Towards a dynamic representation of irrigation in land surface models
Prof. Dr. Stefan Siebert
University of Göttingen | +49 551 39-24359 |
In B05 we will systematically collect spatial data providing the extent of irrigated lands (total and for specific crops) in specific years (around every three years) for the Europe / Euroasia modeling domain from 1990 to 2020 mainly at sub-national levels (NUTS 2); then the new annual irrigation database at the period of 1990 to 2020 will be generated via the combination of process-based model simulation and ground survey observations. The new annual irrigation database will be applied in community land model (CLM) to quantify differences in dynamics and trends of irrigation water use across the region compared to the use of the current static data products. We will analyze the impact of climate variability on the extent of irrigated crops, irrigation water requirements, and irrigation water use. The impact of the dynamic irrigation data on spatial patterns, dynamic trends of water storages, and related drying and wetting patterns across the project regions will be analyzed as well.
Contribution to CRC
To test the hypothesis of the CRC project, it is needed to develop datasets and methods to quantify the annual extent of specific irrigated crops dynamically in response to climate variability, site conditions, and crop characteristics. In collaboration with several other projects (B04, A05, C01, and A06), B05 will develop new datasets and innovative methods to improve the implementation of irrigation water use in the CRC IMS and thereby help to better quantify human impacts on the water cycle and energy fluxes. In particular, the focus on interannual variability in land use and water withdrawals in dry years is essential to better quantify and interpret human interventions in the water and energy cycle for relatively humid regions. Therefore, B05 will considerably contribute to the CRC’s key objectives.
We will collect ground survey data about sub-national irrigated/irrigable extents, methods, and sources for specific crops and years from official statistical departments to generate a standard irrigation database from 1990-2020. The relationships between observed and simulated crop-specific irrigation requirements from the modified global crop water model-GCWM (Siebert and Döll, 2010) will be evaluated to fill the temporal and spatial gaps of the irrigation database; the uncertainties of database generation will be discussed. Factors affecting the dynamic trends of irrigation water use across regions such as potential evapotranspiration, inter-annual variability, crop economic values, and the area equipped for irrigation will be evaluated using the regression analyses. In collaboration with other subprojects to parameterize the CLM for the different irrigated crops and apply CLM for the period 1990-2020 to compute irrigation water requirements based on the present static crop irrigation shares and the improved dynamic crop irrigation shares, to check the consistency of GCWM results and evaluate the impacts of dynamic irrigation data on spatial patterns, dynamics, and trends of water storages, and related drying and wetting patterns across the project region for the period 1990-2020.
Main results in 2022
We have collected and generated the standard irrigation database across Europe/Euroasia regions for the period 1990-2016 with a temporal resolution of around three years, mainly at the NUTS2 level, and for specific years such as 2010, the NUTS3 level database for some countries is available. These irrigation databases include the total irrigable and irrigated extents, and irrigation information for specific crops. Irrigation sources, methods, and management database in 2010 are available. The water use database at the grid and NUTs levels for the period 1990-2020 has been calculated using the GCWM. Besides, an abstract focusing on generating irrigation database of Europe using process based model simulation was submitted to EGU 2023. This preparation work is essential for further generating a complete irrigation database; the current database could be delivered to other subprojects for primary analysis and model simulation or tuning.