observed, with recharge projected to increase in the dry season and at areas that receive high amount of rainfall. Potential recharge zones in the catchment were found mostly around the northern part near Ngorongoro, the south-western part, and around Mbulu region. Findings from this study would help policymakers, and local stakeholders in planning and management of the groundwater resources for sustainable development.

One of the consequences of climate change is the increasing rainfall intensity and frequency leading to flooding. Lately, some major cities in West Africa have been experiencing high frequency of flooding due to extreme rainfall. This study investigated the temporal trends in flash flood and extreme rainfall events in Bamako, Mali for the period 1982–2019. Rainfall observation data from both Mali Meteorological Agency and Climate Hazards Group Infrared Precipitation, and flood ground information’ collected from the Mali Civil protection service were used for this study. Five rainfall extreme indices established by Expert Team for Climate Change Detection Monitoring and Indices (ETCCDI) were analyzed to characterize extreme rainfall intensity and frequency indices. The Gumbel extreme value distribution was used to estimate the return period of flood and extreme rainfall for the period of 5 to 100 years based on the annual maximum daily rainfall. All the five extreme rainfall indices displayed an upward trends except the consecutive wet days (CWD) that showed a decreasing trend. Both the intensity and frequency of extreme rainfall were found to have increased over the study period. The analysis of the flood reports showed an increasing trend in Bamako from 1982 to 2019. The returned period revealed that about 58% of flood events in Bamako are caused by normal rainfall, with 33.3% being caused by extreme rainfall. It was also determined that most flood events were recorded in the years that had higher number of extremely wet days. The findings from this study have demonstrated that floods in Mali are prevalent and adaptation and mitigation strategies are needed.

This study investigated the changes in the climate and the spatiotemporal variations in climate extreme indices of the Dano catchment in Burkina Faso using historical data for the period 1981–2010 and projected for the period 2020–2049. Rainfall and temperature simulations from two RCMs under two Representative Concentration Pathways (RCP 4.5 and RCP 8.5) involved in the CORDEX-Africa project were used in this study. The study found that the climate change signal in the future based on the ensemble mean of the RCMs indicates a decrease in the mean annual rainfall by 25.2% and 25.6% for RCP4.5 and RCP8.5 respectively. A clear temperature increase of about 1.3 °C and 1.5 °C is projected for the catchment using the models. The future rainfall trend projections mostly exhibited a mixed magnitude of increasing and decreasing trends for most areas, indicating no clear pattern of change in the extreme rainfall indices. A non-significant increase in heavy precipitation day events is however projected for the period under RCP 4.5. Projected changes in consecutive dry (wet) days are not significant. Temperature extreme projections showed increasing and decreasing trends in the warm and cold indices respectively, suggesting a warmer climate in the near future. Our study reveals potential climate extremes over the catchment stronger in RCP8.5 which is in agreement with the twenty-first-century warming expected for the region. The spatial distribution investigation highlights extreme dry events across the catchment considerably in the Northern areas. This study finds application for decision-makers to develop more suitable climate change and extremes adaptation strategies for agriculture and water supplies.