In: Wagner W., Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B
ilreamftow
(mm/month)
• 2003
1971
0 1 2 Î 4 5 6 T S 9 10 U 12
months
relative %
difference
Fig. 7. Monthly hydrographs of historic (1972) and current
(2003) naturalized Streamflow stations, and relative percentage
difference of runoff
5. SUMMARY AND CONCLUSIONS
Land use and vegetative cover play an important role in
watershed runoff and streamflow discharge patterns over time,
including peak flows. Increased human interventions have
caused rapid transitions in landcover, adversely affecting the
watershed processes and hydrological cycle in the long run.
Distributed hydrological modelling offers an efficient solution
to evaluate the long term hydrological changes by allowing
quantification of changes in streamflow patterns.The Mahanadi
river basin covering major portions of Chattisgarh and Orissa
(India) has been repetitively facing the adverse hydro
meteorological conditions such as floods, droughts and cyclones
etc. in the recent times. Frequent occurrence of these events
indicates a shift in the hydrological response of the basin
attributed to landcover changes. This study attempts to model
the hydrology of Mahanadi river basin using physically based,
distributed VIC hydrological model and assess landcover
change impacts on streamflows at various locations along the
river.
A detailed remote sensing based landcover mapping of the basin
for years 1972, 1985 and 2003 reveals following changes:
coefficient of determination before calibration was found
to be as 0.747, for Mundali.
• The calibration of the model at Mundali outlet was
performed for year 2003. Streamflow was found sensitive
to variables like upper and lower soil layer depth, velocity
of flow and vegetation parameters. R 2 of 0.836, Ce of
0.821 and Er of 0.085 was obtained during daily
simulation. The model performance was found better for
monthly simulations with Ns of 0.89.
Streamflows were simulated using VIC model for the year
1972, 1985 and 2003. Following conclusions can be drawn from
the analysis carried for predicting changes over years:
• An increase by 4.53% (24.44 mm) in the annual
streamflow is predicted at Mundali outlet of the Mahanadi
basin from 1972 to 2003. It may be concluded that a
decrease in forest cover by 5.71% in the Mahanadi river
basin has caused the river flow to increase by 4.53%. This
is quite a significant amount in terms of volumetric rise
(3514242122 m 3 ).
• The relative percentage increase in streamflow was found
high in the months of May and November in all sub-basins.
It may be concluded that the impact of landcover changes
are most pronounced during low flows and that during high
flows, role of landcover becomes comparatively less.
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• Total forest cover area has been reduced by 5.71% of the
total area of the basin from 1972 to 2003. A reduction in
barren land (0.64%) is followed by an increase in areas of
surface water bodies (0.47%), built up land (0.22%), river
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