Abstract:
This study was carried out to assess the impacts of climate change on the dynamics of surface water
availability for different present and future users in the Mahaweli river basin.
A multi-tier modeling method was applied in the analysis by combining the Soil and Water Assessment
Tool (SWAT) and Water Evaluation and Planning Models (WEAP) to mimic stream flow under climate
change and evaluate situations of future water accessibility for diverse socio-economic activities by the
year 2050. Three standard global circulation models (GCMs), CSIRO Mk3.6, Had, CM2-ES, and
MIROCS, were downscaled, rectifying bias using CMHyd.
The SWAT model was successfully calibrated with R
2
equals 0.65 for calibration period and for
validation the R
2
equals 0.57. The calibrated model shows a Nash- Sutcliff efficiency (NSE) values of
0.68 during the calibration period and 0.73 in validation period. The SWAT model was initially
calibrated using available data to forecast future stream flows. Then those stream flows were used as
inputs for the WEAP model to assess water availability for various socio-economic activities. Results
from GCMs indicate that an increase in annual mean rainfall within a range of 16-18% can be expected
by the 2050s, compared to the rainfall during the period between 2006 to 2009. The average temperature
is forecasted to increase by about 2°C compared to the temperature baseline period. Further, there will
be an increase of about 10% in long-term average stream flow. However, the model predicted a decrease
in peak flows in the 2050s compared to the current average flows. The model forecasted that the overall
total water demand in the Mahaweli basin will increase to 3,249.69 Mm
3
in the year 2050, compared to
the current demand of 1,879.73 Mm
3
. This will create a situation where 51.5% of the total demand
amounting to about 1,673.80 Mm
3
will not be met in the 2050s. A severe water shortage is predicted
that about 71.12% of future irrigation demand will not be fulfilled in the 2050s. Water for hydropower
generation will also be significantly affected as its unmet demand will be around 27.47%. However, the
water demand for livestock will be marginally affected by about 1.41% of unmet demand as per the
model's forecasts.
The modeling results raise the need for paying attention to future water shortages for various socioeconomic
activities,
which
can
be
caused
by
climate
change,
and
the
need
for
taking
necessary
steps
to
address
this
situation
effectively.
Citation:
Fernando, W.B.D.T. (2022). Impact of climate change and socio - economic development on water allocation for ecosystem - water -energy -food services :a case study on Mahaweli river basin, Sri Lanka [Master's theses, University of Moratuwa]. Institutional Repository University of Moratuwa. http://dl.lib.uom.lk/handle/123/21542