The technique  of
RainWater Harevsting is an innovation utilized for gathering water from
housetops, arrive surfaces, street surfaces or shake catchments utilizing
straightforward procedures, for example, pots, tanks and storage and
additionally more perplexing strategies, for example, underground check dams. According
to UN , Urban water request is required to increment radically worldwide from
around 3.3 billion of every 2007 to 6.4 billion of every 2050. Besides,
environmental change will probably expand the inconstancy of precipitations and
the quantity of surge and dry spell scenes (IPCC, 2007). These patterns
emphasize the need to adjust water administration to new and testing natural
and modern techniques. RWH, among different choices, may assume a focal part in
extending water security and decreasing negative effects on the environment.
For a feasible urban future, society must adopt objective of effective and
proper water utilize. RWH has a important part to play in this assignment.
Water accessibility has involved concern everywhere throughout the world. It
has been accounted for that RWH can save a huge amount of water in living
arrangements in various nations.

(RWH) depicts
the, accumulation, its storage and utilization for profitable purposes. One of
the general classes of RWH is Domestic Rainwater Harevesting (DRWH) where water
is gathered from housetops, yards and comparative compacted or treated
surfaces, put away in underground tanks (UGTs) or above ground tank (AGTs) and
utilized for local purposes, plant watering and little scale beneficial
exercises.
( Jean-marc Mwenge Kahinda , Akpofure E. Taigbenu , Jean R. Boroto , 2007)

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RWH is a
technique in which rain water in collected and stored first then it can be
reused for various uses later on e.g. flushing, gardening, floor & car
washing etc. (Ishtiaq Hassan , 2016)

 

The Collection and storage of Rainwater using common and
simple techniques like tanks or pots 
from roads , rooftops and different land surfaces is called RWH.
( Fayez A. Abdulla, A.W. Al-Shareef , 2008)

 

RWH is an innovation utilized for gathering  water from housetops, different land surfaces
and rocks utilizing basic systems, for example, lakes and reservoirs may be
natural or artificial. One litre regular water per meter square is equal to
harvested water having one millimeter depthThen that rainwater can be used for
serveral purposes in homes like for use in kitchen , sanitation and also for
farming purposes.

There
are three major forms of RWH:

 

(a)    Firstly
, Collection of Rainwater ffrom surface and then its storage in the nearby soil
and this is called in situ RWH.

 

(b)   In
External water harvesting , water is collected from external surface and then
stored , which is used for agricultural and farming purposes.

 

(c)
DRHW, in which runoff from roofs and streets are used for water collection. (B.
Helmreich, 2008)

According
to UNESCO report in 2008 there were one billion individuals who don’t approach
safe and pure drinking water. As indicated by the Food and Agriculture
Organization (FAO) nearly 840 million individuals still experiences  the ill effects of undernourishment.
(www.unesco.org , 2008).

Some
Rainfall is so intense that it causes very high intensity storms having utrageous
spatial and worldly precipitation inconsistancy (S.N. Ngigi, 2003 , H.J.
Bruins,1986 , L. Shanan,1976).

The proportion of precipitation to evaporation is frequently
inadmissible.In bone-dry to semi-bone-dry territories , Precipitation regularly
changes in a scope of 200 – 600 mm per year. There is also a fluctuation of
1500 and 2300 mm in case of potential evapotranspiration. This outcomes in poor
products. The connection among potential evapotranspiration and precipitation
decides the developing time frame enduring around two and a half month– four
month in semi-bone-dry  zones.
Precipitation in the semi-dry territories surpasses potential
evapotranspiration  two-four and half
months as it were. (M. Falkenmark,2001).

 

In such a circumstance it is important to build the measure
of water accessible for farming purposes and for human uses over the real
amount of direct precipitation (M. Falkenmark,2001). So we must use RWH to
overcome this issue of water shortage.

 

The demand of urban water is relied upon to increment
radically worldwide from roughly 3.3 billion of to 6.4 billion from 2007 to
2050 respectively. (UN, 2008). Besides, environmental change will probably
build the changeability of precipitations and the quantity of flood and dry
spell scenes (IPCC, 2007). These patterns highlight the need to adjust water
administration to new and changing environment which are also economical and
acceptable to our society.  RWH, among
different alternatives, may assume a focal part in broadening water security
and lessening negative impacts on the earth. (El-Sayed et al.,2010).

 

Our study
also got motivation from the fact that that ground water table in the Potohar
region (Rawalpindi district and its surroundings) has depleted by 116m (380
feet) in the last 30 years as reported by WASA (Water and Sanitation Agency)
Rawalpindi, in its finding in 2012. The underground water table is depleting
very fast as shown. Per capita availability of water is running out on fast
pace as it dropped to 850 cubic meters in 2013 as compared to 5,300 cubic
meters in 1951. Pakistan has been placed in red zone by the Asian Development
Bank (ADB) declaring it as water-stressed country and is likely to face an
acute shortage of water in the next five years. Pakistan is likely to suffer
water-scarcity in terms of major uses like water availability for irrigation,
industry and human consumption. It is dilemma of the day that fresh water that
can be used for potable purposes is also being used bravely for the non-potable
demands at household level. About 45% of the daily domestic needs are
non-potable. These needs can be met best by using rain water stored during the
times of rainfall. (Ishtiaq Hassan , 2016)

 

Water administration in urban communities is vital since
their present water utilization is a long way from being sustainable (Sazakli
et al., 2007), the principle issues identified with it being water lack, degradation
of stream and floods. Pressuret on water assets is expanding, with developing
demand but limitation of water sources.  (Fletcher et al., 2008;EEA, 2009). This
expanding demand decreases sources of fresh water(Sazakli et al., 2007) and is
trailed by the utilization of more inaccessible or second rate quality sources
(van Roon, 2007). Therefore water confinements are turning into an unavoidable
truth in numerous urban communities (Fletcheret al., 2008). Also, developing pressure
on resources of  water  influences biological communities and
debilitates the environment products and ventures on which life depends (World
Water AssessmentProgramme, 2009).Bates says that the practices of current water
management are not good enough to stand with the change on reliability of water
supply and flood risks. (Bates et al., 2008).

For a maintainable urban future, society must move towards
the objective of proficient and proper water utilization. RWH has a huge part
to play in this errand. Water accessibility has involved concern everywhere
throughout the world. It has been accounted for that RWH can advance critical
water sparing in homes in various nations. (A. Appan,1999 , D. Prinz , 1995 ,
K. Zhu,2004).

The
rainwater harvesting has various advantages such as: water is free; its direct
collection & storage near the place of use eliminates need of distribution
system & its maintenance cost; good quality for various applications; it
helps to reduce run-offs which otherwise cause street-flooding; it reduces need
of fresh potable water for uses other than drinking; it decreases the costs of
utility bills and helps to recharge the ground water. (Ishtiaq Hassan , 2016).

 

RWH
decreases the requirement for mains water .Rainwater discharge also decrease
and henceforth may add to lessening flood dangers and the load on storm
drainage and sewer frameworks. Also, rainwater does not require  any substance, physical nor organic treatment
before use. This makes using of RWH frameworks for the most part simple and
modest (Rio House, 2003.) Due to more softening of rainwater , it also reduces
the usage of washing powders . (Burkhard et al., 2000).

 

 

RWH
in Sant Cugat del Vallès from Housetop could conceivably meet around 16% of the
aggregate residential water demand of that town, In Jordan RWH saved 0.270 % to
16.6% (Abdulla and Al-Shareef, 2009). In case of  south-eastern Brazil, RWH saves 41%, average
running from 12% to 80% varies with the study area. (Ghisi et al., 2007).

 

 

 RWH is displayed as a supportable system to be
incorporated into urban water cycle. It have many advantages, i.e. it might
diminish a city’s outer water demand, ease water pressure on the territory,
decrease non-point sources of poison , lessen treatable urban overflow volume,
reduce flooding and aid in reducing environmental change. (Eroksuz and Rahman,
2010;Kim et al., 2005; RiverSides, 2009; van Roon, 2007; Villarreal andDixon,
2005; Zhu et al., 2004).

 

Ishitaq
Hassan conducted a study in which he concluded that that in Rawalpindi, a city
in Pakistan (with appreciable amount of rainfall): (a) 110 m2
(25’x50′) house with flat roof has sufficient size to accommodate 2 persons and
4 persons at the most, (b) 220m2 (35’x50′) house with flat roof has
sufficient size to accommodate 4 persons and 8 persons at the most, (c) 280m2
(40’x80′) house with flat roof has more sufficient size to accommodate 4 person
and 8 persons atthe most and (d) 400m2 (50’x90′) house with flat
roof has much sufficient size to accommodate 4 person and 8 persons. (Ishtiaq
Hassan , 2016).

 

In
Lahore, a city in Pakistan (with lesser amount of rainfall): (a) 110 m2
(25’x50′) house with flat roof has hardly sufficient size to accommodate even 2
persons, (b) 220m2 (35’x50′) house with flat roof has also hardly
sufficient size to accommodate 4 persons, (c) 280m2 (40’x80′) house
with flat roof has sufficient size to accommodate 4 persons and 8 persons at
the most and (d) 400m2 (50’x90′) house with flat roof has more
sufficient size to accommodate 4 persons and 8 persons. (Ishtiaq Hassan , 2016)

 

Ishtiaq
Hassan concluded that the minimum sizes of plot are required to be increased in
new developments so that density of population can be reduced and more
rainwater be captured for less use For
territories with obvious precipitation (like Rawalpindi) the base proposed size
is 35’x70′ for one family having 4 people and 50’x90′ for double families
having 8 people. Then again, for regions with lesser precipitation like Lahore
the base recommended size is 40’x80′ for one family having 4 people and 50’x90′
for double families having 8 people. According to him, adopting rainwater
harvesting system with suggested sizes of storage reservoirs and limiting the
family units/sizes, there will be a saving of 45% of potable water. He further
concluded that even if we do not reuse rain water, if we are able to construct
wells of sizes equal to the suggested rainwater harvesting tank sizes having
soaking mechanism, it will help to raise ground water level to fulfill our
daily needs. Additionally, pouring of 85% daily water demand (15% toilet use
cannot be used for recharging) in to the soakage pit(s) will help a lot in
recharging the ground water reservoir and these steps will help us regain the
water-tension free times of 30 years back. (Ishtiaq Hassan , 2016)

 

For RWH
systems roofs got really importance because the water runoff that we got from
there is usually unpolluted (Fo¨ rster,1999)
or may be of better quality as compared to surface water. (Go¨ bel et al.,
2007).

 

 

Rainwater quality and their collection efficiency greatly
depends upon roof area and construction material . Tiled rooftops or rooftops
sheeted with ridged mellow steel and so forth., are ideal since they are the
most effortless to utilize and give the purest water. (N. Alpaslan, N.B.
Harmancioglu and V.P. Singh, Hydrol. J. IAH, 15 (1992))

 

The best roof of RWH are tiled and Cement roofs in terms of
durability , economy and water quality. But whatever is the roof type , we must
assumea loss of 20% in yearly precipitation due to roofing texture , losses due
to evaporation in storage tanks and ineffieciencies of whole process.
Chemically inert material should be used in the pipes and roof surface to
achieve water of better quality.

A few investigations report that water from housetops by and
large meets the universal rules of drinking water (Sazakli et al.,2007; Zhu et
al., 2004; Handia et al., 2003; Dillaha andZolan, 1984) .Other examinations
reports that synthetic or potentially microbial contaminants are regularly
present in level surpassing global rules of drinking water (Abbott et al.,2006;
Vasudevan and Pathak, 2000; Nevondo and Cloete,1999; Yaziz et al., 1989). The
nature of the gathered and put away water relies upon the attributes of the
thought about zone, for example, the topography, the climate conditions, the
nearness to contamination sources, the kind of the catchment zone, the sort of
water tank and the taking care of and administration of the water (Sazakli et
al., 2007; Zhuet al., 2004; Va’squez et al., 2003; Gould, 1999).

Rainwater quality influenced by being presented to air
contamination and vehicle emanations. Precipitation intensity and the quantity
of dry days going before a precipitation occasion fundamentally influence the
nature of rainwater. The nature of water gathered relies upon when it is
gathered (after the main rain), how it is put away and in addition technique
for utilize. The put away water won’t generally meet WHO guidelines.(WHO)

There are various choices to achieve rainwater of good
quality like washing of rooftop , avoiding the primary flush from rooftops
since the primary flush gets a large portion of the soil, flotsam and jetsam
and flying creature droppings and contaminants from the rooftop. (A prologue to
water gathering—general depiction. Worldwide Development Research Center,
Osaka, Japan, 2002). Usually physical or other type of contaminants are absent
in rainwater, for example, pesticides, lead, and arsenic, routine maintenance
helps with increasing great quality water from water tanks. The cleaning of
underground tank also contribute to water quality. Chlorine must be used for
cleansing of tank. (WHO)

 

According to a study on RWH in Amman and Irbid , rainwater
meets the WHO standards chemically and physically but when it comes to
biological tests , it does not meet with WHO guidelines.

The quantity of pollutants in roof rainwater depends upon
surface , atmosphere and polluntants properties. .(Chang et al., 2004; Sazakli et al., 2007; Simmons et al.,
2001;Skaryska et al., 2007; Villarreal and Dixon, 2005). 4.5 to 6.5 is the range for pH of rainwater .(Go¨ bel et al., 2007; Meera andAhammed, 2006).

The quality of rainwater in rural area is far far better
than the urban area due to their climate. (B. Helmreich, 2008)
so in urban area there should be some treatment before its usage. Rainwater
from streets are not being used due to its lower quality. (Göbel et al., 2007).

Underground water tank (UGTs) gather surface overflow and
also get polluted. On account of housetop RWH, despite the fact that the idea
of water collecting process appears to keep the contamination of water minimum,
it isn’t right to expect that the harvested water achieves the drinking water
standard. ( Jean-marc Mwenge Kahinda , Akpofure E. Taigbenu , Jean R. Boroto ,
2007)

DRWH likewise has the unfriendly potential effect to spread
various water related infections if legitimate measures are not taken. The
insusceptible frameworks of HIV virus in individuals are powerless to a more
extensive scope of basic sicknesses and ailments than people whose resistant
frameworks are not bargained by HIV and AIDS. (Ashton and Ramasar,2002).

Martinson and Thomas (2005) built up a procedure that
empowers to appraise the measure of rain to flush for a rooftop. This infers in
a regions where the rainfalls are inconsistent and unevenly circulated, the
main millimeters of rain after each drought should be either occupied or flushed.
Such a redirecting gadget combined with general cleaning of the water storage
tank will enhance the water quality. Another support technique is the
intermittent expansion of a disinfectant, for example, chlorine to the
reservoir to execute existing microscopic organisms (Dillaha and Zolan, 1984).
The benefit of chlorine is the deactivation of most microorganisms and it is
moderately modest.When water has been removed from the tank then chlorine has
to be applied  since chlorine may respond
with organics remains which settled to the base of the tanks and frame
undesired side-effects. (G. Gordon,1995

Slow
sand filtration is a modest strategy to enhance the bacteriological nature of
water (E. Fewster,2004 , G. Palmateer, 1999). That kind of filters can cure
only biological treatment instead of physical filtration forms for its more
efficeincy. Pasteurization by sun oriented innovation is otherwise called a
cheap disinfection method (M. Wegelin,, 1994 , T.M. Joyce, 1996 , B.
Sommer,1997).It can be accomplished by joining UV-A radiation with warm. Since
sun is available in all over the world and its free which make this technique
is the most cheap one.

 

This
Sunlight technique is good for small families as it only gives us the 100L of
water on an area of 1 Square meter of sunlight. (B. Sommer,1997). Another
strategy created at Fraunhofer Institute furnishes water treatment with rotating
disc filters with a ceramic membrane With a pore size of 0.06 mm microscopic
organisms and infections are securely expelled. This new strategy is costly and
may just be reasonable for focal treatment of water. (M. Mohr,2006)

 

Filtration is
also the technique which is used to remove suspended particles from the water
and most common type of filter is Rapid sand Filter. . ( R.H.
Kim,2005).

 

There
are different types of storage for Rainwater runoff.

 

(a)
Micro-catchment frameworks: They constitute uncommonly formed territories with
slants and berms intended to expand overflow from rain and amass it in a
planting bowl where it invades the dirt profile and is viably put away in that.

 

(b)
Sand dams, Sub-surface dams, or check dams: Water is put away underground in a
artificially raised water table or nearby sub-surface store.

 

(c)
Tanks of different structures made of earth, plastic, concrete,  soil, and so on: They can be constructed
underground or over the ground, contingent upon space, innovation and
speculation limit. ( B. Helmreich, 2008)

 

For determining the size or storage capacity of the tank ,
following points should be kept in mind

(a)    The rainfall frequency , its intensity and distribution which
defines the water availability. attributes of the catchment region like its
size etc

 

(b) The water prerequisite which incorporates that what number of
regular precipitation nations have. The water prerequisite shifts starting with
one precipitation district then onto the next.

 

(c) The specialized requirements, for example, the confinement of
room, absence of work, shakes in the ground, and so forth. Elements that
assistance in choosing whether the capacity tank will be over the ground or
underground are, the rooftop sort and tallness and so forth.

 

(c)    Socio-monetary imperatives, for example, the absence of work
labour,

Above ground tanks are usually good but easy
to recognize breaks and holes, can easily be cleaned and drained. Pumps and
gravity flow , both are used for water extraction and they are economical too. Be
that as it may, they consume up room and furthermore subjected to climate
conditions. (TX, 2005)

 

 

Below ground tanks are usually difficult to clean,
drain, and for detection of any cracks or failures. The risk of contamination
is also more. Trees roots can also damage them. There is also a risk of  human or animals drowning if it left open.
(TX, 2005)  

 

For single family system, the tank limit
extended from 2 to 20 cubic meters and was by and large of 12 cubic meters. The
most effective tank limit in a multifamily assembling was assessed at 45 cubic
meters which meet the 94% of water demand  and spare each year 97 cubic meters. A
promising end-use for water which is especially engaging in single family
houses is flushing. The water powered reenactment display demonstrates that a
tank of 17 cubic meters can completely take care of can flushing demand in a
standard single family house. The most proficient tank measure for can flushing
is 11 cubic meters which empowers to take care of 97.9% of the demand and can
spare 28.4 cubic meters of drinking water every year or 25.9 LCD.( Laia
Domènech, 2011). In case of single family families where water utilization per
capita is high, water displayed an essential potential to diminish per capita
drinking water utilization. If there is a low precipitation in any year,  little tanks could take care of 100% of the
demand for those utilizations with a steady request example, for example,
latrine flushing and clothing cleaning. The utilization of water for garden and
can would empower to spare 37 LCD in a solitary family house.( Laia Domènech,
2011)

 

RWH is in every way an invaluable
procedure for constraining water deficiency in all over the world.  For rural utilize the greater part of the
harvested water can be put away underground in common frameworks shielding it
from evaporation. Then again, water gathered for residential use may be
contaminated by microorganisms so be carefulFor cleansing purposes there are
numerous methods accessible, some of these using regular sources, for example,
sun based vitality. ( B. Helmreich, 2008).

RWH seems, by all accounts, to be a
standout amongst the most encouraging choices for providing freshwater even
with expanding water shortage and raising interest. (Sazakli et al.,2007).
Success of RWH tecnique requires close participation between the
administration, NGOs and Scientists,  and
the country families yet in addition an incorporated framework approach where
the amount/nature of the water provided and in addition the related costs of
implementation are considered. A feasible DRWH systemis one that is executed in
the wake of considering not only the physical characteristics ( area,
precipitation and catchment characteristics) and the financial traits in its
outline yet additionally the nature of the water and the alternativewater
sources.( Jean-marc Mwenge Kahinda , Akpofure E. Taigbenu , Jean R. Boroto ,
2007)