Recent developments of Middle Eastern metropolitans, and the related soaring trend of population increase, is contemporary with the impacts of climate changes. This applies extra pressures to the centralized large-scale water treatment and distribution systems. Rainwater harvesting (RWH) for domestic urban activities can be a sustainable option of adapting with the rising demand of soft water in such an arid/semiarid area. A pilot system of rainwater draining and storage was constructed for alleviating parts of soft water scarcity in Mashhad, the second most populous city of Iran. Measurements were collected for two years at the drainage basin outlet and inside of a storage tank, which has been equipped for water harvesting purposes. We performed some preliminary stochastic analysis and evaluated probabilistic properties of the collected dataset, aiming to explain them with respect to the physical characteristics of the RWH system. Data clustering analysis confirmed that the quality of the water may change during rainwater draining and storage in the RWH tank. Particularly, sodium content of the sampled water in the drainage catchment illustrated higher variations, compared with the ones evaluated for the stored water in the reservoir tank. This can confirm that the quality of the stored water in the RWH reservoir is more stable than that obtained for each separate rainfall–runoff event. We assessed the potential of the harvested water in different consumption contexts, in light of some national and international water quality (physicochemical, biological, and toxic pollutants) guidelines. We relied on water quality indices (WQI) to interpret multiparametric properties of the collected rainwater from urban surfaces; consequently, the quality of the harvested water was categorized with moderate to almost good attributes. This makes it well suited for irrigation uses, which can play a relevant role against water shortages in the analyzed semiarid urban region. Otherwise, infiltration and treatments need to be performed if using harvested water for drinking consumptions (of human or livestock), some of which may be costly for local owners/uses. We provide some suggestions for improving efficiency of the system and enhancing the quality of the harvesting water.

中文翻译：

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中东半干旱城区雨水收集与利用的可行性

中东大都市的最新发展以及相关的人口增长趋势与气候变化的影响是同时发生的。这对集中式大型水处理和分配系统施加了额外的压力。用于国内城市活动的雨水收集 (RWH) 可以成为适应此类干旱/半干旱地区对软水不断增长的需求的可持续选择。为缓解伊朗第二大城市马什哈德的部分软水短缺问题，建造了雨水排放和储存试点系统。在排水池出口和储水箱内部收集了两年的测量数据，该储水箱已配备用于集水目的。我们进行了一些初步的随机分析并评估了收集到的数据集的概率特性，旨在就 RWH 系统的物理特性对它们进行解释。数据聚类分析证实，在雨水排放和储存在 RWH 池中的过程中，水的质量可能会发生变化。特别是，排水集水区采样水的钠含量显示出更高的变化，与对蓄水池中存储的水进行评估的相比。这可以证实 RWH 水库中储存的水的质量比每个单独的降雨-径流事件获得的质量更稳定。根据一些国家和国际水质（物理化学、生物和有毒污染物）指南，我们评估了不同消费环境下收集水的潜力。我们依靠水质指数 (WQI) 来解释从城市表面收集的雨水的多参数特性；因此，收集的水的质量被归类为中等至几乎良好的属性。这使得它非常适合灌溉用途，在所分析的半干旱城市地区，它可以在应对水资源短缺方面发挥相关作用。否则，如果将收获的水用于饮用（人类或牲畜），则需要进行渗透和处理，其中一些对当地所有者/用途而言可能是昂贵的。我们为提高系统效率和提高收集水的质量提供了一些建议。这使得它非常适合灌溉用途，在所分析的半干旱城市地区，它可以在应对水资源短缺方面发挥相关作用。否则，如果将收获的水用于饮用（人类或牲畜），则需要进行渗透和处理，其中一些对当地所有者/用途而言可能是昂贵的。我们为提高系统效率和提高收集水的质量提供了一些建议。这使得它非常适合灌溉用途，在所分析的半干旱城市地区，它可以在应对水资源短缺方面发挥相关作用。否则，如果将收获的水用于饮用（人类或牲畜），则需要进行渗透和处理，其中一些对当地所有者/用途而言可能是昂贵的。我们为提高系统效率和提高收集水的质量提供了一些建议。