Spatiotemporal green water dynamics and their responses to variations of climatic and underlying surface factors: A case study in the Sanjiang Plain, China

The Sanjiang Plain (SJP), located at the confluence reaches of the Heilong, Songhua, and Wusuli Rivers in Northeast China. This study aimed to quantify the effects of varying climate and land-use/land-cover (LULC) dynamics on green water (GW) over the SJP during two distinctive periods (i.e., pre-2000 and post-2000), when synergetic effects of increased precipitation and temperature and rapid development of agriculture occurred. This assessment used the distributed eco-hydrological model ESSI-3. Multivariable and multi-objective calibration approaches (i.e., discharge, evapotranspiration, and terrestrial water storage anomaly) were used to ensure the high accuracies of the model outputs. This research concluded that GW flow and GW storage in the SJP evidently increased after 2000 compared with before. Across the SJP, GW flow and GW storage responded differently to climate changes and LULC dynamics during pre-2000 and post-2000 period. Our results demonstrated that GW storage changes were predominately affected by climatic changes, especially variations in precipitation, whose contribution accounted for more than 56% after 2000. However, GW flow changes were mainly governed by LULC changes, especially the influence of cropland transformation, whose contribution increased over 20% in the post-2000 period. This study posed a deep insight regarding impacts of regional climatic and LULC changes on GW dynamics, which may benefit decision-making for planting structure optimization and adjustment over the region.