Impact of Land use on water resources on Mt Elgon, Uganda Nakileza B.R., Bamutaze Y. Mukwaya Paul, Palesjo P.

Project background 3 year project ( ) funded by SIDA, under a research collaboration program with Makerere University Implementers: Geography Departments at Universities of Makerere (Uganda) and Lund (Sweden) Researchers: Nakileza Bob (PI), Bamutaze Y., Mukwaya P. & Pajesloj P.

Introduction Mountains are key water towers but under stress due to global change (climate change, LUC) Land use/cover dynamics constitute an important factor esp. in fragile mountain areas e.g. Mt Elgon

Introduction LU dynamics: driven by many factors e.g. increasing pop, infrastructural developments Expansion of agriculture into marginal lands and clearance of natural habitats such as forests and wetlands has been a major driving force behind land degradation (Reij & Smaling, 2007).

ctd Human LULCC affect the quantity/quality of surface water resources through various ways e.g. Reducing ET on the land surface Increased river discharge Increased Runoff Erosion and sediment fluxes from the land surface. Reduced river discharge

ctd The LULC impacts (e.g. on Mt. Elgon) transcend the onsite effects There are regional implications on hydrological and sediment flux

Previous related LU studies LU 1960:Wanale/ManafwaLU 1990:Wanale/Manafwa Source: Nantumbwe C. 2004

Spatial-temporal variation of soil erosion by Bamutaze, Y. Experimental plot studies Measured soil erosion on plots and gauged streams in one micro catchment (R. Sijje) of R.Manafwa Significant relation between stream sediment load and footpaths

Project objectives To characterize and quantify the dynamics of land use/cover in the Mt. Elgon region by analysis of sequential satellite images of 1970s to present To map hotspots of land use/cover changes and to identify its major underlying causes To evaluate the impact of land use/cover changes on soil water properties, and their effects on surface runoff and stream water flow fluxes.

Hypothesis There is a relationship between stream water discharge rates and changes in land use/cover on Mt. Elgon.

Analytical framework

Methods Study area Selected for detailed analysis of LULC and hydrological consequences 300km 2 Why? accessibility, economic and political reasons Typical LULC, high pop density, complex topography, existing series data for historical constructions [hydro- meteorological data] Manafwa catchment

Data sets: Socio-economic and biophysical (e.g. land use, rainfall, population) Sequential multispectral satellite images: analysis of types & quantification of LULC

Design & Field measurements: 6 sub-catchments will be purposively selected for detailed studies based on results of LULC analysis Rainfall & stream discharge collected ~24months & covering two rainy seasons.

Sampling/gauging sites

Climate data Rainfall (amount, intensities) Land Use/cover change Trends stream discharge Land use Hydrological Modeling SWAT Stream Discharge data Field measurementsHistorical data

Modeling : LUC changes and water Modeling : LUC changes and water Integrated modeling approach adopted Recent studies (e.g. (Lin et al. 2006; Bithell and Brasington 2009) have demonstrated the potential of an integrated modeling approach to evaluate the impact of land-use changes on water resources Hydrological model (SWAT) will be calibrated for the study area Rainfall, runoff (stream flows) will be measured for 6 sub catchments Soil OM, HC, bulk density will be measured for current LU types/pattern Once the SWAT model is calibrated for the current land use pattern, scenarios will be developed to analyse the effect of land use change and climate change on runoff

Phase 1: Dataset collection and preparation Data typeDescription on gathering and processing climateRainfall intensity, temperature from Met dept, Uganda. Interpolation on measured climate data from weather stations across the study area. SoilsDigital data from Kawanda Research Institute Hydrological (river flow/discharge)Historical data set from DWD; other measurement at established field gauging station PopulationPast census data from UNBS-for detailed analysis of density changes overtime ( ) Land use & TopographyHistorical LU maps created from Landsat images (1970s to 2010) & others obtained from UNBS. DEM secured from UNBS

Guiding question for the future work Will the results of our studies based on historical data, field measurements and hydrological/climate models represent an opportunity to re-examine how we value our water resources?

Thank you