Analysis on the ecological impact of the Xiaolangdi Reservoir on the Yellow River Delta wetland and coastal areas

Abstract

An environmental water supplement through reservoir regulation is an important way to restore the deltaic coastal wetland. In order to quantify the impact of the reservoir on the deltaic coastal wetland ecosystem, this article proposes a quantitative analysis method for the ecological impact and contribution rate of the reservoir, which compares the ecological status in two scenarios with the presence or absence of the reservoir during the assessment period, and reveals the reservoir’s impact on and contribution rate to the ecological status and environmental water supplement conditions. The results show that during 2000–2019, through the regulation of the Xiaolangdi Reservoir, the average annual drying up days at the Lijin section reduced by 81.15 days, the average annual assurance rate of ecological base flow at the Lijin section increased by 20.60%, and the volume of water flowing into the sea from April to June increased by 2.37 billion m³. During 2008–2015, the Xiaolangdi Reservoir increased the environmental water supplement of the Yellow River Delta by 19.95 million m³. Compared with the flow and water withdrawal during 1980–1999, the natural flow of the Yellow River decreased by 10.59% and the measured flow in the lower reaches decreased by 22.15%, and the water withdrawal in the lower reaches increased by 0.32 billion m³ during 2000–2019, which is detrimental to provide environmental water to the Yellow River Delta wetland and coastal areas. The Xiaolangdi Reservoir reversed the adverse effects of flow and water withdrawal and ensured the continuous ecological improvement in the Yellow River Delta and coastal areas, providing the respective contribution rate of 187.85%, 137.24%, and 125.83% to the prevention of drying up at the Lijin section, the increase in the assurance rate of ecological base flow at the Lijin section, and the increase in the volume of water flowing into the sea in the critical period.

Quantitative Analysis of the Influence of the Xiaolangdi Reservoir on Water and Sediment in the Middle and Lower Reaches of the Yellow River

“…After the operation of the Xiaolangdi reservoir, it has had a great influence on the annual runoff distribution, which is mainly manifested as increasing the discharge in the dry season and decreasing the discharge in the wet season. It plays the role of flood control and storage in the lower reaches of the Yellow River, alleviates the flood pressure in the middle and lower reaches of the Yellow River in flood season, and also maintains the flow demand to maintain the normal ecological operation of the river and promotes the ecological restoration of the lower reaches [47]. stations are June, July, and July, and the maximum flows are 1602.64 m 3 /s, 1474.32 m 3 /s, and 1408.33 m 3 /s, accounting for 13.85%, 14.03%, and 18.22% of the whole year, respectively.…”

Reservoir ecological operation on sediment-laden river considering wetland protection

“…Approximately 92.3% of the total area of the Yellow River basin, 87% of the natural runoff of the Yellow River, and 100% of sediment transport are controlled by the reservoir. The primary objective of the XLDR was flood (including ice) prevention and siltation reduction, with subsidiary objectives of water supply, irrigation, power generation, storing clear water and releasing muddy water, elimination of hazards and promotion of benefits, and comprehensive resource utilization (Shang et al, 2022). The normal impounded level, normal dead storage level, flood control level, and abnormal dead storage level of the reservoir are 275, 230, 254, and 220 m, respectively.…”