Impact of rainwater harvesting in India on groundwater quality with specific reference to fluoride and micropollutants.

地下水是世界许多地方淡水的主要来源，但过度抽取地下水正在导致一些地方的地下水位持续下降。在印度西部的拉贾斯坦邦，正在利用各种方法补充地下水，提供可靠的供水。这是通过几种方式实现的，包括使用雨水收集（RWH）系统。这些结构收集雨水和径流，使其渗入地下，随后渗入含水层。在印度，这是通过传统的方法实现的，如在渗滤池和淤地坝中蓄水。还探讨了使用沙坝等更新颖的新方法。沙坝是一种横跨季节性河床的混凝土墙。在雨季，一条季节性河流形成，并携带沙子顺流而下。沙子在大坝后面堆积，充满了水，提供储存，这些水可以被提取或渗透到地下水中。虽然这些技术增加了水的可用性，但它们对地下水质量的影响尚不清楚。根据RWH结构的规模和位置，其中包含的雨水可能含有一系列有害物质。此外，在拉贾斯坦邦，地下水中的高氟化物浓度是一个主要的健康问题。饮用水中过量的氟会导致氟斑牙和氟骨症。这一问题可能会恶化，因为溶解有机物（DOM）存在于收集的雨水，已被发现增加氟含量在recharge.因此，RWH结构中的污染物和DOM的传输分析是至关重要的，在确保地下水质量。这种输送可能受到许多不同因素的影响，最明显的是这些建筑物的设计和位置。将进行为期两年的实地调查，以监测三个RWH建筑物附近用于补给和地下水的水质。这将包括地形测量、地下水位监测、水取样、示踪剂测试、天气记录和获取土壤样本，以提供关于含水层物质矿物特性的资料，此外，还将完成对从实地获取的水样本的实验室测试。将使用各种技术评估雨水和地下水的质量。测试的参数将包括营养素、大肠杆菌、重金属和药物等。为了加深我们对雨水中存在的DOM对地下水中氟化物水平的影响的理解，我们将使用荧光激发-发射矩阵（F-EEM），建立污染物传输模型，模拟RWH结构和整个集水区中污染物传输和DOM与氟化物的相互作用。这些将被编码在印度常用的开源软件中。由于是开源的，这些代码可以很容易地修改，以添加新的或修改现有的过程，以调查可能影响水质的特定情况。他们也可以被任何人使用，因此其他从业者或学者可以在这个项目的工作基础上进行开发。利用实地工作，实验室分析和建模模拟。基于这项研究的建议将包括：-结构的深度和大小以及抽象和提取点。季风事件后地下水抽取事件的时间、持续时间和速率。

Groundwater is the main source of fresh water in many parts of the world however excessive abstraction is causing a continuous decrease in water tables in some places. In Rajasthan on the Western side of India, methods are being utilised to replenish groundwater and provide a reliable water supply. This is achieved in several ways including the use of Rainwater Harvesting (RWH) systems. These structures capture rainwater and runoff and allow it to infiltrate into the subsurface and subsequently aquifers. In India this has been achieved both through traditional approaches such as storing water in percolation ponds and in check dams. The use of more novel emerging approaches such as sand dams has also been explored. A sand dam is a concrete wall built across a seasonal riverbed. During the rainy season, a seasonal river forms and carries sand downstream. The sand accumulates behind the dam and is filled with water providing storage, this water can then be abstracted or percolate into the ground water.Although these techniques increase water availability it is unclear as to their effect on groundwater quality. Depending on the scale and location of RWH structures, rainwater contained within them may contain a range of harmful substances. These pollutants could travel through the RWH structures and contaminate the groundwater.Additionally, in Rajasthan, high fluoride concentrations in the groundwater are a major health concern. Excessive fluoride in drinking water causes dental and skeletal fluorosis. This problem may be worsened as dissolved organic matter (DOM) present in harvested rainwater which has been found to increase fluoride levels during recharge.The analysis of the transport of pollutants and DOM in RWH structures is thus of crucial importance in ensuring groundwater quality. This transport can be effected by a number of different factors most notably design and location of these structures.The fieldwork will be carried out to monitor the water quality used for recharge and groundwater in the vicinity of the three RWH structures over a period of two years. This will include topographical surveys, groundwater level monitoring, water sampling, tracer testing, weather recording and obtaining soil samples to provide information on the mineral characteristics of the aquifer material.In addition laboratory testing will be completed on water samples obtained from the field. The quality of the rainwater and groundwater will be assessed using a variety of techniques. Parameters tested will include nutrients, e.coli, heavy metals and pharmaceuticals amongst others. To enhance our understanding of the impact of DOM present in rainwater on Fluoride levels in groundwater, fluorescence excitation-emission matrix (F-EEM) will be used.Pollutant transport models which simulate pollutant transport and DOM interaction with fluoride in RWH structures and across the whole catchment will be created. These will be coded in open-source software that is commonly used in India. Being open source, these codes can be easily modified to add new or modify existing processes to investigate particular scenarios which may impact water quality. They can also be used by anyone so other practitioners or academics can build on the work of this project.Utilising field work, laboratory analysis and modelling simulations. Recommendations based on this research will include:- Depth and size of structure and abstraction and extraction points.- Timing, duration and rate of groundwater abstraction events after monsoon events.