Newsletter and Technical Publications
of Alternative Technologies for Freshwater Augumentation
America and The Caribbean>
PART B. TECHNOLOGY PROFILES
1.5 Runoff Collection using Surface and Underground Structures
Runoff water can be successfully stored in artificial reservoirs, or
intercepted and impounded by small dams. An extensive body of literature
on the design of local impoundments and dams exists, since this technology
has been used extensively throughout the world. In applying this
technology in developing countries, both the lack of materials and skilled
labor in certain regions and the cost must be taken into consideration.
Local impoundments are storage pools dug into the ground to store
surface water runoff for use at a later date. Dams are designed to
increase the storage capacity of rivers or streams, intercepting runoff
and keeping it in storage for later use. The main difference is that dams
are built where flowing water already exists, while local impoundments are
essentially for harvesting and storing local rainfall runoff. These
impoundments can dry out during drought periods; reservoirs behind dams
usually do not.
General features of dams. Earth or rockfill dams consist
of a foundation, which is either earth or rock; an embankment, resisting
both the vertical and the horizontal loads; an impervious core; and a
shell. The purpose of the core (membrane) is to hold back water. Depending
on the structural requirements of the dam, the core can be located at the
center, upstream from the center, or, in the case of certain rockfill
dams, on the upstream face. When the foundation is not capable of
resisting underseepage, it is necessary to extend the core down into the
foundation to a depth where impervious materials are reached. Such an
extension of the core is termed a cutoff.
The purpose of the shell is to provide structural support for the core
and to distribute the loads over the foundation. An internal drain is an
essential feature of all but the smallest dams, where the downstream shell
may be so pervious that it can act as a drain. Riprap is required to cover
the upstream face to prevent erosion or the washout of fine particles from
the shell by wave action. Ordinarily, the riprap extends from above the
maximum waterline to just below the minimum waterline. If the downstream
face is subject to inundation, it also requires riprap protection.
Three types of dams are commonly used:
- Earth dams, which are constructed of compacted dirt or earth fill
with flat side slopes.
- Rockfill dams, with relatively loose, open embankments of natural
rock, with dimensions suitable for stability.
- Concrete arch dams, which have a concrete wall built in the form of a
horizontal arch curved upstream, and anchored into the bedrock by
abutments on both sides of the valley.
Impoundment description and components. Artificial
impoundments are often dug below the ground surface in a soil which is
naturally impervious or treated to become impervious. The shape of the
impoundment may be rectangular, square, circular, or quasi-circular,
depending on the desired depth and capacity of the pool. The side slopes
may range from 2:3 to 1:2 (vertical:horizontal) depending on the types and
angle of repose of the soils. Impoundments may be dug by hand or machine.
The capacities of typical impoundments of this type range between 500 m3
and one million m3 depending on the availability of runoff and the demand
for water. A filtration plant or chlorination unit may be added if the
water from is to be used for domestic consumption.
Criteria for construction sites. Criteria for a good dam
and impoundment site include the following:
- Topography which permits the enclosure of a large volume of stored
- Strong and impervious rock formations and soils which permit a sound
- No existing roads or buildings.
- Availability of construction and fill materials near or within the
- Short distances between the reservoir and the agricultural lands to
be irrigated or other potential points of use.
Extent of Use
Dams and impoundments are extensively used in Latin American countries
and in some Caribbean islands. For example, both Argentina and Aruba use
such facilities to collect and store runoff. This is one of the most
productive freshwater augmentation technologies. In the northeastern
region of Brazil, for example, dams and local impoundments have been built
for water supply and irrigation purposes, as shown in Figures 10 and 11.
In Panama, this technology has been applied on a regional basis in the
provinces of Herrera, Los Santos, and Coclé. In Suriname, an
artificial lake, Lake Brokopondo, was built after the construction of the
Apolaka Dam on the Suriname River in 1964. The lake is used as a source of
water for hydroelectric power generation. In Venezuela, this technology
has been applied to augment water supplies from the Monón River. In
Costa Rica, it has been used in the Chorotega region for hydroelectric
power generation and for irrigation supply purposes along the Arenal
River. In Argentina, impoundments have been constructed on several rivers
for hydroelectric power generation and irrigation supply purposes. In
Ecuador, reservoirs have been used extensively for water supply and flood
control purposes. On Aruba, there are 32 possible catchment areas which
are suitable for reservoirs, dams, or storage tanks. Underground barriers
were built in Brazil to confine and better utilize surficial aquifers (see
case study in Part C, Chapter 5).
Operation and Maintenance
The collection area should be highly impermeable to reduce
infiltration losses, and the impoundment should be provided with an
overflow device to avoid flooding of adjacent lands during heavy rains. A
sedimentation basin at the inlet of the impoundment is also recommended.
In general, most of the construction work is done with local materials,
which facilitates maintenance. Dams and reservoir facilities should be
inspected at least once a year. Operation of the dam and related
facilities, such as pumping stations, hydroelectric power generators, or
sluice gates, should be by trained personnel.
In cases where the impounded water is used for hydroelectric production,
as in Lake Brokopondo, Suriname, the reservoir level needs to be managed
within a predetermined range of elevations. Excessive growths of water
hyacinth or other aquatic plants may occur in some lakes and local
impoundments, such as Lake Brokopondo, and in extreme cases may interfere
with reservoir operations, clogging mechanical devices and increasing
local evapotranspiration rates. Further, thermal stratification, which is
common in warm water lakes, may lead to deoxygenation in the hypolimnion
or bottom waters of the lake. Use of this water can create corrosion
problems in the hydroelectric power plants.
Where the user community is not immediately adjacent to the reservoir or
dam and a distribution system is required, proper operation and
maintenance of the system are essential to avoid leaks, stoppages, and/or
other water losses.
In Brazil, large and complex systems, like the one operated by the State
of São Paulo (to collect and store water and then redistribute it
for multiple uses), are equipped with highly sophisticated
hydro-meteorological and telemetry systems to provide real-time
information to operators on the status of the system, water levels, and
water flows. The operation and maintenance of these systems require highly
Figure 10: Dam or Reservoir System used for Irrigation
Purposes in Northeastern Brazil.
Source: L. de L.
Brito, et. al., "Barragem Subterranea. I. Construção e
Manejo," EMBRAPA-CPATSA Boletim de Pesquisa 36, 1989.
Level of Involvement
Government participation is essential in the construction phase of
reservoir and dam systems. In some cases, private companies involved in
hydroelectric power generation and large agricultural enterprises are also
capable of building these systems. Small systems can be built by local
communities or individuals, usually with government assistance to ensure
the integrity of the dam structure and management of the water resource.
Operation and maintenance can be performed at the community level. The
university community in some countries, such as Ecuador, has also provided
technical guidelines in the design and construction of local impoundments.
Figure 11: A Schematic Representation of an Underground
Barrier in Brazil.
Source: L. de L. Brito, et. al., "Barragem
Subterranea. I. Construção e Manejo," EMBRAPA-CPATSA
Boletim de Pesquisa 36, 1989.
The construction cost per cubic meter of water varies
considerably depending on the region and the size and type of project. In
Ecuador, the average cost was estimated at $0.93/m3 of water,
but the range was from $0.10 to $2.00/m3.
A reservoir and dam system in northeastern Brazil, with a storage
capacity of 3 000 m3, in a drainage area of 3.8 ha, was built
at a cost of $2 500, including soil preparation for cultivation of 1.5 ha
of corn. The construction cost of an underground barrier to facilitate
utilization of 1.0 ha of surficial aquifer in Brazil was estimated at
In Costa Rica, water in excess of base flows from the Arenal River is
stored in a reservoir and then used for hydroelectric power generation and
in an irrigation system in the Tempisque River basin, where precipitation
is considerably less than in the Arenal basin. This 6 000 ha reservoir and
irrigation project cost $19.8 million to develop. A second phase of the
irrigation project, providing water to 11 600 ha, is estimated to cost
$45.4 million. The annual operation and maintenance cost is estimated at
A small-scale, 1 600 m3 impoundment in Costa Rica cost $1
The cost of reservoirs built in the western region of Argentina ranges
between $0.60 and $1.20/m3 of storage capacity. The operation
and maintenance costs range between $0.01 and $0.03/m3 of
Effectiveness of the Technology
The effectiveness of this technology can be measured by the amount of
water that can be stored in the reservoirs or dams, but it is usually
measured as a function of the benefits obtained by the utilization of the
additional water. For example, in Mendoza, Argentina, irrigation
efficiency increased between 8% and 15% following the construction of a
reservoir. In Brazil, water stored in the São Paulo area and
transferred to the Santista basin supplies 100% of the water demand.
Previously, the natural water in the Santista basin was able to supply
only 10% of the industrial demand. In the region of Llazhatar, Ecuador,
the availability of water for domestic and agricultural use has increased
four times, from 6 l/s to 25 l/s. In Suriname, because of the construction
of the Afobaka Dam, the minimum discharge to Lake Brokopondo increased ten
times, from 20 m3/sec to 224 m3/sec. Also, the
salinity intrusion in the Suriname River moved 30 km downstream after
construction of the Dam. Increased irrigation efficiencies of up to 55%
were reported in Costa Rica after the construction of the reservoir in the
Arenal River. Judging by these experiences, the use of dams and
impoundments is a highly effective technology.
These methods are applicable in regions where the time and spatial
distribution of rainfall are highly variable and storage is required to
meet specific demands, such as water supply for irrigation and
hydroelectric power generation. Their suitability depends on favorable
topography, geology, and economic conditions.
- Impoundments provide water for agricultural production and domestic
water use in arid and semi-arid regions.
- Impoundments provide water for hydroelectric power generation and
other, non-consumptive uses.
- The flora and fauna of a region, and particularly the fisheries, may
be enhanced, although large dams develop a lacustrine fauna over time
that gradually replaces the pre-existing riverine fishes.
- The degree of water pollution may be decreased by dilution of
- The perennial flows from impoundments could reduce saltwater
intrusion in certain rivers by increasing minimum flows and levels.
- Impoundments are ideal for multiple-use water projects.
- Reservoirs can be used as recreational areas.
- Impoundments require the availability of land with the proper
topography, and generally consume valuable agricultural land when the
lake basins are filled.
- To minimize seepage losses, impoundments need impermeable soils (soil
with less than 15% content of clay).
- Impoundments can lose an average of 50% of the total volume of water
stored in the reservoir to evaporation and infiltration in arid and
- Construction costs are relatively high.
- There is a risk of possible failure.
- Impoundments can flood adjacent lands during wet periods.
- Impoundments can produce environmental impacts and exacerbate public
health and other problems as people and animals are attracted to the
Dams, reservoirs, and impoundments are widely accepted as a water supply
augmentation method for developed and developing countries. Both the
engineering and the local communities have used this technology in
small-scale (e.g., farm dams) and large-scale projects.
Further Development of the Technology
Research has improved the design of local impoundments and small-scale
dams, making them more efficient in retaining water, preventing failures,
and reducing evaporative losses. Improvements in operation can be very
beneficial. Methods to further reduce evaporation should be developed.
Impermeable, low cost materials to line the local impoundments and reduce
infiltration should also be developed.
Carlos A Salzedo, Director Nacional de Ingeniería
Rural, Ministerio de Desarrollo Agropecuario, Panamá, República
de Panamá. Tel. (507)998-4595. Fax (507)998-4595.
Carmen Fermín, Dirección de Hidrología
y Meteorología, Ministerio del Medio Ambiente y de los Recursos
Naturales Renovables (MARNR), Esquina Camejo, Edificio Camejo 5o piso,
Caracas, Venezuela. Tel. (58-2) 408-1952. Fax (58-2)545-0607. E-mail: dhm
Everaldo Rocha Porto and Luiza Teixeira de Lima
Brito, Empresa Brasileira de Pesquisa Agropecuária
(EMBRAPA), Centro de Pesquisa Agropecuária do Trópico Semi-Árido
(CPATSA), BR-428 km 152, Zona Rural, Caixa Postal 23, 56300-000 Petrolina,
Pernambuco, Brasil. Tel. (55-81) 862-171. Fax (55-81) 862-1744. E-mail:
Dinarte Aéda da Silva, Universidade Federal do
Rio Grande do Norte (UFRN), Departamento de Agropecuária, Centro de
Tecnologia, 59000-000 Natal, Rio Grande do Norte, Brasil. Tel. (55-84)
231-1266, ramal 322. Fax (55-84) 231-9048.
Eduardo Torres, Instituto Argentino de Investigaciones
de las Zonas Aridas (IADIZA), Dependiente del Consejo Nacional de Ciencia
y Tecnología (CONICET), Parque General San Martín, Casilla
de Correo 507, 5500 Mendoza, Argentina. Tel. (54-61) 28-7995. Fax (54-61)
Ernesto Bondy Reyes and Mario Montes,
Dirección General de Recursos Hídricos, Ministerio de
Recursos Naturales, Tegucigalpa, Honduras. Tel. (504) 32-6250. Fax (504)
Felipe Cisneros Espinoza, Instituto de Investigaciones
de Ciencias Técnicas (IICT), Facultad Argentina de la Universidad
de Cuenca, Ave. 12 de Abril s/n, Cuenca, Ecuador. Tel. (593-7) 831-688.
Fax (593-7) 832-183, E-mail: firstname.lastname@example.org.
Alberto I. J. Vich, Coordinador del Programa de
Investigación y Desarrollo, Manejo Ecológico del Piedemonte
(Mendoza), 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: email@example.com .
José Artur Padilha, Frassinete Queiroz de
Medeiros, and Maria Claudino, Centro Administrativo, Bloco IV, 5o Andar,
Avenida João da Mata s/n, Jaguaribe, Paraíba, Brasil. Tel.
(55-83) 241-3210, ramal 569. Fax (55-83) 241-1727.
Amatali A. Moekiran, Director, Hydraulic Research
Division, Ministry of Public Works, Paramaribo, Suriname. Tel.
(59-7)49-0968. Fax (59-7)46-0627.
Brito, L. de L., et al. 1989. Barragem Subterrânea. I. Construção
e Manejo. Petrolina, PE, Brazil, EMBRAPA-CPATSA. (Boletim de Pesquisa
Centro de Reconversión del Azuay, Cañar y Morona Santiago
(CREA). n.d. 1982. Construccion de Reservorios en el Azuay y Cañar
desde 1982. Cuenca, Ecuador, Departamento de Obras de Riego.
-. 1989. Estudio de Prefactibilidad de Reservorios para
Almacenamiento de Agua para Riego y Desarrollo Agropecuario de su Area de
Influencia en las Provincias. Cuenca, Ecuador, Asociación
Cuomo, A.R., and Palermo, M.A. 1987. Introdução as Técnicas
de Correção de Cursos d'Água Torrenciais. São
Paulo, Universidade de São Paulo, Centro Tecnológico de Hidráulica
da Escola Politécnica. (Boletim 6)
Departamento de Águas e Energia Elétrica (DAEE). 1988.
Relatório sobre a atuação da Comissão
Especial para a Restauração da Serra do Mar em Cubatao.
Atuhuayco, Provincia del Cañar. 1992. Estudio de
Prefactibilidad del Proyecto de Riego para Las Comunidades de Sigsihuaico.
Cuenca, Ecuador, Universidad de Cuenca. (Tesis conjunta de la Facultad
de Ingeniería y la Facultad de Agronomía)(?)
Vázquez R., C. Chaca, G. Pesantez y C. Verdugo, 1993. Estudio de
Pre-factibilidad del Sistema de Riego para la Comunidad de Sigsihuaico
en la provincia del Cañar. Tesina de grado de Ingeniero Civil (2
volúmenes), Facultad de Ingeniería - Universidad de Cuenca,
Cuenca, Ecuador: 209 pp
Evenari, M., L. Shanan, and N. Tadmor. 1971. The Negev: The
Challenge of a Desert. Cambridge, Mass., Harvard.
International Crops Research Institute for the Semi-Arid Tropics. 1974.
Annual Report 1973-1974. Hyderabad, India.
Lloret, C.L., and M.A. Palermo. 1989. "Critérios para Avaliação
de Impactos Ambientais em Obras de Correção de Cursos d'Água.
In Anais do VIII Simpósio Brasileiro de Hidrologia e Recursos
Hidricos, Foz do Iguaçu, Brasil. São Paulo, Associação
Brasileira de Recursos Hídricos.
National Academy of Sciences. 1974. More Water for Arid Lands:
Promising Technologies and Research Opportunities. Washington, D.C.
Public Works Department of Western Australia. 1956. "Roaded
Catchments for Farm Water Supplies," Western Australia Department
of Agriculture Journal, 5(6), pp. 667-679.
Reboucas, A. da C., and M.E. Marinho. 1972. Hidrologia das Secas do
Nordeste do Brasil. Recife, PE, Brazil, SUDENE. (Hidrologia 40)
Santos, Junior A. 1983. Cheias na Bacia do Rio Pinheirost. São
Silva, A. Porto, and P.C.F. Gomes. 1981. Seleção de Áreas
e Construção de Barreiros para Uso de Irrigaçães
de Salvação no Trópico Semi-árido.
Petrolina, PE, Brazil, EMBRAPA-CPATSA. (Circular Técnica 3)
Silva, D.A., and J. Rego Neto. 1992. "Avaliação da
Barragens Sumersíveis para Fins de Exploração Agrícola
no Semi-árido." In Congresso Nacional de Irrigação
e Drenagem, 9, Natal, RN, 1992: Anais., vol. 1. Natal, RN, Brazil,
ABID. pp. 335-361.
Sowers, George F., and H.L. Sally. 1962. Earth and Rockfill Dam
Engineering. New York, Asia Publishing.
Tigre, C.B. 1949. "Barragens Subterrâneas e Submersas Como
Meio Rápido e Economico de Armazenamento d'Água," Inst.
Nordeste, pp. 13-29.