Abstract:
Reviving the Ganges Water Machine (GWM), coined 40 years ago, is the most opportune solution for
mitigating the impacts of recurrent droughts and floods in the Ganges River Basin in South Asia. GWM
create subsurface storage (SSS) by pumping more groundwater from the aquifers before the monsoon
for irrigation and other uses and recharge it during the monsoon. The present study uses fully processed
and physically based numerical models, MODFLOW and SWAT, in a semi-coupled modelling framework
to examine the technical feasibility of recharging the SSS. The aquifer was simulated as a two-layer sys-
tem using hydrogeological and groundwater data, model was calibrated from 1999 to 2005 and validated
from 2006 to 2010. It assesses the impacts of gradual increase of SSS in 10 years from the base year 2010
under two scenarios (increased rainfall or controlled pumping and recharge) to meet a potential unmet
demand of 1.68 billion cubic meters (Bm3) in the Ramganga sub-basin with an area of 18,668 km2. The
results show that 3–4 m of subsurface storage can be created by groundwater pumping of 0.25 Bm3/year
by 2020. Under the controlled pumping and recharge scenario, groundwater recharge and river seepage
could increase by 14% (4.21–4.80 Bm3) and 31% (1.10–1.44 Bm3), respectively. However, baseflow will
decrease by 30% (0.18–0.12 Bm3) over the same time period. The results also show that recharge
increased 44% (4.21–6.05 Bm3) under an increased rainfall scenario. Simultaneously, river seepage and
baseflows would increase 36% (1.10–1.14 Bm3) and 11% (0.18–0.20 Bm3), respectively. A well-designed
managed aquifer recharge program is required to eliminate the negative impact of river flows in the
low flow season.
