Data interpretation of water through water harvesting in India
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Abstract
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.
Step-by-step explanation:
Effectiveness of in-situ water conservation through rainwater harvesting is a function of an interaction between the climate, soil and plant properties. Biological methods of water harvesting, such as vegetative barriers and agroforestry barriers, are cost-effective. Conditions and design criteria for different in-situ rainwater harvesting measures are discussed in the paper. In-situ water harvesting through full moon terracing, coupled with moisture conservation through paddy straw mulching has been found to be beneficial for litchi in uplands. Rainwater harvesting in watershed and multi-tier horticulture model are also discussed.