乌东德水库水温结构时空演化特性及下泄水温时滞效应

Spatiotemporal evolution characteristics of water temperature structure and lag effect of discharge water temperature in Wudongde Reservoir

摘要

【目的】明晰高坝大库水温结构时空演化特性和滞温效应，可为叠梁门调度提供科学依据，是缓解低温水下泄，保护下游河段鱼类生存繁衍的基础性工作。【方法】通过数值模拟的方法，基于2020—2022年实测水文数据、水温数据、气象边界数据以及平水年设计运行资料，构建乌东德库区三维水温数值模拟模型，分析了水库运行后库区水温结构的时空演化特性和下泄水温的时滞效应。【结果】结果显示：(1)春夏季，乌东德水库垂向水温存在明显分层现象，温差可达11~12℃,汛期过后随着水体热交换程度的增加，垂向水温逐渐混匀，秋冬季节未发现明显的水温分层现象；(2)水库出流水温明显存在春夏季低温水，冬季高温水下泄问题，2020—2022年监测数据显示，5月下泄水温比坝址天然水温平均降低2.68℃,12月下泄水温平均升高4.78℃;稳定运行期模拟结果显示，3—6月，下泄月均水温比坝址天然水温降低0.91~4.09℃,12月—次年2月，下泄月均水温升高1.34~4.34℃;(3)蓄水后，各年份相比建坝前水温达到14℃、18℃的时间皆有不同程度的推迟，河段鱼类适宜产卵水温出现时间向后推迟30~50 d,推迟时间排序为：长鳍吻鮈>中华金沙鳅、四大家鱼、鲤、鲫>犁头鳅。【结论】结果表明：乌东德水库水温分层及其引发的低温水下泄问题对下游河段鱼类繁殖产生了不同程度的不利影响，需要科学采取应对措施。

Abstract

[Objective] Clarifying the spatiotemporal evolution characteristics and temperature lag effect of high dams and large reservoirs can provide a scientific basis for stacked beam gate scheduling, which is fundamental for alleviating discharge of low-temperature water and protecting the survival and reproduction of fish in the lower reaches. [Methods] Through numerical simulation and based on the measured hydrological data, water temperature data, meteorological boundary data from 2020 to 2022, and design operation data in an average water year, a three-dimensional numerical simulation model of water temperature for the Wudongde Reservoir area was developed. The spatiotemporal evolution characteristics of water temperature structure and lag effect of discharge water temperature after reservoir operation were analyzed. [Results] The result showed that:(1) In spring and summer, a distinct vertical stratification of water temperature was observed in the Wudongde Reservoir, with a temperature difference of 11~12 ℃. After the flood season, as the thermal exchange within the water body increased, the vertical water temperature gradually became uniform. No significant water temperature stratification was observed in autumn and winter.(2) There was a clear issue of low-temperature water discharge in spring and summer, and high-temperature water discharge in winter from the reservoir. Monitoring data from 2020 to 2022 indicated that the discharge water temperature in May was, on average, 2.68℃ lower than the natural water temperature at the dam site, and the discharge water temperature in December was, on average, 4.78℃ higher. Simulation result during the stable operation period indicated that from March to June, the monthly average discharge water temperature was 0.91~4.09 ℃ lower than the natural water temperature at the dam site. From December to February of the following year, the monthly average discharge water temperature was 1.34~4.34 ℃ higher.(3) After the impounding of reservoir, the time for the water temperature to reach 14℃ and 18℃ each year was delayed to varying degrees compared to before the dam construction. The occurrence time of suitable spawning water temperature for fish in the lower reaches was postponed by 30~50 days, with the delay ranked as follows: Rhinogobio ventralis > Jinshaia sinensis, Four major Chinese carps, Common carp, Crucian carp > Lepturichthys fimbriata. [Conclusion] The result show that the stratification of water temperature in the Wudongde Reservoir, along with the low-temperature discharge water it causes, has varying degrees of negative effects on fish reproduction in the lower reaches of the river. Therefore, scientific measures must be implemented to address these issues.

关键词

乌东德水库 / 库区水温结构 / 下泄水温 / 滞温效应 / 鱼类繁殖 / 数值模拟

Key words

Wudongde Reservoir / water temperature structure in reservoir area / discharge water temperature / temperature lag effect / fish reproduction / numerical simulation

基金资助

国家自然科学基金青年科学基金项目(52209107)

智慧长江与水电科学湖北省重点实验室基金项目(2422020009)

中国华能集团有限公司总部科技项目(HNKJ20-H26)