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The adverse effects of climate change on agriculture have been felt across the globe. Smallholder farmers in sub-Sahara Africa are particularly more vulnerable to the effects of climate change leading to loss of income and livelihood thus affecting global food security. Rainwater harvesting (RWH) is emerging as a viable option to mitigate the negative effects of climate change by supporting rain-fed agriculture through supplemental irrigation. However, smallholder farmers are still grappling with a myriad of challenges hindering them from reaping the benefits of their investment in RWH systems. This review explores some of the factors behind the poor performance of RWH systems in Kenya and also seeks to suggest techniques that can be applied to optimize the design parameters for improved performance and the adoption of RWH systems. According to the review, RWH has the potential to mitigate the adverse effects of climate change among smallholder farmers. It allows for crop production beyond the growing season through supplemental irrigation. However, their impacts have been minimal due to the consistent poor performance of RWH systems. This is attributed to inefficiencies in design and construction brought about by lack of required technical skills among RWH system designers and implementers. Proper design and implementation are therefore paramount for better performance and adoption of RWH systems in the region. This will ensure that RWH systems are reliable, technically and economically feasible as well as possess a desirable water-saving efficiency.

Rainwater harvesting (RWH) is emerging as a promising alternative source of water in sub-Saharan Africa. It can be an alternative source of good-quality water to substitute other freshwater sources, to enable crop production beyond the growing season through supplemental irrigation as well as to improve the environment by minimizing the effect of drought and floods. The Rachuonyo North Sub-County of Kenya experiences low rainfall coupled with high population with limited access to reliable water sources. The study assessed the RWH potential of the Rachuonyo North Sub-Catchment with the aim of providing information on alternative water resources to meet the water demands for agriculture as well as domestic use in the region. The Australian water balance model (AWBM) was used to simulate the RWH potential of the Rachuonyo North Sub-Catchment using the area rainfall, evapotranspiration and river flow data. The calibration and validation of the model were performed with calibration and validation results yielding Nash–Sutcliffe efficiency (NSE) values of 0.503 and 1.00, respectively. Research findings indicated that the area has a potential for RWH with runoff harvest of between 104,496 and 43,646,142 m3/month, which can significantly support the residential and irrigation water demands for the area. Policymakers and development agencies in the region should pro-actively put in place measures to promote RWH interventions as a tool for increasing access to water. The methodology in the study is suitable for adaption for rainfall–runoff simulation in other sub-Saharan African regions where data are limiting.

Eutrophication is a serious problem in Lake Victoria as a result of enrichment by nutrients transported by the rivers draining into it. River Nzoia is one of the main rivers draining into the lake. The main aim of this study was to simulate the level of nitrates using MIKE 11 and to establish relationship between nitrogen and phosphorus. The model was calibrated using water quality data for 2009 and validated with March 2013 data and then it was used to simulate nitrate concentration for the wet month of April 2013. The model performance was good with R2 values of between 0.87 and 0.98 and EF values of between 0.73 and 0.96. From the simulations, the effluent discharge from municipal and industrial wastewater ponds elevated the concentration of the nitrates in the river. Analysis of the concentrations of nitrates for wet and dry periods showed significant variations indicating significant contributions from the catchment through run-off. The relationship between total nitrogen and total phosphorus was analysed and found to have a strong positive correlation (r = 0.714, p < 0.05) indicating that both originate from similar sources or are influenced by the same factors such as agriculture.

River Nzoia is the largest river draining into the Kenyan portion of Lake Victoria. This river receives both point sources of pollution from industrial and municipal wastes, and non-point sources from agricultural runoff in the catchment. The objective of this study was to simulate dissolved oxygen (DO) and biochemical oxygen demand (BOD) of the middle section of River Nzoia using MIKE 11 model. The model was calibrated using discharge and water quality data for 2009 and validated with March–April 2013 data. The model performance was good with coefficient of determination (R2) values of between 0.845 and 0.995, Nash–Sutcliffe efficiency values of between 0.748 and 0.993 and percent bias of less than 10 for both calibration and validation of electrical conductivity (EC), DO and BOD. EC and BOD values were lower for April compared to March which could be attributed to dilution during high flows. DO values were above the recommended minimum level of 4 mg/l in all the sections of the river in the wet period but some sections had lower than 4 mg/l during low flow period. The government agencies such as Water Resources Management Authority and National Environment Management Authority should enforce the effluent standards to ensure that industries and wastewater treatment plants adhere to the maximum allowable limit for BOD and also improve their treatment efficiencies of wastewater plants so as to improve the quality of River Nzoia which is important in the overall management of the Lake Victoria basin.

Water-energy-food (WEF) nexus is a concept that aims at integrating these three key economic drivers which are very crucial for the improving the livelihood of the people, general economic sustainable development and social well-being of the world population. The effective utilization and management of these key resources require in-depth planning assessment of symbiosis, competitions and concession with an essential contribution in the nexus. This paper aims at reviewing the WEF in the Great Lakes region of Africa with a focus in Kenya, Democratic Republic of Congo, Rwanda and Uganda. The status and prospects in each country has been assessed and the interconnection between the three fundamental resources together with the effects of climate change towards the security of these resources in the selected countries have been discussed. The review has found out that the selected countries are indeed WEF insecure since the impacts of climate change and poor infrastructure play a vital role in the insecurities highlighted. In the focused countries, it was realized that the existence of weak institutional and legal frameworks, political instability and poor infrastructure indeed hinders the regional attainment of the WEF nexus for sustainable economic development. This therefore calls for a dire need for the adoption of climate change adaptation and mitigation measures in the WEF nexus through an integrated and holistic approach in the Great Lakes Region of Africa.