A Hydro-Climatic Analysis with Policy Implications for the Logone catchment, Lake Chad Basin

As a response to the generally perceived divide between the scientists and policy makers in decision making, this thesis seeks to bridge the gap between science and policy by framing the research questions based on the views expressed by policy makers. The thesis attempts to develop an approach for linking biophysical and social sciences research to support the use of scientific knowledge in decision making within the policy arena. Q methodology was used to derive discourses obtained from interviews with a range of stakeholders in government, non-governmental organizations, civil society, and academia in Cameroun. The aim was to reveal the different discourses in climate change in general and on the relationship between science and policy and how it can be applied in hydro – climatic research. Three different discourses emerged from the study. These highlighted concerns that water resources in the Sudano-Sahel zone of the country were vulnerable to climate change owing to past climate variability which could lead to food insecurity in Cameroun. The policy makers expressed the need for the scientists to conduct climate change impact studies on water resources in the region, stating that results from such studies could be useful for developing climate change adaptation policies.
Results from the different homogeneity tests indicated that rainfall was homogenous across the Logone catchment during the period under study (1951 – 2000). A yearly trend analysis revealed the presence of statistically significant negative trends in annual rainfall time series at all stations across the catchment; while trend analysis using a monthly time-step revealed the presence of statistically insignificant positive trends at 32% of rain gauge stations. CMIP5 model validation against historical observations (1980 – 2005) indicated that the models were able to simulate the annual precipitation cycle in the LCB although some models overestimated precipitation during the dry season and underestimated during the rainy season. Furthermore, analysis revealed that by the middle of the century (2050 – 2075), future annual precipitation is projected to increase in the LCB by 2.5% and 5% while monsoon precipitation will decrease by 11.60% and 5.30% respectively under RCP4.5 and RCP8.5 scenarios relative to the historical period. The uncertainty range for annual precipitation is about 12% and 17% for annual and monsoon precipitation respectively under RCP4.5 and RCP8.5 scenarios. Although the uncertainty range for future precipitation projections for most models and the reliability ensemble average (REA) mean lie within the range of natural climate variability, additional analysis are needed for results to be useful for any future planning to enhance water resources management in the study area.
Hydrological modelling in the Logone catchment using the SWAT model indicated that by using different calibration techniques, it is possible to reveal differences in the hydrological behavior in the different parts of the catchment using different parameter values. Results of SPI and SSI analysis showed that both the Sudano and Sahelian zones of the catchment are equally prone to droughts and floods. However, the Sudano zone is more sensitive to drier conditions while the Sahelian zone is sensitive to wetter conditions.
In this thesis, meeting the needs of the policy makers could not be achieved without gaining an understanding of the hydrological behaviour of the study area which is a pre-requisite for any such studies that involves the simulation of climate change impacts on water resources. Therefore, the hydrological modelling exercise and the different statistical analysis carried out in the context of this thesis were all aimed at developing a rich portfolio of peer reviewed information database which the policy makers will find useful to develop relevant climate change adaptation policies and also enhance the management of water resources in the region.