Department of Irrigation and Hydraulics Engineering, Faculty of Engineering, Tanta University, Tanta, Egypt.
Department of Civil Engineering, Higher Institute of Engineering and Technology, Kafr El-Sheikh, Egypt.
Environ Sci Pollut Res Int. 2020 Sep;27(26):32304-32317. doi: 10.1007/s11356-019-06529-5. Epub 2019 Oct 22.
Egypt's limited water resources, rapid population growth, and climate change are increasing the gap between water demand and supply. Meanwhile, significant amounts of rain fall in some regions in Egypt during specific storm events, which in some cases, lead to disasters like flash floods and inundations. Rainwater harvesting (RWH) can be considered as a sustainable promising solution to water shortage and inundation problems. In this work, the feasibility of RWH for urban areas was assessed over 22 cities throughout Egypt. Results show that the annual volume of rainwater harvested can reach 142.5 MCM in the considered cities, provided that all rain falling on the urban areas is collected. High potential of rainfall harvesting was found for cities that located on the North Coast, e.g., the potential water saving from the share of RWH in Alexandria can satisfy around 12% of its future supplementary domestic water needs. In contrast, rainfall over the cities located on the middle and the south of the country is insignificant to be harvested. A case study for the 5th settlement region in Cairo was discussed in terms of groundwater recharge and surface runoff estimation for two conditions: No-RWH and RWH systems by implementing recharge wells to store rainwater into the aquifer. Land cover classification maps of urban areas were created by using the ARCGIS software to estimate equivalent infiltration coefficients. The results demonstrate that the implementation of such RWH system has a significant impact on the regional water cycle, where the effective infiltration coefficient increased from 10% (No-RWH) to 75% (RWH) in the case study. Accordingly, the runoff coefficient decreased in the case study from 0.8 (No-RWH) to 0.15 (RWH), and the volume of runoff decreased in the case of RWH by around 82% lower than that of the No-RWH condition. Thus, direct infiltration of RWH into an aquifer can play an important role in sound water management for urban environments, as this may lead to a significant reduction in risks of flooding and expenses of municipal drainage systems installation and operation.
埃及有限的水资源、快速的人口增长和气候变化正在扩大水需求和供应之间的差距。与此同时，埃及的一些地区在特定的风暴事件中会有大量降雨，这些降雨有时会导致洪水和泛滥等灾害。雨水收集（RWH）可以被认为是解决水资源短缺和泛滥问题的一种可持续的有前途的解决方案。在这项工作中，评估了雨水收集在埃及 22 个城市的可行性。结果表明，如果收集所有降落在城市地区的雨水，那么每年可以从考虑的城市中收集 142.5 立方米的雨水。位于北部海岸的城市具有很高的雨水收集潜力，例如，从雨水收集份额中节约的水可以满足亚历山大里亚未来 12%左右的补充国内用水需求。相比之下，该国中部和南部地区的降雨量则微不足道，无法收集。本文以开罗的第 5 定居区为例，讨论了在两种情况下（不采用雨水收集系统和采用雨水收集系统），通过实施蓄水井将雨水注入含水层，对地下水补给和地表径流的估算：采用雨水收集系统。利用 ARCGIS 软件创建了城市地区的土地覆盖分类图，以估计等效渗透系数。结果表明，实施这种雨水收集系统对区域水循环有重大影响，在研究案例中，有效渗透系数从 10%（不采用雨水收集系统）增加到 75%（采用雨水收集系统）。因此，研究案例中的径流系数从 0.8（不采用雨水收集系统）降低到 0.15（采用雨水收集系统），采用雨水收集系统的情况下，径流体积降低了约 82%，低于不采用雨水收集系统的情况。因此，雨水收集直接渗透到含水层中可以在城市环境的健全水资源管理中发挥重要作用，因为这可能会显著降低洪水风险和市政排水系统安装和运营的费用。
