水库渗漏水流溶解氧与水温沿程恢复的试验研究

水库底层低温低氧水从坝体下泄或渗漏，可能对下游生态产生不利影响。通过对湖北温峡水库下游温峡河225 km河段的野外试验，测量溶解氧、水温等指标的日变化和沿程变化，开展复氧试验研究阶梯深潭结构和沙洲对溶解氧的影响，并取样分析大型底栖无脊椎动物的沿程分布。结果表明，流速对水温与溶解氧日变化规律无明显影响。试验河段水温和溶解氧恢复很快，经过17 km的河段，水温从123℃升高至300℃，且溶解氧饱和度基本达到饱和。河宽对水温恢复起重要作用，对溶解氧影响较小，对复氧速度基本无影响。流量通过改变淹没程度影响阶梯深潭的复氧能力。溶解氧在沙洲下游存在横向分布，滞水区溶解氧高于左右汊道。溶解氧是水库下游水生态的控制因素，物种多样性随溶解氧的升高而增加

EXPERIMENTAL STUDY ON THE RECOVERY OF DISSOLVED OXYGEN AND WATER TEMPERATURE OF LEAKAGE WATER IN THE DOWNSTREAM RIVER OF WENXIA RESERVOIR

Leakage water from the bottom layer of a reservoir, which is low in dissolved oxygen (DO) and water temperature (WT), would cause ecological problems if flowing into the downstream channel without any recovery methods. The recovery of DO and WT in leakage water from a reservoir along the stream remains poorly understood, although studies of stratification of WT and DO in such a reservoir have been more numerous in recent years. In this study, field investigation and field experiment were carried out on the 2.25 kilometer long test section of Wenxia River, downstream of the Wenxia Reservoir. DO and WT values were measured along the test reach as well as their diurnal variation. Effects of step pool on channel reaeration abilities and influence of sandbar on the transverse distribution of DO downstream were preliminarily analyzed based on the data collected in the field experiment. Besides, macro invertebrates were sampled to evaluate aquatic ecology. Results show that flow velocity almost has no effect on the diurnal variation of DO and WT for a single spot in the test reach. Both WT and DO increased along the downstream reach of the reservoir and almost got completely recovered at the end of the test reach.WT experienced an 18.7 °C rise and was close to the air temperature at the end of the test reach; DO reached saturated state from 16.1% in saturation through a 1.7 kilometer long reach. Channel width is well correlated with the recovery of both DO and WT, however, WT is more susceptible to channel width than DO.WT experienced a growth spurt but DO did not at where the channel is broadened to a large extent. Reaeration rate had a limited variation along the test reach except at the experiment site, uncorrelated with channel width. For a step pool, the reaeration ability was weaker in the morning than in the afternoon under large discharge, which was opposite to the situations under small discharge or in plane bed. The phenomenon could be explained by different submergence of step pool under different discharges. Submergence affected turbulence intensity and thus had impact on air entrainment. DO is sectional in the downstream area of a sandbar, high at the tail but low in the two branches flowing by. Besides, the difference of DO concentration between the branches and bar tail grew with larger flow velocity difference, indicating a remarkable influence of flow velocity on DO distribution for this river pattern. Biodiversity increased with the reaeration process and a species succession, from species with high tolerance against low DO to species without the capacity, occured with higher DO concentration, implying a controlling effect of DO on the downstream aquatic ecology of the reservoir