Rainwater harvesting (RWH) for domestic uses is widely regarded as an economic and ecological solution in water conservation and storm management programs. This paper aims at evaluating long-term trends in 20-day cumulative rainfall periods per year in Poland, for assessing its impact on the design and operation conditions for RWH systems and resource availability. The time-series employed corresponds to a set of 50-year long time-series of rainfall (from 1970 to 2019) recorded at 19 synoptic meteorological stations scattered across Poland, one of the European countries with the lowest water availability index. The methods employed for assessing trends were the Mann–Kendall test (M–K) and the Sen’s slope estimator. Most of the datasets exhibit stationary behaviour during the 50-year long period, however, statistically significant downward trends were detected for precipitations in Wroclaw and Opole. The findings of this study are valuable assets for integrated water management and sustainable planning in Poland.

中文翻译：

---

波兰住宅雨水收集 20 天累积降水量的长期趋势

家用雨水收集 (RWH) 被广泛认为是节水和风暴管理计划中的经济和生态解决方案。本文旨在评估波兰每年 20 天累积降雨期的长期趋势，以评估其对 RWH 系统的设计和运行条件以及资源可用性的影响。所采用的时间序列对应于分布在波兰各地的 19 个天气气象站记录的一组 50 年长的降雨时间序列（从 1970 年到 2019 年），波兰是可用水指数最低的欧洲国家之一。用于评估趋势的方法是 Mann-Kendall 检验 (M-K) 和 Sen 斜率估计器。大多数数据集在 50 年的时间里表现出平稳的行为，然而，弗罗茨瓦夫和奥波莱的降水有统计上显着的下降趋势。这项研究的结果是波兰综合水资源管理和可持续规划的宝贵资产。