Spatial and temporal dynamics of water resources in typical ecosystems of the Dongjiang River Basin, China

In hydrology research, how to quantitatively analyze the spatial and temporal changes of water resources in the ecosystem of a watershed is one of the focuses of attention. Especially in the strategically important Dongjiang River Basin, which is the source of water for three world-class cities of Hong Kong, Shenzhen and Guangzhou. Hence, it is important to quantitatively analyze the spatial and temporal variation of water resources at the basin and ecosystem scale of Dongjiang river basin. The Soil and Water Assessment Tool (SWAT) was used in this study to analyze the spatial and temporal dynamics of typical ecosystem water resources in the Dongjiang River basin over the last 50 years. The objectives of the study were to: (1) identify the distribution of water resources in typical ecosystems; (2) determine the quantity of water in the forest ecosystem; and (3) characterize the spatial and temporal changes. The findings revealed that: (1) the average water resources in the Dongjiang River Basin from 1971 to 2020 were 37.944 Bm3, and there were obvious changes in the basin's total quantity of water resources. The most important climatic factors influencing water resources were precipitation and temperature. (2) From 1971 to 2020, the total water resources of typical Donjiang River Basin ecosystems exhibited a declining trend. The total average water resources of the forest ecosystem were 27.532 Bm3, which first increased and then decreased from upstream to downstream. The total quantity of water resources in the grassland ecosystem increases with the amount of water per unit area. (3) The change in total water resources has been decreasing over the last decade, which is consistent with the change in the water resources of the forest ecosystem in the Dongjiang River Basin. Changes in water resources were greater in the lower and middle reaches than in the upper reaches. Changes in land use were a significant factor in the evolution of water re-sources in typical ecosystems. This study can provide theoretical support for the comprehensive management of typical ecosystems and water resources in the Dongjiang River Basin.