Multi-Temporal Analysis of Water Conservation in the Zengjiang River Basin during 1959-2018

Abstract

With water resource shortages becoming a global concern, water conservation is one of the key factors in the sustainable development of watershed ecosystems. However, previous studies of water conservation have focused on annual mean water conservation, which does not reflect changes in water conservation on shorter time scales. Shorter time scales have more significant responses than longer timescales. An annual scale reflects the supply function of the water culverts, whereas a shorter time scale reflects the function of stagnant flood replenishment. Thus, we analyzed the annual, monthly, and daily changes in water conservation in the Zengjiang River Basin, an important water source area and ecological barrier in Guangzhou, from 1959 to 2018. The WEP-L distributed hydrological model and water-balance equations were used to explore the supply, regulation, and peak reduction and replenishment of the water conservation dryness functions. The results indicate that the annual mean water conservation in the Zengjiang River Basin was 685.7 mm from 1959 to 2018, with a non-significant decreasing rate (-1.30 mm/a) during this period. This decreasing trend indicates that the water supply capacity of the basin decreased, which is not conducive to the water security of the basin and downstream areas. Therefore, relevant policies should be formulated and measures should be taken to improve the water conservation capacity of the basin. The multi-year average monthly water conservation in the Zengjiang River Basin was positive in January‒September and negative in October‒December, with non-significant increases in water conservation in January, March, June, November, and December, and non-significant decreases in the other months. The trend ranged from -0.04 to -0.67 mm/a during the entire study period. Water conservation changes in the Zengjiang River Basin during pre-flood, post-flood, and dry-water periods indicate that the basin's ability to regulate water conservation runoff weakened. The maximum 1-day, 3-day, 5-day, and 7-day periods in the Zengjiang River Basin were positive, whereas the minimum 1-day, 3-day, 5-day, and 7-day periods were negative. Except for the minimum 5-day and 7-day periods, the other six daily extreme water conservation indicators exhibited non-significant increasing trends. The maximum water conservation values indicate that the peak reduction capacity increased, while the minimum water conservation values indicate that the capacity to replenish depletion decreased in 1- and 3-day periods and increased in 5- and 7-day periods. Spatially, the annual water conservation trend was low in the southeastern and northern parts of the basin, and high in the southwestern part of the basin. Annual, monthly, and daily water conservation levels in the Zengjiang River Basin from 1959 to 2018 embodied its supply, regulation, peak reduction, and replenishment of depletion functions, respectively. The correlation coefficients between water conservation and precipitation were significantly higher than those between evapotranspiration and surface runoff, thereby indicating that precipitation was the most important factor influencing water conservation. The findings of this study reveal multi-temporal evolutionary processes and functional differences in water conservation and provide a scientific basis for ecological protection and construction.

Keywords

• water conservation
• multi-temporal
• wep-l hydrological model
• water balance method
• zengjiang river basin