CGWB - Publications and Media Warehouse
Category | Artificial Recharge |
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State | All |
District | All |
Block | All |
Year of Issue | 2007 |
Number of Authors | 1 |
Name of Authors | CGWB CHQ Faridabad |
Keywords | Introduction, Water Resources Development Scenario, Artificial Recharge of Ground Water, Source Water, Planning of Artificial Recharge Schemes, Artificial Recharge Techniques and Designs, Roof Top Rainwater Harvesting, Impact Assessment, Economic Evaluation of Recharge Schemes, Operation and Maintenance. |
File | Download |
A ‘Manual on Artificial Recharge of Ground Water’, providing detailed guidelines on investigative techniques for selection of sites, planning and design of artificial recharge structures, monitoring and economic evaluation of artificial recharge schemes was brought out by Central Ground Water Board in 1994. It also included elaborate case studies and field examples of artificial recharge schemes from different parts of the world. The manual has been used extensively for planning and implementation of schemes for augmentation of ground water resources by various agencies. Subsequent to the publication of the manual, Central Ground Water Board has brought out five publications on the topic in an attempt to disseminate the experiences gained during various ground water augmentation projects implemented by the Board in the country. Water Resources Development Scenario- India’s agricultural output comes from areas irrigated with ground water. Because agriculture and allied activities contribute roughly 30 percent of India’s Gross Domestic Product (GDP), with crops accounting for three- fourths of this, the contribution of ground water (with a package of associate inputs) to India’s GDP is about 9 percent. The relation between new technology and ground water development has been two-way. Not only has ground water irrigation helped to spread new technology, some of the profits earned through new technologies have been ploughed back into ground water development, leading to the well- known “tub well explosion” in northwest India. Artificial Recharge of Ground Water- Artificial recharge aims at augmenting the natural replenishment of ground water storage by some method of construction, spreading of water, or by artificially changing natural conditions. It is useful for reducing overdraft, conserving surface run-off, and increasing available ground water supplies. Recharge may be incidental or deliberate, depending on whether or not it is a by-product of normal water utilization. Source Water-Availability of source water is one of the basic prerequisites for taking up any artificial recharge scheme. The source water available for artificial recharge could be of the following types as Insitu precipitation in the watershed / area, Nearby stream/ spring / aquifer system, Surface water (canal) supplies from large reservoirs located within the watershed/basin, Surface water supplies through trans-basin water transfer, Treated Municipal/industrial wastewaters, Any other specific source(s). Planning of Artificial Recharge Schemes- The area involved in artificial recharge projects may range from a watershed, a limited area covering an urban, rural or industrial centre or administrative units like Mandal/Block to large basins or larger administrative units like Districts/States. Though the steps involved in planning are essentially the same, the planning is done on different scales as per the required objectives and the area involved. Thus, planning of recharge scheme may be done at Mega level (State or Basin level), Macro level (District or sub-basin level) and Micro level (Block or Watershed level) at progressively larger scales. It is advisable to do State/Basin level planning at 1: 2000,000 scale, District / Sub-basin level planning at 1:250,000 scale and Block / Watershed level planning at 1:50,000 scale and so on. Artificial Recharge Techniques and Designs- The selection of a suitable technique for artificial recharge of ground water depends on various factors. They include: Quantum of non-committed surface run-off available, Rainfall pattern, Land use and vegetation, Topography and terrain profile, Soil type and soil depth, Thickness of weathered / granular zones, Hydrological and hydrogeological characteristics, Socio-economic conditions and infrastructural facilities available, Environmental and ecological impacts of artificial recharge scheme proposed. Impact Assessment- Artificial recharge structures are constructed mostly with the objective of augmenting ground water resources and/or to improve its quality. Assessment of impacts of the artificial recharge schemes implemented is essential to assess the efficacy of structures constructed for artificial recharge and helps in identification of cost-effective recharge mechanisms for optimal recharge into the ground water system. It also helps to make necessary modifications in site selection, design and construction of structures in future. Impact assessment may require monitoring of the recharge structure, ground water regime, changes in pattern of water supply, cropping pattern, crop productivity and/or water quality. In recent years, tracers such as Tritium, Rhodomine B, fluorescent dyes and environmental isotopes are also being used for demarcating the area benefited by artificial recharge structures. Operation and Maintenance- Periodic maintenance of artificial recharge structures are essential because infiltration capacity reduces rapidly as a result of silting, chemical precipitation and accumulation of organic matter. In case of surface spreading structures, annual maintenance consists of scraping the infiltration surfaces to remove accumulated silt and organic matter. In the case of injection wells, periodic maintenance of the system consists of pumping and /or flushing with a mildly acidic solution to remove encrusting chemical precipitates and bacterial growths on the well screens. The intervals between periodic cleanings can be extended by converting injection wells into dual purpose wells. However, in the case of spreading structures constructed with an overflow or outlet mechanism, annual desilting is a must. Structural maintenance is normally carried out either by government agencies or through initiatives of stakeholders. Several issues are to be considered in the operation and maintenance of artificial recharge structures. These have been categorized as issues of high concern and moderate concern (ASCE, 2001). Safety, optimization's techniques and programs, value of wet-dry cycles, frequency of pond cleaning and condition of filters attached to the structures fall under issues of high concern, whereas security issues and rising ground water levels are among those of moderate concern in this regard.