Water availability, demand and use in the hydrological model CWatM, the example of the Bhima basin in India with a focus on groundwater

L. Guillaumota, M. Smilovic, P. Burek, Y. Wada, J-Y. Lee, A. Jain Figueroa, S.M. Gorelick

2020 American Geophysical Union December meeting

Abstract: The Community Water Model (CWatM) is an open-source hydrological model designed to assess water availability for anthropogenic and environmental needs (Burek et al., 2020). Several developments to CWatM to better simulate human interactions within the water cycle, particularly the groundwater cycle, are discussed herein. CWatM is able to simulate continental hydrological processes from global to regional scale, and is demonstrated here at hyper resolution for the Bhima basin in India of around 50,000 km2. The basin and its largest growing urban centre Pune are increasing water demands leading to competition between urban and agricultural sectors.

The hydrologic model is run at a daily time step at ~1km resolution (30 arc seconds), including a 2D diffusive groundwater model (ModFlow) at 500m resolution. The groundwater model is dynamically coupled with the soil model and water demand can be satisfied with groundwater pumping, as well from surface reservoirs and available channel storage. Groundwater outflow through baseflow and capillary rise, as well as groundwater recharge through soil percolation, preferential flow, leaking canals, and riverbed exchange are included. Further, an improved reservoir management scheme is developed to distribute water daily between satisfying demands within a command area and downstream discharge, including reservoir-specific conveyance losses along canal lines. The objective is to assess the interactions across the basin concerning changes in land cover, climate, water use, as well as reservoir and groundwater management. 

This study is part of the Food-water-energy for Urban Sustainable Environments (FUSE) project, which looks at the interactions among food, water and energy (FWE) and requires an integrated approach that takes into account coupled human-natural systems and incorporates stakeholder participation in the form of Living Labs. In this project frame the improved model representation will enable us to test pathways of sustainable land use for different sectors and to develop together with the stakeholders potential policy interventions that improve the sustainability of FWE resources.