Department of Civil and Environmental Engineering, Maroun Semaan Faculty of Engineering and Architecture, American University of Beirut, Bliss Street, Beirut, Lebanon.
Environ Monit Assess. 2018 Dec 28;191(1):41. doi: 10.1007/s10661-018-7180-7.
In situ monitoring of freshwater systems is often constrained by cost and accessibility, particularly in developing countries and in remote areas. Satellite remote sensing is therefore increasingly being integrated with existing in situ water quality monitoring programs. In this study, we use the Landsat TM/ETM+ image record collected between 1984 and 2015 to track temporal changes in trophic status, chlorophyll-a levels, algal bloom incidences, water clarity, water temperature, and reservoir water volume in a poorly monitored hypereutrophic semi-arid reservoir. Historical reservoir water quality data are inferred from calibrated Landsat-based empirical algorithms. The results show that, although the reservoir has existed in a eutrophic to hypereutrophic state over the past 30 years, its water quality has significantly deteriorated in the most recent decade. Mean summer chlorophyll-a concentrations were found to have increased by around 163% between 1984 and 2015, while water clarity dropped by more than 58% over the same period. Statistically significant changes in surface water temperatures were also apparent for the month of August, with a cumulative increase of 1.24 °C over the 31-year study period. The rise in temperature appears to correlate with the incidence of Microcystis blooms observed in the reservoir over the past decade. On the other hand, the water volume in the reservoir was found to have been fairly stable over time, likely as a result of adaptive reservoir management. This study demonstrates the strength of using Landsat data to hindcast and quantify changes in water quality and quantity in poorly monitored freshwater systems.
原位监测淡水系统通常受到成本和可达性的限制，尤其是在发展中国家和偏远地区。因此，卫星遥感越来越多地被整合到现有的水质原位监测计划中。在这项研究中，我们使用 1984 年至 2015 年间收集的 Landsat TM/ETM+图像记录来跟踪富营养化半干旱水库中营养状况、叶绿素-a 水平、藻类爆发频率、水清澈度、水温以及水库水量的时间变化，该水库的监测较差。历史水库水质数据是从经过校准的基于 Landsat 的经验算法推断出来的。结果表明，尽管在过去的 30 年里，该水库一直处于富营养化到超富营养化状态，但在最近的十年里，其水质已经显著恶化。1984 年至 2015 年间，夏季平均叶绿素-a 浓度增加了约 163%，而同期水清澈度下降了 58%以上。8 月份的地表水温度也发生了明显的统计学变化，在 31 年的研究期间，累计增加了 1.24°C。温度的上升似乎与过去十年中在水库中观察到的微囊藻爆发的发生率有关。另一方面，水库的水量随着时间的推移被发现相当稳定，这可能是由于水库管理的适应性。本研究证明了使用 Landsat 数据来回溯和量化水质和水量在监测较差的淡水系统中的变化的优势。
