Chennai River Basin

INTRODUCTION

The Centre for Science and Environment, New Delhi, envisages a detailed Scientific Study to assess the Surface Water and Groundwater Resources and the utilisation of Ground and Surface Water Resources in the Chennai Basin since the total available potential, goes beyond the Static Reserve, due to the indiscriminate growth of population, industries and agricultural development, causes depletion of groundwater levels and seawater incursion. Meanwhile due to the discharge of the industrial and municipal sewerages into most of the surface water bodies and into groundwater aquifer system either directly or indirectly, in most of the places, both the surface water and groundwater get polluted and contaminated to a maximum extent. Now it is necessitated to assess the quantum of such impact and its appropriate remedial measures to find a lasting solution.

This present study entrusted by The Centre for Science and Environment, New Delhi, aims at to assess the total Surface Water and Groundwater potential to meet the water requirement of the people of the stakeholders of Chennai Basin Area and Chennai Metropolitan Area and its suburb, especially to find a solution within a permissible financial constraint. This type of study aims to substitute and to reduce the impact on natural resources within the study areas, to preserve the groundwater and surface water reserve for sustainable development.

Through intervention of innovative technologies, the limit can be enhanced and reset at a higher level of scientific ways and means, discharges within the limit of collection with suitable population growth, with a new set of gradual increase in collection of sewage from point source which should again bring the mutual balance as stated above. Till date many studies were carry out in these areas by estimating both the surface water and groundwater potential either by Adhoc norms or by collection of hydrological and hydrogeological data collection and rapid assessment. Almost all these studies estimated the total available water potential, its usage and its balance but as on date the condition of both the surface water and groundwater reserve is very much limited due to various changes in the hydrological and hydrogeological changes. Till date all effective steps taken for solving the water crisis was overcome and were futile by inorderly growth of population, housing, industries and agriculturists, that was indiscriminate, unpredicted, uncontrolled and irrational, taking place both in urban and in rural areas. But within a given set of technology, the present status of surface water and groundwater can be make use off by doing better water management, conservation and by recycling of waste water generated and wasted.

Water pollution can be diluted, minimize the aerial extent and its intensity with space, depth and time, at a finite / definite limit. The developmental activities are compatible with its special, physical & ecological characteristics. A Eco friendly approach for sustainable development, there is a greater need to involve the private sector for the distribution and supply for utlisation of such treated effluent for better use so as to maximize the returns for the expenditure involved in such projects, which will also meet the daily recurring expenditure involved for the maintenance of the project and also to improve the socio economic status of the peoples in those areas fully. Briefly, when we analyze problems and their causes we must use a systems framework. Problems should be described using systems terminologies: entities, attributes, levels, and interrelations. The nature of interrelations between various attributes belonging to different entities must also be studied in the context of the three basic aspects - direct vs.inverse, linear vs. non-linear and immediate vs. delayed effects.

While doing so it will be possible to develop a visual perspective of the problem being analyzed and avoid delayed effects. The systems approach involves the use of specific tools, which enable the development of a visual description of a problem. Once a visual description of a problem is available then it is possible to model the system's behavior using other tools such as cross-impact analysis, and system dynamics. Through the application of these tools we can understand better and can hope to gain greater control over the development and environment, which should go hand in hand to create a database.

If such systems are developed for one river basin, this may be adopted and implemented in other metropolitan areas of other river basins where huge quantity of treated sewages are utilised for non-commercial purposes or thrown as a waste, which causes the contamination of groundwater reserve and can be used for many number of productivity purposes. A pilot project can be designed, implemented, executed and commissioned for Chennai city as a forerunner in India by Tamilnadu Government. The concept behind in suggesting this sample study is to develop such technology to other major cities in Tamilnadu itself as a whole for, proper utilization. The Center for Science and Environment, New Delhi, has requested us to study and prepare a Micro-level Status Report of Chennai River Basin with a Special Emphasis on Chennai City and its Environs including Chennai Metropolitan Area. The study now taken covers the assessment of surface water and groundwater potential, present condition of groundwater levels and quality, future demand and stages of development.

2.OBJECTIVES OF THE STUDY:

The objectives of this study addressing the above issues needs elaborate data base on the past 10 to 30 years data on groundwater and surface water resources, present Groundwater and Water Supply Status and the future demand of water resources for various disciplines of Chennai Metropolitan Limit and its Environs covering whole Greater Chennai Metropolitan Area on the following aspects: -

  1. Assess the Surface water and Groundwater Potential, utilisation, extraction and balance available to meet the future demand.
  2. Analysis of the Surface Water & Groundwater quality of the whole Chennai River Basins over long period of 10 years.
  3. Land value, land use and the economic benefits / losses attained over a long run by the landholders.
  4. Socio and Economic analysis to increase the status of the people settled in the entire river basin covering the Greater Chennai Metropolitan Limit and its environs covering parts of Thiruvallore, Kanjeepuram and Vellore Districts, especially to find out a lasting solution within a permissible financial constraint.
  5. To assess the level of groundwater pollution by the discharge of effluent in the Cooum and Adyar Rivers and Buckingham Canal.
  6. To assess the groundwater quality, utilisation of such treated effluent for appropriate usage; create awareness among the people, the ways and means to solve these issues forever.

The detailed work plan also includes: -

i.Collection of hydrological, hydrogeological and hydrometeriological data both secondary and at primary level to create a comprehensive database for Greater Chennai Metropolitan Area on Hydrology and Hydrogeology.

ii.Preparation of Thematic Maps of Chennai & its environs, such as Geology, Geomorphology, Landuse, Soil using conventional data and satellite / aerial data and geophysical data.

iii.Generation of map showing recharge and catchment areas of Greater Chennai.

iv.Data processing and location sketches, hydrogeological cross-sections, wherever possible groundwater conditions, groundwater quality and groundwater recharge. Integration of the above data and preparation of action plan, documentation and analysis.

3.CHENNAI RIVER BASIN.

The most fundamental concept of the Micro-level Status Report of Chennai RiverBasinmainly to evaluate the optional utilisation of surface and ground water resources.

3.1General

The Chennai Basin is situated between latitudes 12°40'N and 13°40'N and longitudes 79°10'E and 80°25'E at the north east corner of Tamilnadu. Andhra Pradesh lies on it north; Palar River basin lies on west and south and the Bay of Bengal on the east were the main boundaries of this basin. The total area of the basin is 7282 km². Out of that 5542 km² lies in Tamilnadu and the rest is in Andhra Pradesh. Araniyar (covers 763 km²), Kosathalayar (covers 3.240 km²), Cooum (682 km²) and Adayar (857 km²) are the four rivers of this basin group. This basin group covers partly or fully 26 blocks of Tiruthani, Thiruvallore, Saidapet, Tambaram, Ponneri, Sriperumbudur, Arakonam, and Walajapet taluks of Thiruvallore, Kanjeepuram, Chennai and Vellore districts. The major part of the basin area comes under Thiruvallore and Chennai districts (fully covered) and only a few area covers Vellore and Kanjeepuram districts. Of the four rivers, the Adayar River carries the floodwater and drainage of Chennai city and its environs. It does not have any direct irrigation and carries only the flood discharge during the northeast monsoon period for few days. The Cooum River serves as drainage and sewerage carrier within the Chennai city limit.

The Administrative boundary of the Chennai Basin is enclosed vide Plate: I.

Chennai River basin, models of inter department basin transfer of surface water from western Nagari Hills and originate from Andhra Pradesh hilly area and also forms part one of the seventeen important river basins of Tamilnadu. This has got a very good network distribution for irrigation, contributes a very high agricultural production of the state exchequer. It attributes greater importance in the existence, climate, physiography, unpredictable rainfall, distinct hydrogeology and water quality problems due to pollution on various grounds and also due to coastal environment. To evaluate the water resources of the basin various monitoring network data observed were employed.

3.2Physiography.

Physiographically the basin can be divided into three units viz. they are Western mountainous terrain with valley complex; Central elevated terrain and Eastern coastal plain. Physiography deals with the actual existing in-situ conditions of the land, depending upon the structures, formational changes and available natural agencies such as Hydrogiene and Epigiene agents.

The Physiography of an area can be classified as hills, plateau, plains, deltaic plain and coast. Physiographically the Chennai River Basin is an interdependent river basin of Araniar, Kosathalayar, Cooum and Adyar all rivers mostly flow from west to east with a man made artificial Buckingham canal runs from north to south. The river Araniar and Kosathalayar originate from Andhra Pradesh whereas the Cooum and Adyar originate from surplus courses of Cooum tank in Thiruvallore Taluk and Chembarambakkam Tank in Sriperumbudur Taluk. All these four rivers stretching from west to east and confluence with Bay of Bengal in the East.

The length of the river is 200 km.; width varies from 180 to 120 km. The Maximum elevation 1219 m above m.s.l. and minimum elevation is 5 to 15 m above mean sea level. The main tributaries are Nagari River, Araniar, Korathalayar, Cooum, Adyar and Buckingham canal. There are four major reservoirs situated in this basin. They are Poondi (Sathyamoorthy Sagar), Red Hills, Sholavaram and Chembarambakkam.

The total command area in Chennai Basin: is 1,31,665 hectares. There are 1,304 tanks by which 85,208 ha are irrigated. The storage capacity of the tanks is 410 mcm and the total capacity of the basin is 1069 mcm. The main study area of Greater Chennai, is more or less lays on the East Coast, hence the plain to gentle and the Coastal Physiography only occurs. The trend of coast is more or less uniform throughout the length of the study area. However broken natures in the trendline forms small parts and fishing point's etc.

Normally the coast spreads 750 m to 1000 m towards west from the tidal points with coverage of sands and sandy clay materials. In coastal area of the study, more or less plain topography is seen. Physiographically this basin is covered by parts of 12 Taluks & 26 Blocks falls in four districts of Tamilnadu State alone, mostly occupies the northern boundaries of Tamilnadu State. This is entry point to Tamilnadu from other states.

Small beach ridges and sand hillocks are occurring in and around the coastal belt near Pulicat Lake to Adayar creek and extend upto Injambakkam. Mostly backwater zones are seen in Pulicat and at Adayar Estuary in this basin area. Sea erosion prone, broken coasts are observed in Thiruvottiuyur to Ennore area. In Inland, topography, Insel bergs, (at Manjankaranai near Periyapalayam) smaller hillocks and elevated social forests were present. The maximum and minimum elevations of the study area are between 2 to 15 m in the coastal plain, 10 to 25 m in the central region and more in the hills and reserve forests, which covers a small area mostly on the northwest and west. The nominal topography is generally slopping towards the East and Southeast. The general trend of dipping ranges from West to East. The Hydraulic gradient and the flow lines of ground and surface water are towards east, the sea.

They’re some small hills and hillocks lie just near Pallavaram, Thiruneermalai and Tambaram, leaving the major hills and hill ranges lies on the northwestern and western part of the study area. Most of the hill catchments lie on the Andhrapradesh region.

The study area comprises of the major rivers like Araniyar and Korathalayar in the north and the Adyar and Cooum in the south. Apart from these rivers, there is a manmade canal, the Buckingham Canal runs north to south along the eastern narrow coastal strip, which actually starts from Visakhapattnam (Andhrapradesh State) in the north and ends near Marakkanam at Kaluveli tank in Tamilnadu State. Some years back, it was used for navigation and transportation, which has to be rejuvenated and revived. This canal will be very well useful and beneficial for tourism, resorts and for transportation. There is a large catchment area commanded by the rivers Araniar and Korathalayar, leaving the rest of the rivers such as Adyar and Cooum are having a very small catchment.

There is more number of systems and non-system rainfed tanks lies in the study area. These water bodies were very specifically useful in meeting the drinking water needs of the Chennai Metropolitan Area and rarely for irrigation and for industrial uses of many number of industries located around Chennai city and its urban agglomerate. All the drainages of the study area flow from west to east and confluence into Bay of Bengal. The specific drainage pattern in Araniar and Kosathalayar are interdependent. Leaving this some quantum of surface water too transferred from Palar River for irrigation purposes.

Road Network (Plate No: II), Elevation (Plate No: III), the Physiographic Map showing the Drainages and Water bodies (Plate No: IV) and Slope (Plat No: V) are enclosed.

3.3.Climate & Rainfall

For any water resources evaluation, planning, development and management studies, knowledge of the rainfall over the basin area as well as other hydrometeriological features is a pre-requisite. The basic factors, which influence agriculture, are climatological features such as rainfall, temperature, humidity, wind, sunshine and evaporation. Rainfall is the major input for the water resources in a basin and is a vital component to be studied in detail. Another important Hydrometeriological parameter is evaporation.

As Tamilnadu falls in the tropical zone, (arid, semi-arid climatic regions) evaporation plays a major role in agriculture and the same has to be studied in detail. The study now made on the hydrometeriological characteristics of the Chennai Basin (Araniar, Kosathalayar, Cooum and Adayar) includes analysis of rainfall, temperature, humidity, wind speed and sunshine.

A study of the rainfall pattern, its distribution in time and space and its variability and probability of occurrence is highly useful for water resources evaluation and planning. A detailed study has been made on the hydrometeriological parameters for Chennai Basin and the results of the analysis of the data collected are tabulated and analysed below.

Rain Gauge Stations

The Araniar and Kosathalayar River Basin – Chennai Basin has an aerial extent of 7282 km². Out of that 5542 km² lies in Tamilnadu and the rest in Andhra Pradesh. There are 46 non-recording rain gauge stations installed in this basin. Out of this, 24 stations having long-term records spatially distributed are considered for this study. In addition to that there are also 15 self-recording Auto Graphic Rain Gauge Stations located in this basin.

Araniar & Kosathalayar River Basin has a monsoonal climate as it lies within the tropical monsoon zone. Based on the hydrometeriological feature of the basin, year is divided into 2 periods Monsoon period spanning from June to December and Non-monsoon period spanning from January to May. The monsoon period is further sub-divided into 1) South West monsoon period spanning from June to September (4 months) and 2) Northeast monsoon period spanning from October to December (3 months). Similarly, the non-monsoon period is further sub-divided into (1) Winter period spanning January and February (2 months) and (2) Summer period spanning from March to May (3 months). As the monsoon period brings heavy rainfall it improves the recharging of ground water and storage of surface water. Hence, the monsoon period is hydrologically significant for water resources analysis, but whereas the Non-monsoon, it is insignificant.