Twin trouble in Thiruvananthapuram BURGEONING population in Thiruvananthapuram, Kerala’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.