Reach-scale streamflow projections in intermittent riversthrough a multivariate dowscaling method and a distributed hydrologcal model

Global bias-adjusted daily climate projections have been recently set up as part of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) phase 3 based on CMIP6 projections (Lange et Büchner., 2021). This dataset is aimed at being used as input to global hydrological models, and their coarse resolution however prevents them to be used for catchment-scale and reach-scale applications.

This work proposes to downscale these global climate projections through multivariate analog downscaling method and to derive catchment-scale streamflow time series through a fully-distributed hydrological model. The final objective is to produce future daily streamflow series over a high-resolution hydrographic network of 6 European catchment case studies for the DRYvER project (Datry et al., 2021). The method is applied on precipitation, temperature, and potential evapotranspiration serving as input to the distributed JAMS-J2K model (Krause et al., 2006).

This setup led to the creation of daily hydrological projections at high spatial resolution over the 1985-2100 period. These experiments are conducted using one run from 5 different global climate models and 3 emission/socio-economic scenarios (SSP1-RCP2.6, SSP3-RCP7.0 and SSP5-RCP8.5) from the CMIP6 experiments. This methodology allows to grasp the range of future changes in daily streamflow over the entire catchments. The comparison between the historical period (1985-2014) and future periods is used to describe possible changes over seasonal discharge and low flow characteristics.

This approach provides hydrological projections with a spatial resolution sufficiently high to apply flow intermittence detection, thus allowing to study plausible futures for European intermittent rivers in terms of hydrology, biodiversity, ecosystem functioning and services, and adaptive management. Future steps will refine such futures using an innovative downscaling approach combining global and catchment-scale transient projections to better grasp the joint influence of climate change and climate variability on reach-scale intermittence.

 

Datry et al. (2021) Securing Biodiversity, Functional Integrity, and Ecosystem Services in Drying River Networks (DRYvER). Research Ideas and Outcomes. https://doi.org/10.3897/rio.7.e77750.

Krause et al. (2006) Multiscale investigations in a mesoscale catchment: hydrological modelling in the Gera catchment. Advances in Geosciences. doi:10.5194/adgeo-9-53-2006.

Lange et Büchner (2021) ISIMIP3b bias-adjusted atmospheric climate input data (v1.1), ISIMIP Repository. doi:10.48364/ISIMIP.842396.1.

Clemins et al. (2019) An analog approach for weather estimation using climate projections and reanalysis data. Journal of Applied Meteorology and Climatology. doi:10.1175/JAMC-D-18-0255.1