State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, China.
PLoS One. 2020 Dec 21;15(12):e0243198. doi: 10.1371/journal.pone.0243198. eCollection 2020.
The Qinghai-Tibetan Plateau region has unique meteorological characteristics, with low air temperature, low air pressure, low humidity, little precipitation, and strong diurnal variation. A two-dimensional hydrodynamic CE-QUAL-W2 model was configured for the Pangduo Reservoir to better understand the thermal structure and diurnal variation inside the reservoir under the local climate and hydrological conditions on the Qinghai-Tibetan Plateau. Observation data were used to verify the model, and the results showed that the average error of the 6 profile measured monthly from August to December 2016 was 0.1°C, and the root-mean-square error (RMSE) was 0.173°C. The water temperature from August 2016 to September 2017 was simulated by inputting measured data as model inputs. The results revealed that the reservoir of the Qinghai-Tibetan Plateau was a typical dimictic reservoir and the water mixed vertically at the end of March and the end of October. During the heating period, thermal stratification occurred, with strong diurnal variation in the epilimnion. The mean variance of the diurnal water temperature was 0.10 within a 5 m water depth but 0.04 in the whole water column. The mixing mode of inflow changed from undercurrent, horizontal-invaded flow and surface layer flow in one day. In winter, the diurnal variation was weak due to the thermal protection of the ice cover, while the mean variance of diurnal water temperature was 0.00 within both 5 m and the whole water column. Compared to reservoirs in areas with low altitude but the same latitude, significant differences occurred between the temperature structure of the low-altitude reservoir and the Pangduo Reservoir (P<0.01). The Pangduo Reservoir presented a shorter stratification period and weaker stratification stability, and the annual average SI value was 26.4 kg/m2, which was only 7.5% that of the low-altitude reservoir. The seasonal changes in the net heat flux received by the surface layers determined the seasonal cycle of stratification and mixing in reservoirs. This study provided a scientific understanding of the thermal changes in stratified reservoirs under the special geographical and meteorological conditions on the Qinghai-Tibetan Plateau. Moreover, this model can serve as a reference for adaptive management of similar dimictic reservoirs in cold and high-altitude areas.
青藏高原地区具有独特的气象特征，气温低、气压低、湿度低、降水少且日变化大。为了更好地了解青藏高原局部气候和水文条件下的水库热力结构和日变化，针对庞多水库配置了二维水动力 CE-QUAL-W2 模型。利用观测数据对模型进行了验证，结果表明，2016 年 8 月至 12 月逐月实测 6 个剖面的平均误差为 0.1°C，均方根误差（RMSE）为 0.173°C。输入实测数据作为模型输入，模拟了 2016 年 8 月至 2017 年 9 月的水温。结果表明，青藏高原水库是典型的双温层水库，3 月底和 10 月底垂直混合。加热期发生热力分层，表水层日变化强烈。5m 水深内日水温均方差为 0.10，整个水柱为 0.04。入流混合模式在一天内由底层流、水平入侵流和表层流转变。冬季由于冰盖的热保护，日变化较弱，5m 和整个水柱内日水温均方差均为 0.00。与低海拔但同一纬度的水库相比，低海拔水库与庞多水库的温度结构存在显著差异（P<0.01）。庞多水库分层期较短，分层稳定性较弱，年平均 SI 值为 26.4kg/m2，仅为低海拔水库的 7.5%。表层接收到的净热通量的季节性变化决定了水库的分层和混合的季节性周期。本研究为了解青藏高原特殊地理和气象条件下分层水库的热力变化提供了科学依据，为高寒地区类似的双温层水库的自适应管理提供了参考。
