How do climate extremes impact agricultural water scarcity in China?

Water scarcity occurs when the demand for water in agriculture and other economic sectors exceeds the available water resources. Since the late 1990s, factors such as climate change, agricultural expansion, industrial development, and population growth have intensified water extraction, exacerbating water scarcity in many regions worldwide. Agriculture, as the largest consumer of water globally, is particularly affected by climate change. Green water, which is crucial for agriculture, is often overlooked in water scarcity assessments.

In China, per capita renewable freshwater resources are about one-third of the global average. In recent years, water scarcity has become increasingly severe in many regions, leading to declines in both agricultural output and water quality. However, previous studies have lacked in-depth exploration of the spatial characteristics and underlying drivers of regional water scarcity, highlighting the need to consider scale effects when studying water scarcity and the urgency of conducting multi-scale research across China.

Professor Wenfeng Liu and his research team at China Agricultural University developed the Agricultural Water Scarcity Index (AWSI), which integrates the availability of both blue and green water resources. Focusing on secondary and tertiary river basins in China, they used AWSI to explore the effects of compound extreme precipitation and temperature conditions on AWSI from 1971 to 2010, as well as the associated scale effects. This research has enhanced the understanding of the dynamic interactions between extreme climate events and AWSI across different basin scales in China.

The study found that AWSI significantly increased during drought and hot years, with precipitation changes having a greater impact on AWSI than temperature. In secondary basins, AWSI was 26% higher than the long-term average during drought years, rising to 49% under exceptionally dry conditions. In tertiary basins, the increases were 28% and 55%, respectively. During hot years, AWSI increased by approximately 6.8% (7.3% in tertiary basins) compared to the average, and surged to 19.1% (15.5% in tertiary basins) during extremely hot periods. These findings suggest that AWSI assessments at the tertiary basin level provide a more accurate reflection of the impact of extreme climate events on agricultural water scarcity compared to secondary basins. This underscores the importance of finer spatial scales for forecasting water scarcity within basins and highlights the urgency of developing water management strategies to address compound drought and heat conditions.

This study was published in the Journal of Frontiers of Agricultural Science and Engineering in 2024, 11(4) (DOI: 10.15302/J-FASE-2024574).