Harvesting rainwater means harnessing life
Lionel Wijesiri
Regulations will be introduced to make rainwater harvesting for daily
use compulsory for all government institutions, Water Supply and
Drainage Minister Dinesh Gunawardane said in Parliament recently. The
minister said he introduced this concept when he was the Urban
Development Minister. He said rainwater harvesting is done successfully
in countries such as India and Nepal.
Water professionals in Sri Lanka are becoming increasingly worried
about the country's impending water scarcity. They suggest that the
population growth, pollution and climate change are likely to produce a
drastic decline in the amount of water available per person in many
parts of the country.
Water conservation, therefore, has become the need of the day. And it
is here that the concept of Domestic Roof Water Harvesting (DRWH) comes
into place. DRWH provides an additional source from which to meet local
water needs. In recent years, DRWH systems have become cheaper and more
predictable in performance. There is a better understanding of the way
to mix DRWH with other water supply options, in which DRWH is usually
used to provide full coverage in the wet season and partial coverage
during the dry season as well as providing short-term security against
the failure of other sources. Interest in DRWH technology is reflected
in the water policies of many developing countries, where it is now
cited as a possible source of household water.
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Schematic diagram of domestic rainwater harvesting system |
Rainwater systems deliver water directly to the household, relieving
the burden of water-carrying, particularly for women and children.
Collecting the water that falls onto household roofs provides an
attractive method of conserving water delivered directly to the home.
'Water without walking' relieves families of much of the burden of
water-carrying.
Activities
There has been much recent activity concerning domestic roof water
harvesting in countries as far apart as Kenya, China, Brazil and
Germany. Many countries now have Rainwater (Harvesting) Associations.
Lanka Rain Water Harvesting forum (LRWHF), a similar organization, was
launched in Sri Lanka in 1996 with the vision of 'leading the nation in
rainwater harvesting technology, construction and utilization to sustain
water needs'. The organization was instrumental in spreading the concept
and technology to many parts of the country. It is said that there are
more than 30,000 domestic rainwater systems in the country.
Domestic rainwater harvesting has been revived in Sri Lanka in 1995.
Ten years later, in 2005 the government, realizing the importance of
rainwater harvesting as a solution to overcome the water scarcity in the
country, passed a national policy on rainwater harvesting.
The policy objective is aimed at encouraging communities to control
water near its source by harvesting rainwater. The policy was followed
by necessary legislation which was gazetted on April 17, 2009, to amend
the Urban Development Authority By-Laws on drainage, which makes
rainwater harvesting mandatory in certain categories of new buildings in
areas under municipal and urban council jurisdiction.
Why rainwater harvesting?
Like in many regions of the world, in Sri Lanka, too, clean drinking
water is not always available and this is only possible with tremendous
investment costs and expenditure. Rainwater is a free source and
relatively clean and with proper treatment it can be even used as a
potable water source. In Sri Lanka, rainfall is the primary source of
water. The mean annual rainfall is around 1,800 mm with some areas
receiving only about 900 mm. The total amount of water received in the
form of rain is around 100 billion cubic metres per year. It is
estimated that out of the total water received, over 50 percent escapes
to the sea as run-off. It means, around 50 billion cubic metres of water
finally ends up in rivers, reservoirs and sea.
Rainwater harvesting saves high-quality drinking water sources and
relieves the pressure on sewers and the environment by mitigating
floods, soil erosions and replenishing groundwater levels. In addition,
rainwater harvesting reduces the potable water consumption and
consequently, the volume of generated wastewater.
There are numerous positive benefits for harvesting rainwater. The
technology is low cost, highly decentralized empowering individuals and
communities to manage their water. It has been used to improve access to
water and sanitation at the local level. In agriculture rainwater
harvesting has demonstrated the potential of doubling food production by
100 percent compared to the 10 percent increase from irrigation.
The biggest challenge with using rainwater harvesting is that in many
cases water management is based on renewable water, which is surface and
groundwater with little consideration of rainwater. Rainwater is taken
as a 'free for all' resource and the last few years have seen an
increase in its use. This has resulted in over abstracting, drastically
reducing water downstream users including ecosystems. For the
sustainable use of water resources, it is critical that rainwater
harvesting is included as a water sources as is the case for ground wand
surface water.
Ecosystem
There is an immediate need to find innovative opportunities enabling
development and human wellbeing without undermining ecosystem services.
Among such opportunities one can ask: What potential can rainwater
harvesting offer to enable increased human well-being whilst protecting
our environment? What role can small-scale decentralized rainfall
harvesting and storage play in integrated water resource management? And
in which specific contexts may rainwater harvesting create synergies
between good ecosystems management and human well-being?
Today, more people live in urban areas than in rural areas globally.
Cities can be considered as 'artificial ecosystems', where controlled
flows of water and energy provide a habitat for the urban population.
Accordingly, the principles of ecosystem management also apply to
sustainable urban water management. Rainwater harvesting has
increasingly been promoted and implemented in urban areas for a variety
of reasons.
The effect of multiple rainwater harvesting interventions on
ecosystem services in urban areas are two-fold. Firstly, it can reduce
pressures of demand on surrounding surface and groundwater resources.
Secondly, the rainwater harvesting interventions can reduce storm flow,
decreasing incidence of flooding and short peak flows.
Experiences
In Australia, withdrawals of water supply to the urban areas have
been diminishing due to recurrent droughts. This has spurred private,
commercial and public house owners to invest in rainwater harvesting for
household consumption. The increased use of rainwater harvesting
provides additional water supply and reduce pressures of demand on
surrounding surface and groundwater resources.
In most of Indian states, all commercial and institutional buildings,
tourist and industrial complexes, hotels etc, existing or coming up and
having a plinth area of more than specified square metres should have
rainwater storage facilities commensurate with the size of roof area.
Toilet flush systems will have to be connected with the rainwater
storage tank.
In parts of Japan and South Korea, rainwater harvesting with storage
has been implemented also as a way to reduce vulnerability in
emergencies, such as earth quakes or severe flooding which can disrupt
public water supply.
Network
To promote rainwater harvesting and utilization as an environmentally
sound approach for sustainable water management, a network should be
established involving government administrators, citizens, architects,
plumbers and representatives of equipment manufacturers.
It is essential to encourage regional exchanges amongst public
servants, citizens and industry representatives involved in rainwater
storage, seepage and use, as well as the conservation and reclamation of
water. The relevant implementation policies should then be established
to make rainwater utilization and other measures a part of the social
system.
* Let us accept rainfall as an important manageable resource in water
management policies, strategies and plans. Then rainwater harvesting
interventions are included as a potential option in land and water
resource management for human well-being and ecosystems productivity.
* Let us realize that rainwater harvesting is not a 'silver bullet',
but it can be efficient as a complementary and viable alternative to
large-scale water withdrawals, and reduce negative impacts on ecosystems
services, not least in emerging water-stressed basin
* Let us treat rainwater harvesting as a local intervention with
primarily local benefits on ecosystems and human livelihoods.
Stakeholder consultation and public participation are, therefore, key to
negotiate positive and negative trade-offs potentially emerging,
comparing rainwater harvesting interventions with alternative water
management interventions.
* Let us agree that the access and right to land can be a first step
to rainwater harvesting interventions. Special measures should be in
place so rainwater harvesting interventions also benefit land-poor and
landless in a community.
*Let us establish enabling policies and cost -sharing strategies,
(including subsides) to be provided together with technical know-how and
capacity building. |
