Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
New Era and Development in Civil Engineering Research Group, Scientific Research Center, Al-Ayen University, Thi-Qar, Nasiriyah, 64001, Iraq.
Environ Sci Pollut Res Int. 2023 Jul;30(32):79049-79066. doi: 10.1007/s11356-023-27498-w. Epub 2023 Jun 6.
Drought is a gradual phenomenon that occurs slowly and directly impacts human life and agricultural products. Due to its significant damage, comprehensive studies must be conducted on drought events. This research employs precipitation and temperature from a satellite-based gridded dataset (i.e., NASA-POWER) and runoff from an observation-based gridded dataset (i.e., GRUN) to calculate hydrological and meteorological gical droughts in Iran during 1981-2014 based on the Standardised Precipitation-Evapotranspiration Index (SPEI) and Hydrological Drought Index (SSI) indices, respectively. In addition, the relationship between the meteorological and hydrological droughts is assessed over various regions of Iran. Afterward, this study employed the Long Short-Term Memory (LSTM) method to predict the hydrological drought based on the meteorological drought over the northwest region of Iran. Results show that hydrological droughts are less dependent on precipitation in the northern regions and the coastal strip of the Caspian Sea. These regions also have a poor correlation between meteorological and hydrological droughts. The correlation between hydrological and meteorological drought in this region is 0.44, the lowest value among the studied regions. Also, on the margins of the Persian Gulf and southwestern Iran, meteorological droughts affect hydrological droughts for 4 months. Besides, except the central plateau, most regions experienced meteorological and hydrological droughts in the spring. The correlation between droughts in the center of the Iranian plateau, which has a hot climate, is less than 0.2. The correlation between these two droughts in the spring is stronger than in other seasons (CC = 0.6). Also, this season is more prone to drought than other seasons. In general, hydrological droughts occurred one to two months after the meteorological drought in most regions of Iran. LSTM model for northwest Iran showed that the predicted values had a high correlation with the observed values, and their RMSE was less than 1 in this region. CC, RMSE, NSE, and R-square of the LSTM model are 0.7, 0.55, 0.44, and 0.6, respectively. Overall, these results can be used to manage water resources and allocate water downstream to deal with hydrological droughts.
干旱是一种缓慢而直接影响人类生活和农业生产的渐进现象。由于其造成的重大破坏，必须对干旱事件进行全面研究。本研究利用基于卫星的网格化数据集（即 NASA-POWER）中的降水和温度以及基于观测的网格化数据集（即 GRUN）中的径流量，分别使用标准化降水蒸散指数（SPEI）和水文干旱指数（SSI）来计算 1981-2014 年期间伊朗的水文和气象干旱。此外，还评估了伊朗不同地区气象干旱和水文干旱之间的关系。然后，本研究使用长短时记忆（LSTM）方法，基于伊朗西北部的气象干旱预测水文干旱。结果表明，北部地区和里海沿海地区的水文干旱对降水的依赖性较小。这些地区气象干旱和水文干旱之间的相关性也较差。该地区水文干旱和气象干旱之间的相关性为 0.44，是研究地区中最低的。此外，在波斯湾边缘和伊朗西南部，气象干旱会影响水文干旱 4 个月。此外，除了中央高原，大多数地区在春季都经历了气象和水文干旱。气候炎热的伊朗高原中心地区的干旱之间的相关性小于 0.2。这两个干旱在春季的相关性强于其他季节（CC=0.6）。此外，这个季节比其他季节更容易发生干旱。一般来说，在伊朗大多数地区，水文干旱在气象干旱后一到两个月发生。LSTM 模型在伊朗西北部的预测值与观测值高度相关，其 RMSE 在该地区小于 1。LSTM 模型的 CC、RMSE、NSE 和 R-square 分别为 0.7、0.55、0.44 和 0.6。总体而言，这些结果可用于水资源管理和向下游分配水资源，以应对水文干旱。
