**Abstract**

This paper presents a critical analysis of the water quality changes and their impacts on water resources within the Athi River Catchment and its implications of the people's livelihoods. The paper analyses the effects of land use activities on water quality in the headwater areas of the basin which has a profound impacts on the downstream water uses within the basin. The paper in addition makes an attempt to relate the impacts of human activities on water quality degradation trends within the basin against the available and potential water resources in the basin. The Athi River is the second largest in Kenya and traverses areas of diverse land use activities from the more agricultural head water areas through the industrial hub of Kenya in Nairobi to the Indian Ocean discharging its waters near Malindi town north of Mombasa. The paper gives a detailed analysis of the impacts of human activities on the water resources in regard to water quality degradation, pollution and mitigation measures. The study was based on field data collection and measurements and laboratory analysis. The researcher used 10 sampling points located within the Nairobi sub-basin and distributed along the river profile to examine the trends in water quality degradation and its implication on human livelihoods in the basin. The researcher noted a declining trend in water quality status downstream the river profile. A close analysis of the water situation in the basin paints a blink future on the available water resources in the basin against the projected water uses and increasing population compounded by the impacts of water pollution and climate change. This is likely to increase incidences of water shortage and food insecurity in many parts of the basin. The researcher recommends more investments in water harvesting infrastructure, environmental conservation and adoption of modern water management technologies.

**Keywords:** Water resources, water quality critical analysis, livelihoods, increasing water demands
