This study aims to analyze the dependence of reservoirs (locally called tanks or wewas) in the headwaters of the Aruvi Aru catchment on precipitation and thus to evaluate their efficiency. The Aruvi Aru is located in the Dry Zone of Sri Lanka, and numerous human made reservoirs characterize the study area. The methodology is based on the application and correlation of climatic and hydrological drought indices. The Standardized Precipitation Index (SPI) is applied to precipitation data at different time scales and the Standardized Water-Level Index (SWLI) is applied to water-level data of five major tanks in the catchment. The results show that near normal present-day average precipitation is appropriate to fill the investigated tanks. The precipitation of the previous 6–12 months has the highest impact on water-level changes. A moderate to strong positive correlation between SWLI and SPI point to other factors besides precipitation affecting the water level of the tanks. These are: (i) catchment size together with the buffering capacity of the upstream catchment and (ii) management practices. As the overall conclusion of our study shows, the tanks functioned efficiently within their system boundaries.

中文翻译：

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分析 Aruvi Aru 流域源头中主要坦克对降水的依赖性。将干旱指数应用于气象和水文数据

本研究旨在分析 Aruvi Aru 流域源头中的水库（当地称为水箱或 Wewas）对降水的依赖性，从而评估其效率。Aruvi Aru 位于斯里兰卡的干旱区，众多人造水库是研究区的特征。该方法基于气候和水文干旱指数的应用和相关性。标准化降水指数（SPI）适用于不同时间尺度的降水数据，标准化水位指数（SWLI）适用于流域内五个主要水库的水位数据。结果表明，接近正常的当今平均降水量适合填充调查的水箱。前 6-12 个月的降水对水位变化的影响最大。SWLI 和 SPI 之间的中度至强正相关表明除影响水箱水位的降水之外的其他因素。它们是：(i) 流域大小以及上游流域的缓冲能力和 (ii) 管理实践。正如我们研究的总体结论所示，坦克在其系统边界内有效运作。