Impacts of land cover and land use changes on stream flow: A case from the Nile Basin

1. Impacts of land cover and land use changes on stream flow:A case from the Nile Basin By Simon Mutie, Hussein Gadain, and Guleid Artan

2. Background • Since 1960’s LULC changes have been a threat to life in the Nile Basin; • High population increases has led to changes in land tenure systems resulting in deforestation expansion and intensification of agriculture; • These changes in land cover have caused changes in the water balance of the basin.

3. Deforestation-Mau Problem Statement • Population growth rate 7.5%, • High population = changes in land tenure systems, • Deforestation and intensification of agriculture and overstocking, • Reduction of perennial natural vegetation, • Rise in bare and agricultural lands. • Modifications of land cover and soils affect runoff hence water availability, • High sedimentation and water quality concerns. Wheat-Narok Flooding-Nzoia

4. Study Area Upper Nile Basin

5. Economic Importance of the basins • Both basins originate from the indigenous and exotic greater Mau, Mt. Elgon and Cherangany forests. • Large-scale/cash crop plantation • Tea, sugarcane, rice, wheat and high value horticultural crops. Small-scale mixed farming also practised • Pastoralists with the nomadic Maasai community in Mara River basin. • Mara basin houses the Serena-Mara-Serengeti wildlife sanctuary declared the seventh wonder in the world • Swamps (Yala & Mosirori) which support a lot of biodiversity.

6. Deforestation-Mau Major Ecosystem Threats • Widespread encroachment and deforestation of the Mau forest tower, Mt Elgon Forest • Rapid population growth and immigration into the basins. • Expansion and intensification of agriculture • Conversion and rehabilitation of basin wetlands for agricultural production e.g. Yala swamp Rice Growing-Yala swamp Source: Nation media Mosirori Swamp Overstocking-Mara

7. Overall objective To determine the effects of land use & land cover changes on the river flow in the two basins

8. Data and Methods • LANDSAT images for the dry season (MSS and TM/ETM, for the years 1973, 1986 and the 2000 respectively) • Image processing and classification; GPS used for surveys to collect ground-truth data on vegetation and land use/cover Pixel Resolution MSS – 79 * 56 m TM and ETM – 28.5 * 28.5 m Source: USGS

9. False Color composite of bands 2,3&4 – 1986 data LULC Mapping

10. LULC Changes Mara River Basin

11. Nzoia River Basin

12. Nzoia River Basin

13. Stream Flow Model Data Preprocessing Rain MAP Water Balance MAE Evap Basin Soil Lumped Routing Linkage Routing Parameters LU/LC Dist. Routing Soil Parameters DEM Obsv. S.Flow Data Streamflow Geo-spatial SFM System Diagram

14. Effects of Land use change on stream flow • Earlier than normal peaks • Higher peaks • Change in evaporation process • Soil erosion and sedimentation • produced streamflow at rainfall magnitudes that did not generate any streamflow with the 1973 dataset. • Changes are slight in Nzoia

15. Conclusions • There has been decline of natural vegetation in the two basins and a rise in land covers due to anthropogenic influences in the basin. • The changes have caused higher and earlier occurrence of flood peaks. • Increase in agriculture coupled with poor farming practices in the two basins has led to high sediment loads deposited on the river mouths. • In Mara basin, sediment deposition at river mouth has caused backwater flow which has increased the wetland submerging farms. • In Nzoia basin, deposition at lower river stages is raising the river channel, hence water topping the flood dykes every season

16. Potentialities/Limitations RS Limitations • Data Availability • Cost • High cost analysing Potentialities • Descision making and planning