Quantifying the impact of land use on water and nutrient cycling in the South-West Mau, Kenya

Project leaderChristopher Martius
Emailc.martius@cgiar.org
Location Kenya
Project statusON-GOING
Project start2020-01-01
Project end2020-12-31

The Mau Forest is the largest closed canopy forest system and montane forest in Kenya, covering over 400,000 ha. It is one of Kenya's five 'water towers' providing large parts of Kenya with fresh water. In the past decades significant deforestation and land use change took place. Although there is much speculation around the consequences of these changes for water supply in areas downstream of the Mau, there is little scientific evidence to support this.

This project aims to address this through a long-term assessment of the effect of land use on hydro-biogeochemical processes in an East African tropical montane forest. The project therefor 
- Long-term, high-resolution data set on water quality and quality;
- Robust data base for hydro-biogeochemical impact model development, verification and application;
- Exploration of future land use and management as well as climate change scenarios. 
- Quantification of water related ecosystem services in view of land use and climate change. 

The study area is located in the Sondu river basin, in the South-West Mau, an area that experienced significant forest loss through conversion of natural forest to smallholder agriculture and tea and tree plantations. A nested catchment approach has been applied, where automatic measurement equipment has been set up at the outlet of three sub-catchments in 2015. The land use in these sub-catchments is either natural forest, tea/tree plantations or smallholder agriculture. The equipment measures water level, turbidity, nitrate, dissolved and total organic carbon, electrical conductivity and water temperature at a ten minute interval. A fourth station is placed at the outlet of the larger catchment and data from this site will be used for modelling and upscaling. The resulting high resolution dataset will give a good estimation of the effect land use on stream flow patterns and water quality across seasons.

Such monitoring programs become more valuable the longer they run. Worldwide, there are hardly any long-term measurements in the tropics with the high temporal resolution that we have for the Sondu catchment. The planned extension of the monitoring programme by a further 12 months will further improve the existing time series. In the long term, it is planned to acquire further research funds for the operation of the stations, latest from 2021 onwards.

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