Improvement of the Irrigation Scheme in the ORCHIDEE Land Surface Model and Impacts of Irrigation on Regional Water Budgets Over China

Z Yin (1, 2) , X.H. Wang (1, 2) , Catherine Ottle (1, 3) , F Zhou (4) , M. Guimberteau (1, 5) , J Polcher (2) , S S Peng (4) , S.L. Piao , L Li (2) , Y Bo (4) , X L Chen (6) , X.-D. Zhou (2) , H Kim (1) , Philippe Ciais (1, 7)

1 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
2 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
3 MOSAIC - Modélisation des Surfaces et Interfaces Continentales
4 Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences
5 METIS - Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols
6 Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China
7 ICOS-ATC - ICOS-ATC

In China, irrigation is widespread in 40.7% cropland to sustain crop yields. By its action on water cycle, irrigation affects water resources and local climate. In this study, a new irrigation module, including flood and paddy irrigation technologies, was developed in the ORCHIDEE-CROP land surface model which describes crop phenology and growth in order to estimate irrigation demands over China from 1982 to 2014. Three simulations were performed including NI (no irrigation), IR (with irrigation limited by local water resources), and FI (with irrigation demand fulfilled). Observations and census data were used to validate the simulations. Results showed that the estimated irrigation water withdrawal (W) based on IR and FI scenarios bracket statistical W with fair spatial agreements (r = 0.68 ± 0.07; p < 0.01). Improving irrigation efficiency was found to be the dominant factor leading to the observed W decrease. By comparing simulated total water storage (TWS) with GRACE observations, we found that simulated TWS with irrigation well explained the TWS variation over China. However, our simulation overestimated the seasonality of TWS in the Yangtze River Basin due to ignoring regulation of artificial reservoirs. The observed TWS decrease in the Yellow River Basin caused by groundwater depletion was not totally captured in our simulation, but it can be inferred by combining simulated TWS with census data. Moreover, we demonstrated that land use change tended to drive W locally but had little effect on total W over China due to water resources limitation.

Domaines: Milieux et Changements globaux

Z Yin, X.H. Wang, Catherine Ottle, F Zhou, M. Guimberteau, et al.. Improvement of the Irrigation Scheme in the ORCHIDEE Land Surface Model and Impacts of Irrigation on Regional Water Budgets Over China. Journal of Advances in Modeling Earth Systems, 2020, 12 (4), ⟨10.1029/2019MS001770⟩. ⟨hal-03024505⟩