Rainwater harvesting for domestic use
by Indra Dissanayake
Beside all other things that the economic development is globally
concerned paramount importance objective. Similarly this scenario has
been considered as highly valuable for countries to achieve
individually. In this context more emphasis are to be given by countries
for sustainable development.
 Sustainable development means optimum utilization of natural and
other resources while giving more emphasis to the benefit of future
generations. The prime objective of Sri Lanka is also to achieve
sustainable economic development through the optimum utilization of it's
natural resources.
At present Sri Lanka is confronted with series of problems in the
areas of specially loss of forest cover, contamination of waters,
degradation of rural lands, and highest rate of pollution in air, water
and discharging of liquid and solid waste.
It is also required to be concerned about increasing population and
as a result unprecedented demand for food, urbanization which include
supply of clean water or pipe born water, sanitation and better housing
etc.
Without proper management and such action related strategies, the
overall stress towards natural resources would be aggravated creating
negative impacts leading to a disastrous situation.
The social benefit of the Sri Lankan could be enhanced through better
practice of well balanced utilization of natural resources such as
water, land, air and also other biological resources.
It can increase the wealth of Sri Lanka by avoiding costly
environmental abuses. There can be significant improvement of the
livelihood through implementation of well planning, which based with
sound policies, result oriented strategies and decision making as well
as applying of best practices of technologies.
This would enhance the status of natural resources resulting the well
being of the people. Similarly it is also require understanding of
complex interaction among ecological and social systems. Rainwater
Harvesting (RWH) in Sri Lanka has a historical consideration in many
ways.
Specially the location of Sri Lanka and specific phenomena of two
monsoonal and intermonsoonal patterns of rain are favorable to receive
fair amount of rainwater for almost all part of the island.
Rainwater harvesting was evolved for more than many centuries of
years. Our ancestral kings were very keen to collect rainwater using
different methodologies such as construction of giant tanks and
reservoirs connected to cascade system which are used for retaining of
water for domestic uses, agriculture and recharge of ground water
aquifers.
Even at present in urban areas there are a large number of water
retention low lands kept undisturbed (called wetlands or marshes) in
order to retain storm water and to prevent flooding and allowed natural
process of ground water recharge system.
Therefore these marshy wetland areas are called 'the green lungs of
the environment'. It support to maintaining of ground water table and
natural services of entire ecosystem as well as safe guard the food
security. In the 5th century, the construction of Sigiriya rock fortress
by the king Kasyapa was the unique and magnificent showpiece with
storage tanks and swimming pools etc. to present as rain water
collection model.
This system worked much vital manner when we consider the following
valuable quotation expressed by one of our ancient kings the great
Parakramabahu (1153-1186 A.D.) during Polonnaruwa kingdom. Not a single
drop of water received from rain should be allowed to escape in to the
sea without being utilized for the benefit of human kind. (Chulawamsa)
In view of the reasons out lined as follows it is possible to
highlight how far that the Sri Lanka is confronted with water related
stresses at present and even in the future.
However, most of the people are unaware about exact picture and kept
in the dark until the situation become worse and starts suffering in
many ways. Therefore it is vital to disseminate more information on
water and situation of the water resources at least for the general
public to become vigilant on these issues.
Basic issue
At present the adequate level of water supply for the people of Sri
Lanka has becoming an issue to the government .The growing trend of
population is the basic issue for all other problems in relation to the
water scarcity.
Therefore, water consumption and demand for water was naturally lower
and hardly manageable. The beginning of the twentieth century Sri Lanka
had only few millions of people. In 1871 Sri Lanka population was only
2.4 million.
From this level of population from 1871 to 1981 it was increased by
518.5 percent. For many decades average annual rate of growth was about
1.7 and crude birth rate (CBR) came down, higher life span, improvement
of health and sanitation, eradication of many types of epidemics were
taken place.
The population of Sri Lanka was estimated to be more than 20m at the
end of 2007 which implies an average density of around 320 persons per
sq. km. This situation is some what higher rate compare to world
average. The increase of population is directly affect to the demand for
additional water usage for day to day life including sanitary
requirements.
Along with the increase of population, additional housing for
dwelling were also required to be constructed. There are different types
of settlements can be seen in Sri Lanka.
Traditional folk villages, estate settlements, rural service centre
based hamlets/villages, commercial activity centered villages and urban
centers based settlements. Based on these categories our administrative
and political setup also established such as pradeshiya Saba, town
councils and urban councils and Municipal councils.
Based on the various reports of the respective authorities we can
glance the trend and the present picture of housing and settlement
development. The demand for new houses in Sri Lanka is rising around
100,000 unit per year (CB Report 2005).
In addition there is need for upgrading of 1,325,880 substandard
units requiring improvement. On top of that there are about 100,000
housing units either completely or partially damaged due to December,
26th 2004 tsunami disaster. Accordingly, the National Housing
Development Authority (NHDA) has implemented a housing programme for
building of 175,000 houses during the period from 2005 to 2007. At the
same time NHDA distributed roofing materials for 43,625 during 2005.
Under the Real Estate exchange (Pvt) ltd also planed to construct
3,000 houses during 2005 to 2007. In comparison with the financial
facilities provided by various institutions that the private sector
organizations are leading the way.
They have issued 89,333 loan facilities to assist housing
development. While state mortgage bank has issued 23,305 during the year
2005. In addition to all these efforts there are many NGOO and a number
of foreign donor agencies commenced construction of thousands of houses
for homeless needy people.
At the same time Urban Development Authority commenced it's programme
for developing 62 Large, medium and small township encouraging private
sector to construct series of luxury apartments.
This would give an idea of how far we are to be ready for facilitate
and ready to cope up with the requirement of water and sanitation
facilities at least for the above development programmes and other
proposed developments.
Demand
The demand for water has increased along with the new settlements.
New housing complexes were erected to facilitate the demand for
shelters. The traditional well water supply became unsuitable and
polluted mainly due to increase of development schemes, factories,
housing and condominiums, dumping of garbage, and so on.
They were required to be supplied with pipe borne water mainly for
drinking purposes and sanitation facilities.
In this manner the demand for potable water has also increased. In
2005 there were 291 water supply schemes operated for 907,662 water
connections and 383 million cu. mtr. supplied under the national water
supply and drainage board (NWSDB), (Central Bank 2005).
However, this supply is only for 39% of the population had access to
pipe borne water. The United nation requires that all citizens in the
country should access safe drinking water and adequate sanitation
facilities by 2015. The NWSDB has estimated that the investment
requirement of the water supply sector up to 2010 would be Rs. 140
billion.
In Sri Lanka large portion of pipe borne purified water is used for
toilet flushing, washing of clothes and other cleaning activities such
as vehicles, machineries and equipments etc. Specially, in major
institutions and industries where large number of people visit for work
and day to day personal matters have to be provided with mainly wash
room facilities where thousands of liters of pipe borne water is wasted
daily due to carelessness and negligence.
Let us consider what is happening to the water resources in Sri
Lanka. In many ways water resources are depleting due to adverse impacts
of the present activities taking place in the name of so called economic
development .
As mentioned above, along with the infrastructure development and
expansion of settlement there are large extent of lands became under
land clearing and or reclamation and development. These activities are
much adverse to the ground water resources. The low lying areas natural
functions were retarded due to destruction to flood detention and storm
water collection and limitations to seepage that water in to ground and
not allowing recharge of aquifer has created a situation of availability
of less ground water quantities.
Labour force
As visualized in the table below there are a large number of
industries established throughout the island and commence implementation
of activities. In considering the labour force many thousands of liters
of water used for washing and cleaning.
Similarly, many factories which are using water for their production
process finally discharge in to the environment. Of these factories many
are discharging waste water without any treatment and releases chemicals
such as arsenic, cadmium, chromium, mercury, nickel, copper, lead and
zinc and other toxic compounds.
This would leads to pollute water ways as well as reducing available
utilizable ground water. Best example is Ratmalana industrial zone which
consist of large number of chemical and other types of production
industries such as textile dying, paints and asbestos etc. Today ground
water pollution level in Ratmalana is very much adverse.
There are many studies carried out by various agencies indicated that
in Ratmalana area ground water contamination is very much adverse and
suggested to implement central purifying treatment plant in order to
arrest further pollution.
However, due to inefficient and backward beaurocratic system, funding
allocation for treatment plant for Ratmalana was not seen the day light.
Now the situation is worse due to escalation of costs and devaluation of
rupee in the world market those costs cannot be bare up.
One better known another example is faecal contamination and
agrochemical leaching in to ground in Jaffna district there is a disease
called Blue baby syndrome among the users of contaminated water.
Specially ,shrimp farming in puttalam/Chilaw area is also another
example. We have the experience of higher levels of unrestricted water
uses even ground water pumping and discharging of polluted water to the
surrounding environment. Ultimately it was ended up with destruction to
the industry as well as total destruction of environment affecting to
the peoples livelihood.
As a result total collapse of prawn farms were taken place and
recovery of previous environmental condition was also became impossible.
Prawn farming was one time very much lucrative business and attractive
investment. However, within few years later it became an uncodusive and
unprofitable venture.
Not only these shrimp farms were unsuitable for aquaculture farming,
but also any other type of agriculture practices or any other types of
plantation. At present these lands cannot be utilized for any other
types of viable economic activities.
This shows that due to prawn farming activities both surface water
and ground water became contaminated in Chillaw, Mundalama areas.
Dumping of waste is also an adverse impact to the water resources.
most of the occasion many factories discharge most of their solid wastes
to the marshy or reclaimable low lying areas.
Specially due to leachet flowing or seepage as well as decomposing of
waste to the sub soil, that ground water contamination take place. Most
of our local authorities are indiscriminately discharge waste including
hospital wastes without any sorting out and no proper records about
those areas or records about dumping grounds. After certain years, which
would lead erupt to an unknown reasons for diseases or some kinds of
environmental disastrous situation. Then people may try to find facts as
to what has happened but no body would be able to find the exact reason.
By that time there is no remedies or rectification measures for
averting the adverse impacts. E.g. Japanese mercury poisoning and mina
Mata diseases discovered after many years of suffering by thousands of
people.
In addition to the above there are many other sources of pollutants
such as agro based chemical such as carbofuran and other types of
weedisides and fertilizer nutrients dissolve in to the water resources.
Algae formation in number of reservoirs is a common example to show the
pollution level. Specially, Kotmale reservoir has badly developed algae
formation during dry seasons.
At the same time large number of hotels and restaurants are another
sources of pollution, discharging waste to the environment specially
affecting the water resources.
At this point it is important to mention here that the reduction of
reservoir capacity due to siltation is also alarmingly concerned by
authorities as it is again affecting to reduce water retention capacity
of the reservoirs.
Water bodies
Throughout Sri Lanka, there are a large number of water bodies
already polluted due to discharge of domestic, industry, hotel and
hospital effluent, agriculture chemicals, fertilizers and solid wastes.
It is very commonly known factor that Beira lake, Kandy lake and Lake
Gregory, Negombo lagoon and so many other water bodies seriously
polluted and very difficult to rehabilitate to the natural state. As a
result not only surface water bodies but also ground water resources too
affected.
Similarly the development of modern irrigation system as well as
concrete canals and drains are also adversely affect to the depletion of
ground water resources due to non availability of seepage in to the
ground soil.
Therefore storm water straight away flowing in to the rivers and to
sea. No body is able to utilize storm water like most of the developed
countries use and recycle these water for many other uses.
On the other hand there are certain factors to be considered in
relation to storm water. Specially our road network consist of many
thousands of Kilometers. The storm water flowing along those roads are
polluted due to dissolving of various substances, such as tar and waste
oil dropped on the road from the vehicles. This polluted water goes in
to the water bodies canals and rivers.
As mentioned above, up to 2006 Central Environmental Authority (CEA)
has issued Environmental Protection Licenses (EPL) which details are as
follows:
Site clearance for industries from 1990 to 2006 = 5,701
EPLissued in 2006 including renewals of 1351 = 2,129
Application for EPL 2006 = 3,035
(These figures are inclusive of high, medium and low polluting
industries scattered around the country).
According to economic performance indicators the annual mining sector
development is also a major contributor to the economy. Mainly gem
mining is encouraged to increase foreign income earning. Mining sector
includes gem, sand and other minerals, clay and quarry etc mining.
Specially gem and mineral mining process are involve removal of ground
water and as a result depletion of water resources affecting the bio
diversity too.
There are many instances of reduction in ground water level, during
minor dry period even drying of lands and dieing of plants and such
symptoms specially in Ratnapura district which is mainly a wet zone with
high level of ground water resources.
At the same time unattended pits are become as origin of mosquito
breeding and spreading so many diseases. Also these pits are the causes
of land slides and earth slips specially in hilly areas.
In Gampaha District along Maha oya sand mining and clay mining has
been destructively developed. Even in Kelani river and many other main
rivers are badly damaged due to rapid level of sand mining. As a result
it is clearly visible that river beds lowering and saline water
intrution in to the inland areas.
Also there is another problem along coastal belt low land areas
lanward salinity. This is mainly because of obstruction of land ward
fresh water flow due to adhoc construction and filling of marshy lands
without proper management measures.
We can see most of the coastal areas specially Southern, Western and
North western belt have been affected due to salinity intrution. In view
of this adverse impact there are changes in biodiversity and many other
human activities.
Geological and geographical set up of Sri Lanka is also influenced to
its water availability. Many of the hilly areas are not possible to
access water easily due to non retention of water and deep in ground
water table.
This may be due to forest clearing, soil erosion and destruction of
water sources. In some remote settlements of Kegalle, Kandy and Matale
districts are having general feature of hilly condition and it is
difficult to retain water in those hilly areas.
People who are living in those areas are confronted with many
hardships for fetching water for day to day water requirements. Some
villages of Anuradhapura, Puttlam and Hambantota districts are
confronted with seasonal dry spells. Also certain areas of coastal belt
are confronted with water scarcity due to salinity intrution.
Availability
Having considered the facts mentioned above, we can visualized the
main features of water availability and the condition of water resources
in Sri Lanka. It is an eye opener to our decision makers and policy
makers at least to act promptly and quickly to develop a mechanism for
best use of roof rain water which is a gift from the nature.
Roof water collection means getting clean water just from out side
their door step. It reduce arduous method and time spent for fetching
water. It is economical and ensure health and sanitation of the family,
specially in the areas of lime mixed and water containing of high
fluoride etc. substances.
There are very few studies to examine the economic issues involved in
conservation of water resources mainly through Roof Rain Water
Harvesting (RRWH) in Sri Lanka. Roof rainwater collection was a very
primitive and isolated method until recent time.
This forgotten resource of RRWH has received considerable attention
during the period of mid 1990s within the water shortage districts of
Sri Lanka. During the past few years RRWH were evolved as a result of
various studies as well as development of various technical inputs due
to recent efforts of both government and non government organizations
and several groups of innovative communities.
However, it was given a much less emphasis towards the impact of
harvested RRW consumption, Many developed countries such as Germany, USA
and Asian region countries such as India have given much attention and
priorities for collection of rainwater for domestic uses.
Therefore, it is vital to consider Economic Valuation(EV) and benefit
analysis to the rural and urban livelihood as well as to the society as
a whole. If we consider these benefits and values of savings which is
beneficial in many ways.
Through rainwater harvesting it is beneficial individually and as a
family in many ways. Those benefits have to be calculated separately
taking in to account that labour time savings, health, medicine and many
other components in order to show costs and benefits individually and
the society as a whole.
Like any other goods in the market there can be main three categories
for rain water harvesting system such as demand, water collection and
storing and distribution or reuse system. RRWH can be simple or complex
system depending on the requirement and the severity of the water
scarcity to be addressed. Rainwater harvesting cost calculation can be
done in consideration of materials used for this purpose.
It's main costs include labour charges and materials such as gutters,
down pipes, filters (not very complicated ones) and water retention tank
(capacity/size according to the daily and monthly requirements).
If any one is not happy to use rainwater for drinking purposes or
required to use rainwater as separately then water pump together with
separate overhead tank. These costs can be recovered within very short
period as the water supply is exclusively free and no water bills or no
hazel for fetching of daily water requirements.
Also no hazard of salinity, chemical, toxic or harmful external
particles and as a result it save medical or medicine cost for diseases
and labour time savings for people to engage in other activities. An
average calculation shows that 30 to 50 percent water is used by
consumers for toilets flushing and gardening including washing utensils
and cars etc.
According to the 2005 water supply data, this waste water quantity is
equivalent to approximately 100 m. cu mtrs. which is equivalent to Rs.
billions in monitory terms. On the other hand rainwater is the best
source of water for plants because it is free of salts and other
minerals that can be harmful to root growth.
Therefore use of free rainwater can reduce the use of drinking water
unnecessarily and massive cost to the government to supply purified
costly pipe water.
It is also support to reduce dependence on ground water and some what
control of off site flooding as well as erosion.
This mechanism has been successfully implemented by the Japanese
through their rainwater programmes. Rainwater harvesting can be
incorporated to large scale water uses such as schools, temples,
Government buildings, meeting halls and places where large gathering in
the Parking sites, pavilions and other complexes etc.
Supply system in order to utilize them mainly for toilet flushing and
gardening. On this purpose it can be suggested to incorporate at the
planning stage or in to new landscape during design phase.
****
Water Supply by National Water Supply and Drainage Board
2004 2005 Growth
Rate
2004 2005
Total number of water supply schemes 284 291 2.5 1.4
Total number of new connections
given during the period 58,781 66,117 18.1 12.5
Total number of connections
(as at end yr) 841,505 907,662 7.5 7.9
Total water production(Mn.,Cu.,Mtr.) 368 383 3.1 4.1
Unaccounted water %
Greater Colombo 36.5 35.9 -1.2 -1.7
Regions 29.6 30.9 -4.7 4.3
Source: Central Bank 2005 |
