Newsletter and Technical Publications
of Alternative Technologies for Freshwater Augumentation
America and The Caribbean>
PART B. TECHNOLOGY PROFILES
1.9 Artificial Recharge of Aquifers
The use of artificial recharge to store surplus surface water
underground can be expected to increase as growing populations demand more
water, and as the number of good dam sites still available for
construction becomes fewer. For example, artificial recharge may be used
to store treated sewage effluent and excess stormwater runoff for later
use. Groundwater recharge may also be used to mitigate or control
saltwater intrusion into coastal aquifers. However, in order to accomplish
the uses without deleterious environmental consequences, the optimum
combination of treatment methodologies before recharge and after recovery
from the aquifer must be identified. It will also be necessary to consider
the sustainability of soil-aquifer treatment and health effects of water
reuse when using treated wastewater as the recharge medium.
The main purpose of artificial aquifer recharge technology is to store
excess water for later use, while improving water quality (decreasing the
salinity level) by recharging the aquifer with better water. There are
several artificial recharge techniques in use in Latin America and the
Caribbean, including infiltration basins and canals, water traps,
cutwaters, surface runoff drainage wells, septic-tank-effluent disposal
wells, and diversion of excess flows from irrigation canals into
Basins and Canals
This technology has been used extensively in the San Juan River basin of
Argentina, where two artificial recharge experiments have been conducted.
The first experiment consisted of the construction of infiltration basins,
200 m by 90 m and 1.2 m deep. These basins were combined with 9.30 ha of
infiltration canals in the second experiment. This system was used to
recharge the 10 hm3 aquifer in the Valley of Tulum. The system of canals
was found to be more efficient than the infiltration basins because the
high circulation velocities in the canals precluded the settling of fine
material and resulted in higher infiltration rates.
Water traps are used to increase infiltration in streambeds. The traps
are earthen dams of variable height, usually 1 m to 3 m, that are
constructed of locally available materials. They are normally
perpendicular to river banks, depending on the characteristics of the
stream system. Water traps are designed to operate during rainfalls of up
to a 1-in-50-year frequency. They are typically constructed along a 1 km
stretch of river, at intervals of 70 m to 100 m. Their storage capacities
fluctuate between 250 and 400 m3. They have an estimated life
span of 20 to 25 years, given proper maintenance.
This technology can be used in areas where there are no rivers and
creeks, such as in the Paraguayan Chaco. Cutwaters are excavations of
variable dimensions, used as reservoirs, built in low-lying areas. Their
primary objective is the harvesting of surface waters. Those to be used
for artificial recharge are built on top of permeable strata; those for
surface water storage are built on impermeable substrates.
The limestone and coral rock formations that comprise the principal
aquifer in Barbados consist of very pure calcium carbonate. Drainage
wells, or "suckwells", are used to dispose of drainage waters
(see Figure 13). The depth of the drainage wells is determined by the well
digger and is based on reaching an adequate fissure or "suck" in
the rock. They range in area from 16 ft2 to 36 ft2,
and are either square or circular in shape.
Figure 13: Suckwell Construction.
Government of Barbados, Stanley Associates Eng. Ltd., and Consulting
Engineers Partnership Ltd. Barbados Water Resources Study, Vol. 3: Water
Resources and Geohydrology, 1978.
They are provided with guard walls of concrete or coral
stone above the ground surface and drainage ports or underground pipes or
culverts to conduct runoff into the wells.
Tanks and Effluent Disposal Wells
Another source of artificial groundwater recharge is
effluents from septic tanks, using soakaways. The Barbados Water Resources
Study of 1978 estimated that about half of the 128 million l/day water
used for domestic consumption, or approximately 64 million l/day, is
returned to the groundwater as septic tank effluent. The soakaways used
for this purpose are very similar to suckwells in design and construction,
except that they are used in conjunction with septic tanks and are always
Injection of Excess Surface Flows
In Jamaica, excess surface runoff is treated and discharged
into sinkholes in karstic limestone aquifers. These aquifers are commonly
associated with seawater intrusion and are highly saline. The recharged
water is monitored through a series of monitoring and production wells.
Monitoring is carried out to measure changes in groundwater levels and
water quality (salinity levels).
Extent of Use
Artificial recharge has been widely used in several Latin
American countries and the Caribbean. It may be expected to be utilized
more frequently as demand for water increases and as surface water
resources are fully committed.
In Argentina, a system of canals and infiltration basins
has been used in the provinces of San Juan, Mendoza, and Santa Fe with
relative success. Water traps have also been used in Mendoza. This is an
effective technology for use in arid and semi-arid regions.
Cutwaters have been used in the Paraguayan Chaco, where
rainwater is the main source of aquifer recharge. This technology is
normally used for recharge of surficial aquifers, and its application is
limited by the hydrogeologic conditions. In Barbados, suckwells are
extensively used for recharge, except in areas on the east coast which
lack the necessary coral formations and where the exposed oceanic soil
(consisting of a mixture of clay, marl, silt, and sand) has a low
permeability. There are probably more than 10 000 suckwells, mostly on
private lands or estates. They are at elevations of 20 ft above sea level
or higher, and usually are well maintained.
The technology in Jamaica of using sinkholes as injection
points is applicable where karstification of a limestone aquifer has taken
place. Artificial recharge is suitable for areas upgradient of an aquifer
where there is significant water for recharge purposes and land area
available for treatment of the runoff before recharge. Treatment consists
primarily of settling suspended solids. It is best used in areas where
pumping is not needed to move the water to the sinkholes.
Operation and Maintenance
Infiltration basins and canals require minimal maintenance,
consisting mostly of avoiding excessive sedimentation in the basins and
canals and preventing erosion of canal banks. A bulldozer is often used in
the infiltration basins to remove accumulated sediments and to
rehabilitate the system.
Water traps require maintenance during the first few years
of operation, until the natural vegetation grows again in the area.
Intense rainfalls may damage or destroy the traps, and they will have to
Maintenance of cutwaters is similar to that required in
infiltration basins. Runoff from areas with unpaved streets can carry
large loads of sediment, which may be deposited in cutwaters and will need
to be removed during dry periods.
Road drainage is also a source of water for suckwells in
Barbados. These roadside wells are built and maintained by the government.
Other suckwells, on residential and plantation lands, are maintained by
the landowners. Maintenance is labor-intensive and generally involves the
removal of silt, which accumulates at the bottom of the well and may plug
the "suck", rendering it useless. Repairs to the guard walls,
covers, and iron grilles are also needed. Unfortunately, owing to
increased labor costs and declines in profitability at most sites, many of
these wells have fallen into a state of disrepair and have been either
plugged, stuffed up, or overgrown with trees. Some of these wells have
been contaminated by garbage dumped into them.
In sinkhole injection, operations are simple. The canal
attendant, who normally resides nearby, visits the site twice a day to
read the Parshall flumes, collect water samples, and open or close sluice
gates. The earth canals need to be kept clear to ensure maximum delivery
of water. The settling basin has to be cleaned of accumulated sediment and
vegetative growths once every four to five months. Vandalism, resulting in
damage to sluice gates, sinkholes, and monitor wells, is also a problem in
the maintenance of the system.
Level of Involvement
In Argentina, most of the experimental use of this
technology has been done by the government in both the provinces of San
Juan and Mendoza.
In Paraguay, the government, in conjunction with
international organizations, has been conducting experiments to quantify
the recharge provided by different recharge systems. In general, the
implementation and maintenance of these technologies in urban areas have
been carried out by municipal governments, but in rural areas by the
Both the private sector and the Government of Barbados have
been involved in the successful implementation of artificial recharge
schemes. The private sector, primarily represented by the sugar industry,
has encouraged the development of this technology and provided land,
manpower, and water. The government, represented by the Water Authority,
has provided technical expertise and financing.
In Jamaica, there is a cadre of well-diggers who can be
contracted by the government, plantation owners, and other landowners to
both dig and maintain drainage wells. An ongoing educational program
informs landowners of the need to maintain wells on a regular basis, the
potential for groundwater recharge from the wells, and the need to monitor
contamination of the groundwater.
The estimated cost of infiltration of surface water in
Argentina, using basins and canals, is $0.20/m3. The basins
and canals used in the 1977 experiment in the San Juan River basin
incurred a capital cost of $31 300. The comparable cost of water traps in
Argentina has been estimated at between $133 and $167. The capital cost of
a 5 700 m3 cutwater, equipped with a 14 m extraction well, is
estimated at $6 325. The operation and maintenance cost is estimated at
$248 per year. The production costs are estimated to be about $0.30/m3
for the first five years of operation, $0.17/m3 for the next
five years (five to ten years of operation), and $0.15/m3 for
the following five years (ten to fifteen years of operation).
In Jamaica, the initial capital cost of the sinkhole
injection system is estimated at less than $15 000. This cost is primarily
related to the construction of the inflow settling basin and channels
conveying the runoff water to the sinkholes. Maintenance costs are low,
less than $5 000 for the 18-month project (or under $3 500/year).
Effectiveness of the Technology
In Argentina, sites near the San Juan and Mendoza rivers
recharged the underlying groundwater aquifer at the rate of 60 l/sec/ha
during a three-month period.
Water traps have been successfully used for more than 25
years in Argentina. They have been very useful in reducing sedimentation
and risk of flooding.
Cutwaters proved a significant source of water to
communities during the droughts of 1993 and 1994 in the Paraguayan Chaco.
Recovery of 75% of the infiltrated water has been reported in that region.
Even though groundwater recharge is not the principal
intended use of drainage wells, it is a major indirect beneficiary.
Infiltration rates in coral rock in Barbados have been estimated at
between 6.0 and 6.5 cm/hr and are known to be highest where solution
openings (or "sucks") occur.
In Jamaica, total recharge over 18 months amounted to 4
million m3. Two groundwater mounds were detected downgradient
of sinkholes. One mound indicated an increase of 4.1 m in water levels,
while at the other the increase was 6.7 m. Divergent radial flows
developed from both of these mounds. Once recharge ceased, the mounds
gradually disappeared over a two-month period. Chloride concentrations in
some wells in Jamaica have decreased from 2 300 mg/l to 1 700 mg/l and in
others from 170 mg/l to 25 mg/l before reaching an equilibrium at 50 mg/l.
In general, most wells influenced by artificial recharge have shown
declines in salinity levels.
In areas where groundwater is an important component of the
water supply, and rainfall variability does not allow for a sufficient
level of aquifer recharge by natural means, these technologies provide for
the artificial enhancement of the natural recharge. Storage of surface
runoff in underground aquifers in arid and semi-arid areas has the
advantage of minimizing evaporative losses. However, use of these
technologies requires an appropriate geological structure. In areas
underlain by igneous rock, the natural fracture lines can be expanded by
injection of water under pressure and infusion of a sand slurry into the
gaps thus created. Given the cost of this latter measure, however, use of
natural limestone or sandstone formations, such as are common in the
Caribbean islands, is preferred and most cost-effective.
- The technology is appropriate and generally well understood
by both the technicians and the general population.
- Very few special tools are needed to dig drainage wells.
- Because of the structural integrity of the coral rock formations, few
additional materials are required (concrete, softstone or coral rock
blocks, metal rods) to construct the wells.
- Groundwater recharge stores water during the wet season for use in
the dry season, when demand is highest.
- Aquifer water can be improved by recharging with high quality
- Recharge can significantly increase the sustainable yield of an
- Recharge methods are environmentally attractive, particularly in arid
- Most aquifer recharge systems are easy to operate.
- In many river basins, control of surface water runoff to provide
aquifer recharge reduces sedimentation problems.
- Recharge with less-saline surface waters or treated effluents
improves the quality of saline aquifers, facilitating the use of the
water for agriculture and livestock.
- In the absence of financial incentives, laws, or other
regulations to encourage landowners to maintain drainage wells
adequately, the wells may fall into disrepair and ultimately become
sources of groundwater contamination.
- There is a potential for contamination of the groundwater from
injected surface water runoff, especially from agricultural fields and
roads surfaces. In most cases, the surface water runoff is not
pre-treated before injection.
- Recharge can degrade the aquifer unless quality control of the
injected water is adequate.
- Unless significant volumes can be injected into an aquifer,
groundwater recharge may not be economically feasible. The hydrogeology
of an aquifer should be investigated and understood before any future
full-scale recharge project is implemented. In karstic terrain, dye
tracer studies can assist in acquiring this knowledge.
- During the construction of water traps, disturbances of soil and
vegetation cover may cause environmental damage to the project area.
Artificial groundwater recharge is generally well accepted by
communities in areas where it is used.
Further Development of the Technology
Potential improvements in artificial recharge technologies include:
- Improvements in the design of pre-injection silt chambers, grease
traps, and oil interceptors to reduce the amount of contaminants
entering drainage wells.
- Improvements in the design of injection wells to eliminate the use of
- Evaluation of groundwater contamination potentials from various
sources of artificial recharge, and the adoption of techniques to reduce
the associated impacts or risks.
- Improvements in the design of water traps to increase groundwater
recharge efficiency. A better understanding of the causes and
consequences of bacterial and viral contamination of aquifer systems,
and the means of minimizing and mitigating such risks.
B. J. Mwansa, Project Manager, Barbados Water Resources
Management & Water Loss Studies, "Invermark," Hastings,
Christ Church, Barbados. Tel. (809)430-9373. Fax (809)430-9374.
Basil P. Fernandez, Hydrogeologist and Managing
Director, Water Resources Authority, Hope Gardens, Post Office Box 91,
Kingston 7, Jamaica. Tel. (809)927-1878. Fax (809)977-0179.
Alberto I. J. Vich, Coordinador, Programa de
Investigaci6n y Desarrollo Manejo Ecológico del Piedemonte,
Instituto Argentino de Nivología, Glaciología y Ciencias
Ambientales, Unidad Ecología y Manejo de Cuencas Hídricos,
Casilla de Correo N° 330, 5500 Mendoza, Argentina. Tel.
(64-61)28-7029. Fax (64-61)28-7029 / 28-7370. E-mail:
Eduardo Torres, Profesional Principal, Instituto
Argentino de Investigaciones de las Zonas Aridas (IADIZA), Casilla de
Correo 507, 5500 Provincia de Mendoza, Argentina. Fax (54-61)28-7995.
Daniel O. Caoria, Universidad Nacional de San Juan,
Departamento de Hidráulica, Fundación Agua, Desarrollo y
Ambiente, Mendoza 769 (Sur), 5400 San Juan, Argentina. Tel. (54-64)22-2427
/ 22-4558. Fax (54-64)21-4421.
Eugenio Godoy Valdovinos, Comisión Nacional de
Desarrollo Regional Integrado del Chaco Paraguayo, Dirección de
Recursos Hídricos, Casilla de Correo 984/273, Filadelfia, Paraguay.
Tel. (595-91)275. Fax (595-91)493.
Valeria Mendoza, Investigadora, Centro de Economía,
Legislación y Administración del Agua y del Ambiente
(INCYTH/CELAA), Belgrano 210 (Oeste), 5500 Mendoza, Argentina. Tel
(54-61)28-7921/28-5416. Fax (54-61)28-5416.
Everardo Rocha Porto, EMBRAPA-CPATSA, BR-428 km 52, Zona
Rural, Caixa Postal 23, 56300-000, Petrolina, Pernambuco, Brasil. Tel.
(55-81) 862-1711. Fax (55-81) 862-1744. E-mail: evrporto@cpatsa.
Eduardo Torres, Investigador, Instituto argentino de
Investigaciones de las Zonas Aridas (IADIZA), Bajada del Cerro de la
Gloria s/n, Parque General San Martín, Casilla de Correo 507, 5500
Mendoza, Argentina. Tel (54-61)28-7995. Fax (54-61)28-7995. E-mail:
Adrián Vargas Araníbar: Investigador,
Centro Regional Andino (INCYTH/CRA), Belgrano 210, Ciudad, Casilla de
Correo 6, 5500 Mendoza Argentina. Tel. (54-61)28-6998/28-8005. Fax
(54-61)28-8251. E-mail: firstname.lastname@example.org.
Alberto I. J. Vich, Responsable Unidad Ecología y
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Glaciología y Ciencias Ambientales, Bajo del Cerro de la Gloria
s/n, Parque General San Martín, Casilla de Correo 330, 5500
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