A combined bottom-up and top-down approach for assessment of climate change adaptation options

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• We integrate stakeholder perceptions and modelling for robust adaptation planning. • High resolution RCMs and ensemble mean projections are used to force WEAP model. • Effect of stakeholder prioritized adaptation options on future streamflow analysed. • Increasing forest cover best address local climate change adaptation requirements. Focus of recent scientific research in the water sector has shifted from analysis of climate change impacts to assessment of climate change adaptation options. However, limited attention has been given to integration of bottom-up and top-down methods for assessment of adaptation options. The integrated approach used in this study uses hydrological modelling to assess the effect of stakeholder prioritized adaptation options for the Kangsabati river catchment in India. A series of 14 multi-level stakeholder consultations are used to ascertain locally relevant no-regret adaptation options using Multi-Criteria Analysis (MCA) and scenario analysis methods. A validated Water Evaluation And Planning (WEAP) model is then used to project the effect of three options; option 1 check dams (CD), option 2 increasing forest cover (IFC) and option 3 combined CD and IFC, on future (2021–2050) streamflow. High resolution (∼25 km) climatic projections from four Regional Climate Models (RCMs) and their ensemble based on the SRES A1B scenario for the mid-21st century period are used to force the WEAP model. Results indicate that although all three adaptation options reduce streamflow, in comparison with scenario without adaptation, their magnitude, temporal pattern and effect on high and low streamflows are different. Options 2 and 3 reduce streamflow percentage by an order of magnitude greater than option 1. These characteristics affect their ability to address key adaptation requirements and therefore, we find that IFC emerges as a hydrologically suitable adaptation option for the study area. Based on study results we also conclude that such an integrated approach is advantageous and is a valuable tool for locally relevant climate change adaptation policymaking.