Dynamic modeling of the Ganga river system: impacts of future climate and socio-economic change on flows and nitrogen fluxes in India and Bangladesh

Abstract

This study investigates the potential impacts of future climate and socio-economic change on the flow and nitrogen fluxes of the Ganga river system. This is the first basin scale water quality study for the Ganga considering climate change at 25 km resolution together with socio-economic scenarios. The revised dynamic, process-based INCA model was used to simulate hydrology and water quality within the complex multi-branched river basins. All climate realizations utilized in the study predict increases in temperature and rainfall by the 2050s with significant increase by the 2090s. These changes generate associated increases in monsoon flows and increased availability of water for groundwater recharge and irrigation, but also more frequent flooding. Decreased concentrations of nitrate and ammonia are expected due to increased dilution. Different future socio-economic scenarios were found to have a significant impact on water quality at the downstream end of the Ganga. A less sustainable future resulted in a deterioration of water quality due to the pressures from higher population growth, land use change, increased sewage treatment discharges, enhanced atmospheric nitrogen deposition, and water abstraction. However, water quality was found to improve under a more sustainable strategy as envisaged in the Ganga clean-up plan.

Modelling the increased frequency of extreme sea levels in the Ganges–Brahmaputra–Meghna delta due to sea level rise and other effects of climate change

“…Inputs of freshwater at river mouths in the GBM delta area were provided using outputs from a hydrological model of the river basins 33,34 : these were created using the same HadRM3P Q0, Q8 and Q16 climate forcing data as the Bay of Bengal model. The GBM rivers provide 40% of the modelled freshwater flow into the entire domain and dominate in the delta area.…”

River Systems in India: The Anthropocene Context

“…Further, water quality may be significantly impacted by different socio-economic scenarios. Model outputs suggest major alteration of nutrient flux transfer into the delta region (Whitehead et al, 2015a;2015b). However, the increase in flow amount will also cause decrease in nitrogen and ammonium concentration.…”

“…The future of Ganges-Brahmaputra-Meghna in terms of flow and water quality in the near future were defined through Integrated Catchment Model (INCA-N) for the following three scenarios of socio-economic pathways-(1) a business as usual future, (2) a more sustainable future, and (3) a less sustainable future (Whitehead et al, 2015a). The INCA-N was integrated with higher resolution 25 km Regional Climate Model (RCM).…”

“…A few attempts have been made in recent years to assess the river futures in response to climate change and anthropogenic disturbances with the use of different climatological, and hydrological models, and through its integration with social diversity. Whitehead et al (2015a) used a dynamic, process-based INCA model to simulate hydrology and water quality for the Ganga basin for 2050s and 2090s and predicted an increase in monsoon flows and increased availability of groundwater recharge, but also more frequent flooding. Model results for the 2050's and the 2090's are similar to the climate driven prediction, which suggest a significant increase in the monsoon flows and more likelihood of flooding during monsoon period.…”

Biophysical Modelling of the Ganges, Brahmaputra, and Meghna Catchment

“…INCA is one such model that has been applied extensively to heterogeneous catchments and has the advantage that it is dynamic, process-based, and integrates hydrology and water quality. The INCA model has been developed over 20 years as part of the UK Research Council (NERC) and EU-funded projects (Whitehead et al 2015b), and the model simulates hydrology flow pathways in the surface and groundwater systems and tracks fluxes of solutes/pollutants on a daily time step in both terrestrial and aquatic portions of catchments. The model allows the user to specify the spatial nature of a river basin or catchment, to alter reach lengths, rate coefficients, land use, velocity-flow relationships and to vary input pollutant deposition loads from point sources, diffuse land sources, and diffuse atmospheric sources.…”