基于Landsat影像的近40年来(1982—2021年)三峡库区水面面积及其蒸发损失变化

Evolutions of water surface area and evaporation loss of Three Gorges Reservoir based on Landsat images,1982-2021

三峡水库蓄水引起库区水位抬升,水面面积显著增加,对区域水文循环过程产生了一定影响。为揭示三峡水库蓄水前后水面面积及蒸发损失变化规律,选取三峡库区坝前至寸滩区间作为研究区,利用Landsat影像数据提取1982—2021年水面面积,分区建立水位与面积关系曲线,进而推求库区逐日水面面积。在估计三峡库区水面面积的基础上,结合站点潜在蒸发资料推求水面蒸发损失量。研究结果表明:2010年三峡水库全面运行后,坝前至寸滩库区平均水面面积由蓄水前的372.96km^(2),增加到761.31km^(2),较蓄水前增加了1.04倍。同时,三峡水库的蓄泄调节改变了库区河段原有的水文节律,使得库区水面面积的季节性变化特征较蓄水前发生了显著变化。蓄水后,冬季水面面积最大,平均为843.81km^(2),较蓄水前增加了1.89倍;秋季、春季次之,水面面积分别为818.73和735.28km^(2),较蓄水前分别增加了97.17%和1.28倍;夏季水面面积最小,为653.03km^(2),较蓄水前仅增加了39.06%。水库全面运行后,蒸发损失量随水面面积扩大而急剧增加,多年平均蒸发损失量由蓄水前的2.68亿m^(3)增加到5.65亿m^(3)。库区水面蒸发损失量的季节性节律较蓄水前并未发生实质性变化,春季蒸发损失量为1.26亿m^(3),较蓄水前增加了1.4倍;夏季仍是蒸发损失最大的季节,其蒸发损失量为2.11亿m^(3),较蓄水前增加了61.14%,但其占全年总蒸发损失的比重却由蓄水前的48.80%减少至37.32%;秋季蒸发损失量为1.49亿m^(3),较蓄水前增加了1.23倍;而冬季水面蒸发损失量为0.80亿m^(3),较蓄水前增加了3.34倍,其占全年总蒸发损失的比重也由蓄水前的6.85%增加至14.11%,该季节水面面积虽然最大,但其蒸发量仍然最小。本文研究结果有助于更加全面地揭示三峡水库运行对库区水文循环要素的影响。

The damming of Three Gorges Reservoir(TGR)has caused the upstream water level to rise and the water surface area to increase significantly.In order to show the changes in water surface area and evaporation loss before and after the construction of TGR dam,this study used Landsat image data to extract the water surface area from Cuntan to the TGR dam during the period 1982-2021.Then,the daily water surface area was calculated by the water level and area relationship established by cubic polynomial.Based on the estimated daily water surface area of the TGR and the corresponding potential evaporation data,the evaporation loss of the reservoir was estimated.The results showed that after full operation of the TGR in 2010,the average water surface area in the reservoir area increased from^(3)72.96 km^(2) before damming to 761.31 km^(2).At the same time,the storage and discharge regulation of TGR had altered the original hydrological rhythm of the river reach in the reservoir area,causing the seasonal variation of the water surface area in the reservoir area to change significantly compared to the pre-storage period.After impoundment,the largest water surface area occurred in winter with an average of 843.81 km^(2),an increase of 1.89 times compared to that before impoundment;followed by areas in autumn and spring with 818.73 km^(2) and 735.28 km^(2),respectively,an increase of 97.17% and 1.28 times compared to that before impoundment;and the smallest water surface area occurred in summer with 653.03 km^(2),an increase of only 39.06% compared to that before impoundment.After full operation of the reservoir,the average annual evaporation loss from the reservoir increased to 565 million m^(3) from^(2)68 million m^(3) in the pre-TGR period.The seasonal rhythm of evaporation loss from the water surface in the TGR area had not changed significantly compared to that before impoundment,with an evaporation loss of 126 million m^(3) in spring,an increase of 1.4 times compared to that before impoundment.Summer was still the season with the highest evaporation loss,with an evaporation loss of 211 million m^(3),an increase of 61.14% compared to that before damming,but its share in the total annual evaporation loss was reduced from 48.80% before damming to 37.32%.The evaporation loss in autumn was 149 million m^(3),which was 1.23 times higher than before damming.Although the water surface area in winter was the largest,its evaporation loss was still the smallest at 80 million m^(3),which was 3.34 times more than before damming,and its proportion of the total annual evaporation loss increased from 6.85% to 14.11% before damming.The above results are useful in showing the impact of the TGR on the regional hydrological cycle.