NCN grant in the Preludium BIS 5 competition for Dr hab. Mikołaj Pniewski, prof. SGGW
Prediction of how much water will be available under future climatic conditions, and how the flood and drought hazard will change, is currently the core of hydrological research. Hydrologists are using various tools of different complexity, called hydrological models, to mimic hydrological processes occurring at different scales: from small river basins to the entire globe. Unfortunately, the simulated future response of the hydrological system to analyzed drivers depends on numerous factors, of which many are unknown. Some of these factors are well-studied, while others are not. For example, the review paper by Piniewski et al. (2022) showed that projections of changes in hydrological droughts in Central Europe are subject to large uncertainties, and the direction of their changes may even differ from the trends we have observed in recent years. Factors such as greenhouse gas emission scenarios or climate models have been studied well. However, elevated atmospheric CO2 concentration (eCO2) and its effect on plant growth is a factor that has not attracted sufficient attention yet. This project will try to bridge this gap by studying the role of eCO2 on hydrological projections in different climate zones.
eCO2 is the direct driver for all climate models resulting in future projections of temperature, precipitation, etc., widely disseminated in the IPCC reports. At the same time, with increased CO2, plants can use water more efficiently because of the reduced degree of plant stomata opening, which leads to increased photosynthesis. eCO2 also leads to an increased leaf material in the canopy, which leads to increased evapotranspiration. These processes are either neglected in current hydrological models or they are accounted for in a very simplified way. This is a clear shortcoming because plants cover the vast majority of land areas, they transpire large amounts of water from the soil, and thus indirectly affect the catchment water balance. In this project, we will focus on one specific process-based hydrological model called SWAT+, which is one of the few models of this type that include a plant growth component and eCO2 effect. However, it suffers from a few limitations in its description of the effect of eCO2 on other processes, i.e. lack of dynamic changes in CO2, lack of plant-specific response to eCO2, incorrect process description for very high CO2 levels (that will likely be experienced in 30-40 years). The ambition of this project is to address all these limitations and develop a modified model version that will ultimately help to derive more reliable projections for the future. The developed model will be applied in catchments located in four different climate zones, allowing it to be comprehensively tested and to better understand the variability of the response of the hydrological system to climatic forcing on a global scale.
A PhD student employed in the PRELUDIUM BIS project will undertake a six-month internship at Texas A&M University (TAMU) and the Texas A&M AgriLife Research Blackland Research and Extension Center (BREC) under the supervision of Prof. Raghavan Srinivasan, funded by NAWA, where he will implement new developments in the model source code in collaboration with the SWAT+ model developers.