By Mr. M Mehta, Former Commissioner, Ministry of Water Resources Govt. of India, New Delhi
More than 46 years of experience in planning, implementation monitoring and supervision of projects/schemes related to ground water exploration/development, Rain Water Harvesting and Artificial Recharge to Ground Water and Minor Irrigation, Policy planning at National & State level. During the last 46 years worked in varied climatological & hydro-geological situations covering deserts, humid areas, hilly areas of Himalayas and trans Himalayas, hard rock and alluvial terrain. During this period developed indigenous technology and design for rain water harvesting and Artificial recharge to ground water. Also having administrative experience for Human Resources Development, technical monitoring and planning since worked as Director Administration and Regional Director (HQ) Central Ground Water Board & Commissioner Ministry of Water Resources, Govt. of India. Developed specialization in Rain Water Harvesting and Artificial Recharge to Ground Water. Implemented various schemes including at President Estate, New Delhi, Golden Temple, Amritsar, largest Recharge Shaft (300 m) in Dhuri Drain, Punjab, etc.
*Principal Advisor, India Water Foundation Australia Chapter
Abstract: Over the past two decades, ground water has assumed the role of primary source of water for drinking, domestic, agriculture, industries etc in India. This is evidenced in the fact that ground water as the source for rural drinking purposes ranges from 50 to 91% while for agriculture, it ranges from 40 to 60% in various States. Productivity of irrigated areas using ground water is significantly higher than from use of surface water sources. The adverse implications are that the stage of ground water development is ever increasing due to increasing use of ground water reflected as 40 to 90%, and importantly, the water levels are also declining in some parts at an alarming rate, i.e. at greater than 3 meters per year. In some pockets, the stage of development has reached even 300%.
Both the government and the civil society have responded to the groundwater challenges in a variety of ways. The primary approaches include augmenting the natural rainfall recharge, rain water harvesting and artificial recharge measures. The governments too have designed programs to promote water harvesting. Various public and private agencies are involved in ground water recharge programs by need or compulsion as the case may be and the impact is also being reflected in the changing trend of ground water levels especially in Gujrat and Andhra Pradesh. However, water quality standards for recharging water is required to be worked out to prevent ground water contamination due to recharge as well as utilized the available large quantum of waste and effluent water in different sectors such as Municiple, Industries, Mining etc. There is a need to develop BIS standards for from quality of source water which should be allowed to recharge ground water.
BACKGROUND
Ground Water is the primary source of water for drinking, domestic, agriculture, industries etc in India. Dependence on ground water for drinking ranges from 50 to 91% in rural areas while it caters the need of agriculture 40 to 60% in various states. Ground water gives the higher productivity in comparison to areas irrigated from surface water sources. Thus sustainable management of ground water resources is fundamental importance for the country. The stage of ground water development in various states rages from less than 50 to more than 80 % and water levels are declining in some parts at an alarming rate i.e. more than 2m/yr. In some isolated pockets the stage of development has reached to even more than 300%.
Traditionally Rainfall is the major source of ground water recharge, which is supplemented by other sources such as recharge from canals, irrigated fields and surface water bodies. The rainfall is unevenly distributed. The amount of ground water withdrawal and situation of low rainfall are factors responsible for overall stress on ground water. Groundwater resource management is not a new field of activity; some aspects have been practiced for a long time in our country. Such practices have been developed one by one with time whenever the need arose, sometimes without fully recognizing the principles of ground water management. A wealth of professional creativity, however, has been accumulated in the numerous approaches and tactics for water management that have been developed over the years in several parts of the world.
Ground water resources development and related engineering activities have gained paramount importance as the risks from pollution to resource have increased year after year. As a result, the interferences are becoming more and more pronounced which brings about a growing need for integrated management of the resources with special reference to the water quality.
The challenge to manage the ground water resources cannot be solved only by augmenting the natural rainfall recharge or even by Rainwater harvesting and artificial recharge. We have to look new avenues for water which is going waste and to be harvested and recharge to ground water. Over the years the ground water resources are depilating due to which the water levels are declining and the quality is also deteriorating. Realizing the seriousness of the, Central Ground Water Board, Ministry of Water Resources, prepared the “Perspective Plan for Artificial Recharge” followed by “ Master Plan for Artificial Recharge Plan” and presently in the process of revising State wise master plan for artificial recharge.
The artificial recharge was addressed at National level in last four plans and even the BIS had also prepared the guide lines for Rain Water Harvesting and Artificial Recharge. Considering the need, CGWB had prepared the document “Guide to Artificial Recharge”. However, so far little attention was paid about the quality of source water and also about the native ground water. The attempts for artificial recharge, so far has been towards popularizing the concept of artificial recharge to ground water and Roof top rain water harvesting but little for other catchment areas. The rate at which the ground water is being exploited and declining of ground water levels, resulting in to failure of tube wells and increase in energy consumption. The situation now warrants for new avenues of artificial recharge which are available. The paper deals mainly with such aspects for which guide lines have to be prepared.
NEW SOURCES OF ARTIFICIAL RECHARGE TO GROUND WATER
Natural replenishment of ground water reservoir is a slow process and is often unable to keep pace with the excessive and continued exploitation of ground water resources in various parts of the country. Water conservation and artificial recharge to ground water efforts are basically aimed at augmentation of the natural movement of surface water into ground water reservoir through suitable engineering construction techniques. Such techniques inter-relate and integrate the source water to ground water reservoir and are dependent on the soil, topography and hydrogeological situation of an area. Occurrence of rainfall in NCR is mostly limited to about three
months in a year, with the number of rainy days ranging from around 80 to 100. The natural recharge to ground water reservoir is restricted to this period only in a major part of the country. Artificial recharge techniques aim at extending the recharge period in the post-monsoon season for about three or more months, resulting in enhanced sustainability of ground water resources during the lean season.
Evolving a groundwater recharge strategies with an appreciation of the variety of factors that can contribute through various kinds of recharge structures are to be meticulously be looked in to. Harvesting of rain water and excess monsoon runoff which is going unutilized, to create additional ground water storage is the most attractive and technically feasible option. However, beside this several other sectors generating sources water such as municipal waste water, Industrial waster water, abandoned mining pits, roads and highways, parks etc. are some of the catchments which can also be utilized for source water for recharge.
The sub surface reservoirs can store substantial quantity of water. Artificial recharge aims at augmenting the natural replenishment of ground water storage by methods 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 bye-product of normal water utilization. The process of supplementing may be either planned such as storing water in pits, tanks etc. for feeding the aquifer or unplanned and incidental to human activities like applied irrigation seepage from canal, lakes and ponds as well as leakages from pipes etc.
As a matter of fact, artificial recharge is a process of induced replenishment of ground water reservoir by human activities.
Harnessing Sewage water
A large percentage of sewage water can be beneficially harnessed for reuse after appropriate treatment. World over, several countries have developed techniques and technologies for such reuse; in addition to reuse, such water is also recharged into the ground for later recovery, the technique being called as the Aquifer Storage and Recovery. The degree of treatment may vary depending upon the purpose. Standards for quality of treatment levels are also developed. In India too, there is a dire need to put in place standards for reuse and recharge for different levels of quality immediately.
There are several sewage treatment plants that have recently come up in Yamuna basin of NCR areas. Presently only a part of urban sewage gets treated. It varies from 2.92 MCM/ year to 91.25 MCM/ year. NCT of Delhi produces 539.47 MCM/ year of sewage. This treated sewage is primarily being used for irrigation in most of the districts of NCR.
For example, in Delhi, 7.3 MCM/ year (20 MLD) of treated sewage from sewage treatment plant is being used by Indraprasth Thermal Power station. Remaining 7.3 MCM/ year (20 MLD) Sewage Treated water is being used for Horticulture at Rashtrapati Bhawan. Similarly, treated sewage from Vasant Kunj sewage treatment plant is being used by DDA for Horticulture. In addition to this, MoEF plans to set up the pilot scale STP (YAP – II) at Keshavpur wherein the effluent of STP will comply with drinking water standards.
This quantity of treated sewerage will increase with time. As per information, due to improvement in sanitation infrastructure, approximately 90% of urban and 30 % of rural sewage will get treated by 2021. The quantity of available treated sewage is summarized in table 1 below.
Table 1: Quantity of Treated sewage in different sub-regions of NCR.
Quantity of Treated Sewage in MCM/ year
Sl. No Sub-Regi Presently 2011 2021
1 Haryana 113.16 360.56 444.49
2 Rajasthan 0 93.49 124.60
3 Uttar-Pradesh 136.37 549.64 674.54
4 NCT Delhi 539.47 1741.64 2029.85
Total NCR 789 2745.33 3273.48
Source : WAPCOS Report on NCR
Sewage water can be properly treated and either directly used and/or recharged in the areas where the stage of ground water development is very high. Suitable quality criteria to be developed especially for Artificial Recharge. Further the treated water can be used for flushing for which suitable technology with dual piping to be developed
Abandoned Quarries
Mining is a huge activity across many States in India. Open cast mining in particular offers huge opportunity for recharge into ground after appropriate treatment, or for locally relevant purposes. Standards need to be developed for such uses and for recharge. Haryana and Rajasthan and part of NCT Delhi sub-region is characterized by quartzites ridges of Aravali range. From years together the rock and sand mining activity was taking place in these areas. Now after intervention of Hon’ble Supreme Court the mining activity has been banned. As a result of mining activity abandoned queries in form of large cavity and depressions have been created. In mining areas for excavation of sand and rock material heavy pumping of ground water has been made. Huge water is available in abandoned and also in open cast mining pits. This water can be used for recharge by converting the pits as recharge structures and/or by constructing the recharge structures. The unused abandoned queries can be utilized for recharge to ground water after making certain modifications. The depressions will be used as storage spaces where rain water will be stored. Revival and channelization of drainage around such abandoned queries by construction of embankments & modifications in surface drainage towards these depressions will provide surface storage of rain water during monsoon period.
As the quartzites are already fractured and jointed most of the water will automatically gets recharged to ground water. At places were fractured, weathered and jointed quartzites are not present recharge shafts will be constructed to the depth of existent fractures in sub surface which will facilitate the augmentation of ground water aquifers.
Recharge from Mega Urban Structures
In urban areas mega structures like flyover, Airports, Stadium etc. covers huge area with concrete and prevents natural recharge to take place. Such giant civil structures generates large amount of surface runoff during the rains because of their runoff coefficient range varying from 0.6 to 0.8. In order to provide a conduit to rain water to reach to aquifer certain recharge structures should be constructed in the vicinity of these mega civil structures.
From the road surface lot of runoff goes waste through storm water drains. To harness available runoff, either trenches or shafts with recharge wells are constructed in series along the road side at a spacing of 100 to 300 m depending upon the availability of runoff. In Delhi 45 Flyovers and
26 Subways projects have been executed or being executed. These flyovers will generate enormous amount of surface runoff. The available runoff from the flyovers can be harvested by making shaft or trenches with recharge wells along the storm water drains.
Trenches with length up to 20 m can be constructed with two or more than two recharge tube wells. Generally these trenches are recommended tapping runoff generated from whole campus/catchment of areas ranging from 10000 sq.m to 40000 sq.m. As the runoff from the whole catchment consists of lot of silt, the same can be removed by constructing a de-siltation chamber. If the trenches are constructed in storm water drains where the polluted water is expected during the lean period or non-monsoon months, a bye pass arrangement may be made so that no polluted water enters into the recharge trenches.
Waste Water Recharge
Drinking water supply is a top priority for all states in India and the Central government. Efforts to realise this has led to construction of innumerable GLRs which are also sources of waste water of 3000-5000 litres /day per site; hand pumps are another such source of waste water where around 500 litres /day is estimated to go waste from each HP. Recharge standards should include suitable guidelines to harness such unavoidable waste water.
Treated wastewater reuse is conventionally carried out through direct application and/or mixed with fresh surface water wastewater in irrigation. Another way of reusing wastewater is through Artificial Recharge (AR) of the aquifer system with partially treated wastewater. Where soil and groundwater conditions are favorable, a high degree of upgrading can be achieved by allowing waste water after necessary treatment to infiltrate into the soil and move down to the groundwater. The unsaturated zone then acts as a natural filter and can remove essentially all suspended solids, biodegradable materials, bacteria, viruses and other microorganisms. Significant reductions in nitrogen, phosphorus, and heavy metals concentrations can also be achieved. This gives an advantage of AR with wastewater over the direct application method. This process is known as Soil-Aquifer Treatment (SAT). Another advantage of AR over application of
waste water is the fact that water recovered from an AR system is not only clear and odor-free but also comes from a well, drain or via natural drainage to a stream or low area, rather than from a sewer or sewage treatment plant.
Hydrogeological considerations: Based on other recharge experiments (i.e. fresh water recharge) in many of the western countries, the following intrinsic characteristics of the aquifer were recommended to ensure successful basin recharge operations. These recommendations were slightly modified to form the required hydrogeological criteria for the selection of possible application locations.
A minimum of 18m depth to the groundwater was required to allow for geo-purification processes (i.e. filtration, adsorption, etc.) before the infiltrating water reaches the groundwater. This depth also allows for groundwater mounding during the recharge process without affecting the infiltration process. The unsaturated zone must realize an infiltration rate not less than 0.25 m/day.
High values of saturated zone transmissivity and porosity are recommended to prevent water mounding below the basin bottom that can cause a decrease in infiltration rate and recharge capacity (effective porosity > 0.1, and transmissivity > 500 m3/day). Aquifer characteristics downstream the recharging sites must have good hydrogeological conditions to allow water recovery at the desired rates.
Planning considerations: Water resources plans can be developed considering Waste water & sewerage water reuse as a source for irrigation water. Accordingly, replacement of river water by recharged sewage water for irrigating existing or planned reclamation lands can be the main criterion for the selection of possible sites for Artificial recharge through wastewater.
Environmental and health safety considerations: Detailed environmental impact assessments should be carried out for each of the individual sites before the application that will include mitigation and monitoring plans. However, for the purpose of the general selection of sites, two factors were taken into considerations. Firstly, the site should not be within or upstream of a groundwater-drinking community, and secondly, no recharge should be considered where groundwater is flowing into the River.
▪ Artificial recharge through Waste water can be an added dimension for the reuse policies. The technique has far superior advantages over the direct application of treated wastewater. However, restrictions and precautions should be imposed to prevent a damaging impact on the groundwater.
▪ The framework included possible locations, amounts of available wastewater for these locations, general environment and health safety considerations, recharge method, and range of applications. Artificial recharge through waster water application should be restricted to basin recharge which to be used for irrigation purposes in the reclaimed areas.
▪ Due to the presence of thick clay cap and the dependence on groundwater for drinking hydro geologically unsuitable areas and regions should be excluded from the artificial recharge through waster water plans.
▪ Columns experiments to be conducted to study the processes that take place during the infiltration of treated wastewater through the unsaturated zone and to estimate the attenuation capacity of the soil at the location selected for the experimental scale basin recharge.
Recycling and Reuse of water
Water recycling is an essential component of managing our water resources efficiently and making the most of a resource that is often wasted. Water recycling adopts the concept of using water that is ‘fit for purpose’. In practice this means using high quality water for drinking and other personal uses, but not necessarily for purposes where alternative water sources can be safely used, such as toilet flushing, garden watering and crop irrigation.
The world’s population is expected to increase manifolds in the couple of decades -and with this growth will come an increased need for water to meet various needs, as well as an increased production of wastewater. Moreover, there has been significant decline in runoff in the surface water catchments and recharge to groundwater resources, in general. This has increased pressure on the water resources in the area.
Many areas throughout the world are approaching, or have already reached, the limits of their available water supplies. This subsection details out the recycle or reuse of wastewater with the sole objective to minimize the water demand during the operation phase of the project.
Benefits: The benefits of water reuse and recycling are:
▪ Lower use of drinking water resources
▪ Less fresh water extracted from rivers/groundwater for irrigation
▪ Less wastewater discharged into our rivers and stream channels
▪ Potential to release recycled water (instead of drinking water) to mimic natural environmental river/stream flow
Application: Quantity and quality requirements are considered for each reuse application, as well as any special considerations necessary when reclaimed water is substituted for more traditional sources of water. The common key elements of water reuse are supply and demand, treatment requirements, storage, and distribution. There are a number of practical options for using recycled water which is as listed below.
Urban Reuse: Urban reuse systems provide reclaimed water for various non-potable purposes including:
▪ Irrigation of parks and recreation centers, athletic fields, school yards and playing fields, highway medians and shoulders, and landscaped areas surrounding buildings and facilities
▪ Irrigation of landscaped areas surrounding residences, general wash down, and other maintenance activities.
▪ Irrigation of landscaped areas surrounding commercial, office, and industrial developments
▪ Ornamental landscape uses and decorative water features, such as fountains, reflecting pools, and waterfalls
▪ Dust control and concrete production for construction projects
▪ Fire protection through reclaimed water fire hydrants
▪ Toilet and urinal flushing in commercial and industrial buildings
Water reclamation facilities must provide the required treatment to meet appropriate water quality standards for the intended use. In addition to secondary treatment, filtration, and disinfection are generally required for reuse in an urban setting. Because urban reuse usually involves irrigation of properties with unrestricted public access or other types of reuse where human exposure to the reclaimed water is likely, reclaimed water must be of a higher quality than may be necessary for other reuse applications.
Recreational Reuse: Uses of reclaimed water for recreational purposes range from landscape impoundments, water hazards on golf courses, to full-scale development of water-based recreational impoundments, incidental contact (fishing and boating) and full body contact (swimming and wading). As with any form of reuse, the development of recreational water reuse will be a function of a water demand coupled with a cost-effective source of suitable quality reclaimed water.
Playing fields and parks: Recycled water can be used in playing fields, parks and golf courses where usually large quantities of water is required. Replacing this supply with recycled water can be practical and offers significant benefits.
Horticulture/Agriculture: Horticulture and agriculture can be significant user of water. Using recycled water for irrigation is possible and could provide significant reuse of the nutrients contained in recycled water. Recycled water is currently used to irrigate horticultural and orchard crops in some industrial setups.
Abandoned wells
The non performing water assets in the form of tubewells and dugwells exist in millions across the country. These abandoned Hand pumps and tube wells can be used as recharge wells after proper cleaning/development and constructing a recharge pit with de-silting chamber along with them. These wells have proper connectivity with ground water aquifers which got de-saturated with depletion of ground water levels. They offer a huge opportunity to be converted into recharge structures. Therefore an effective recharge through these wells takes place. Similarly, the runoff from the large (ever increasing) network of roads, and open fields should also be considered as sources of recharge and standards developed. One requirement is to improve upon the road design, and incorporate recharge structures at regular intervals to harness the road run off through appropriate maintenance-free filter system.
GUIDELINES FOR MANAGED AQUIFER RECHARGE
India should develop Guidelines for Managed Aquifer Recharge (MAR). The Guidelines for protecting human health and the environment at Managed Aquifer Recharge operations, for all types of recharge method, source water, aquifers and all types of uses of recovered water. The Guidelines should show how to evaluate safety parameters, due to the wide range of conditions encountered. The strategy as part of MAR shall be to trap the flash floods and other runoff going as rejected water overtopping the surface water bodies into the subsurface and store them in the space provided by dewatered aquifers.
Recharge methods include the conventional and innovative method both using th available sources water recharging into the aquifers. Thus MAR includes direct aquifer recharge for safe storage or aquifer recharge followed by abstraction in times of stress using the same well or bore well through which it is recharged. Pyne (1995) states that MAR may be used as a means of storing water underground in times of surplus to meet need in times of demand.
The successful operation of MAR will depends largely on an effective participation of the farmers, and stakeholders through appropriate management strategy and on the availability of sufficiently skilled or competent staff to carry out the necessary tasks. Maximum benefit from the programme usually involves integrating with planning and management of overall water supply within the entire groundwater basin. This includes optimising both surface and groundwater resources and their storage capacities.
Recycling of Sewage Water-STP to be implemented at in city/urban area level by civic authority and at the level of societies, big establishments through concerns associations. The technology is well developed and available however it is to be recognized by govt. aftr developing certain standards for the same. This treated sewage water can be used for flushing purposes, parks, lawns, car wash, paved area in societies washing, construction activity etc. Results in a saving up to 40-50% of total water supply, e.g. in Jaipur about 40% of 300 MLD = 120 Million liters per day can be saved. While developing guidelines following aspects can be kept in mind to facilitate formulation of effective strategies.
Relevant changes in building by-laws and urban planning
Make Reuse of urban wastewater mandatory through dual piping system for flushing, parks, lawns etc. after treatment
Mandatory STP for commercial establishments, hospitals, educational institutions and private/government townships, and all other bulk water users.
Floods as potential groundwater recharge source in western Rajasthan
Storm water harvesting in urban areas
Preparedness Plans to harness periodic excessive rainfall events
Conversion of abandoned mines and quarries as recharge structures
Conclusion:
The need is to make groundwater sustainability a national issue on par with development of surface water resources. The approach should be to graduate from the conventional thinking of containing groundwater development through legislations and licenses for restricting the mushrooming of borewells to resource conservation, flood flow management and rehabilitation of already existing structures.
A new approach of looking “Beyond wells & borewells” is required. The new approach while not ignoring the necessity of producing food through new investments in borewells/tube wells will aim at producing food keeping in focus groundwater sustainability issues. This new approach should look at groundwater development from a societal context and ensure those society aspirations from the groundwater sector.
Unless more challenging measures are adopted, we will not be in a position to tackle the ever increasing water scarcity. While preparing the guide lines and design criteria, local hydrogeology has to be considered and also the quality aspects of source water and its long term impact on ground water. Even if the harvested water is directly used either for irrigation or for domestic purposes (flushing), it will reduce the stress on ground water as water demand will be reduced. The guide lines so prepared, should be translated in local languages and wide publicized so that common people can understand and implement.
