Analysis of Water and Salt Spatio-Temporal Distribution along Irrigation Canals in Ningxia Yellow River Irrigation Area, China

Abstract

The large amount of salinized soil in the Yellow River irrigation area is a threat to the sustainable development of agriculture, and in order to efficiently control the soil salinization trend, it is necessary to research water and salt variations and the distribution of soil in the area. In this study, soil salinization along two typical canals (West Main Canal and Tanglai Canal) in the Ningxia Yellow River irrigation area in China is investigated using data regarding water content, salt ions and pH from soil samples collected at 165 points along these canals. At each of these points, soil samples from various layers were collected for measurement from August 2019 to December 2020. Various methods, such as Pearson’s correlation analysis and Kriging interpolation, were employed to obtain the temporal and spatial distributions of water content, pH value and salt ions from the soil samples. It was found that the mean total salt value is 2.75 g/kg, which indicates that the soil in the study area is moderately salinized soil. The average value of soil pH is 8.5, indicating that the soil in this area is alkaline. Furthermore, it is evident that the coefficient of variation for certain soil ions, including HCO3−, Cl−, Ca2+, Na+ and K+, is greater than one, which indicates that their spatial distribution in the study area is severely uneven. Moreover, the soil salt content in the study area gradually increases from the southwest to the northeast, in the flow direction of the West Main Canal and the Tanglai Canal. The water content distribution along the two canals also exhibits notable non-uniformity, displaying a pattern higher in the north and east and less in the south and west. Moreover, the annual distribution of total salt content in the surface layer demonstrates an initial increase followed by a decrease, with the peak value typically occurring in August or September. The research results have an important significance on agriculture in the Ningxia Yellow River irrigation area.