Twin trouble in

BURGEONING population in Thiruvananthapuram, ’s capital, has put the coastal city’s natural resources such as water and land under heavy stress.

On one hand, the city’s water bodies are being encroached upon. On the other, lack of proper sewage management and drinking water crisis is affecting the quality of life. Seawater and untreated sewage often contaminate the freshwater supply, aggravating the crisis.

Growing population: Can the city keep up? Source: Economic Review, 2003, Kerala Planning Board

900000 800000 7.89 700000 600000 500000 400000 300000 200000 1.0 100000

Population (in lakhs) 0 1930 2004 Year

The city gets ample rain but most of it is wasted as runoff to the sea due to the sloping terrain. As a result, the aquifers hardly get recharged.

Most of the city’s traditional water supply sources like lakes and open wells are no longer in use. The few remaining ones face the threat of contamination from soak pits used for sewage disposal, as less than 30 per cent of the city is connected to the main sewage line.

Several lakes have been filled up to make way for settlements. According Dr Thomas Vergese, former professor of Kerala Agricultural University, “There were seven major water bodies in Thiruvananthapuram and 12 temple tanks. Most of these tanks have been filled up and converted into settlements. Only two temple tanks – the ones in Padmatheertham and Sreevaraham temples – have been reclaimed.”

According to Dr Vergese, Lake Vellayani can be a vital source of water supply if it is maintained and utilised properly. The lake covers about 200 hectares. Earlier, a part of the lake was used for paddy cultivation. But the agricultural university later decided to stop using the tank bed for agriculture. The lake now supplies drinking water to the adjacent villages.

Demand and supply

Kerala Planning Board’s economic review for 2003 claims that 83.36 per cent of the urban population in Thiruvananthapuram is being provided with piped water supply. All areas, barring the ones located at an altitude or situated in the fringes, get water supply.

Ever increasing demand

300 273 250 235 200 200 150 100 in million litres 50 0 1991 2006 2021 Souce : KWA

As per the estimates, in 1991, the water requirement in Thiruvananthapuram was 200 million litres per day. This is expected to go up to 235 million litres by 2006 and by 2021 it may go up to 273 million litres.

Falling short

350 300 300 250 203 200 150 97 100

in Million litres per day per in Million litres 50 0 Demand Supply Gap Source : Kerala Water Authority

History of water supply The water supply system for Thiruvananthapuram was designed in 1928 and commissioned in 1933. The source of supply is the Karamana river. The flow through the river is much in excess of the actual daily requirements during the whole of the year, except for a few days in summer when the flow is less than the city’s daily water supply requirements. Hence, a 4.6 metre high overflow type dam was constructed in 1931 across the river at Aruvikara, about 16 kilometres away from the city to store water when in

surplus. The project, named Wellington Water Works, had a distribution capacity of 20 million litres.

Wellington Water Works The capacity of the impounding reservoir up to the crest level of the dam was computed to be in the order of 618 million litres, which is equivalent to about a months supply at the rate of 20.5 million litres per day.

Thanks to the commendable forethought and vision of late Shri Balakrishna Rao, the then water works engineer; the dam was constructed in such a way that the height could be raised by another 2.4 mm by installation of shutters in the event of any abnormal increase in the water demand in future.

In those days, water was brought from Aruvikkara through cast iron pipes of 840 mm diameter. It was then treated at the Vallayampalam water treatment plant (popularly known as the Wellingdon water works) and stored in two tanks – one overhead reservoir with a capacity of 5 million litres and another one at the ground-level with a capacity of 5.8 million litres.

Water treatment The water drawn from the impounding reservoir is subjected to preliminary purification at the Aruvikkara Head Works by way of aeration, lime treatment, plain sedimentation, etc. Then, the water is conveyed through a cast iron main to the water works at Vellayambalam for further purification.

Taking advantage of the higher elevation of Aruvikkara Head Works in relation to the purification plant in the city, the transmission main was designed to convey a supply of 20.5 million litres per day by gravitational force and for the first 6.5 km it has a diameter of 884 mm and for the second half a diameter of 793 mm.

As originally designed the treatment plant in the city comprising coagulation tanks, rapid gravity sand type filter beds and chlorination units is sufficient to purify 20.5 million litres per day to the desired standards. The purified water is collected in a service reservoir, 5.5 million litres from where a portion of the supply is pumped into a high level service reservoir of about 5 million litres capacity located on the nearby observatory hills.

For distribution purposes, the city has been broadly divided into two water supply zones a high-level zone covering areas above nine metres contour receiving supply from the low level reservoir in the water works compound. The distribution system was designed to give a minimum terminal pressure of 9 m at all points of supply.

This system was intended to serve a population of 1.35 lakh, the projected population for the city by 1961. It is indeed a great tribute to the ingenuity of Shri Rao that he could design and implement such an excellent scheme, with liberal provisions for future expansion, as early as 1928, when water works engineering was still in its infancy in this country.

Increasing demand Thiruvananthapuram was spread over a mere 2,900 hectares in 1928 and had a population of about 65,000. But in 1961, the city expanded to 4,300 hectares and the population increased to nearly double the anticipated figure.

In fact the estimated population figure of 1.35 lakh was reached by mid 1940s. As per the 1941 census, Thiruvananthapuram had a population of 1,28,365. This increased to 2.38 lakh by 1961. The city limits have also been extended to encompass an area of about 7,500 hectares. Such an enormous increase in population or the spurt of expansion in terms of area was certainly not foreseen while the water supply was designed in 1928.

The initial planners envisaged an average daily consumption of 113.6 litres per capita per day and the maximum summer consumption as 133.3 litres per capita per day. However, contrary to the calculations, Thiruvananthapuram grew much faster. This was partly due to the fact that Thiruvananthapuram is the capital of Kerala.

The growing population, however, led to the scarcity of drinking water. In 1962, the capacity of the reservoir at Aruvikkara was increased to 32 million litres by installing mechanised shutters and more untreated water was pumped to the water treatment plant at Vellayampalam using booster pump sets. The capacity of the treatment plant was increased to 36 million litres by installing more filter units. In order to make the water distribution possible at high-altitude localities, an overhead tank with a capacity of 7 million litres was built at Observatory Hill.

Interim augmentation scheme The augmentation scheme was taken up only by 1962. Fortunately the scheme, as originally designed, provided for supply at the rate of 133.3 litres per capita per day. But, actually the per capita consumption has been only about half this figure even by 1961. Again on the distribution side, the original design has been a liberal one, facilitating further expansion without causing a serious imbalance in the supply position. But there is a limit to which a facility, which has been designed to take future expansion in mind, can be stretched.

By 1962, the people residing in the high altitude areas of the city began experiencing some water scarcity during the severe summer months and the water supply system had to be strained to the utmost to cope up with the increasing demand.

Anticipating that difficult days were looming ahead, the Public Health Engineering Department was ready with a scheme for an Interim augmentation of the supply. This included raising the dam of Aruvikkara by providing 2.4 m high shutters, boosting up the supply through the gravity transmission main and expansion of the treatment plant at Vellayambalam. These works were completed in 1964.

With the completion of the interim augmentation scheme, the capacity of the city water supply system was raised from 20.5 million litres per day to 36.4 million litres per day.

This distribution system, however, did not improve with interim augmentation works. Normally, the relaying of the distribution pipelines is very costly and so it could be taken up only as part of a major scheme. Therefore, the same network that has been in existence since 1933 was used to supply water. The city has an undulating terrain with much diversity of levels, being interspersed with hillocks and valleys. With such topography, an equitable distribution of the supply is difficult to achieve till a new network, designed to suit the special conditions of the city, is provided.

The comprehensive augmentation scheme The comprehensive augmentation scheme, the first phase of which was informally commissioned on January 25, 1973, provides for supplying 109 million litres of water per day. This is more than five times the original capacity of 20.5 million litres per day. This scheme is designed to meet the water supply requirements of the city till 1991. The scheme makes provision for supply at the rate of 159 litres per capita per day for an estimated ultimate population of 6.5 lakh in 1991.

In addition, provision has also been made for supply to the industrial consumers and a few government institutions outside the city limits and also to the University Centre at Karyavattom, the panchayats of Ulloor, , Attipra and portions of the Chettivilakom Panchayat. The major components of the scheme include a water treatment plant of capacity 73 million liters per day at the Aruvikkara water works, to be constructed in two stages.

A transmission main from Aruvikkara to Thiruvananthapuram in addition to the existing one (the main is of 1,219 mm diameter) cast iron pipe from Aruvikkara to Peroorkada and is of 1,016 mm diameter from Peroorkada to Vellayambalam.

Three additional high level and one low level service reservoirs at cardinal points at the Observatory Hills, Peroorkada, Thirumala and Vellayambalam from where an economic and equitable supply can be commanded.

A new network of distribution pipelines designed to ensure a minimum terminal pressure of 10.5 m at all points in the system, even during the hours of peak demand.

The first phase of this comprehensive augmentation scheme, with a new treatment plant of 50 million litres per day capacity and 3 zonal service reservoirs has been completed. The zonal reservoir at Thirumala is nearing completion and the expansion of the distribution network for catering to the entire population of the city is progressing at a very rapid pace.

The first stage of the augmentation scheme satisfied the requirements of the people till about 1980 by which time the second phase of the augmentation scheme, which includes the construction of a new storage dam upstream of the existing dam at Aruvikkara and further expansion of the treatment plant, was done. The project was completed after a detailed investigation was carried out to ascertain the demand.

Financial Aspects The estimated cost of the comprehensive augmentation scheme was Rs 52.9 crore for the first stage of the scheme including the extension to the University Center at Kariavattom and the neighbouring panchayats. Want of adequate finances has been the major bottleneck in the speedy execution of the report. The annual budgetary allotment for the scheme ranged from Rs. 15 to 20 lakh only. But since 1970, the Life Insurance Corporation of India (LIC) has been giving loan assistance for the execution of the project. The loan assistance given by LIC for this scheme worked out to Rs 16.4 crore. The total amount spent on the augmentation scheme till December 31,1972 was Rs 42.4 crore.

Peppara dam project This project envisages the construction of Concrete Gravity Dam at Peppara, 45 km north-east of Thiruvananthapuram to ensure a steady discharge into the existing reservoir at Aruvikkara. The dam is located about 25 km upstream of Aruvikkara and is accessible by road via Nedumangad and Vithura from Thiruvananthapuram. The road from Vithura to the dam site was constructed by the Public Health Engineering Department as part of the project.

Brief history of the project The existing reservoir at Aruvikkara with a capacity of 2 million cubic metres (450 million gallons) is sufficient to meet a daily demand of 12 million gallons only for about 35 days during the summer months. But the demand contemplated in the Thiruvananthapuram Water Supply Augmentation Scheme, the first phase of which was commissioned in 1973, is 24 million gallons per day exclusively for Thiruvananthapuram. It was then decided to augment the source to cope with this demand. With this end in view, the investigation for the construction of a dam higher up in the same river was taken up in 1972. Four alternative sites in the Karamana river were examined in detail and finally the site at Peppara, which was found to be the most suitable, was fixed for the location of the dam. With the unprecedented drought and consequent water shortage in Thiruvananthapuram experienced in March, 1976, the need of implementing the project on a priority basis came up for serious and urgent consideration and the government sanctioned the construction of the dam at Peppara.

Construction programme Ancillary work such as construction of access road to the dam site for a distance of 10 km, construction of staff quarters, water supply arrangements and extension of power supply had been completed by December, 1977. The first stage was completed by July 1982. Since December 1982, water is being released from the dam to Aruvikkara reservoir to maintain steady level there.

The second stage work of providing four of radial gates was taken up and the project was to be completed by March, 1987.The total cost of the project came to Rs 10.48 crore.

New Water Treatment Plant at Aruvikkara In 1972, the new water treatment plant was built at Aruvikkara, from where water was taken to the newly built tanks, with eight million litre capacity each, at Observatory Hill, Tirumala and Perurkkada. With this, the capacity of water distribution network in Thiruvananthapuram was increased and the distribution was extended to neighbouring panchayats like Kadakampally, Ulloor, Atipra, Srikaryam, Chettivilakam, Vattiyurkavu, Nemon, Thiruvallom and Kovalam.

Benefits The estimated demand of water supply to Thiruvananthapuram and the suburban panchyats for 2005 is 45 million gallons per day and for 2025 is 75 million gallons per day. The storage of the dam for the first stage is 70 million cubic meter (15,000 million gallons), which will be sufficient for the demand of 200 days.

The beginning of the Interim Expansion Plan On the basis of this, Kerala government decided to materialise a fast track drinking water distribution project. The Tata Consulting Engineers, a private company, was assigned the responsibility of making the project report for this. They conceived a project that could be completed in 14 years in three stages and submitted the report.

The project cost was Rs 200 crore. In order to implement this project, Kerala government sought the help of many agencies including a foreign one. It was decided that in the first stage, a water treatment plant with a capacity of 82 million litres would be completed. HUDCO approved of this project and sanctioned a loan of Rs 26.5 crore.

Thus, the interim expansion work of the Thiruvananthapuram water distribution project began in 1993. Though it was aimed that the project should be completed by 1996, owing to technical as well as administrative reasons, the commissioning of this project got delayed. It is estimated that it would require Rs 36.5 crore to complete this project. As part of the project, an overhead tank was built at Manvila and a pipeline was laid from Perurkkada to Manvila.

On January 26, 1999, the then chief minister, E.K. Nayanar, inaugurated the facility to provide drinking water to Thiruvananthapuram and neighboring panchayats. With this project, the capacity of Thiruvananthapuram drinking water distribution project increased to 200 million litres from 118 million litres. The water treatment plant provided an additional capacity of 82 million litres.

Future project With the financial aid from The Overseas Economic Cooperation Fund of Japan (OECF), the steps to build yet another water treatment plant at Aruvikkara, with a capacity of 82 million litres, is also going on and it is expected that it would be commissioned in 2004. With this, the city will be able to meet its drinking water requirement till 2021.

With the commissioning of the new water treatment plant the efficiency of water distribution will be enhanced at all areas of the city. However, in order to make the water

distribution efficient in all areas, the old and narrow pipes in the distribution network has to be replaced with the new ones. Actions are underway to implement the project of replacing these pipes stage by stage.

Main components of this project are:

1. Pump house to transport river water to the water treatment plant 2. 11 KV electricity substation 3. 1200 mm cast iron pipeline to take the river water to the treatment plant 4. A water treatment plant at Aruvikkara, with a capacity of 82 million litres 5. Drinking water tank and pump house at Aruvikkara 6. Aruvikkara–Perurkkada drinking water pipeline (9 km concrete pipe) 7. Perurkkada–Manvila drinking water pipeline 8. Drinking water tanks at Perurkkada, water works compound and Manvila

Water tariff

Water tariff in effect from April 1999

Section Monthly consumption Monthly tariff Household Up to 10 kilo litre Rs 20 10 to 30 KL Rs 20 plus Rs 3 per additional unit 30 to 50 KL Rs 80 plus Rs 5 per additional unit Above 50 units Rs 180 plus Rs 7.35 per additional unit

Other Up to 50 KL Rs 7.35 per unit than (Minimum rate will be Rs 100) household Above 50 KL Rs 368 plus Rs 10.60 per extra unit

Industrial --- Rs 10.60 per unit (Minimum rate will be Rs 200)

NB: Metre inspection charge of Rs 2 per month will be extra

Other existing rates

1. Household connection fees Rs 500 2. Fees for industrial, temporary and connections Household Rs 1000 3. Alteration fees Rs 100 4. Straight main extension Rs 500 5. Permission for plumbing jobs in the building Rs 50 6. Extension fees Rs 50 7. Disconnection fees Rs 50 8. Reconnection fees Rs 50 9. Metre testing fees Rs 1 0 10. Metre replacement fees Rs 10 11. Ownership change fees Rs 15 12. Duplicate PIC/metre reading card fees Rs 10 13. Fees to extend the period of special casual connection (for one year) Rs 250 14. Fine for violating water works laws Rs 50 to 500 15. Temporary connection deposit Rs 26.50 per sq m (Maximum of Rs 20,000)

Wasted river of Thiruvananthapuram In 1928, Thiruvananthapuram became one of the first cities to have a piped water connection in India. In 2004, it is yet to have a sewage treatment plant.

Thiruvananthapuram is a medium sized town of Kerala with an increasing population situated near the sea on the banks of the Parvati Puthan.

The Parvati Puthan river plays a fundamental role in the local ecosystem by providing habitat for small organisms, as a source for biodiversity and acting as a natural filter. It passes through city and countryside, finally flowing into the sea. Today its ecological function has been destroyed and has become a major health hazard as it carries over 150 MLD (million liters per day) of untreated sewage.

The existing sewage treatment system, the “Comprehensive sewage scheme” (CSS), was set up in 1938. It was basically designed to use the local river (Parvati Puthan) as a sewage conveying channel. In those days the population was much less significant and the sewage outflow was ten times less (16 MLD). The major environmental impact it had was therefore less noticeable.

Currently the city has increased ten fold and is divided into seven zones. The sewage water is pumped, untreated, into the Parvati Puthan river which is flowing open channel by the city and countryside. Further down stream (a few kilometers upstream of a well known recreation beach) water (and sewage) is pumped from the river to fodder cultivating land at Vaiyathura near the airport. This is what the Kerala Water Authority (KWA) calls a sewage treatment scheme.

This method of sewage disposal is not only a source of environmental degradation to the river and surrounding ecosystem but also a major health hazard for the local population. “There are a lot of health related issues”, according to Dr Thomas Vergese, former levies professor of Kerala Agri University, referring to the use of untreated sewage for fodder cultivation. The amount of sewage generated has increased exponentially containing more dangerous chemicals and waste. The health hazards do not stop there: after flowing about 8km open channel, full of sewage, smelly and black in colour, it arrives at Kovalam beach and finally into the sea, a place of recreation and fishing.

According to Viji Titus, Executive Engineer of KWA, 40 per cent of the city is connected to this sewage system. The economic review 2003 of Government of Kerala State Planning Board notes 83.36 per cent of urban population in Thiruvananthapuram is provided with piped water supply and only 23 per cent of the house holds in Thiruvananthapuram city have access to a common sewage collection system. The remaining houses either have soak pits or septic tanks. The soak pits lead to contamination of surrounding open wells, which were the traditional source of water supply in the past and concernedly remain so in some areas today.

The Kerala Water Authority (KWA) in charge of water supply and sewage, is currently focusing on a new project across the Karamana River to bring more water to the city. The planners seem to forget that about 80 per cent of this water will leave the city as sewage and a proper sewage treatment plant is urgently required. Further more, in 2007 about 85 MLD of water will be pumped into the city from Karamana river through a Japan Aided project. The magnitude of the problem will increase every year.

Instead of focusing on big pipe water projects the city should concentrate on responding to the cry for environmental sanitation. It should focus on a proper sewage treatment plant which treats the sewage at source before pumping it into the river. The river water could still be used for fodder cultivation but would be also able to fulfill its ecological functions. If no action is taken soon, not only will the river ecosystem be destroyed, but the health hazards will increase, the groundwater be contaminated and the city unlivable. By providing proper sewage connection the contamination of open wells in the city can be prevented. These open wells can therefore be restored and respond to the increasing demand for water also avoiding the investment in large unsustainable pipe water projects.

The city of Thiruvananthapuram cannot afford reactive planning. Will it have to wait for an epidemic before realizing the impact of its waste? Action is required now to prevent further damage to its people, rivers and environment.

Rainwater harvesting The current focus is on construction of water projects across Karamana river and bringing water to city. Instead of this the city focus of rooftop rainwater harvesting. Most of the houses in Thiruvananthapuram in the outskirts of the city are dependent on openwells for drinking purposes. The yield from these open wells gets reduced during non rainy days. Diverting the rooftop rainwater to the open wells can enhance their yield. This will be a cost effective option. Since we have to provide a simple sand and pebble filter to filter the silt and then through PVC pipe the rainwater should be diverted to existing open well.

Thiruvananthapuram has a tough geological setup, which will reduce the rate of recharge. The laterite cappings will increase the runoff and prevent natural recharge. The occurrence of Charnockite provides less storage volume due to its compact nature. The coastal aquifers are sandy in nature and good for recharging. Diversion of rooftop rainwater to open wells and storing of rainwater in tanks will be ideal option for Thiruvananthapuram.

What’s the government doing? The Government Kerala has made rainwater harvesting mandatory for buildings with a floor area of 100 sq.m or more and plots measuring 200 sq.m or more.

The details of the notification by the Government of Kerala is given below:

Government of Kerala Local Self Government (D) Department Extraordinary Gazette No. 92/2004, dated 12-01-2004

Notification GO.(MS) NO. 19/2004/LSGD Dated Thiruvananthapuram, 12 th January 2004 S R O No. 25/2004.- In exercise of the powers conferred by sections 381, 382,383 A, 387, 398 and 406 of the Kerala Municipality Act, 1994 (20 of 1994) read with section 565 thereof, the Government of Kerala hereby make the following rules further to amend the Kerala Municipality Building Rules, 1999 issued in GO (Ms) No. 188/99/LSGD dated 1 st October, 1999 and published as S R O No 777/99 in the Kerala Gazette Extraordinary No. 1786 dated 1 st October, 1999, namely:-

Rules 1. Short title and commencement:- (1) These rules may be called the Kerala Municipality Building (Amendment) Rules, 2004 (2) They shall come into force at once 2. Amendment of the Rules.- In the Kerala Municipality Building Rules, 1999 after Chapter XVI, the following Chapter shall be inserted, namely:- “Chapter XVI-A

Rainwater Harvesting

109A. Rooftop Rain Water Harvesting Arrangements.- (1) Unless otherwise stipulated specifically in a town Planning Scheme, workable rooftop rainwater harvesting arrangements shall be provided as an integral part of all new building constructions for the following occupancies, namely:- i) Group A1 Residential (with floor area of 100 sq.m or more and plot area of 200 sq.m or more) ii) Group A2 Special Residential iii) Group B Educational; iv) Group C Medical/Hospital v) Group D Assembly vi) Group E Office/Business vii) Group G1 and Group G2 Industrial (only for workshops, assembly plants, laboratories, dry cleaning plants, power plants, Gas plants refineries, diaries food processing units and any other occupancies notified by the Government from time to time) viii) Group1(1) Hazardous (Automobile wash stall, automobile Service Stations, Service Garages with repairing facilities and any other occupancies notified by the Government from time to time);

Provided that the floor area to be considered shall be the total floor area in all floors: Provided further that, the rainwater harvesting arrangement is not mandatory for thatched roofed buildings. 2) The components of workable rooftop rainwater harvesting arrangement as stipulated in Sub-rule (1) above, shall include: i) Roof catchment area ii) Roof gutters iii) Down pipe and first flush pipe arrangement iv) Filter unit and v) Storage tank with provision for drawing water and spillover 3) The minimum capacity of the storage rank as stipulated in Sub-rule (2) (v) of the rooftop rainwater harvesting arrangement shall be at the rate given below:

Group A1 25 litres/Sq.m Group A2 25litres/sq.m Group B 50 litres/Sq.m Group C 50 litres/Sq.m Group D 50 litres/Sqm Group E 50 litres/Sq.m Group F Nil Group G1 and Group G2 50 litres/Sq.m Group H 25 litres/Sq.m Group I Nil

4) The municipality shall enforce workable artificial ground water recharging arrangements as an integral part of all new building constructions through collection of roof top rainwater.

5) The component of workable artificial ground water recharging arrangements as stipulated in sub rule (4) above, shall include: i) Roof catchment area ii) Roof gutters iii) Down pipe iv) Filter unit v) Recharge well/percolation pit

6) Wherever rooftop rainwater harvesting arrangements as stipulated in sub rules (1) to (3) above are provided, additional arrangements for carrying the spill over water from storage tank to recharge well or percolation pit need only be provided

7) The owner(s)/occupier(s) shall maintain the rooftop rainwater harvesting arrangements and artificial ground water recharge arrangements in healthy working condition

8) The Municipality may, in exceptional cases such as water logging or impermeable subsoil conditions to considerable depths, exempt construction from he mandatory groundwater recharging arrangements”.

By Order of the Governor P KAMALKUTTY Secretary to Government

Explanatory Note This does not form part of the Notification, but is intended to indicate its general purport. The Government of India has directed the State Government to provide certain provisions in building rules, pertaining to incorporation of rooftop rainwater harvesting arrangements in building. In the above context, the Government consider it necessary to make further amendments to the Kerala Municipality Building Rules, 1999. This notification is intended to achieve the above purpose.

Rainwater harvesting in Thiruvananthapuram: Is it viable? To look at potential of rainwater harvesting it is essential to look at the climate, especially rainfall pattern. The climate is equable with very little seasonal fluctuation. January, the coolest month, has a mean temperature of 24 degrees Celsius. May, the warmest month, averages 30 degrees Celsius. Seasonal fluctuations of humidity and rainfall are more significant than those of temperature. The 50 years average annual rainfall is around 1,800 mm and it is distributed as given below.

Rainfall pattern at Thiruvananthapuram

400 356.4 350 300 273.3 223 250 207.8 205.3 200 145.5137.9 150 105.7

in millimeters 100 74.7 38.6 50 22.9 20.8 0 July May April June March August January October February Setember November December Source: State planning commission

Water harvesting potential of Thiruvananthapuram

Area of Thiruvananthapuram: 7,400 hectares Annual avg. rainfall: 1,800 mm Total rainwater falling over the city = 74 (area in sq km) x 10,00,000 x 1800 = 133.2 billion litres = 365 MLD

Present water supply = 300 MLD Even if we assume 70 per cent of the area to be developed, 50 per cent of it to be roofed and we collect 70 per cent of the water falling over it, the quantity of rainwater that can be harvested works out to 23.31 MLD. This is a sizeable quantity compared to water supply to Thiruvananthapuram.

How much water can be harvested from residential houses

One can harvest 1.44 lakh litres of water from a rooftop measuring100 sq m. This is calculated as follows: considering the rainfall the annual rainfall as 1800 mm or 1.8m, with run off coefficient factor of 0.80 for rooftop area, then you can harvest about 1,44,000 litres of water. The formula for calculating is as follows.

Runoff =A x R x C A=Area (100 m2) R=Rainfall in metres (1800 mm = 1.8m) C=Runoff coefficient (0.80)

Hence, the water that can be harvested from a house having 100 sq m rooftop is 14,40,00 liters .

Monthwise rainy days in Thiruvananthapuram (average of 50 years)

19 20 17 18 16 14 12 11 12 10 9 9 10 8 6

Rainy days days Rainy 6 3 3 4 2 1 2 0 Jan Feb Mar Apr May Jun July Aug Sep Oct Nov Dec Source: IMC

The above graph shows that we consider that the number of dry spell or non-rainy days as 200. So we have to design the size of our storage tank in such a way that during the dry periods, water is available for drinking. The below mentioned calculation can be applied to determine the size of the storage tank.

No of persons in a household : 10 No. of dry days in a year : 200 Per capita consumption(lpcd) : 6 Average annual rainfall (mm) : 1800 Rooftop area : 20 sqm Runoff coefficient : 0.80 Size of the storage tank : 10 x 200 x 6 : 12,000 litres Check : Water available from rooftop : 1800 x 20 x 0.8 : 28,800

Hence sufficient water is available to meet the demand of 12,000 litres

The storage tank can be ferrocement tank, plastic tank or a brickwork tank. The tanks can be placed of surface or below the ground level also.

Plastic tank Brickwork tank Ferrocement tank

Case studies

I. Peoples College, Mitraniketan, Vellanadu, Thiruvananthapuram district.

Case background The area of the property is about three acres or 12,138 sq m with rooftop area of 800 sq m. The college is a part of the Mitraniketan complex, where the water supply is through a common borewells, which comes through pipeline. About 150 students are staying in the premise and daily requirement works out to be 15000 litres at the rate of 100 litres per day per person. During summer the supply reduces due to fall in water level. At that period the stored rainwater in ferrocement tanks fulfills the water requirement.

Measures taken for water harvesting The rooftop rainwater from three building in the college premise is harvested. Annual water harvesting potential from the rooftop area of 800 sq m works out to be 12.24 lakh litres at 85 per cent efficiency for rooftop.

The cost of installing three storage tanks works out to be Rs 36,000.0 at the rate Rs 2 per Litre.The implementation carried out at stages starting from 1997 and completed in 2001.

Rainwater Harvesting System In this college the rooftop rainwater is harvested and utilized for storing and used for non potable (see Figure 1).

Figure 1 : Site plan showing the building and location of storage tanks.

Rooftop rainwater harvesting The rooftop rainwater from the Main college building, Staff quarters and Girls hostel building are harvested. The roofwater from the above mentioned buildings are diverted to three separate storage tanks of 6000 litres capacity each. The silt from the rooftop is arrested by the use of first flush device and filtering tank (see figure 2).

During the peak summer time when supply from the borewells decrease the stored rainwater is used for drinking and non-potable purposes. The rainwater collected from the main building is used for drinking purpose. At the same time the rainwater collected from the Staff quarters and Girls hostel is used for washing and bathing purposes.

Figure 2 : Drawing showing storage tank with first flush device

II. Indoor stadium, Mitraniketan, Vellanadu, Thiruvananthapuram district.

Case background The area of the property is about 740 sq m of rooftop area. The roof top rainwater is utilized for both storing and recharging purposes. The rooftop rainwater is utilised by around 150 students for washing and bathing purposes during summer period.

Measures taken for water harvesting The rooftop rainwater from the indoor stadium is stored in three rainwater storage tanks and part of the rainwater is diverted to three existing open wells for recharge purposes. Annual water harvesting potential from the rooftop area of 740 sq m works out to be 11.32 lakh litres at 85 per cent efficiency for rooftop.

The cost of installing three storage tanks works out to be Rs 55,500 at the rate Rs 3.5 per litre for the brick work tank of 12,000 litres capacity, Rs 1.5 for the sub surface storage ferrocement tank of 1000 litres capacity and Rs 2 per litres for the surface ferrocement tank of 6,000 litres capacity. The implementation carried out at stages and completed in 2,000.

Rainwater harvesting system In this college the rooftop rainwater is harvested and utilized for storing and recharging purposes (see Figure 1).

Figure 1: Site plan showing the building showing both recharge and storing.

Rooftop rainwater harvesting

I. Storing of rainwater

The rooftop rainwater is diverted to three separate storage tanks of 12,000 litres, 1,000 litres and 6,000 litres capacity each. The tanks are of three different types and all the three storage tanks are located in the backside of the stadium. The 12,000 litres surface tank is made of brick work. The sub surface tank of 1000 litres capacity is a ferrocement tank fixed with a handpump for extracting water for day to day use (see Figure 2). The 6,000 litres ferrocement tank is used for washing and bathing purposes.

Figure 2 : Drawing showing sub surface storage tank with hand pump.

The over flow water from the storage tanks are diverted to the existing pond at the backside of the indoor stadium. The grey water generated from the bathing and washing purposes is diverted to the garden located at the backside of the stadium.

II. Recharging of rainwater

In the front entrance of the stadium two open wells of 10 m depths is used for recharging purposes. The rooftop rainwater from the front side of the building is diverted open well through a 6 inch PVC pipe. The open well is currently covered by slab and the water is not utilized, hence the open wells now act only as recharge wells.

The rooftop rainwater from eastern side of the building are diverted to a abandoned open well. The roofout lets are interconnected using a series of collection chamber (refer site plan drawing) and then diverted to the open well.

III. Kapikkad, Poovachal Post Office, Thiruvananthapuram district

Case Background

This farmhouse of Ms Nazeema is located in a hilly terrain. The open well which is 9m depth is the main water source for drinking purposes. But during the peak summer period the open well becomes dry. The rooftop area of the farmhouse is 56 sq m, which is tiled in nature.

Measures taken for water harvesting The rooftop rainwater is diverted to existing open well after proper filtration (see figure 1). Annual water harvesting potential from the rooftop area of 56 sq m works out to be 85,680 litres at 85 per cent efficiency for rooftop. The cost for recharging the existing open well works outs to be Rs 3000.00. The project was implemented in August, 2003.

Rainwater Harvesting System

Figure 1 : Site plan showing the diversion of rooftop rainwater to existing open well.

Rooftop rainwater harvesting

I. Recharging of rainwater

The rooftop of the farmhouse is tiled and sloping in nature. Hence a PVC gutter is provided to collect the rainwater. The collected rainwater is taken by a PVC down pipe of 6 inch pipe to a filtering tank containing pebbles and sand. The filtering tank is circular in shape of 1m dia and 1m depth. The filtered water is then diverted to the existing open well through a underground pipe connection. The existing open well is of 9m depth and 1.5 m in diameter. (see figure 1)