Watershed futures: Mekong, 2050
Channel: Mikhail Smilovic
Date: 2023-09-27

Exploring the water cycle of the Danube basin, historically and up to 2050.

The water cycle is simulated with the hydrological model CWatM: https://cwatm.iiasa.ac.at. Playlist to download and run CWatM: https://shorturl.at/eozFG

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- Precipitation: falling water (snow, rain, hail, sleet, etc.)
- Evapotranspiration: rising water over soils (transforming from liquid to vapour), either from wet soils or through plants (transported through the roots and out of the plants and leaves)
- Evaporation: rising water from waterbodies, like rivers, lakes, and reservoirs (transforming from liquid to vapour)
- River discharge: water flowing through rivers. River discharge at a basin scale often refers to the amount of water flowing out at the end of the basin into the sea, ocean, or a downstream basin.

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The Intergovernmental Panel on Climate Change (IPCC), a United Nations organization tasked with advancing knowledge on climate change, uses a collection of climate and socio-economic projections for modelling and research. The climate/emission scenarios, the Representative Concentration Pathways (RCPs), are four projections of how concentrations of greenhouse gases in the atmosphere will change due to human activities. The four RCPs (i.e., RCP2.6, RCP4.5, RCP6.0, and RCP8.5) range from low future concentrations (RCP2.6) to high (RCP8.5). In this assessment, three RCPs are considered. For each RCP, we used the projections of five climate models: GFDL-ESM4, IPSL-CM6A-LR, MPI-ESM1-2-HR, MRI-ESM2-0, and UKESM1-0-LL6F6F. Climate models provide projections of climate conditions (e.g., temperature, precipitation) under the various RCP scenarios. 

The socioeconomic scenarios, the Shared Socioeconomic Pathways (SSPs), are five narratives of development, cooperation, and priorities. For example, SSP1 is called the Sustainability Path and imagines a world acknowledging environmental boundaries, increasing equality and education, economic growth motivated by human well-being, and decreasing the use of resources and energy. SSP5 is called Fossil-Fueled Development. Each of the SSPs is associated with quantitative projections of population and GDP (Jones et al., 2016), which drive the changes in water demand. Population and GDP per capita projections are translated into water demands following the methodology of Wada et al. (2011)[https://doi.org/10.5194/hess-15-3785-2011].