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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 (2010-2014) 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. Reduced river discharge Reducing ET on the land surface Increased Runoff Increased river discharge Erosion and sediment fluxes from the land surface. 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/Manafwa Source: Nantumbwe C. 2004 LU 1990:Wanale/Manafwa 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 Manafwa catchment • Selected for detailed analysis of LULC and hydrological consequences • 300km2 • Why? accessibility, economic and political reasons • Typical LULC, high pop density, complex topography, existing series data for historical constructions [hydrometeorological data] 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 300 200 Mbale st 150 Buginyanya st 100 50 Month Nov Sep Jul May Mar 0 Jan Amount(mm) 250 Rainfall (amount, intensities) Trends •stream discharge •Land use Stream Discharge data Historical data Field measurements •SWAT Land Use/cover change Hydrological Modeling Climate data 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 type Description on gathering and processing climate Rainfall intensity, temperature from Met dept, Uganda. Interpolation on measured climate data from weather stations across the study area. Soils Digital data from Kawanda Research Institute Hydrological (river flow/discharge) Historical data set from DWD; other measurement at established field gauging station Population Past census data from UNBS-for detailed analysis of density changes overtime (1969-2010) Land use & Topography Historical 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? 300 200 Mbale s t 150 Buginyanya s t 100 50 Nov Sep Jul May Mar 0 Jan Amount(mm) 250 Month Thank you