[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
dam-l "River Keepers Handbook": New report from IRN/LS
The following is an excerpt from "River Keepers Handbook: A Guide to
Protecting Rivers and Catchments in Southern Africa," a new report by IRN.
"Southern Africa is, by and large, a dry place. Water is one of the
region's most precious resources, and yet the region's life-giving sources
of water -- the catchments that funnel water to rivers, wetlands and lakes
-- are increasingly under threat. To avoid irreparable harm to these
essential natural systems will require a regional 'catchment protectors'
movement, a critical mass of people who make the protection of water
resources their top priority. Such a movement will require citizens who
understand the complex workings of their catchments, and their own place
within these systems."
So begins "River Keepers Handbook: A Guide to Protecting Rivers and
Catchments in Southern Africa". The 52-page report contains information
that will help activists, communities, educators and individuals become
informed river advocates, able to ask the right questions about
river-development schemes and to press for better alternatives. The booklet
includes sections on what is a catchment, threats to catchments, and how to
become a "catchment keeper."
The report is available for US$15 from IRN (email von@irn.org), or in South
Africa for R60 from Environmental Monitoring Group, PO Box 18977, Wynberg,
South Africa 7824; Email: liane@kingsley.co.za; Ph: +2721.761.0549; Fax:
+2721.762 2238.
-------------------------------------
This excerpt describes some of the many alternatives to water supply which
can help human society flourish without undermining the integrity of the
ecological systems we depend on.
New Approaches to Water Supply
Using water more efficiently can in effect create a new source of supply.
According to Sandra Postel, an expert in international water scarcity
problems, technologies and methods are now available which could cut water
demand between 40-90 percent in industry, 30 percent or more in cities, and
between 10-50 percent in agriculture without reducing economic output or
quality of life. In developing countries, the potential benefits of water
demand-side management programs are huge in terms of money saved and
ecological damage avoided, as well as freeing up water supply to extend
coverage to the unserved.
Water management expert S. Mtetwa of Zimbabwe described the goals
of demand management programs for water at a 1998 United Nations conference
on freshwater management in Zimbabwe:
"Water demand management aims to:
* safeguard the rights of access to water for future generations;
* limit water demands;
* ensure equitable distribution;
* protect the environment;
* maximise the socio-economic output of a unit volume of water, and
* increase the efficiency of water use."
Demand management includes several approaches to conserve water,
including economic policies, notably water pricing; laws and regulations,
such as restrictions on certain types of water use; public and community
participation, to ensure that solutions are workable and have public
support, and technical solutions, such as installing water flow
restrictors. Reducing the amount of water consumed is key to cutting water
expenses. Demand management cannot be thought of only from a technical
angle. Water-saving technical measures always have economic, legal,
institutional and political aspects that must be considered as well.
Industrial Water Conservation
Industry is, generally speaking, water-intensive. According to South
Africa's Department of Water Affairs, a factory can use 450,000 litres of
water to produce a small car, 130 litres to produce a bicycle, and 53
litres to make a pair of shoes. Coal mining in Mozambique has been
estimated to use up to 1 cubic meter per second in the mining and washing
process. Although water use for industry is rather low in Africa (for
example, it is under 8% in South Africa), there is still room for
improvement. In some parts of the world, certain water-intensive industries
have greatly reduced the amount of water needed for production, including
chemicals, iron and steel, and paper. In some countries these industries
are both reusing and recycling water in current production processes and
redesigning production to require less water. For example, in the US,
industrial water use dropped by over one-third between 1950 and 1990, while
industrial output nearly quadrupled. In the former West Germany the total
amount of water used in industry today is the same as in 1975, while
industrial output has risen by nearly 45 percent. In Sweden, strict
pollution-control measures have cut water use in half in the pulp and paper
industry, while production has doubled in little more than a decade.
Progress has been slow in developing countries, however. In China,
for instance, the amount of water needed to produce a ton of steel ranges
from 23 to 56 cubic metres, whereas in the US, Japan and Germany, the
average is less than 6 cubic metres. Similarly, a ton of paper produced in
China requires around 450 cubic metres of water, twice as much as used in
European countries. China now faces severe, chronic water shortages in many
of its largest watersheds. China's Yellow River, one of its largest rivers,
is now considered to be ephemeral because it is so over-allocated. China
also has more than 100 cities that are sinking dangerously due to excessive
extraction of groundwater.
Modified Agricultural Practices
Since agriculture accounts for nearly 70 percent of the world's fresh water
withdrawn from rivers, lakes, and underground aquifers for human use, the
greatest potential for conservation lies with increasing irrigation
efficiency. By reducing irrigation by 10 percent, we could double the
amount available for domestic water worldwide. This can be done by
converting to water-conserving irrigation systems; taking the poorest and
steepest lands out of production; switching to less-thirsty crops (which
may require changes to government subsidies for certain crops);
implementing proper agricultural land drainage and soil management
practices, and reducing fertilizer and pesticide use.
Typically, governments provide water to large commercial farmers at
greatly subsidized rates, decreasing the need for conservation and
promoting wasteful practices. This has led to widespread use of wasteful
irrigation systems. Studies show that just 35-50 percent of water withdrawn
for irrigated agriculture actually reaches the crops. Most soaks into the
ground through unlined canals, leaks out of pipes, or evaporates before
reaching the fields. Although some of the water lost in inefficient
irrigation systems returns to streams or aquifers, where it can be tapped
again, water quality is invariably degraded by pesticides, fertilizers and
salts that run off the land. This is in fact another way that commercial
agriculture "uses" water: by polluting it so that it is no longer safe to
drink. In areas where commercial agriculture is prevalent, runoff from
farms has poisoned rivers, groundwater and lakes with dangerous levels of
pesticides and fertilizers. Poorly planned and poorly built irrigation
systems not only harm water quality, but can also irreparably harm the
crop-growing capability of the land through salinization. Especially in
arid areas, salts that occur naturally in the soil are drained away with
irrigation runoff. Unless properly drained, the salts accumulate in the
upper layers of soil, poisoning crops. Poorly drained irrigation water can
also raise the groundwater table until it reaches the root zone,
waterlogging and drowning crops. Globally, some 80 million hectares of
farmland have been degraded by a combination of salinization and
waterlogging.
Switching to conserving irrigation systems has the biggest
potential to save water. Experts say drip irrigation could potentially save
40-60 percent of water now used for agriculture. Conventional sprinklers
spray water over crops, not only irrigating more land than is needed to
grow the crop but also losing much to evaporation. Drip irrigation,
however, supplies water directly to the crop's root system in small doses,
where it can be used by the plant's roots. Water is delivered through
emitters that drip water at each plant, or perforated piping, installed on
the surface or below ground. This keeps evaporation losses low, at an
efficiency rate of 95 percent. Although by 1991 some 1.6 million hectares
were using drip irrigation worldwide, this is still less than one percent
of all irrigated land worldwide. Some countries have made drip irrigation a
serious national priority, such as Israel, which uses drip irrigation on 50
percent of its total irrigated area. But clearly it is the exception, and
most dry countries have a long way to go.
Another promising irrigation system, called low-energy precision
application (LEPA), offers substantial improvements over conventional spray
sprinkler systems. The LEPA method delivers water to the crops from drop
tubes that extend from the sprinkler's arm. When applied together with
appropriate water-saving farming techniques, this method also can achieve
efficiencies as high as 95 percent, according to the report Solutions for a
Water-Short World, published by the Johns Hopkins Population Information
Program (see "Resources"). Since this method operates at low pressure,
energy costs also drop by 20 percent to 50 percent compared with
conventional systems. Farmers in the US state of Texas who have retrofitted
conventional sprinkler systems with LEPA have reported that their yields
have increased by as much as 20 percent and that their investment costs
have been recouped within one or two years, the report states.
Another growing practice is to reuse urban wastewater on nearby
farms growing vegetables and fruits. Today, at least half a million
hectares in 15 countries are being irrigated with treated urban wastewater,
often referred to as "brown water." Israel has the most ambitious
brown-water program of any country. Most of Israel's sewage is purified and
reused to irrigate 20,000 hectares of farm land. One-third of the
vegetables grown in Asmara, Eritrea, are irrigated with treated urban
wastewater. In Lusaka, Zambia, one of the city's biggest informal
settlements irrigates its vegetable crops with sewage water from nearby
settling ponds.
Traditional water harvesting and irrigation
Southern Africa has a rich tradition in small-holder farming. Water
consumption in such systems is usually sustainable. Such systems may
include rain- and groundwater harvesting, micro-dams, shallow wells,
low-cost pumps, and moisture-conserving agricultural practices. Careful
consideration of traditional water-saving techniques combined with
effective modern methods may help to balance the needs of dryland
agriculture and help to meet the developing world's water demand.
Up until recently, many of these traditional irrigation methods
were excluded from official irrigation programs in southern Africa, such as
UN Food and Agricultural programs. According to water expert Sandra Postel,
although they are getting greater recognition now, Africa's small-scale
irrigation methods are rarely offered the investment credits, extension
services and other forms of support given to large public irrigation
schemes. "As a result, small-scale irrigation's potential in Africa remains
constrained and underdeveloped, and food production remains less secure,"
Postel writes in her 1992 book Last Oasis (see Resources).
Runoff agriculture has been used in regions where the average
yearly rainfall is 100mm or less. During high rainfall, rainwater is
collected and diverted into storage tanks and used throughout the dry
season.
The Sonjo of Tanzania divert water with small brushwood dams, up to
three metres high, to irrigate the slopes of Mount Kilimanjaro. Small dams
of this type are easily destroyed by floods, a feature which can enhance
the sustainability of the overall system as the floods then wash away most
of the sediments behind the dams. Unlike large dams, brushwood dams still
permit water to flow through, thereby decreasing ecological damage
downstream. Because the dams are built with local materials and labour,
rebuilding them is usually not a major expense.
Another traditional method involves placing long lines of stones
along the contours of gently sloping ground to slow runoff and spread the
water across a wider area. Developed in the Yatenga region of Burkina Faso,
this method is now being used on over 8,000 hectares in 400 villages
throughout the country. It is also used in Kenya and Niger. This practice
has increased crop production by about 50 percent, according to Solutions
for a Water-Short World.
Dambo farming in Zimbabwe is a classic example of the sustainable
uses of a natural water resource. Dambos are small (usually less than half
a hectare), seasonally waterlogged valleys at the head of a drainage basin
where water makes its way to larger channels. Water collected from the
runoff of higher ground and channels support the many gardens growing in
these valleys. Dambos can maintain water during prolonged droughts, and
have been the only regions to produce maize during some droughts.
Permaculture
A more comprehensive approach to reducing all agricultural inputs, from
water to fertilizer, is to adopt the lessons of permaculture. This is a
sustainable agricultural system based on observing natural systems and
working with, rather than against, nature. It integrates animal husbandry,
energy-efficiency, and water harvesting and conservation techniques. It
emphasizes growing a variety of crops which offer different benefits and
soil management. Plants and animals are grown for their fertilizer or
because they produce natural pesticides; plant and animal waste is
composted and put back in the soil. Pests such as snails are "harvested" to
feed livestock such as ducks and geese, and the land is contoured to catch
rainwater and mulched to reduce evaporation. Multipurpose use of the land
helps makes the system stronger against floods, fires, and pests.
Permaculture's particular practices can vary from place to place,
based on observation on what works for that climate, soil and cultural
setting. Some traditional farmers in Africa practice their own version of
what is now known as permaculture. The modern system of permaculture has
been practised in Botswana, South Africa and Lesotho.
New Sources for Water
Although demand-management should always be examined first when additional
water is needed, conservation will not always preclude the need for new
sources of supply. There are many sustainable ways to get water which cause
less damage to ecosystems and communities than the large-scale
infrastructure projects currently in favor with planners.
Rainwater Harvesting
In Africa and elsewhere around the world, more communities are returning to
small-scale water harvesting, usually using a system that collects water
from house rooftops. A January 19, 1999 article in the Ethiopian newspaper
The Monitor describes a successful roof water harvesting program begun by
the Ministry of Agriculture with help from the Swedish International
Development Agency (SIDA) and a local NGO called Water Action. "Imagine, if
you may, hundreds of thousands of households or even whole communities,
throughout the country, that chronically have water shortages during a good
part of the year; even drinking water. And water for livestock, too," the
article says. "This new introduction (not a new technique, mind you, the
Mesopotamians practiced it) can enable households to save water that they
can use for drinking purposes for up to five months, and with an average
size reservoir. Such households might even have some extra water to spare
for garden plants." The only issue for most Ethiopians, the article notes,
is the cost. The water tank, water conduit system and gutter cost more than
most farmers can afford. It is hoped that the program will get wider usage
with the help of subsidies through international aid agencies, and research
efforts to bring down the cost of the materials.
A South African group, Association for Water and Rural Development
(AWARD), has created an information sheet on how to collect water from the
roof of a house, school or other building. The group calculates that for
every 30mm of rain falling, a house with a 50m2 roof designed to funnel it
into a water tank could collect 1200 litres. AWARD estimates that this
could save a person 16 trips to the local water-collection source. The
group estimates tank costs at anywhere from R180 for a 2500 litre concrete
block tank to R1000 for a 4500 litre steel tank purchased from a
manufacturer. (See Contacts for information on how to reach AWARD.)
Desalination: Some 70 percent of the earth's surface is water, but most of
that is undrinkable seawater. By volume, only 3 percent of all water on
earth is fresh water, and only about 1 percent is easily accessible surface
freshwater. Water desalination is a process used to remove salt and other
dissolved solids to create fresh water.
Desalination is an attractive water source for many reasons,
especially because the supply is virtually limitless and unaffected by
drought. For coastal countries, desalted water is not vulnerable to
political changes, unlike water supply from shared rivers. Desalting
technologies can be built in stages to meet demand, unlike most large-scale
water infrastructure projects. Desalination projects also do not lead to
the displacement of indigenous peoples, changed agricultural lifestyles or
serious ecological impacts.
In most cases, desalted water is not the sole source of a
community's water supply (though this may change as the cost of desalted
water goes down); it is usually combined with water from less expensive
sources. In 1991, desalting plants in approximately 120 countries worldwide
had the capacity to produce 4.1 billion gallons a day.
The most common concerns about desalination are that the process is
too expensive and consumes too much energy. In some places, desalinized
water costs many times more than conventional local water sources. However,
technical breakthroughs are beginning to lower the price (although still
not to the artificially low levels that agribusiness is used to paying for
water). Cost comparisons for desalted water are often made to existing
water supplies, which generally did not include a full, fair cost-benefit
analysis when they were developed. To be fair, comparisons should be made
to the cost of developing other new sources (including environmental and
social costs in the analysis).
The amount of salt to be removed greatly affects the cost of
desalting, as does the method used to remove salts. The most significant
factor in desalinated water is energy. Energy for most current technologies
amounts to about 30-40 percent of the total cost.
There have also been recent breakthroughs that are expected to
reduce the costs for desalination, primarily by cutting back how much
energy is required. For example, in 1998 the Singapore-based company
AquaGen International announced that it has developed a cheaper, portable
water desalination plant that can be assembled anywhere quickly. AquaGen
says the modular system of its plant makes installation easy. The unit can
produce 100 cubic meters (25,000 gallons) of water for less than
US$300,000. The company says that its plants are up to three times more
energy efficient than those now in use. The plants are relatively small,
producing up to 5,000 cubic meters of drinking water per day (compared to
up to 327,000 cubic meters/day for the big plants in the Middle East).
AquaGen is doing a feasibility study for a plant that can process 45,000
cubic meters and hoped would be operational in four years.
Israeli, Palestinian and US scientists are embarking on an
ambitious desalination program that is intended to create a "New
Desalinized Middle East." One of the program's goals is to build
solar-powered desalination machines that can fit on a truck, then teach
villagers to use them and even make them. The program will also look at how
water is affected by salt and pollutants. The fully self-supporting
desalination system was being evaluated in early 1999 by Al-Azhar
University in Gaza, Palestine. The system can desalinate up to 600 liters
of brackish water a day. It is being designed with irrigation in mind, and
the plan is to develop micro-irrigation systems in parallel. The units
require little maintenance, as they have few moving parts.
New developments in alternative energy may prove to be a boost for
desalination as well. Solar thermal power and fuel cells may provide good
sources of power for desalination plants. Since places with good solar
power potential are usually the places most in need of water, there is a
huge potential to link the two.
Recycling Waste Water: A largely untapped source of water for irrigation
and groundwater recharge is treated municipal wastewater. Recycling this
"waste" product into a reliable water supply has huge benefits. It makes
use of the nutrients in sewage to feed crops and keeps them from polluting
waterways. It postpones the need to enlarge and update costly new sewage
discharge systems, and eliminates the problems from discharging wastewater
into rivers and oceans. It protects freshwater ecosystems by reducing the
amount of water extracted from rivers and lakes. Recycled wastewater can
also be used to help restore aquatic ecosystems harmed from
over-extraction. Using recycled wastewater instead of importing water from
hundreds of kilometers away can also result in significant energy savings.
Israel has the most advanced system of waste water recycling.
Currently, 70 percent of sewage is treated and used for irrigation.
Officials predict that by 2010, one-fifth of the nation's total water
supply will come from recycled waste water. Israel uses many different
treatment schemes for its many water-reuse projects. One method relies on
algae-activated organisms to treat the waste water. The waste water is
initially stored in a series of ponds in which the anaerobic and aerobic
treatment is sufficient to irrigate crops.
Calcutta, India, channels much of its raw sewage into a system of
natural lagoons, where fish are raised. The city's 3,000 hectares of
lagoons produce about 6,000 metric tons of fish a year for urban consumers.
The fish are safe to eat because the complex biological interactions in the
lagoons remove harmful pathogens from the sewage.
As the technology to treat wastewater has improved, so have the
applications for the use of the water. A small but growing number of cities
are beginning to use highly treated wastewater to supplement drinking water
supplies. Windhoek, Namibia, for example, was the first city in southern
Africa to used recycled waste water in its public supply and has been doing
so for more than 15 years.
Highly treated wastewater cannot be piped directly into a water
supply. Most commonly, wastewater is used to augment the drinking-water
supply by adding it first to a lake, reservoir, or underground aquifer. The
mixture of natural and reclaimed water is then subjected to normal water
treatment before it is distributed as drinking water for the community.
There is also much water to be gained by reducing that used for
sewage treatment. Treating waste is a hugely water-intensive process, and
the commonly used systems cannot be sustainably expanded to serve the three
billion people now without access to sewage treatment. Natural water
treatment systems such as using wetlands often can be an alternative to
modern water treatment technologies. Recycling waste for agricultural
purposes by using oxidation ponds and aerated lagoons does not require as
much land as is often assumed; however, the land requirement of oxidation
ponds is a stumbling block for their use - particularly in urban areas.
Moreover, it decreases pollution, reduces the need for fertilizers, and
often can be accomplished with small-scale, low-cost technology that is
based on local traditions, is decentralized and ecologically sound.
Groundwater Replenishment
Groundwater currently makes up a large part of the water supply of many
Southern African countries. While some countries appear to have plentiful
groundwater resources, others recognize that in some cases their water
supply aquifers are being rapidly depleted. Because of the region's erratic
rainfall pattern, it is not uncommon for water managers to temporarily
over-extract water from certain aquifers to make it through dry periods,
and allow aquifers to recharge during wetter years. But longterm
over-pumping of groundwater can cause the water table to drop (up to
hundreds of metres), or allow salty water to be move into the water table,
making it unpotable or causing land subsidence. Usually aquifers will
recover if allowed to rest and recharge, but they can compress when water
is removed and never regain their previous storage capacity.
Namibia has been studying the possibility of using aquifers as
underground reservoirs to stretch existing surface supplies. By
artificially injecting certain aquifers with purified surface water to be
extracted later, the Windhoek municipality hopes to reduce the amount of
water lost each year to evaporation. The city estimates that it could save
more than 10 percent of its water supply using this method.
In India, two-thirds of the villages in Gujarat now have no
permanent, reliable source of water, mainly because of the
over-exploitation of groundwater. To help solve the problem, villagers are
building small earthen impoundments across seasonal streams to create a
small pond during the monsoon, which is used to recharge groundwater
supplies. After the monsoon, the pond gradually recedes. The impoundments
are only used to restore the groundwater, and are never tapped directly for
water supply. The technology is very simple, relatively cheap to build, and
easy to maintain. A government-funded group helps villagers design and pay
for the impoundments. Villagers are responsible for building and
maintaining their impoundments, and about 20 percent of the building costs.
One Indian engineer believes such projects could ultimately collect up to
50 percent of the water that falls on the state.
-end-
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Lori Pottinger, Director, Southern Africa Program,
and Editor, World Rivers Review
International Rivers Network
1847 Berkeley Way, Berkeley, California 94703, USA
Tel. (510) 848 1155 Fax (510) 848 1008
http://www.irn.org
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::