Evaluation for Moroccan dynamically downscaled precipitation from GCM CHAM5 and its regional hydrologic response

• Dynamically-downscaled precipitation for Moroccan northern territory is evaluated.
• Bias corrections are applied and validated for present-day and future precipitation.
• Varying uncertainties are found among both uncorrected and corrected runs.
• Hydrologic modeling validates reasonable downscaled present-day precipitation.
• Diverse future precipitation and corresponding regional streamflow are predicted.

Study regionMorocco (excluding Western Sahara).Study focusThis study evaluated Moroccan precipitation, dynamically downscaled (0.18-degree) from three runs of the studied GCM ECHAM5/MPI-OM, under the present-day (1971–2000/20C3M) and future (2036–2065/A1B) climate scenarios. The spatial and quantitative properties of the downscaled precipitation were evaluated by a verified, fine-resolution reference. The effectiveness of the hydrologic responses, driven by the downscaled precipitation, was further evaluated for the study region over the upstream watershed of Oum er Rbia River located in Central Morocco.New hydrological insights for the regionThe raw downscaling runs reasonably featured the spatial properties but quantitatively misrepresented the mean and extreme intensities of present-day precipitation. Two proposed bias correction approaches, namely stationary Quantile-Mapping (QM) and non-stationary Equidistant CDF Matching model (EDCDFm), successfully reduced the system biases existing in the raw downscaling runs. However, both raw and corrected runs projected great diversity in terms of the quantity of future precipitation. Hydrologic simulations performed by a well-calibrated Variable Infiltration Capacity model successfully reproduced the present-day streamflow. The driven flows were identified highly correlated with the effectiveness of the downscaled precipitation. The future flows were projected to be markedly diverse, mainly due to the varied precipitation projections. Two of the three flow simulation runs projected slight to severe drying scenarios, while another projected an opposite trend for the evaluated future period.