Analyzing Needs for Climate Change Adaptation in the Magdalena River Basin in Colombia

In 2010 and 2011 Colombia was hit by severe floods. After this situation, Colombian government and river basin authorities started developing plans and preparing actions for adaptation to climate change. Together with Dutch institutes a demonstration study and capacity building program was executed in 2013–2014. A systematic analysis of future extreme discharges (as a proxy for the risks of flooding) for the upper and middle Magdalena river basin and water shortages for the Coello sub catchment was done using state of the art downscaling and hydrological modeling tools. In this analysis plausible future projections of climate (based on IPCC fifth assessment), land use and water demand (based on expert workshops and literature) were used to explore consequences of climate change. Recent maps, data and expertise of Colombian partners contributed for necessary input data and to validate the tools used. The study is presenting main results and is discussing its limitations and replicability. Climate scenarios show a persistent increase in the occurrence of extreme rainfall events and that, as a consequence, extreme discharges like during the recent floods in 2011 are likely to increase as well. The return period of the 2011 discharge is already quite high under current climate and might increase by a factor five under climate change. For water shortages the results are more ambiguous showing both the possibility of an increase and decrease of the unmet water demand depending on different future scenarios, the water use category and location within the catchment. The unmet demand is however also under the current climate substantial. The question whether this unmet demand is critical or not could not be answered. The modest length of the reference period in comparison with time period of the ENSO phenomenon, the relatively restricted modeling effort (only using hydrological and no hydrodynamic and damage-cost models) are limitations to keep in mind when interpreting these results. There are no principle barriers for replication the methodology in countries like Colombia that in addition is steadily increasing its data, modeling and knowledge capacities. For the adaptation tipping point analysis presented in this study the main challenge is to derive the necessary objectives, sufficiently supported by the relevant stakeholders and policies, as the starting point for a targeted adaptation process.