Groundwater table monitoring and analysis of optimum groundwater table depth for crops in 1.6 million km<sup>2</sup> of major grain-producing regions in China

Abstract

Grain is the only source for the survival of humans and also serves as the foundation for social prosperity and stability. In China, 1.4 billion people are supported by 1.2 million km² of arable land. In this case, Chinese hydrogeologists make every effort to satisfy agricultural water needs, contributing substantially to the stable development of agriculture. This paper focuses on the functions of the 58 functional areas for agricultural product supply in the seven major grain-producing regions in China determined according geography, environment, and hydrologic conditions, as well as the construction of the National Groundwater Monitoring Project implemented by the Ministry of Natural Resources (also referred to as the Project) that cover 47 functional areas. Moreover, this paper makes the statistics of the data of 3177 monitoring points in the major grain-producing regions in China in 2020, obtaining the following results. Different crops have different optimum groundwater tables. For instance, the optimum groundwater table for wheat, soybean, and maize is 0.6‒1.5 m, 0.4‒1.0 m, and 0.4‒1.0 m, respectively in the case of loam soil and is 0.4‒1.5 m, 0.6‒1.5 m, and 1.5‒2 m, respectively in the case of sandy loam soil in the Huang-Huai-Hai Plain. For the 47 functional areas for agricultural product supply in China with a high density of groundwater monitoring points, the average annual groundwater tables were all lower than the lower limits of the optimum groundwater table depth ranges for crops in 2020, with the groundwater table depths occasionally higher than the lower limits in only seven of the functional areas throughout 2020. These data will contribute to high and stable crop yields, basic grain supply, and the elimination of extreme poverty.