Ecological Regulation and Effectiveness Evaluation of Elodea nuttallii Controlling in Danjiangkou-Wangfuzhou Section of Hanjiang River
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摘要: 为科学有效控制汉江丹江口至王甫洲区间伊乐藻(Elodea nuttallii)过度生长繁殖,研究生态调度的实施效果,采用生物量调查法、分布面积统计法、数学模型模拟法等方法分析生态调度实施前后伊乐藻总生物量和分布面积的变化情况,并探讨对丹江口水库下泄流量的需求。结果表明,连续3年实施生态调度,伊乐藻总生物量由2019年的4.8万t减少至2022年的40.11 t,分布面积由11.60 km2减少至0.23 km2,减幅均达到了95%以上;伊乐藻生物量占沉水植物总生物的比重从99.99%减少至17%,生态调度效果较好;春季生态调度应重点从增加流量极值比出发进行中度干扰,夏秋季生态调度重点从满足0.14 m/s临界流速出发进行大流速冲刷。研究结果明确了王甫洲水库伊乐藻的生态调度需求,为持续开展伊乐藻“灾害”防控提供了参考基础。Abstract: In recent years, excessive growth of Elodea nuttallii in the Wangfuzhou reservoir area of Hanjiang River has adversely effected the ecological environment and services. It is therefore important to control E. nuttallii growth. Previous research has shown that ecological control of E. nuttallii, is feasible and reliable, and it was used in the Wangfuzhou reservoir area during the period2020-2022. We studied Hanjiang River from Danjiangkou to Wangfuzhou, measured the effectiveness of ecological control and identified the Danjiangkou reservoir discharge pattern that most effectively controlled E. nuttallii. The study was based on data collected over the 3 years(2020-2022) of monitoring ecological regulation in Wangfuzhou reservoir and 4 years of in situ ecological monitoring in the study area(2019-2022). Biomass surveys, statistics on the area of distribution, and mathematical model simulations were used to analyze and evaluate the changes in biomass, and distribution area before and after implementation of ecological control. The total biomass of E. nuttallii decreased from 48 000 tons in 2019 to 40.11 tons in 2022 and, after ecological control for 3 years,the distribution area decreased from 11.60 km2 to 0.23 km2, a decrease of over 95%. The proportion of E. nuttallii biomass in the total biomass of submerged plants decreased from 99.99% to 17%, indicating effective control. We recommend ecological discharge regulation that focuses on moderate E. nuttallii control by increasing the extreme flow ratio in spring, and focuses on high flow velocity erosion with a critical flow velocity of 0.14 m/s in summer and autumn. Our study identified the optimal discharge flows from Danjiangkou reservoir for controlling E. nuttallii, and provides a reference for preventing excessive E. nuttallii growth.
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