Kshipra Sub Basin - Asian Development Bank

Support to the National Water Mission NAPCC
Appendix 3 Kshipra Sub Basin
century (MC) climate scenario and 30 years belong to IPCC SRES A1B long term or end-century (EC)
climate scenario.
199. Projected changes in precipitation in the Kshipra catchment have been discussed as part of the
climatic assessment reported in section III of this report. The detailed outputs of the SWAT
hydrological model were analysed with respect to the two major water balance components of water
yield and actual evapotranspiration. These are significantly influenced by the intensity and temporal
distribution of precipitation, and by the weather conditions dictated by temperature and allied
parameters. All the analyses have been performed by aggregating the inputs/outputs at the sub-basin
level that are the natural boundaries controlling the hydrological processes.
200. Analysis of Change in Water balance components: the outputs have been analyzed with
respect to the baseline considering possible impacts on the runoff, baseflow, actual evapotranspiration
and ground water recharge to mid-century and end-century. Table 43 gives the summary of changes
in water balance components as percentage of the change in precipitation from baseline to mid
century.
201. The PRECIS A1B scenario indicates an increase in annual precipitation in the Kshipra basin of
about 16% by mid-century. The model results indicate that around 83% of this increase in precipitation
will get converted to runoff. Baseflow which contributes to stream flow during dry periods will increase
by 4%. An increase in aquifer recharge of 17% is projected, and a decrease in evapotranspiration of
4% is projected.
202. Figure 58 shows the distribution of the major water balance components expressed in terms of
percentage change to mid-century. The figure also shows the change in water balance component
averaged over the entire basin expressed as a depth (mm) in bar chart form.
203. Precipitation changes vary locally in magnitude, sign, and seasonal details for the Kshipra
basin. Seasonal changes in precipitation and its effect on water balance components obtained from
the SWAT model for the A1B scenario are included for JJAS (southwest monsoon) and OND (North
east monsoon) in Table 43. There is an increase in JJAS precipitation in the Kshipra basin of about
23% by mid-century. The model results indicate that around 70% of this increase in precipitation will
get converted to runoff and 4% to baseflow. Aquifer recharge increases by 29% and
evapotranspiration decreases by 4%.
204. Figure 59 shows the change in the major water balance components expressed in terms of
percentage for the JJAS season to mid-century. From Figure 59 it can be seen that most of the
increased precipitation forms runoff and groundwater recharge. The indication is that in parts of the
basin surface runoff would double under the A1B scenario. This should be treated as a very optimistic
projection from a water resources perspective, but would offer opportunities for increased water
harvesting and groundwater recharge. A concern should be the potential impact on drainage and on
flood risk. Clearly this should be investigated further, and drainage design criteria reviewed. The bar
chart depicts the water balance component averaged over the entire basin and expressed as a depth
(mm).
Table 43: Summary of Change in water balance ++ expressed as percent change in precipitation
Scenario/Season Precipitation Evapotranspiration Surface
Runoff
Baseflow+ Total
Water
Yield*
Avg Annual (A1B-
Baseline)
883 699 180 42 222 354
Avg Annual (A1B-
Mid Century)
1023 694 297 47 345 378
Percent Change 16
in precipitation
Net change (mm) 141 -6 117 6 122 25
Change (%)*** -4 83 4 87 17
Avg JJAS (A1B-
Baseline)
745 274 155 17 173 311
Avg JJAS (A1B- 918 266 275 25 300 362
92
Ground
Recharge**