RWATER HARVESTING IN LATIN AMERICA AND
THE CARIBBEAN: CAUSES OF FAILURES,
RECOMMENDATIONS AND TRENDS
Luiz Rafael Palmier
Department of Hydraulic Engineering and Water Resources
Federal University of Minas Gerais
Avenida Contorno, 842/809
Belo Horizonte - MG
30110-060 Brazil
Phone: 55 31 3238-1003
Fax: 55 31 3238-1001
e-mail: [email protected]
Invited keynote paper for the XI International Conference on Rainwater Catchment Systems
Mexico, 25-29 August 2003
Abstract
Water resources management in water scarce regions is of crucial importance for water
assessments, water allocation, design and management of environmental systems. The
overgrowing population, as is the case observed in Latin America and the Caribbean, and the
prospective of climate change are calling for new approaches for water planning. Among the
several strategies to cope with water scarcity, the water harvesting techniques have
increasingly been used in many countries, although its full potential is far from being reached
in Latin America and the Caribbean. Moreover, in numerous cases the water harvesting
projects have not achieved their expected goal as the technologies and designs were not
suitable for either the environment or the cultural habits of the beneficiaries. In addition,
operation and maintenance of the schemes turned out to be either too costly and/or timeconsuming. In this paper a review of the difficulties in implementing the former water
harvesting techniques in Latin America and the Caribbean is presented emphasising the
most frequent errors which often cause failures. Some recommendations to avoid these
errors are also discussed, including the use of an environmental impact assessment
approach.
Introduction
The development of civilizations has always been strongly dependent on availability of water.
The very high rate of increase in total global water use witnessed since the middle of last
century is responsible for critical situations in attending water demands in several regions of
the world. In most countries situated in arid and semi-arid regions, water availability per
capita is already below the level that would allow enough food to be locally grown to feed
their population.
Considering the persistently growing pressure on finite freshwater and soil resources, it is
becoming increasingly clear that the challenge of feeding tomorrow’s population is to a large
extend about improving productivity of water within present land use, as new arable land is
relatively limited. Irrigated lands, which account for almost twenty percent of world’s cropland,
consume around three-quarters of the annual renewable freshwater resources used by man
and yield around forty percent of the world’s food. For that reason, agricultural specialists are
counting on irrigated land to produce most of the additional food that will be needed
worldwide (Kirpich et al., 1999; Postel, 2001). However, in order to achieve this it is well
recognized that irrigation efficiency must be greater and the low-cost irrigation developments
must be available for poor farmers.
Meanwhile, it should be remembered that rainfed agriculture still plays, and will continue to
do so, a critical role in food production as eighty percent of the agricultural land worldwide is
under rainfed agriculture – ninety percent in Latin America and the Caribbean (values for
some countries in the region are shown in Table 1). Moreover, ninety-five percent of current
population growth occurs in developing countries with a significant proportion still depending
on a predominantly rainfed-based economy. Unfortunately, in several regions, including Latin
America and the Caribbean, rainfed agriculture has generally been associated to low yield
levels and high on-farm water losses. In fact, it is fundamental that crop output per unit of
water input increases in both irrigated and rainfed systems, as per capita arable land area is
declining even without considering the risks of soil degradation. In Latin America the per
capita arable land area in 1995 was two-thousand square meters and there is an estimate
that it will decrease to one-thousand-and-one hundred square meters in 2050 even if there is
no soil degradation and conversion to non-agricultural uses (Lal, 2001).
Table 1: Irrigated land as a percentage of cropland for some countries in Latin America and
the Caribbean, 1997 (WRI, 2000)
Country
Argentina
Brazil
Chile
Mexico
Peru
Irrigated land as a percent of cropland
6
5
55
24
42
New concepts in water management in scarcity regions based on the use of water harvesting
techniques have been proposed and successfully applied in several countries to augment the
available water resource to enable an upgrading of rainfed agriculture and to supply drinking
water for human consumption both in urban and rural areas. Those cases tend to receive the
most attention in the literature. However, the overall success is much less than expected in
combining technical efficiency with low cost and acceptability to potential beneficiaries. In this
paper the most frequent errors in water harvesting projects implemented in Latin America and
the Caribbean, mainly in rural areas, are presented and some recommendations for further
projects are discussed, emphasising the role of environment impact assessment approaches.
Historical approach of water harvesting in Latin America and the Caribbean
Water harvesting techniques were already the basis of livelihood in arid and semi-arid areas
many thousands of years ago, allowing the establishment of cities in the desert (Evenari et al,
1971). These techniques were independently invented and used in various parts of the world
and on different continents with a variety of local adaptations depending on specific
conditions and cultures, aiming at the solution of localized problems. Many investigators
argue that water harvesting techniques were pivotal in sustaining the high population
densities associated with the evolution of Meso-American civilization as, among other things,
these techniques were in close association with the key staples of pre-Columbian diet, which
includes maize, beans, squash and a drink made from agave (UNEP, 1983).
Although millions of hectares of land of the world were once used for water harvesting, a
variety of causes have brought a steady decline. One of the main reasons for this decline
could be related to the European expansion in the 16th century from when the colonizers
introduced and imposed a different type of agricultural system, as well as various new
domestic animals, plants and European construction methods. Sometimes these new
methods were not compatible to the environmental features of the colonies and former water
harvesting techniques were then abandoned. This was the case in Mexico, where aguadas
and aguaditas (artificial reservoirs) were used in pre-Columbian times to irrigate fruit trees
and/or forests and to provide water for the plantation of vegetables and corn on small areas
(Gnadlinger, 2000). Archaeological remains indicate that ground catchment systems known
as chultus were used in the Yucatan Peninsula as early as 300 AD (Gould and NissenPetersen, 1999) and they can still be seen, for example, in the Kabah archaeological site.
The European influence in this process appears to have a major hole after the middle of the
19th century as the technological development lead to a steady increase in area under
classical irrigation techniques with preference to large schemes – large dams, groundwater
development and piped irrigation projects with high input of fossil energy and electricity.
Small-scale irrigation and traditional irrigation techniques, which include the various
techniques of water harvesting and supplementary irrigation, have then received inadequate
attention or were totally forgotten.
During recent decades the interest in water harvesting techniques has increased as
agriculture and water projects based on high energy input and sophisticated technology
appear unsustainable for several countries, including those from Latin America and the
Caribbean. In fact, per capita irrigated area has declined by about seven percent since 1980
(Postel, 1996) due to the stagnation of irrigation development which is probably related to
rising costs and environmental constraints, including soil structure degradation, accelerated
erosion and soil salinization. About seventeen percent of South America irrigated land is
already moderately to severely degraded (Lal, 2001). Moreover, it is worth mentioned that
half the world’s large dams were built exclusively or primarily for irrigation and they supply
thirty to forty percent of irrigated area (Bird and Wallace, 2001). However, the social and
environmental opposition against large dams is growing.
Therefore, developing new or adapting old water harvesting techniques associated with the
use of modern materials have increasingly been adopted. Several national and international
bodies have launched programmes to investigate the potential of water harvesting techniques
but it is well recognised that much has to be done in order to clearly identify their real
capabilities in several environments conditions. Much of the efforts of the international bodies
are concentrated in Africa, for sure due to the critical social, economical and environmental
situation verified in several countries of this continent. Unfortunately, millions of people in
Latin America and the Caribbean have also been suffering all the detrimental consequences
of water scarcity.
Water resources crisis in Latin America and the Caribbean
Poverty, especially rural one, continues to be one of the major problem assailing Latin
America and the Caribbean region, with approximately fourty-four percent of its entire
population and sixty-four of the rural population living below the poverty line. Around thirtyeight percent of the rural population live in extreme poverty conditions (IFAD, 2002). Rural
poverty is one of the main causes of migration to urban areas. Currently, there are five cities
with more than five million inhabitants – Buenos Aires, Lima, Mexico City, Rio de Janeiro and
São Paulo – and around thirty cities which populations exceed one million inhabitants.
Agriculture and rural economic activities are major sources of employment and are of critical
importance in terms of eradicating poverty. Although a variety of policies and development
models have been experimented in the region, at both macro and micro levels, much has still
to be done to change the current poverty situation. However, the region has some features
that must be borne in mind when designing and implementing rural development strategies
aimed at poverty eradication (IFAD, 2002):
•
the marked inequality in the distribution of wealth and income in the region;
•
indigenous people constitute the largest group (about one third) of all rural poor
people;
•
the region as a whole (particularly the rural areas) is highly vulnerable to devastating
effects of recent natural disasters, including droughts;
•
there is a serious policy and institutional weakness throughout the region, especially
in terms of providing rural people with (direct and indirect) access to assets and the
services they require;
•
access to and use of land constitutes a serious problem throughout the region, as the
majority of agricultural producers work small plots, usually located in marginal, lowproductivity areas, and this contributes to the deterioration of natural resources; and
•
as a general rule, the countries in the region have been receptive to innovation and
novel approaches to rural development.
Thirty-two percent of the entire rural poor population of the region lives in arid and semi-arid
subtropical areas. Therefore, rural development programs, which should include projects
oriented towards land and farming, depend, among other factors, on adequate water
availability, which is always a problem in drought-prone areas. However, it should be
remembered that the urban high concentrations could represent a pressure to shift water out
of agriculture to supply cities.
From a nationwide point of view it could be said that there is no water crisis facing any
country in Latin America and the Caribbean if the analysis is based on general water indices.
As an example, one may consider the water scarcity index (WSI) – relationship between the
annual used water and the long-term annual renewable water resources. Four levels are then
identified (WMO/UNESCO, 1997):
(1) WSI < 10%: low water scarcity – only a little water management is needed;
(2) 10% < WSI < 20%: moderate water scarcity – water supply commonly becomes a
significant problem and a need arises for water planning and investment in water
facilities;
(3) 20% < WSI < 40%: medium to high water scarcity – careful management is needed to
ensure that uses remain sustainable; and
(4) WSI > 40%: high water scarcity – severe water supply problems can be expected
requiring intensive management and high investments.
In the majority of the countries in Latin America and the Caribbean the water scarcity index is
less then 10% and only for Mexico and for some Caribbean countries the values of the above
index indicate the occurrence of water scarcity problems. However, it should be remembered
that the use of indices could not identify the regional and local water scarcity problems that
occur in great continental areas. In addition, water scarcity problems can be observed even in
regions with an abundant quantity of superficial water resources, due to, for example, the lack
of geological conditions to accumulate significant groundwater reserves. And this is the case
of the North-eastern Brazil, a semi-arid region where its habitants have been subjected to
water scarcity situations. Apart from the arid zones of Northern Mexico and part of the Pacific
Coast of South America, water shortage problems have also been reported, among others, in
some regions of Argentina, Brazil, Bolivia, Paraguay, Uruguay, Venezuela, Central America
and the Caribbean.
Although the Latin America and the Caribbean region has relatively high water supply service
levels, with approximately eighty-five percent of the population having coverage, a large
disparity is apparent between urban and rural areas as ninety-three percent of the urban
population have water supply coverage in contrast with sixty-two percent of the rural one
(WHO/UNICEF, 2001). The awareness and understanding of existing water problems at local
and regional scales have already gone a long way both in Latin America and the Caribbean.
Nevertheless, the greatest challenge is still to be overcome, which is to provide water to the
over concentrated urban and to the still unattended rural areas, and to supply the food
production in a sustainable manner.
The major constraint is one of instituting more rational and better water management
practices, for which instruments from the following phases must be considered: a) the
management of supplies, to obtain more water; b) the management of demands, to achieve
more use of water; c) the allocation, to achieve more value from water; and d) the
environmental integrity, to protect water quality (Petry, 2001). Unfortunately, only in rare
cases all these phases have properly been analysed in Latin America and the Caribbean and
the consequence is the current water resources crisis in the region. The main reasons for the
water problems are enormous, including the lack of water policies, mismanagement and illplanned development, water quality degradation and wasteful practices.
Despite the current financial crisis in the region, in most cases when surface water sources
are exhausted or degraded, the decision makers prefer to choose the management of
supplies based on large-scale schemes rather than to consider the management of demands
or a better water allocation policy, which include the following preventive instruments: water
use efficiency, water conservation and changes in production. Therefore, considerable funds
are allocated to the construction of new dams, interbasin transfer systems and pipelines to
bring water from remote sources instead of opting for local solutions such as the use of water
harvesting techniques.
Water quality has been deteriorating in several water bodies in Latin America and the
Caribbean due to rapid destructive actions such as unregulated domestic and industrial
waste dumping and rare or inadequate sewage treatment. Furthermore, the wide application
of fertilizers and pesticides has heavily polluted irrigation percolate and return flows,
presenting a significant threat to the aquatic environment. Although some countries have a
relatively strong legal framework related to the above, enforcement is generally weak.
In this manner, the environmental integrity has not been a priority and besides water
mismanagement, owing to inappropriate land use and soil mismanagement, the arid and
semi-arid zones in the region have been subjected to desertification that decreases the
productive capacity by reducing soil fertility, water retention capacity and protective ground
cover, causing soil erosion, compaction and salinization. Soils in semi-arid regions, and
particularly those in the tropics, suffer significant declines under the pressure of excessive
cultivation, livestock herds and polluting industrial processes.
Climatic events interact with the effects of human actions exacerbating degradation. It should
be noted that global warming represents a threat for a more widespread crisis in the arid and
semi-arid zones of Latin America and the Caribbean. Some of the most severe impacts of
climate change are likely to come not from the expected increase in temperature but from the
changes in precipitation – which will probably decrease in arid and semi-arid regions –,
evapotranspiration, runoff and soil moisture, which are crucial factors for water planning and
management. With respect to agriculture, the scenario of impact in tropical regions includes
the following aspects (Rabag and Prudhomme, 2002):
•
the growing season will be reduced;
•
increased carbon dioxide may benefit dry matter production but not grain yield; and
•
an increased in disease and pests’ incidence could occur and new pests may emerge.
The rapid population growth in the Latin America and the Caribbean corresponds to a stress
to natural systems as a whole, and water systems in particular. The growth rate has been
greater than the food production rate in recent years and the problem of food supply is
already enormous in several countries in the region, mainly in urban centres. The basic food
basket for most of the population is increasing in cost, while experiencing both quantitative
and qualitative reductions. It is a common belief the region has large areas for future
agriculture expansion. However, so far agriculture has been basically developed in areas with
favourable soil and climate. The land available to support agricultural production is
decreasing at a rapid rate due to erosion, ecological deterioration and urbanization. Besides
that, there is a continuous decrease in the availability of land that can be incorporated into
agricultural production at a reasonable economical and ecological cost. Therefore, increased
food production should mainly be achieved through improving productivity of water within
present land use. As already mention, rainfed agriculture is fundamental in this respect. The
use of water harvesting techniques shows good prospective for expanding supplies at a
relatively low cost, enabling an improvement in soil and water productivity and attending part
of drinking water demand.
Sustainable agriculture and food production
Although per capita world food production has grown by twenty-five percent over the last forty
years, the world still faces a persistent food security challenge, as almost eight-hundred
million people are lacking adequate access to food – eight percent are in Latin America and
the Caribbean. Bolivia, Haiti and Nicaragua (based on data from WRI, 2000), for example,
still have an average per capita food consumption of less than the minimum human
requirement for nutrition. Modern agriculture methods have been helping to raise average per
capita consumption of food but, on the other hand, poor and hunger people worldwide need
low cost and readily available technologies. Nonetheless, this needs to happen without
damage to an environment increasingly harmed by existing agricultural practices.
Basically food supply can be increased by:
•
expanding the area of agriculture, by converting new lands but resulting in losses of
important ecosystems; and/or
•
increasing per hectare production, both in rainfed and irrigated lands.
The latter could be done by applying demand management strategies for agricultural
systems, which includes, especially for water scarcity regions, practices and management
decision of agronomic, economic and technical natures, as illustrated in Table 2. Irrigation
management under water scarcity requires innovative and sustainable research, which
includes the use of non-conventional waters, such as treated wastewater and saline waters,
and deficit irrigation scheduling – optimising strategy under which crops are deliberately
allowed to sustain some degree of water deficit and yield reduction.
Table 2: Demand management strategies for agricultural systems, especially for water
scarcity regions (adapted from Pereira et al., 2002)
Objective
reduced demand
water saving/conservation
Technology
• low demand crop varieties/crop pattern
• cultivation practices for water stress control
• surface mulch and soil management for controlling
evaporation from soil
• water harvesting and conservation tillage for
augmenting soil infiltration and the soil water
reserve
higher yields per unit of water
•
higher farmer incomes
•
•
improved farming practices (e.g. fertilizing, pest and
diseases control)
select cash crops
high quality of products
Environmental and health problems have been associated with the stresses on
agroecosystems due to agriculture intensification – obtaining more output from a given area
of agricultural land. There is a growing concern about the long-term capacity of
agroecosystems to produce food. These stresses include increased erosion, soil nutrition
depletion, salinization and waterlogging of soils, and reduction of genetic diversity among
major crops. Moreover, agriculture intensification may accentuate negative impacts on other
ecosystems, including the harmful effects of increased soil erosion on downstream fisheries
and reservoirs, the damage to both aquatic ecosystems and human health from fertilizer and
pesticide residues in water sources, in the air, and on crops, and even broader
consequences for biodiversity and for alteration of the global carbon, nitrogen and
hydrological cycles (WRI, 2000).
Due to all those impacts, although it has been well recognized the successfully increase in
food production by using the former type of agriculture, there have been a greater support for
the use of more sustainable agriculture measures. As for the case of the concept of
sustainable development, the general philosophy behind the concept of agricultural
sustainability is not new and encompasses the best use of nature’s goods and services
mainly to integrate natural processes into food production processes and to minimize the use
of non-renewable inputs that damage the environment or harm the health of farmers and
consumers. However, it is fundamental to evaluate to what level agricultural production can
be increased without sacrificing sustainability, especially in water scarcity regions.
Pretty et al. (2003), after analysing by survey during 1999-2000 two-hundred-and-eight
projects – forty-five in Latin America, sixty-three in Asia and one-hundred in Africa –
concluded that there have been promising advances in the adoption and spread of more
sustainable agriculture, by using low cost, locally available and environmentally sensitive
technologies, to increase food production. They discerned in their dataset three types of
technical improvement in these food production increases:
•
pest control with minimal or zero-pesticide use;
•
improvements in soil health and fertility; and
•
more efficient water use in both rainfed and irrigated farming.
In several regions of the world modern agriculture depends on a great variety of pesticides to
control pests, weeds and diseases. Pretty et al. (2003) pointed out that in the projects
surveyed by them the farmers had found many effective and more sustainable alternatives.
Besides the pest control with minimal or zero-pesticide use, agricultural sustainability seeks
both to reduce soil erosion and to make improvements to soil physical structure, organic
matter content, water holding capacity and nutrient balance. Soil health may be improved
through the incorporation of plants with capacity to release phosphate from the soil into
rotations, use of inorganic fertilizers where necessary, and adoption of conservation tillage
methods.
In Latin America the conservation tillage methods have found a widespread utilization in the
last decade, although the experience began in the early 1970’s. There are now fifteen million
hectares under zero-tillage – even though there is some disturbance of the soil – in Brazil,
eleven million in Argentina and one million in Paraguay (Pretty et al., 2003). The ratio
between the areas under zero-tillage and the total cropped area in Brazil is greater than the
same for the United States of America (Saturnino and Landers, 2002). Apart from large
farmers, small ones in Brazil are also benefiting from the technology, as zero-tillage adoption
has been based on research at microcatchment level. The environmental benefits of zerotillage are substantial and include: reduced use of fertilizers, improved rainfall infiltration,
reduced siltation of reservoirs, less flooding, higher aquifer recharge, lowered costs of water
treatment and cleaner rivers.
Water resources are very inefficiently used in both rainfed and irrigated agriculture.
Improvements in agriculture productivity can be achieved by allowing new or formerly
degraded lands to be brought under farming and by increasing cropping intensity on existing
lands. Water harvesting techniques can be applied in order to increase the water availability,
either to directly increase the soil water content or to be stored for further application as
supplemental irrigation in order to mitigate water stress periods occurring during the cropping
season.
In the dataset used in the survey carried out by Pretty et al. (2003) there were forty-five
representations from Latin America, but only water harvesting experiences from Africa and
Asia were mentioned by the authors. Although this fact may be not relevant to obtain general
conclusions, it is in agreement with the ascertainment that the full potential of water
harvesting techniques is far from being reached in Latin America and the Caribbean. In the
sequence of this paper some aspects of the water harvesting techniques will be considered,
mainly related to their application in Latin America and the Caribbean.
Current context of water harvesting in Latin America and the Caribbean
Water harvesting is usually employed as an umbrella term describing a range of methods of
collecting, concentration and storage of water that runs off a natural or a man-made
catchment surface. In its broadest sense, water harvesting can be defined as the collection of
water for its productive use (Siegert, 1994). In fact, several definitions of water harvesting
have been suggested and there is no generally accepted one.
Normally the water harvesting techniques have been used to:
•
restore the productivity of land which suffers from inadequate rainfall
•
increase yields of rainfed farming
•
minimize the risk in drought-prone areas
•
combat desertification by tree cultivation
•
supply drinking water for human and livestock consumption
•
fight soil erosion
The main components of a water harvesting system are the catchment area, the storage
facility and the target area. The catchment area is the part of the land that contributes some
or all its share of rainwater to a target area outside its boundaries and includes rooftops
compounds, rock outcrops and hill slopes. Storage takes place in surface and subsurface
reservoirs, in the soil profile as soil moisture and in groundwater aquifers. The harvested
water is used in the target area; in agricultural production, the target is the plant or the
animal, while in domestic use, it is the human being or the enterprise and its needs.
As for the case of its definition, several classifications of water harvesting have been
presented and it is beyond the scope of this paper to discuss them. The water harvesting
methods can be subdivided according to the source of water used – water in the air, runoff
water, groundwater – and to the kind of storage applied – above-ground and underground. In
general terms then four main groups of water harvesting can be distinguished according to
the source of water used, as presented in Figure 1.
WATER HARVESTING
water in the air
fog and dew
harvesting
surface runoff
rainwater
harvesting
floodwater
harvesting
groundwater
Groundwater
harvesting
Figure 1: The four main groups of water harvesting techniques (Prinz, 1999)
Recent field studies suggest that the prospect of doubling yields, or even quadrupling, is
realistic by producing more crop per drop of rain. However, such large yield cannot be
achieved with water management alone and at the establishment of water harvesting projects
agronomic practices should also be improved (Falkenmark et al, 2001). Therefore, a water
harvesting project for agriculture purposes should be linked with simultaneous soil fertility
management – including the use of agricultural implements and addition of organic matter –,
pest management, crop rotation, capacity building among farmers and extension services.
Although water harvesting techniques had extensively been used in Latin America and the
Caribbean, in modern times their utilization appears to be relatively limited and their
performance is at least badly reported. With few exceptions, currently research in Latin
America and the Caribbean on this topic has not been published in widely circulated journals
– such as Agricultural and Forest Meteorology, Agricultural Water Management, Journal of
Arid Environments, Journal of Irrigation and Drainage Engineering etc. A relatively small
number of experiences are published in reports having limited circulation which are not easily
available to the scientific community.
In a Water Harvesting Symposium held in Arizona in March 1974 (Frasier, 1975) the
representation from Latin American and the Caribbean countries were limited to few
experiences from Mexico. Following this, a workshop was organized in 1980 to present an
overview of water harvesting use in the United States of America and Mexico (Dutt et al.,
1981). Apart from experiences developed in Brazil and Mexico, only experiences from few
Caribbean islands, Peru (one about fog harvesting), Nicaragua (one) and Venezuela (one),
the last two about rainfall collection by roof catchments, were presented in the last three
international conferences on rainfall catchment systems – Iran (IRCSA, 1997), Brazil (IRCSA,
1999) and Germany (IRCSA, 2001) – promoted by the International Rainwater Catchment
System Association. In fact, Mexico and Brazil have been putting some efforts to propagate
their own experiences in water harvesting by promoting national conferences about the
theme. The first national conference in Mexico was held in 1990 and the ninth in 2002. In
Brazil the first occurred in 1997 and the fourth in 2003.
In a general basis, the only initiative to carry out a comprehensive analysis of the state-of-the
art in water harvesting use in Latin America and the Caribbean was that of the Organization
of American States, which published in 1997 a Source Book of Alternative technologies for
Freshwater Augmentation in Latin America and the Caribbean (OAS, 1997), based on the
results of two workshops, one held in Peru and the other in Barbados, both in 1995. An
inventory of available technologies were then listed, which includes the implementation of
rainfall collection by roof catchments – the most widespread used technique – in situ
rainwater harvesting, fog harvesting, runoff collection using surface and underground
structures, flood diversion and artificial recharge of aquifers all over the region.
With respect to rainfall collection by roof catchments, records show that on the Island of
Bermuda evidence of those systems dates back to 1628; today they are required by law
(Gould and Nissen-Petersen, 1999). The use of rainwater harvesting systems in the United
States Virgin Islands has been mandated by the government and the specifications for the
systems are overseen by the national agency and since 1996 water storage facilities are
required to be constructed in residences in Barbados if the roof or living area exceeds twohundred-and seventy-eight square meters (OAS, 1997). In quantitative terms, the most
impressive initiative has been recently proposed and put into operation in Brazil, which is the
Program of One Million Rural Water Tanks, aiming to attend families in the country’s semiarid region. In this same region hand-dug cisterns made from lime mortar and bricks were
introduced by the Portuguese and were commonly used until about forty years ago (Gould
and Nissen-Petersen, 1999).
It is worth mention that fog harvesting technology is well developed in Latin America and the
Caribbean and the experiences in Chile are disseminated in the scientific community (König,
2001). In fact, the technology has also been used in other countries in the region – Ecuador,
Honduras, Mexico and Peru, for example –, but as pointed out by Schemenauer and
Cereceda (1997), the application to other locations is neither simple nor automatic.
Therefore, it remains a localized water supply option, dependent on local climatic conditions
(OAS, 1997).
Much has still to be done in terms of water harvesting applications in Latin America and the
Caribbean. The challenge is to learn from both positive and negative examples of water
harvesting applications to, in the former case, establish policies that enable their proliferation,
and in the latter, understand the causes of failures and draw up recommendations for
improvement and further development. However, it should be remembered that the
experience with water harvesting applications gained in countries such as Israel, Australia
and the United States of America may have limited relevance to Latin America and the
Caribbean as in the first country the research emphasis is on microcatchments for fruit trees
and in the last two the research is directed towards improving runoff yields from treated
catchment surfaces (Critchley and Siegert, 1991). On the other hand, the experience in other
parts of the world – Africa and Asia – is very useful as the causes of failures are common to
the majority of attempts to implement water harvesting projects in Latin America and the
Caribbean.
Frequent errors in water harvesting projects in Latin America and the Caribbean
Being an attractive innovation is not enough and the reasons why efforts to implement water
harvesting techniques fail are numerous and have been discussed by several authors
(Barrow, 1999; Gould and Nissen-Petersen, 1999; OAS, 1997; Oweis et al, 1999; Siegert,
1994). Although only the publication by OAS refers specifically to water harvesting
applications in Latin America and the Caribbean, the conclusions are generally similar.
Notably, future policies to over come the listed problems must take into account the particular
features of the considered regions.
The reasons of failures can be broadly divided in institutional, technical, economic and social,
although some may be included in more than one division. There is no agreed-upon definition
and terminology with regard to water harvesting and this ambiguity impedes the exchange of
information (Siegert, 1994). In fact, the term water harvesting encompasses a broad
spectrum of techniques to obtain water from different sources, as shown in Figure 1.
However, in Latin America and the Caribbean it is still common to associate the term just to
the direct utilization of rainwater. Although several books and manuals on the subject have
been published in the last decades, the great majority of them are in English, which can
represent a great restriction for their spread consultation in Portuguese- and Spanish-spoken
countries, which are by far the most populated in Latin American and the Caribbean. It is
necessary to standardize both the terminology related to the technical terms used in water
harvesting systems, including the classification of the various techniques, and the formats for
data collection.
There is a lack of awareness about the existence and importance of these techniques at
several decision-making and public participation levels (OAS, 1997). Most water harvesting
activities are carried out in certain isolation and/or without proper interinstitutional, multidisciplinary and intersectoral coordination. In most countries where water harvesting has
been practising there is an absence of an adequate institutional structure, which includes
beneficiary organizations and government training programmes for farmers, pastoralists and
extension staff. Moreover, there is an absence of adequate legislation (OAS, 1997) and of a
long-term government policy as its strategies related to water harvesting development are
insufficiently supported (Siegert, 1994).
An incompatibility of water harvesting techniques with traditional food production strategies
has frequently been observed as some technologies may not be appropriate for the region as
designs can be based on wrong assumptions and be not flexible. In some cases they require
high labour for construction and maintenance and heavy reliance on machinery, which is
often unavailable in the post-project phase, while farmers are discouraged from using their
own equipment. The lack of farmer training in activities related to design, construction and
maintenance could make farmers dependent on technicians and unable to understand the
technical design parameters – for example, rainfall intensity, runoff coefficients etc – and to
treat their lands when and where they want to. The lack of adequate hydrological data and
information is a limiting factor for confident planning, design and implementation of water
harvesting projects resulting in systems with poor performance. For example, incorrect
estimates of likely annual rainfall and reliance on mean estimates when precipitation varies
from year to year can be dangerous (Barrow, 1999).
Water harvesting projects are notoriously weak with regard to monitoring and evaluation and
it was observed that most projects fail to collect data even at the most basic level (Siegert,
1994). This fact, of course, contributes to the difficulties of sharing information about
successful experiences and causes of failures. Although some manuals describing the most
common techniques have been recently published, mostly with experiences in Africa,
normally they do not present a guideline for selecting a proper water harvesting technique to
be applied in a given region.
During all phases – but especially in the planning one – of water harvesting projects often
insufficient attention is given to social and economic aspects such as land tenure,
unemployment and involvement of beneficiaries (Siegert, 1994). And this has turned out to be
the major constraint for a successful implementation of a water harvesting project. This is the
case for rainwater-tank projects as failure to fully engage individuals and communities in the
planning, managing and maintenance of their own water supply projects will almost certainly
ensure that the project will not succeed. Even when the technology is adequate to ensure
high-quality construction of tanks failure may occur due to a lack of training, quality control or
poor management, or use of inappropriate materials. Moreover, although regular system
maintenance and cleaning are strongly recommended, both are often neglected, increasing
the water contamination risks (Gould and Nissen-Petersen, 1999).
It is simple fundamental to check early on whether innovations are attractive to farmers who
normally seek and need short-term gains (financial or labour saving or improved security of
livelihood) rather than long-term benefits or those to people off-farm – for example, reduced
erosion (achieved by farmer’s efforts) benefits water users elsewhere by reducing siltation or
recharging groundwater, but does little for the farmer who expended the effort (Barrow,
1999). The farmers who are not adequately consulted or involved normally become resentful.
In this sense, to prevent greater inequality at the village level as a result of the introduction of
water harvesting techniques, special care should be taken to make sure that poor farmers
and woman farmers have equal access to the techniques (Oweis et al., 1999). In general,
there has been an emphasis on engineering and/or new crops, leading to neglect crucial
factors such as storage, transport and marketing. In fact, if there is no good storage, transport
or way of getting a satisfactory return there is little point in improvements (Barrow, 1999).
Notably, in several cases the costs of the water harvesting projects can be a major constraint
for their widespread use. Therefore, a comprehensive computation of the costs to implement,
operate and maintain a water harvesting project is crucial to support any economic analysis,
which besides the direct benefits, should take into account the indirect ones provided to
beneficiaries and society in general. Although frequently available, there is a considerable
variability about the costs of water harvesting projects, which means that the often required
comparison between those and the costs of other supply technology should be undertaken
with caution. Generally, benefits are not available within the literature. In the source book
published by OAS (1997), a detailed evaluation of costs per volume of water of some
alternative technologies for freshwater augmentation in Latin America and the Caribbean was
carried out and the values can be seen in Table 3.
It is interesting to note the similarities of the above reasons with part of the general
conclusions from a workshop to discuss the state-of-the-art of agroforestry systems in the
arid and semi-arid areas of Latin America and the Caribbean (FAO, 1994) – in which the
adoption of water harvesting techniques should be considered. The final report pointed out
that important advances had been achieved to the sustainable development of arid and semiarid zones in the region. However, some limitations were listed: lack of awareness about the
existence and importance of the agroforestry systems at several decision-making levels; lack
of knowledge to project and implement these systems; problems related to the land tenure;
due to the innovative features, these systems could not be attractive; there is a limited
experience in implementing, evaluating (especially economically) and developing these
systems; and lack of diffusion of successful experiences.
Table 3: Costs (expressed in United States dollars of 1995) to augment freshwater in Latin
America and the Caribbean using alternative technologies (OAS, 1997)
Technology
Applications
rainwater harvesting from domestic water supply
Costs (U$ per m3 Extend of use
of water)
2 to 5
widespread use,
rooftop catchment
and small-scale
agriculture
fog harvesting
agriculture, domestic
and industrial
runoff collection using domestic water supply,
surface and underground agriculture, livestock,
structures
industrial and mining
water conveyance by primarily domestic water
marine vessels
supply
3 (Chile)
but decrease as
other options
become available
limited to Pacific
coastal areas
1.20 widespread
0.60
to
(Argentina)
0.1 to 2 (Chile)
1.5 (Bahamas)
limited to
Caribbean small
islands
It should be emphasized that there are some constraints in transferring water harvesting
systems from one area to another due to the enormous variations in climate, soil types,
topography, cropping patters, culture and economic situation. A successfully transfer is
normally associated with two areas closely related in most of the above features (Critchley et
al., 1994). Even though, the implementation of improved systems should be developed
considering past and current lessons learned from the shortcomings of previous applications.
And those failures point out to the necessity of new approaches in planning and decision
mechanisms of future water harvesting projects.
The role of Environmental Impact Assessment in the implementation of water
harvesting projects
Although it is widely accepted that the water management in drought-prone regions must be
a part of an environmental strategic plan, the conventional planning tools to tackle the related
problems have been generally disintegrated. It has become increasingly clear that the search
for sustainable and optimized ways to cope with water scarcity needs a more comprehensive
and broadly response from society in general or, in other words, water management must be
the concern of all population living in areas under water scarcity risk (Petry, 2001).
The Environmental Impact Assessment process has been adopted, accepted and legally
required in several countries in the last decades. Although some improvements are still
needed, its procedures and methodologies have successfully been applied in water resource
development projects and in the design and implementation of agricultural projects. In both
cases, the suitability of water harvesting techniques must be always considered as an
alternative to augment water availability.
With respect to the implementation of large-scale water harvesting projects as a part of a
rural development strategy to supply drinking water for human and livestock consumption in
rural communities and to provide water for agriculture, the main reasons for mandatory
Environmental Impact Assessment are presented below (adapted from Kakonge, 1995):
•
interdisciplinary nature, as institutional, social, economical, physical, technical and
environmental issues are considered in order to proceed an adequate planning;
•
uncertainties, as agricultural projects have a complex interactions with natural
systems and many of the intrinsic uncertainties would be addressed to obtain a longterm beneficial effect;
•
feedback mechanisms, which would provide crucial information to enable planners to
revise or adjust the project cycle; and
•
importance of local knowledge, which can be fully incorporated by making provision
for the assessment of indigenous environmental knowledge, by understanding local
resource-use details and by use of local value sets to evaluate predicted impacts.
The experience already acquired is fundamental for the design and implementation of water
harvesting programs, and the adoption of a pilot project is a useful and convenient starting
point, especially in areas with limited data. Potential synergies can be achieved by the
establishing of guidelines for the systematic application of the well known and approved
phases of Environmental Impact Assessment – namely screening, scoping, prediction and
mitigation, management and monitoring, auditing –, in the implementation of water harvesting
projects and by the definition of a comprehensive performance criteria for different water
harvesting techniques on the basis of social and economic indicators.
Concluding remarks
Several recommendations to implement better water harvesting projects have largely been
repeated in many publications. Nevertheless, they deserve to be still widely republished in
order to motivate the use of the water harvesting techniques in a successful manner. Their
general aspects enable them also to be used in Latin America and the Caribbean.
The planning of water harvesting systems should be a part of an integrated land and water
resource management plan, and should include the improvement of agronomic practices and
farmer training. In fact, in each country practising water harvesting, one agency/institution
should take the lead to coordinate water harvesting activities among the various involved and
be assigned to establish a regional data base for the storage, processing and analysis of
collected data from water harvesting systems (Siegert, 1994). National hydrological institution
should be strengthened with regard to the collection of data relevant to water harvesting.
In order to standardize definition and terminology with reference to technical terms used in
the design of water harvesting systems, the International Rainwater Catchment Systems
Association could suggest a series of definitions and classification of the various water
harvesting techniques. In Latin America and the Caribbean, the Brazilian and Mexican
Rainwater Catchment Systems Association would have the task to prepare the technical
material, respectively, in Portuguese and Spanish.
There is a need to emulate water harvesting techniques developed at experimental stations
on a larger scale of a field situation to assess their viability and effect on agricultural
productivity. Moreover, water harvesting projects should be planned, designed and
implemented by a multi-disciplinary team of experts in order to ensure that technical, social,
economic and environmental aspects are adequately covered (Siegert, 1994), which
indicates that an environmental impact assessment application has a fundamental role to
play in obtaining an appropriate and effective approach.
Technical aspects of water harvesting projects are likely to be improved with further research
on: development of methodologies to evaluate the water harvesting potential of a given
region; application of geographical information system and remote sensing to identify
potential sites for water harvesting; development of methodologies to evaluate the efficiency
of water harvesting systems; and development of methodologies to help the choice of a
proper water harvesting techniques to be applied in a given region.
Finally, it is important to emphasize that sustainability in agriculture is a goal, which is only
reached in very rare cases. Soil and water conservation, which can be achieved by using
water harvesting techniques, represent then part of the basic infrastructure for this
sustainable development and can effectively decrease risks of rainfed agriculture.
References
Barrow, C.J. (1999); Alternative irrigation: the promise of runoff agriculture, Earthscan
Publications, United Kingdom.
Bird, J. and Wallace, P. (2001); Dams and development - an insight to the report of the World
Commission on Dams, Irrigation and Drainage, volume 50, issue 1, pages 53-64.
Critchley, W. and Siegert, K. (1991); Water harvesting: a manual for the design and
construction of water harvesting schemes for plant production, FAO paper AGL/MISC/17/91,
Food and Agriculture Organization, Rome, Italy.
Critchley, W. R. S., Reij, C. and Willcocks, T.J. (1994); Indigenous soil and water
conservation: a review of the state of knowledge and prospects for building on traditions,
Land Degradation & Rehabilitation, volume 5, pages 293-314.
Dutt, G.R., Hutchinson, C.F. and Anaya-Garduño, M. (1981); Rainfall collection for agriculture
in arid and semiarid regions, Proceedings of a workshop hosted by the University of Arizona,
United States of America, and the Chapingo Postgraduate College, Mexico, Commonwealth
Agriculture Bureau, United Kingdom.
Evenari, M., Shanan, L. and Tadmore, N. (1971); The Negev: the challenge of a desert,
Harvard University Press, Cambridge, United Kingdom.
Falkenmark, M., Fox, P., Persson, G. and Rockström, J. (2001); Water harvesting for
upgrading of rainfed agriculture: problem analysis and research needs, SIWI report 11,
Stockholm International Water Institute, Sweden.
FAO (1994); Consulta de expertos sobre el avance de la agroforestería en las zones áridas y
semiáridas de América Latina y el Caribe, Food and Agriculture Organization, Santiago,
Chile.
Frasier, G.W. (1975); Proceedings of the water harvesting symposium – March 1974, United
States Department of Agriculture, Arizona, United States of America.
Gnadlinger, J. (2000), Rainwater harvesting in rural areas, 2nd World Water Forum, The
Hague, The Netherlands.
Gould, J. and Nissen-Petersen, E. (1999); Rainwater catchment systems for domestic supply
– design, construction and implementation, Intermediate Technology Publications, London,
United Kingdom.
IFAD (2002); IFAD Strategy for rural poverty reduction in Latin America and the Caribbean,
International Fund for Agricultural Development, Rome, Italy.
IRCSA (1997); Proceedings of the 8th international rainwater catchment systems conference,
International Rainwater Catchment Systems Association, Tehran, Iran.
IRCSA (1999); Proceedings of the 9th international rainwater catchment systems conference,
International Rainwater Catchment Systems Association, Petrolina, Brazil.
IRCSA (2001); Proceedings of the 10th international rainwater catchment systems
conference, International Rainwater Catchment Systems Association, Mannheim, Germany.
Kakonge, J.O. (1995); Dilemmas in the design and implementation of agricultural projects in
various African countries: the role of environmental impact assessment, Environmental
Impact Assessment Review, volume 15, issue 3, pages 275-285.
Kirpich, P.Z., Haman, D.Z. and Styles, S.W. (1999); Problems of irrigation in developing
countries, Journal of Irrigation and Drainage Engineering, volume 125, issue 1, pages 1-6.
König, K.W. (2001); The rainwater technology handbook: rain harvesting in building, WiloBrain, Dortmund, Germany.
Lal, R. (2001); Managing world soils for food security and environmental quality, Advances in
Agronomy, volume 74, pages 155-192.
OAS (1997); Source book of alternative technologies for freshwater augmentation in Latin
America and the Caribbean, Organization of American States, Washington, United States of
America.
Oweis, T., Hachum, A. and Kijne, J. (1999); Water harvesting and supplemental irrigation for
improved water use efficiency in dry areas, SWIM paper 7, International Water Management
Institute, Sri Lanka.
Pereira, L.S., Oweis, T and Zairi, A. (2002); Irrigation management under water scarcity,
Agricultural Water Management, volume 57, issue 3, pages 175-206.
Petry, B. (2001); Water Management in arid and semi-arid regions – issues and expectations,
Key note in the IV Interamerican dialogue on water management, Foz do Iguaçu, Brazil.
Postel, S. (1996); Dividing the waters: food security, ecosystem health, and the new politics
of scarcity, Worldwatch Paper 132, Worldwatch Institute, Washington, United States of
America.
Postel, S. (2001); Growing more food with less water, Scientific American, February issue.
Pretty, J. N., Morison, J. I. L. and Hine (2003); R. E., Reducing food poverty by increasing
agricultural sustainability in developing countries, Agriculture, Ecosystems & Environment,
volume 95, issue 1, Pages 217-234.
Prinz, D. (1999); Traditional irrigation techniques to ease future water scarcity, XVII
International congress of the international commission on irrigation and drainage, Spain.
Ragab, R and Prudhomme, C. (2002); Climate Change and Water Resources Management
in Arid and Semi-arid Regions: Prospective and Challenges for the 21st Century, Biosystems
Engineering, volume 81, issue 1, pages 3-34.
Saturnino, H.M. and Landers, J.N. (2002); Zero tillage and technology transfer in the tropics
and sub-tropics, in: The Environment and Zero Tillage, edited by: Saturnino, H.M. and
Landers, J.N., Associação de Plantio Direto no Cerrado, Brasília, Brasil.
Schemenauer, R.S. and Cereceda, P. (1997); Fog-water collection in arid coastal locations,
IV Reunión Nacional sobre Sistemas de Captación de Lluvia, Torreón, Mexico.
Siegert, K. (1994); Introduction to water harvesting: some basic principles for planning,
design and monitoring. In: Water harvesting for improved agricultural production, Food and
Agriculture Organization, Rome, Italy.
UNEP (1983); Rain and stormwater harvesting in rural areas, United Nations Environment
Programme, Tycooly International, Dublin, Ireland.
WHO/UNICEF (2000); Global water supply and sanitation assessment 2000 report, World
Health Organization/ United Nations Children's Fund, New York, United States of America.
WMO/UNESCO (1997); The World’s water – is there enough?, World Meteorological
Organization/United Nations Educational, Scientific and Cultural Organization, WMO-No.
857.
WRI (2000); World resources 2000-2001: people and ecosystems – the fraying web of life,
World Resources Institute, Washington, United States of America.