Towards a system dynamics model of the Indo-Gangetic Plain for sustainable water resources management

Water resources in the Indian portion of the Indo-Gangetic Plain are increasingly threatened by population growth, agricultural intensification, urbanisation and climate change. Considering the region's scale, as well as its biophysical, socioeconomic and institutional complexity, we argue that a systems approach is required to understand the socio-eco-hydrology of the region and achieve sustainable food and water security under future development and climate change scenarios. Focusing on the Gandak basin, a subbasin of the Ganges basin in which river discharge is regulated by a large barrage on the India-Nepal border, we develop a conceptual system dynamics model which elucidates the feedbacks and interactions between diverse, interconnected subsystems. Key relationships we explore include the link between barrage operation, surface water and groundwater irrigation and food production and farmer livelihood, the contribution of canal seepage to groundwater resources, and the effect of barrage operation and irrigation activities on the habitat of two critically endangered riverine species which reside downstream of the barrage. The physical system is modelled using conceptual relationships informed by coupled process-based models, which are described in an accompanying submission (O'Keeffe et al.). At the same time we use the system dynamics model to identify important human-water interactions for inclusion in the process-based framework. We highlight the key challenges associated with the development of the model, which include issues to do with the representation of groundwater dynamics and the contribution of groundwater to river baseflow, model resolution and data scarcity. To conclude, we assert that system dynamics modelling is an appropriate paradigm for analysing water resources in the Indo-Gangetic Plain, and suggest that, ultimately, the model could be used for developing policy options and strategies for sustainable water resources management in the basin.