Abstract

Assessment of rainfall variability and drought is essential to address the existing water crisis and water resources management. This study was carried out to assess the rainfall variability, meteorological drought and relative response of a water supply reservoir located in Chennai Metropolitan, India. Spatial and temporal variation of rainfall and drought across the river basin was assessed using historical rainfall records from 1978 to 2016. A significant number of rainfall stations show increasing trends in post-monsoon and northeast monsoon. The annual rainfall is concentrated for less than six months and shows an irregular to strongly irregular distribution. The degree of variability in monthly rainfall reveals markedly seasonal with long dry periods. Three different drought indices such as rainfall deviation method, Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI) were used and compared to identify the meteorological droughts. The duration of meteorological drought events in this region ranged from 3 to 9 months. Identified drought events reveal that the rainfall deficiency in the northeast monsoon causes most of the meteorological drought. The reservoir system has higher response and coherence with SPI at a higher time scale. So, SPI can be used to represent the hydrological drought in higher time scales. Hence, SPI is recommended as more appropriate for drought assessments for this region. The large scale atmospheric circulations have moderate impacts on drought events in this region. The outcomes of this study could be useful for better drought and water resources management.

Research Highlights

• Chennai region has higher interannual rainfall variability and susceptible to droughts once in about four years.

• About 44.44% of droughts in this region when India witnessed drought indicating large scale atmospheric circulations.

• Deficiency in rainfall during both southwest and northeast monsoon increase the gap between water demand and supply.

中文翻译：

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印度钦奈特大城市的降雨，气象干旱和供水水库响应的时空分析

摘要

评估降雨多变性和干旱对于解决现有的水危机和水资源管理至关重要。这项研究旨在评估位于印度钦奈都会区的一个供水水库的降雨变异性，气象干旱和相对响应。利用1978年至2016年的历史降雨记录对整个流域降雨和干旱的时空变化进行了评估。大量降雨台站显示季风后和东北季风呈上升趋势。年降雨量集中在不到六个月的时间，并且显示出不规则到强烈不规则的分布。月降雨量的变化程度显示出明显的季节性和长期干旱。三种不同的干旱指数，例如降雨偏差法，使用标准降水指数（SPI），标准降水蒸散指数（SPEI）进行比较，以识别气象干旱。该地区气象干旱事件的持续时间为3到9个月。识别出的干旱事件表明，东北季风的降雨不足是造成大多数气象干旱的原因。在更长的时间范围内，储层系统具有更高的响应和与SPI的一致性。因此，SPI可以用来代表较高时间尺度上的水文干旱。因此，建议将SPI更适合于该地区的干旱评估。大规模的大气环流对该地区的干旱事件有中等程度的影响。这项研究的结果可能有助于更好的干旱和水资源管理。使用标准降水蒸散指数（SPEI）并进行比较以识别气象干旱。该地区气象干旱事件的持续时间为3到9个月。识别出的干旱事件表明，东北季风的降雨不足是造成大多数气象干旱的原因。在更长的时间范围内，储层系统具有更高的响应和与SPI的一致性。因此，SPI可以用来代表较高时间尺度上的水文干旱。因此，建议将SPI更适合于该地区的干旱评估。大规模的大气环流对该地区的干旱事件有中等程度的影响。这项研究的结果可能有助于更好的干旱和水资源管理。使用标准降水蒸散指数（SPEI）并进行比较以识别气象干旱。该地区气象干旱事件的持续时间为3到9个月。识别出的干旱事件表明，东北季风的降雨不足是造成大多数气象干旱的原因。在更长的时间范围内，储层系统具有更高的响应和与SPI的一致性。因此，SPI可以用来代表较高时间尺度上的水文干旱。因此，建议将SPI更适合于该地区的干旱评估。大规模的大气环流对该地区的干旱事件有中等程度的影响。这项研究的结果可能有助于更好的干旱和水资源管理。

研究重点

• 钦奈地区的年际降雨量变化较大，并且大约每四年就会遭受一次干旱。

• 印度发生干旱时，该地区约有44.44％的干旱发生，这表明大气环流在不断扩大。

• 西南季风和东北季风期间降雨不足，加剧了供需之间的差距。