Geomatic Engineering Department, Engineering and Nature Sciences Faculty, Konya Technical University, Konya, Turkey.
Environ Monit Assess. 2022 Jun 24;194(8):529. doi: 10.1007/s10661-022-10207-4.
The threat of drought has been felt almost worldwide in recent years. It is critical to determine the causes of drought and how seasonal changes affect it. Additionally, it is necessary to determine the speed and impact area of drought, monitor drought areas, and attempt to find solutions against drought. With the developing satellite sensing systems, remote sensing methods are being used to investigate topics such as the increase and extent of drought, uncontrolled water consumption in agricultural activities, and the effects of unnatural pollutants on freshwater resources such as lakes and rivers. Using Synthetic Aperture Radar (SAR) satellite data to monitor changes in water bodies is a relatively new area of study in remote sensing. The spatial extent and seasonal change (spring and autumn) of droughts between 2017 and 2021 in Akşehir Lake were determined from Sentinel-1A SAR satellite data, and the Normalized Differential Water Index (NDWI) was calculated using Sentinel-2A optical satellite data and Standardized Precipitation Index (SPI) in this research. In addition, a different approach was applied to determine the change of wetland boundaries more accurately by converting the linear Sigma0 band to the decibel (dB) band and applying a non-linear 3 × 3 maximum filter to the dB band to Sentinel-1A data. Consequently, it has been established that Akşehir Lake, which used to have wetlands during the spring seasons but began to dry up in the autumn seasons, had completely dried up in both periods in 2021.
近年来，几乎在全世界都感受到了干旱的威胁。确定干旱的原因以及季节变化如何影响干旱至关重要。此外，还需要确定干旱的速度和影响范围，监测干旱地区，并尝试寻找抗旱解决方案。随着卫星遥感系统的发展，遥感方法正被用于研究干旱的增加和范围、农业活动中不受控制的耗水量以及非自然污染物对湖泊和河流等淡水资源的影响等问题。使用合成孔径雷达（SAR）卫星数据监测水体变化是遥感领域一个相对较新的研究领域。本研究利用 Sentinel-1A SAR 卫星数据确定了 2017 年至 2021 年阿克谢希尔湖的干旱范围和季节性变化（春季和秋季），并利用 Sentinel-2A 光学卫星数据计算了归一化差异水指数（NDWI）和标准化降水指数（SPI）。此外，通过将线性 Sigma0 波段转换为分贝（dB）波段，并对 dB 波段应用非线性 3x3 最大值滤波器，应用了一种不同的方法来更准确地确定湿地边界的变化。结果表明，阿克谢希尔湖在春季有湿地，但在秋季开始干涸，到 2021 年两个季节都完全干涸。
