Download Impact of Land use change on water resources on Mt Elgon

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