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3.10 Artificial Recharge of Groundwater
Artificial recharge is the planned, human activity of augmenting
the amount of groundwater available through works designed to increase the
natural replenishment or percolation of surface waters into the
groundwater aquifers, resulting in a corresponding increase in the amount
of groundwater available for abstraction. Although the primary objective
of this technology is to preserve or enhance groundwater resources,
artificial recharge has been used for many other beneficial purposes. Some
of these purposes include conservation or disposal of floodwaters, control
of saltwater intrusion, storage of water to reduce pumping and piping
costs, temporary regulation of groundwater abstraction, and water quality
improvement by removal of suspended solids by filtration through the
ground or by dilution by mixing with naturally-occurring groundwaters
(Asano, 1985). Artificial recharge also has application in wastewater
disposal, waste treatment, secondary oil recovery, prevention of land
subsidence, storage of freshwater within saline aquifers, crop
development, and streamflow augmentation (Oaksford, 1985).
A variety of methods have been developed and applied to artificially
recharge groundwater reservoirs in various parts of the world. Details of
these methods, as well as related topics, can be found in the literature
(e.g., Todd, 1980; Huisman and Olsthoorn, 1983; Asano, 1985; CGWB, 1994).
The methods may be generally classified in the following four categories
(1) Direct Surface Recharge Technique (ASANO, 1985).
(2) Direct Subsurface Recharge Technique.
(3) Combination surface-subsurface methods, including subsurface
drainage (collectors with wells), basins with pits, shafts, and wells.
(4) Indirect Recharge Techniques.
Direct surface recharge techniques are among the simplest and most
widely applied methods. In this method, water moves from the land surface
to the aquifer by means of percolation through the soil. Most of the
existing large scale artificial recharge schemes in western countries make
use of this technique which typically employs infiltration basins to
enhance the natural percolation of water into the subsurface (Dewan
Mohamed et al., 1983). Field studies of spreading techniques have shown
that, of the many factors governing the amount of water that will enter
the aquifer, the area of recharge and length of time that water is in
contact with soil are the most important (Todd, 1980). In general, these
methods have relatively low construction costs and are easy to operate and
maintain. Direct subsurface recharge techniques convey water directly into
an aquifer. In all the methods of subsurface recharge, the quality of the
recharged water is of primary concern. Recharged water enters the aquifer
without the filtration and oxidation that occurs when water percolates
naturally through the unsaturated zone.
Direct subsurface recharge methods access deeper aquifers and require
less land than the direct surface recharge methods, but are more expensive
to construct and maintain. Recharge wells, commonly called injection
wells, are generally used to replenish groundwater when aquifers are deep
and separated from the land surface by materials of low permeability. All
the subsurface methods are susceptible to clogging by suspended solids,
biological activity or chemical impurities. Recharge wells have been used
to dispose of treated industrial wastewaters, to add freshwater to coastal
aquifers experiencing saltwater intrusion, and to force water under
pressure into permeable bedrock aquifers to arrest land subsidence
resulting from extensive withdrawals of groundwater, although with
variable success (CGWB, 1994). In many places, including the United
States, Japan and Thailand, the use of injection wells is still considered
experimental (Dewan Mohamed et al., 1983).
Combinations of several direct surface and subsurface techniques can be
used in conjunction with one another to meet specific recharge needs.
Indirect methods of artificial recharge include the installation of
groundwater pumping facilities or infiltration galleries near
hydraulically-connected surface waterbodies (such as streams or lakes) to
lower groundwater levels and induce infiltration elsewhere in the drainage
basin, and modification of aquifers or construction of new aquifers to
enhance or create groundwater reserves. The effectiveness of the former,
induced recharge method depends upon the number and proximity of surface
waterbodies, the hydraulic conductivity (or transmissivity) of the
aquifer, the area and permeability of the streambed or lake bottom, and
the hydraulic gradient created by pumping. Using the latter technique,
aquifers can be modified by structures that impede groundwater outflow or
that create additional storage capacity. Groundwater barriers or dams have
been built within river beds in many places, including India, to obstruct
and detain groundwater flows so as to sustain the storage capacity of the
aquifer and meet water demands during periods of greatest need.
Construction of complete small-scale aquifers also seems feasible (Helweg
and Smith, 1978). Notwithstanding, indirect methods generally provide less
control over the quantity and quality of the water than do the direct
Extent of Use
The concept of artificial recharge has been known for a long time. The
practice began in Europe during the early nineteenth century. However, the
practice has rarely been adopted on a large scale, with most large scale
applications being found in countries such as the Netherlands, Germany,
and USA (Dewan Mohamed et al., 1983). Israel transports 300 million cubic
metres of water annually from north to south through the National Water
Carrier System and stores two-thirds of it underground (Ambroggi, 1977).
The water is used to meet high summer demands and offers a reliable source
of supply during dry years. On the North Plain of China, which is prone to
droughts, water from nearby streams is diverted into underground storage
areas with capacities of about 500 million cubic metres. Several counties
in Hebei Province are using artificially recharged aquifers to combat
sinking water tables (Widstrand, 1978). In India, subsurface storage has
caught on as a way of providing a reliable source of irrigation water. A
number of artificial recharge projects have been carried out in that
country (CGWB, 1994) (see Case Studies, Chapter 5).
Operation and Maintenance
To ensure the effective and efficient operation of an artificial
recharge system, a thorough and detailed hydrogeological study must be
conducted before selecting the site and method of recharge. In particular,
the following basic factors should be considered: the locations of
geologic and hydraulic boundaries; the transmissivity, depth to the
aquifer and lithology, storage capacity, porosity, hydraulic conductivity,
and natural inflow and outflow of water to the aquifer; the availability
of land, surrounding land use and topography; the quality and quantity of
water to be recharged; the economic and legal aspects governing recharge;
and the level of public acceptance.
Level of Involvement
Because of the technical complexity involved in siting and regulating
artificial recharge, this technology is generally implemented at the
Rushton and Phadtare (1989) describe artificial recharge pilot projects
in both alluvial and limestone aquifers in Mehsana area of Gujarat, India.
Recharge was accomplished using spreading channels, percolation tanks and
injection wells. Table 11 presents a summary of the initial and
operational costs for the various schemes. The most expensive scheme, an
injection well feeding an alluvial aquifer, had initial and operating
costs per unit volume of recharged water of $100/m3.
TABLE 11. Costs of Various Artificial Recharge
Schemes in India ($/m3).
|Artificial Recharge Structure
|| Running Cost
| Injection well (alluvial area)
|Spreading Channel (alluvial area)
| Percolation Tank (alluvial area)
|Injection well (limestone area)
|Spreading Channel (limestone area)
It is apparent from Table 11 that injection wells
in hard rock areas are less expensive since they tend to be shallower and
have a lesser risks of clogging. Percolation tanks appeared to be least
expensive in terms of initial construction costs; this would be the case
in areas where the tanks already exist. In such cases, the initial cost
only involves the cleaning of the bed of the tank. For economic reasons,
the main uses of artificially recharged water are likely to be providing
water for domestic needs, industry and environmental conservation. Because
of its relatively high cost, recharged water is not generally suited for
irrigation for a total crop, but it can be used to provide supplemental
irrigation water for rain-fed crops or to provide additional water to
crops at a crucial growth stage during periods of water shortage. As a
general rule in this regard, groundwater must be efficiently used and
effectively applied such that the net benefits from its use are maximized
over time. Guidelines for the socio-economic and financial appraisal of
artificial recharge projects in developing countries, necessary to assess
these net benefits, are provided by CGWB (1994).
Groundwater recharge methods are suitable for use in areas
where aquifers exist. Typically, unconfined aquifers are recharged by
surface injection methods, whereas confined aquifers are generally
recharged through subsurface injection. Surface injection methods require
relatively flat or gently sloping lands, while topography has little
effect on subsurface recharge methods. Aquifers best suited for artificial
recharge are those which can absorb and retain large quantities of water.
In temperate humid climates, the alluvial areas which are best suited to
artificial recharge are areas of ancient alluvium, the buried fossil
river-beds and interlinked alluvial fans of their main valley and
tributaries. In the arid zone, recent river alluvium may be more
favourable than in humid zones. In these areas, the water table is subject
to pronounced natural fluctuations. Surface recharge methods are best
suited to these cases. Coastal dunes and deltaic areas are also often very
favourable areas for artificial recharge schemes. Dense urban and
industrial concentrations in such areas may render artificial recharge
schemes desirable, generally using subsurface recharge wells to inject
surface water into the aquifers.
When the quantity and availability of recharge water is
highly variable, such as in an intermittent stream, any of the surface
application methods are suitable. Basin and pit techniques have the
greatest advantages because they can be designed to accommodate expected
flood flows. In contrast, shafts and wells have little storage capacity
and, therefore, require a more uniform supply of water. Indirect methods,
such as induced recharge, are virtually unaffected by changes in surface
water flows because the rate of recharge is controlled by extraction rates
The physical, chemical and biological quality of recharge
water also affects the selection of recharge method. If suspended solids
are present, surface application techniques tend to be more efficient than
subsurface techniques where they can result in clogging of injection
wells. It is also important that the recharge water be chemically
compatible with the aquifer material though which it flows and the
naturally occurring groundwater to avoid chemical reactions that would
reduce aquifer porosity and recharge capacity. Toxic substances must not
be present in the recharge water unless they can be removed by
pretreatment or chemically decomposed by a suitable land or aquifer
treatment system. Similarly, biological agents, such as algae and
bacteria, can cause clogging of infiltration surfaces and wells, limiting
the subsequent use of the recharged water.
Effectiveness of the Technology
Various artificial recharge experiments have been carried
out in India by different organizations, and have established the
technical feasibility of the artificial recharge of unconfined,
semi-confined and confined aquifer systems. However, the most important,
and somewhat elusive, issue in determining the utility of this technology
is the economic and institutional aspects of artificial groundwater
recharge. Experiences with full-scale artificial recharge operations in
India and elsewhere in Asia are limited. As a consequence, cost
information from such operations is incomplete. The available data, from
certain hydrological environs in which recharge experiments have been
initiated and/or are in progress, suggest that the cost of groundwater
recharge can vary substantially. These costs are a function of
availability of source water, conveyance facilities, civil constructions,
land, and groundwater pumping and monitoring facilities (CGWB, 1994).
As surface water augmentation methods, such as dams and
diversions, have become more expensive and less promising in terms of
environmental considerations, the prospects of storing surplus surface
water underground and abstracting it whenever and wherever necessary
appears to be more effective technology. In urban areas, artificial
recharge can maintain groundwater levels in situations where natural
recharge has become severely reduced.
There are a number of problems associated with the use of
artificial recharge techniques. These include disadvantages related to
aspects such as recovery efficiency (e.g., not all of the added water may
be recoverable), cost effectiveness, contamination risks due to injection
of recharge water of poor quality, clogging of aquifers, and a lack of
knowledge about the long term implications of the recharge process. Hence,
careful consideration should be given to the selection of an appropriate
site for artificial recharge in a specific area.
Cultural considerations, stemming from socio-economic
concerns, often enter into the selection of a recharge method and site.
The availability of land, land uses in adjacent areas, public attitudes,
and legal requirements generally play a role in defining the acceptability
of artificial recharge in a given setting. In urban areas, where land
availability, costs and uses in adjacent areas may pose restrictions,
injection wells, shafts or small pits requiring highly controlled water
supplies and little land area may be preferable to larger scale, surface
spreading recharge methods. Surface recharge facilities generally require
protected property boundaries, regular maintenance, and continuous
surveillance if they are to be acceptable to the public.
Further Development of the Technology
The recharge process is extremely complex, and, due to the
numerous factors affecting the process, is only partly understood. The
studies on artificial recharge techniques are mostly site-specific and
descriptive in nature, which gives little insight into the potential
success of implementing this technology in other locations. Thus, there is
a need for further research and development of artificial recharge
techniques for a variety of conditions. In addition, the economic,
managerial and institutional aspects of artificial recharge projects need
to be studied further.
Professor Ashim Das Gupta, Water
Engineering and Management Program, Asian Institute of Technology, Post
Office Box 4, Klong Luang, Pathumthani, Bangkok, Thailand, Tel. 66 2 516
0110, Fax: 66 2 516 21 26, E-mail: email@example.com.
Ambroggi, R.P. 1977. Underground Reservoirs to Control the
Water Cycle, Scientific American, 236(5):21-27.
Asano, T. 1985. Artificial Recharge of Groundwater.
Butterworth Publishers, Boston, 767 pp.
CGWB (Central Ground Water Board) 1994. Manual on
Artificial Recharge of Ground Water. Technical Series-M, No. 3.
Ministry of Water Resources, Government of India, 215 pp.
Helweg, O.J. and G. Smith 1978. Appropriate Technology for
Artificial Aquifers. Groundwater, 16(3):144-148.
Huisman, L. and T.N. Olsthoorn 1983. Artificial
Groundwater Recharge. Pitman Publishing Inc., Massachusetts, 320 pp.
Oaksford, E.T. 1985. Artificial Recharge: Methods,
Hydraulics, and Monitoring, In: Artificial Recharge of
Groundwater, T. Asamo, editor. Butterworth Publishers, Boston, pp.
Rushton, K.R. and P.N. Phadtare 1989. Artificial Recharge
Pilot Projects in Gujarat, India, In: Groundwater Management: Quantity
and Quality, IAHS Publication No. 188, pp. 533-545.
Todd, D.K. 1980. Groundwater Hydrology. Second
Edition. John Wiley & Sons, New York, 535 pp.
Widstrand, C. (Editor) 1978. The Social and Ecological
Effects of Water Development in Developing Countries. Pergamon Press,