Evaluating the Impacts of Climate Change on Catchment Water Quality in Yala River Catchment, Western Kenya.

Climate change poses significant challenges to water quality in river catchments globally, particularly in regions heavily dependent on natural water systems for agriculture, domestic use, and biodiversity conservation. The Yala River Catchment in Western Kenya, a critical water resource in the region, is increasingly threatened by climate variability and its associated impacts. Rising temperatures and changing rainfall patterns exacerbate sediment transport, nutrient runoff, and overall water quality degradation. This study evaluates the long-term impacts of climate change on water quality in the Yala Catchment, providing insights to support adaptive management strategies. The study employed the Soil and Water Assessment Tool Plus (SWAT+), a process-based hydrological model, to simulate climate change impacts on the Yala River Catchment. Climate projections from ISIMIP3b (Inter-Sectoral Impact Model Intercomparison Project) were used to drive the model, capturing changes in temperature and precipitation for the period 2030 to 2100 under various shared socioeconomic pathways (SSPs). The SWAT+ model was calibrated and validated using historical climate and hydrological data. Simulations were run to assess baseline water quality conditions and future scenarios, focusing on key indicators such as sediment yield, nutrient runoff, and surface water quality under varying climate conditions.

Preliminary findings reveal significant climate-driven changes in the Yala River Catchment: Increased temperatures and rainfall: Projections indicate an average temperature rise of 2–3°C and an increase in extreme rainfall events, particularly during the wet season. Enhanced sediment and nutrient runoff: Higher rainfall intensity and frequency contribute to elevated soil erosion and nutrient transport, particularly in agricultural areas and steep terrains. Decline in water quality: Increased sediment and nutrient loads lead to reduced water clarity and heightened concentrations of nitrogen and phosphorus, posing risks to aquatic ecosystems and water usability.

The results demonstrate that climate change will exacerbate water quality challenges in the Yala River Catchment, driven by increased sediment and nutrient fluxes from intensified rainfall and rising temperatures. These impacts highlight the need for urgent, adaptive management strategies to mitigate the adverse effects of climate variability and ensure the sustainability of water resources.

To address the projected impacts of climate change on water quality in the Yala River Catchment, the following actions are recommended: Implement sustainable land and water management practices to reduce sediment and nutrient runoff, such as riparian buffer zones and conservation agriculture. Develop and enforce climate-adaptive policies for catchment management that incorporate long-term climate projections. Enhance monitoring systems to provide real-time data on water quality and climate trends for proactive decision-making. Foster community engagement and capacity-building programs to encourage adoption of climate-resilient practices.