Analysis of Piped Water Supply Demand

Project Aim

To analyze the demand and supply of piped water in Chennai city in order to

understand the water supply network and to suggest measures to conserve and

manage water resources within the requirement.

Members

• Aaron George
• Kunal Motwani
• Suraj Kumar L

Work done

• Identify problems in the water supply system and understand the importance of municipal water management
• Converting features in the study to mathematical form where we can analyze it easily
• Understanding the water supply network of Chennai metropolitan city, detect the problems faced by the supply network across a duration of last 10 years
• Perform analysis of Rainfall, Population, Population Density, Water reservoir capacity among others to define a set of features to be analyzed to reach a conclusion
• Projected the features using time series analysis, logistic regression and other methods to understand the requirement of water of the city as a whole as well as taluk level water demand
• Used QGIS and EPANET in mapping out the water supply network and heat zones of the city
• Suggested ways for better water supply management and conservation

Future Scope

This study is an attempt to map the vulnerability of the population of Chennai in a way to understand how the problem of water is adding up to the existing stress due to urbanization. Further study using advanced techniques is possible but would be of no use if the government doesn’t put enough emphasis on this growing problem and take steps to conserve water resources rather than the ad-hoc practices being done now.

Final Report on Analysis of Piped Water Supply Demand

The purpose of this chapter is twofold. The first goal is to present the macro picture of the demand and supply scenario with regards to Chennai. The second goal is to examine the regions within Chennai city which gain excess water supply and those which have lack of water supply. It can be then worked upon to ensure that all cities receive water supply uniformly.

The 2019 Chennai water crisis is an ongoing water crisis occurring in India, most notably in the city of Chennai in Tamil Nadu. On 19 June 2019, Chennai city officials declared “Day Zero”, or the day when almost no water is left, had been reached, as all the four main reservoirs supplying water to the city had run dry. Two years of deficient monsoon rainfall, particularly in late 2017 and throughout much of 2018 had led to this crisis.

Water Supply by Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB)

The Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB),constituted in 1978, is vested with the responsibility of promoting and securing the planned development of water supply and sewerage services, creation, operation and maintenance of the needed infrastructure and implementation of perspective plans to meet both current and future requirements in the areas falling under the Chennai Metropolitan limit.

The operational area of the CMWSSB has increased from 174 sq. km. to 426sq. km. after the recent inclusion of 42 adjacent local bodies within the Chennai city limits. As per the 2011 census, the provisional population of the expanded city is 6.7 million. The CMWSSB is currently operating its services through 15 Area Offices and 200 Depot Offices.

Chennai’s primary water sources used to be a network of eris (tanks), ponds, temple tanks and dug wells, which were managed by local communities. Several households mostly shared each well. The first public water supply works was set up in 1772 under the control of the British East India Company. It was designed to supply 0.635 million litres per day (MLD) from a cluster of 10 wells to Fort Saint George (now, the state secretariat in the city). Over the next 100 years, the public drinking water supply scheme was completed. This brought water from two eris (Lake)- Cholavaram and Redhills – to municipal waterworks, distributing it across the city. These two tanks met the growing city’s demand till the early 1900s.However, in the 1940s, the city’s population doubled to almost 1 million. To meet this growing demand, a reservoir was constructed at Poondi across the Kosatallaiyar River. This raised the total surface storage capacity from 100 million cubic meters (MCM) to 180 MCM. Till the 1970s, the city’s public water supply system relied exclusively on the above-mentioned three reservoirs, located 20 to 50 km to the city’s northwest. In 1957-1958, the United Nations Development Programme (UNDP) started drilling borewells in the area; the farmers realized the groundwater potential and started drilling borewells.

Today, the drinking water requirement of Chennai is met by drawing raw water from the surface reservoirs around Chennai - Poondi, Redhills, Cholavaram, Chembarambakkam and Veeranam Lake in Cuddalore District. Water is also supplied from the Kandaleru reservoir under the Krishna Water Supply Project. In addition to this, CMWSSB is drawing about 100 MLD of water from the desalination Plant at Minjur constructed on a Design, Build, Own, Operate and Transfer (DBOOT) basis. At present, the Board supplies about 765 MLD4 to domestic consumers in the city area and about 65 MLD of water to bulk consumers such as adjacent local bodies and industries located in the Chennai Metropolitan Area (hereinafter referred to as CMA). CMWSSB is taking necessary action to streamline water supply facilities to the areas that have been recently included within the Chennai City Corporation limits.

Cause

Chennai has historically relied on annual monsoon rains to replenish its water reservoirs since the rivers are polluted with sewage.

Three years of failed monsoon from 2016,2017,2018. The 2018 northeast monsoon season was one of the driest ever recorded in Chennai, as only 343.7 mm of rain had fallen compared to an average of 757.6 mm, which was a 55% rainfall deficit. Additionally, the entire state of Tamil Nadu had recorded a 23% rainfall deficit in that season. A major heat wave in India from May to June 2019 further exacerbated the problem by evaporating any water still left in reservoirs. Government mismanagement and unplanned construction has also been a factor to blame for this crisis.

At the political level, rainwater harvesting (RWH) was initiated in 2000 at Sathyamurthy Bhavan. Subsequently the government under J. Jayalalithaa mandated RWH in Tamil Nadu from 2003 onwards. This meant that building approval for new apartments and dwellings were not to be granted by the Chennai City Corporation unless the building plan included a RWH component. The order also mandated that all existing buildings in Tamil Nadu install RWH structures. Sixteen years later, we are back to square one. An audit by the non-governmental organization Rain Centre has shown that most government buildings in Chennai do not have a functioning RWH structure; these include several police stations and municipality buildings. Now, the Greater Corporation of Chennai has ordered the inspection of RWH structures, much after the crisis.

Impact on Chennai

Millions of people are without consistent access to water. A lack of rainwater and groundwater has left four of the reservoirs that supply the city completely dry. The inability to meet demand for water has forced businesses like hotels and restaurants to close. Water tankers from areas of Tamil Nadu unaffected by drought have been bringing water into some areas of the city. However, government tankers can take up to a month to appear after requested, so some families, wealthy residents, and business owners have opted to pay for costly private water tankers. The poor who live in slums do not have this option; a family in Chennai slums may receive as little as 30 litres (7.9 US gallons) of water every day compared to an average American household which uses 1,150 litres (300 US gallons) of water a day. Many fights over water have also broken out because of the conflict.

Demand Supply Analysis

The figure below shows the total capacity of the major reservoirs of Chennai against their Storage. The storage data is given for 14^th January 2020 and for the same date a year ago in million cubic feet. We observe from the below graph that the water capacity has decreased in each of the reservoirs thus decreasing the total water capacity in the city.

A perusal of the below graph indicates a clear mismatch between the demand for and supply of drinking water in Chennai. The demand supply deficit increased from 137.79 MLD in 1951 to 220.45 MLD in 2008. In2011, the deficit was 400 MLD. The deficit assumed alarming proportions during the drought years of 2003 (630.6 MLD) and 2004 (610.5 MLD). A sudden downfall in the city’s water supply has been noticed in 2001 when compared to the 1991 level. This is largely due to the reservoirs getting completely dry leading to the cessation of piped water supply system in the city. The widening gap between the supply and demand curves indicates that the deficit has been increasing over the years. Observing the graph, the shortfall is expected to rise in the coming decades.

Fig. shows decadal average showing demand for and supply of water in Chennai

The below figure gives the rainfall in millimetre for the past decades. Large inconsistency of rainfall in each year has led to the 2019 Chennai crisis.

Prediction of Future Demand

From the below figure we observe that the demand of water has been increasing over the past few years and will also continue increasing in the future. If Chennai does not take extreme steps, then the city will not overcome this crisis and continue to affect the lives of thousands.

Prediction of Rainfall

According to our forecast, the rainfall in the city will not rise drastically. Thus, residents of the city will have to use their water judiciously.

Conclusions from Water Supply Analysis

The drinking water scenario in Chennai is poor. The absence of a perennial source of water stands out to be a major lacuna. CMWSSB has been entrusted with the sole task of supplying water to Chennai. Local sources constitute only 1/5th of the water supplied; 4/5th of the water supplied (65%) is through inter-basin transfers. However, the supply by CMWSSB only fulfills 40% of the city’s needs. Groundwater only fulfils 60% of the needs of Chennai’s population. Overexploitation of groundwater resources has resulted in the wells becoming dry and high. This has resulted in a huge mismatch between demand for and supply of drinking water in the city. The gap, indicative of the vulnerable situation of the population of Chennai city, has been widening over the years because of the ever-increasing population and limited sources of supply

Demo Video