Risk assessment of agricultural green water security in Northeast China under climate change

Northeast China is an important base for grain production, dominated by rain-fed agriculture that relies on green water. However, in the context of global climate change, rising regional temperatures, changing precipitation patterns, and increasing drought frequency pose threats and challenges to agricultural green water security. This study provides a detailed assessment of the spatiotemporal characteristics and development trends of green water security risks in the Northeast region under the base period (2001-2020) and the future (2031-2090) climate change scenarios (SSP245 and SSP585) using the green water scarcity (GWS) index based on raster-scale crop spatial distribution data, Delta downscaling bias-corrected ERA5 data, and CMIP6 multimodal data. During the base period, the green water risk-free zone for dry crops is mainly distributed in the center and east of the Northeast region (72.4% of the total area), the low-risk zone is primarily located in the center (14.0%), and the medium-risk (8.3%) and high-risk (5.3%) zones are mostly in the west. Under SSP245 and SSP585 future climate change scenarios, the green water security risk shows an overall expansion from the west to the center and east, with the low-risk zone increasing to 21.6% and 23.8%, the medium-risk zone increasing to 16.0% and 17.9%, and the high-risk zone increasing to 6.9% and 6.8%, respectively. Considering dry crops with GWS greater than 0.1 as in need of irrigation, the irrigated area increases from 27.6% (base period) to 44.5% (SSP245) and 48.6% (SSP585), with corresponding increases in irrigation water requirement (IWR) of 4.64 and 5.92 billion m3, respectively, which further exacerbates conflicts between supply and demand of agricultural water resources. In response to agricultural green water security risks, coping strategies such as evapotranspiration (ET)-based water resource management for dry crops and deficit irrigation are proposed. The results of this study can provide scientific basis and decision support for the development of Northeast irrigated agriculture and the construction planning of the national water network.