CHAPTER 1 INTRODUCTION
1.1 GENERAL
As we plunge into a new century and a new millennium, the environment is being called on to supply the growing needs of an expanding human population in the developing countries and increasing affluence in the developed countries. In many areas we are already taking more from the earth’s systems than they can provide in a sustainable fashion. Environmental pollution means the presence in the environment of any environmental pollutant. Environmental pollutant means any solid, liquid or gaseous substance present in such concentration as may be, or tend to be, injurious to environment. Water is a major constituent of all living organisms. Over 70% of the Earth’s surface is covered by water. Without water, life on Earth would be impossible. It is essential for everything on our planet to grow and prosper. Although we as humans recognize this fact, we disregard it by polluting our rivers, lakes, and oceans. Subsequently, we are slowly but surely harming our planet to the point where organisms are dying at a very alarming rate. As per the Water (Prevention and Control of Pollution) Act, 1974, pollution means such concentration of water or such alteration of the physical, chemical and biological properties of water or such discharge of any sewage or trade effluent or any other liquid, gaseous or solid substance into water (whether directly or indirectly) as may, or likely to, create or nuisance or render such water harmful or injurious to public health safety or to domestic, commercial, industrial, agricultural or other legitimate uses, or to the life and health of animals or plants or of aquatic organisms.
1.2 WATER POLLUTION
Water typically referred to as polluted when it is impaired by anthropogenic contaminants and either support a human use or undergoes a marked shift in its ability to
1 support its constituent biotic communities. It is being polluted due to over population in terms of sewage and garbage, agricultural development in terms of pesticide and fertilizer application and rapid industrialization in terms of effluent and hazardous waste. In India, the main culprits for the degradation of water bodies are sewage and garbage generated especially in the urban areas. Absence of sewage treatment plant and garbage treatment leads to discharge of untreated sewage and garbage into water bodies. In Kerala, water bodies are polluted due to sewage and garbage. Wastes generated within households are often disposed of in nearby drains. Rubbish like plastic, glass is dumped into canals and rivers. Industries discharge wastes directly into water bodies leading to death of aquatic organisms due to the decrease in oxygen in water and due to reduction in pH. Some stretch of rivers and lakes namely Periyar are affected due to industrial effluent. Sewage, manure and chemical fertilizers contain nutrients such as nitrate and phosphate and when it enters water body in excess levels, nutrients over stimulate the growth of aquatic plants and algae. Excessive growth of these organisms clogs our water ways and blocks light to deeper waters. When the organisms die, they use up dissolved oxygen as they decompose causing depletion of oxygen in water. Sewage contains pathogens which cause diseases such as cholera, diarrhoea, typhoid and skin diseases. Pathogens include such organisms as bacteria, virus and protozoan. Stagnated water bodies are breeding grounds for mosquitoes causing dreadful diseases like chikunguinea, malaria. Polluted water kills fish, vegetation and other aquatic organisms. Weeds make waterways impassable. When a lot of soil is washed into rivers and drains, this causes aquatic life to perish and floods especially with heavy rainfall.
1.3 LAKE POLLUTION
The lakes are vital ecosystems deserving utmost care. Increasing population pressure and the resultant socio-economic development around this water bodies result in the deterioration of water quality. The problems faced by the lake systems can be generalized as 1) eutrophication 2) siltation 3) shrinkage in water spread 4) reclamation 5) encroachments 6) pollution resulting from natural as well as anthropogenic activities 7) excessive tourism load 8) over fishing[8]. Eutrophication means excessive plant growth
2 in lakes, estuaries and slow moving streams due to excess nutrients mainly from sewage and agricultural runoff. Excessive weed growth leads to high rate of siltation and results in shoaling of the lake. The shrinkage in lake water spread is mainly due to reclamation and rooted weed growth. When sediments enter water bodies, fish respiration becomes impaired, plant productivity and water depth become reduced and aquatic organisms and their environment become suffocated [8].
1.4 WATER QUALITY INDEX Water quality monitoring data consists of routine measurements of physical, chemical and biological variables that are intended to give insight into the aquatic environment. The WQI serves as a tool, to examine the trends, to highlight specific water quality conditions, and help governmental organizations to evaluate the effectiveness or regulatory programs. In essence, WQI has following important purposes. 1. Trend Analysis: Index may be applied to water quality data at different points in time to determine the changes in water quality (degradation or improvement) which have occurred over the period. 2. Public Information: Index may be used to inform the public about environmental conditions. 3. Ranking and Rationalization of locations: Index may be applied to assist in comparing environmental conditions at different locations of geographic areas. 4. Scientific Research: Index may be applied as a means of reducing a large quantity of data to form that give insights to the researcher conducting a study of some water quality processes.
1.5 EUTROPHICATION
Eutrophication is a process whereby water bodies, such as lakes, estuaries, or slow-moving streams receive excess nutrients that stimulate excessive plant growth (algae, periphyton attached algae, and nuisance plants weeds). This enhanced plant growth, often called an algal bloom, reduces dissolved oxygen in the water when dead plant material decomposes and can cause other organisms to die. Nutrients can come
3 from many sources, such as discharge of untreated sewage, fertilizers applied to agricultural fields, golf courses and suburban lawns; deposition of nitrogen from the atmosphere and erosion of soil containing nutrients. Water with a low concentration of dissolved oxygen is called hypoxic. Eutrophication is caused by the increase of an ecosystem with chemical nutrients, typically compounds containing nitrogen or phosphorus. It may occur on land or in the water[16]. Eutrophication is frequently a result of nutrient pollution such as the release of sewage effluent into natural waters (rivers or coasts) although it may occur naturally in situations where nutrients accumulate (e.g. depositional environments) or where they flow into systems on an ephemeral basis (e.g. intermittent upwelling in coastal systems). Estuaries tend to be naturally Eutrophic because land-derived nutrients are concentrated where run-off enters the marine environment in a confined channel and mixing of relatively high nutrient fresh water with low nutrient marine water occurs.
The names of the four trophic states, from the lowest level of biological productivity to the highest, are listed below (Source: http://lakewatch.ifas.ufl.edu) 1. Oligotrophic 2. Mesotrophic 3. Eutrophic 4. Hypereutrophic The root word ’trophic’ means “of or relating to nutrition.”
1. Oligotrophic Oligotrophic water bodies have the lowest level of biological productivity. Oligo means “scant or lacking.”
Criteria: Total chlorophyll is less than 3 μg/L Total phosphorus is less than 15μ g/L
4 Total nitrogen is less than 400μ g/L Water clarity is greater than 13 feet 2. Mesotrophic Mesotrophic water bodies have a moderate level of biological productivity. Meso means “mid-range.”
Criteria: Total chlorophyll is between 3 and 7 μ g/L Total phosphorus is between 15 and 25 μ g/L Total nitrogen is between 400 and 600 μ g/L Water clarity is between 8 and 13 feet 3. Eutrophic Eutrophic water bodies have a high level of biological productivity. Eu means “good or sufficient.”
Criteria: Total chlorophyll is between 7 and 40 μ g/L Total phosphorus is between 25 and 100 μ g/L Total nitrogen is between 600 and 1500 μ g/L Water clarity is between 3 and 8 feet 4. Hypereutrophic Hypereutrophic water bodies have the highest level of biological productivity. Hyper means “over abundant.”
5 Criteria: Total chlorophyll is greater than 40 μ g/L Total phosphorus is greater than 100 μ g/L Total nitrogen is greater than 1500 μ g/L Water clarity is less than 3 feet
Water hyacinth [Eichhornia crassipes], a native of Amazon river basin in South America is a troublesome aquatic weed all over the world. It was introduced into India in 1896 as an ornamental pond plant. Now this weed is seen infesting more than 200,000 ha of water surface, causing concern in 98 out of 246 districts in India. This fast multiplying weed can produce 3000 offspring in 50 days and can double its biomass in 10–12 days. The disadvantages of this weed outweigh its merits. It interferes with production of hydroelectricity, blocks water flow in irrigation and drainage canals, channels and streams leading to flooding and seepage into adjoining areas, hinders anti-mosquito operations and forms a breeding ground for obnoxious insects like mosquitoes which transmit infectious diseases such as malaria and encephalomyelitis. It also affects the aquatic fauna through elimination of habitat and depletion of oxygen level caused by respiration and decomposition of vegetative parts. The excessive weed population is strong enough to stop boats or slow down navigation. It also makes recreational water activity difficult and unsafe in lakes. Algae play an important role in the limnology and ecology. Algae are the predominant photo synthesizers of fresh water and all aquatic environments. The density and distribution of phytoplanktons are determined by the variability and distribution of nutrients in an aquatic system. Certain selected types of algae also are used as indicators of pollution[15].
6 1.6 CARLSON'S TROPHIC STATE INDEX
The cloudiness of lake water is often related to the amount of nutrients in the water. Nutrients promote growth of microscopic plant cells (phytoplankton) that are fed upon by microscopic animals (zooplankton). The more the nutrients, the more the plants and animals and the cloudier the water is. This is a common, but indirect, way to roughly estimate the condition of the lake. This condition, called eutrophication, is a natural aging process of lakes, but which is unnaturally accelerated by too many nutrients. Trophic state is defined as the total weight of living biological material (biomass) in a waterbody at a specific location and time. Algal biomass is used as the basis for trophic state classification. Chlorphyll pigments, secchi depth and total phosphorous independently examines algal biomass.
A Secchi disk is commonly used to measure the depth to which you can easily see through the water, also called its transparency. Secchi disk transparency, chlorophyll a (an indirect measure of phytoplankton), and total phosphorus (an important nutrient and potential pollutant) are often used to define the degree of eutrophication, or trophic status of a lake. The concept of trophic status is based on the fact that changes in nutrient levels (measured by total phosphorus) causes changes in algal biomass (measured by chlorophyll a) which in turn causes changes in lake clarity (measured by Secchi disk transparency). A trophic state index is a convenient way to quantify this relationship. Carlson’s index is a popular index and was developed by Dr. Robert Carlson of Kent State University.
1.7 WATER QUALITY MONITORING
Water quality monitoring gives an idea about the status of water quality and extent of deterioration caused. Water quality results comprise of concentration of various water quality parameters at different stations and hence it is very complex. Analysis of water quality data is essential for arriving at a useful conclusion. Analysis of water quality data is indeed a necessary extension to monitoring of water quality. Statistical analysis converts the water quality data into something deductive by providing useful implications
7 not so obvious from the raw data. Correlation, regression and factor analysis help in developing and interpreting relationship between water quality parameters and rationalizing monitoring network. Detection of trend and violations provide a useful insight into the spatial temporal behaviors or water quality data so as to plan appropriate pollution control measures. The water quality parameters analyzed in the laboratory are given below[10]. pH pH is negative logarithm of hydrogen ion concentration. Fresh sewage is generally alkaline in nature. As time passes, pH tends to fall due to production of acids by bacterial action in anaerobic or nitrification processes.
Turbidity Suspension of particles in water interfering with passage of light is called turbidity. Turbidity is caused by a wide variety of suspended materials, which range in size from colloidal to coarse dispersions.
Electrical Conductivity Electrical conductivity is the capacity of water to carry an electrical current. It depends on the presence of ions and its concentration. Solutions of most inorganic acids, bases and salts are relatively good conductors of electricity. Molecules of organic compounds that do not dissociate in aqueous solution is a poor conductor of electricity. Most dissolved inorganic substance contributes to conductance.
Total Dissolved Solids Solids present in water as suspended solids, colloidal solids, settleable solids and dissolved solids. Total dissolved solids are those solids which remain dissolved in water. Generally carbonates, bicarbonates, chlorides, nitrates and sulphate of sodium, potassium, calcium and magnesium contribute total solids in water.
Suspended Solids Suspended solids are those which remain floating in water.
8 Dissolved Oxygen The oxygen dissolved in surface water is largely derived from the atmosphere and from the photosynthetic activity of algae and higher aquatic plants. Concentration of dissolved oxygen will vary daily and seasonally and depend on the species of phytoplankton present, light penetration, nutrient availability, temperature, salinity, water movement, partial pressure of atmospheric oxygen in contact with the water, thickness of the surface film and biodepletion rates. When oxygen depleting substances from sewage enter water, the self purification capacity of water is affected and the dissolved oxygen concentration decreases to the point of complete disappearance of oxygen from water. This condition results in sign of eutrophication with the growth of algal blooms.
Biochemical Oxygen Demand (BOD) There are two types of organic matter. a. biologically oxidized (oxidized by bacteria) b. can not be biologically oxidized (biologically inactive) Biochemical Oxygen Demand gives the biologically active organic matter present in water. Micro-organisms utilize the atmospheric oxygen dissolved in the water for biochemical oxidation of polluting matter, which is their source of carbon. It is a measure of organic matter present in a water sample and can be defined as the amount of oxygen required by the micro-organism in stabilizing the biologically degradable organic matter under aerobic condition.
Ammoniacal Nitrogen Ammoniacal nitrogen indicates the very first stage of decomposition of organic matter. Ammonia is formed by the deamination of organic nitrogen containing compounds and by the hydrolysis of urea. Ammonia is readily available as a nutrient for plant uptake and this may contribute greatly to increased biological productivity. It is easily oxidized to nitrite and nitrate in the presence of sufficient oxygen (nitrification).
+ Under anaerobic condition, organic nitrogen is converted into ionized (NH4 ) and unionized (HN3) ammonia.
9 Nitrite Nitrogen Nitrite is formed in water by oxidation of ammonium compounds or by reduction of nitrate. As an intermediate stage in the nitrogen cycle, it is unstable. Nitrite indicates the presence of partly decomposed organic matter in water. It is the intermediate stage of conversion of organic matter into stable forms.
Nitrate Nitrogen Nitrate is the most highly oxidized form of nitrogen compounds. It is the end product of the aerobic decomposition of organic nitrogenous matter. The sources of nitrate are chemical fertilizers from cultivated land; drainage from livestock feed lots as well as domestic and some industrial water. Nitrates indicate the presence of fully oxidized organic matter.
Sulphate Sulphates are formed due to the decomposition of sulphur containing compounds. When oxygen level falls to zero (anaerobic zone), some bacteria derive oxygen through reduction of nitrates. On complete exhaustion of nitrate, oxygen may be obtained by reduction of sulphate yielding hydrogen sulphide causing foul smell and putrefied taste for water.
Phosphate Phosphorous compounds are carried into natural waters with waste waters and storm runoff. They may produce a secondary pollution, being essential nutrients. Algal blooms occur where both nitrogen and phosphorous are plentiful. Sewage is relatively rich in phosphorous compounds. Most of the inorganic phosphorous was contributed by human wastes as a result of the metabolic breakdown of proteins and elimination of the liberated phosphates in the urine. The use of polyphosphate in detergents increases the phosphorous content of domestic sewage. The amount of phosphorous released is a function of protein intake.
10 Chloride Chloride ion is generally present in natural waters. A high concentration occurs in waters from chloride containing geological formations. Otherwise, high chloride content may indicate pollution by sewage or some industrial wastes or an intrusion of sea water or other saline water. Human excreta, particularly the urine, contain chloride in an amount equal to chloride consumed with food and water.
Total Hardness Hardness is caused by divalent metallic cations. The principal hardness causing cations are calcium, magnesium, strontium, ferrous iron and manganous ions. The anions responsible for hardness are mainly bicarbonates, carbonates, sulphate, chloride, nitrate, silicates etc.
Total Coliform Total Coliform is an indicator of pollution due to sewage.
Faecal Coliform Faecal coliform indicates the presence of faecal pollution. It is an indicator of faecal contamination.
1.8 GEOGRAPHICAL INFORMATION SYSTEM
The technology of Geographic Information system (GIS) facilitates the organization and management of data with a geographic component. Geographic Information System is an organized collection of hardware, software, geographic data and personnel designed to efficiently capture, store, update, manipulate and display all forms of geographically referenced information. A geographic information system (GIS) is a computer system for capturing, storing, querying, analyzing and displaying geographically referenced data. The ability of a GIS to handle and process geographically referenced data distinguishes GIS from other information system.
11 GIS packages differ according to the data structure they use to store the data. The way in which the spatial data are structured for storing the data will determine how the user can retrieve, analyze and do modeling. The often used data models for spatial data are raster and vector. A raster model divides the entire study area into regular grid of cells, organized into rows and columns. The vector model is that all geographic features in a real world (or on a map) can be represented as points, lines (arcs) or areas(polygon). In this model, the spatial locations of features are defined on the basis of coordinate pairs. A vector model represents more accurately, then features without any blocky appearance and allows complex data to be stored in a minimum space. A point has no dimension. Besides the (x, y) coordinates, other data must be stored to indicate what kind of point it is and other information if any associated with it. Lines requires a minimum of two (x, y) coordinates (straight line) to define a line. Polygons are represented by listing coordinates of points around the boundary of the polygon. The beginning and end are the same point thus making a closed area [9]. A GIS typically made up of a variety of information systems like Artographic Display System, Map Digitizing System, database Management System, Geographic Analysis System, Image Processing System, Statistical Analysis System and Decision Support system.
Fig 1.1 GIS and Related Discipline The most common method of structuring the geography of the real world in the computer is to use a layered approach. Each layer is thematic and reflects either a particular use or the characteristic of the landscape. In GIS, there are two types of data to be managed: spatial data and attribute data. An entity (point, line or area) has both spatial
12 (where things are) and attribute (what things are) data to describe it. Database offer more than just a method of handling the attributes of spatial entities; they can help to convert into information with value [9]. GIS carries out the integrated analysis, so as to spatially combine multiple features to generate a composite theme. Data collection and digitizing/editing (to be compatible for computer storage) are the most time-consuming activity. Visually interpreted thematic maps and topographical maps need to be digitized [5]. GIS links spatial data with the geographical information about a particular feature on a map. The information is stored as attributes of the geographically represented feature. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and benefits of geographic analysis that is offered by the maps [3]. The visual presentation of results of water quality monitoring helps us to give a clear picture of quality of surface water at a glance using GIS. The complex relationship between various parameters can be easily studied if the water quality results are presented in a visually appealing manner as a map rather than a set of rows and columns of figures. The spatial distribution of water contaminants and other water quality parameters can be displayed in an effective manner. This helps authorities in taking effective measures to check water pollution and thereby to restore water quality.
1.9 STUDY AREA
The Akkulam- Veli Lake and their surrounding areas have become a region of tourist attraction in recent years. It is situated approximately 5 km north-west of Thiruvananthapuram between latitudes 825’ and 835’ N and longitudes 7650’ and 7658’ E and the lake is having an area of less than 1km2 surrounded by lateritic hillocks. Serious environmental degradation is being experienced by this system due to sewage and the municipal solid waste generated in the City, eutrophication problem, developmental activities, etc. Lack of flushing results in the piling up of the pollutants. The lake is partially separated into two by the existence of a bund across the lake. The western part of the lake having a length of 1.25 km with an average width of 100 m is the Veli Kayal. The North Eastern part starting from the bund forms the Akkulam part of the
13 lake. For most part of the year these lakes remain separated from the sea by a sand bar which is approximately 150 m and having a width of 20-40 m. The Pozhi remains open usually for a period of 10-14 days depending upon the influx of land drainage to the lake. Usually this episode repeats 6-8 times a year. The weeds which had a prolific growth while the lake had a near fresh water condition are seen dying as they are intolerant to saline water[8]. Two canals, viz. the Kulathur Canal and Parvathy Puthen Ar (Channankara Canal) join the Veli Lake in the northern side. The Chakka Canal, also called as the Parvathy Puthen Ar connects Veli kayal with the Poonthura kayal in the south. Seepage of sewage from Muttathara Sewage Farm makes the canal water extremely polluted. Kannammoola Thodu joins the eastern part of the Akkulam Lake. Sewage from the Thiruvananthapuram City and drainage from the suburbs are brought into the lake through the Kannammoola Thodu. The Kulathur canal brings in substantial quantities of fresh water to lake during the southwest and northeast monsoon. The Veli lake is connected to the Akkulam lake by a narrow channel. English India Clay Ltd is situated in southern bank of the Veli lake. There is chance of entry of effluent from Travancore Titanium Products through sea during the period of connection of lake with the sea. The lake is an excellent inland water navigational tract and Kerala Tourism Development Corporation has developed Akkulam and Veli boat club on its banks as major tourist attraction. This is also responsible for man-made changes in the quality of water in the lake[12].
1.10 OBJECTIVES
Akkulam lake is one of the important tourist centers in the capital City and it attracts tourists very much. Amayizhanchan Thodu the major discharge canal drains into the Akkulam lake carrying sewage generated in the City and a heavy mass of silt and debris is deposited in this lake. Other main problems faced by the lake are the weed problem and erosion. A thorough study of the characteristic of the water quality was done in order to study the eutrophication level in the lake. GIS interactive maps were prepared for better understanding. Statistical analysis of water quality data was done. Trend analysis was done through the WASP software.
14 The objectives of the study are:
1. Analysis of water samples monthly from different stations in the lake of various physical, chemical and biological parameters. 2. Analysis of sediment and its interpretation 3. Water Quality assessment using the National Sanitation Foundation Water Quality Index (NSF WQI) 4. Display the variation of water quality parameters in the lake using GIS 5. Display of pollution sources, adjacent local bodies and factories 6. Statistical analysis of various water quality data of different parameters at different stations. 7. Assessment of eutrophic condition of lake using the Water Quality Index 8. Suggest precautionary measures to be taken up for the total quality improvement of the lake.
CHAPTER 2 LITERATURE REVIEW
15 The scarcity of drinking water is one of the most important crises of the 21 st century. Most freshwater bodies the world over are becoming polluted, thus decreasing the potability of the water. Eutrophication of natural waters is one of the significant causes of decline in water quality. It is accompanied by a large quantity of plants in water. Nitrates and phosphates are probably the key nutrients in controlling aquatic plant growth. A lake is a large body of water surrounded by land and inhabited by various aquatic life forms. Lakes are subjected to various natural processes taking place in the environment such as the hydrological cycle. As a consequence of unprecedented development, human beings are responsible for choking several lakes to death. Sudhira et. al. (2000) observed that storm water runoff and discharge of sewage into the lakes are two common ways that various nutrients enter the aquatic ecosystems resulting in the death of those systems. Eutrophication is of great concern as it signifies the aging of a lake. Marsden (1989) describes the variations in aquatic systems due to nutrient enrichment; the eventual consequence of that enrichment is the growth of primary production to nuisance proportions. As per Jana et. al. (1995), the main cause of eutrophication is excessive loading into the system of phosphorous and nitrogen, resulting in high algal biomass, dominance by cyanobacteria and loss of macrophyte. According to Vollenweider (1976), the concept of nutrient overloading has a great impact on all subsequent eutrophication research and lake management. Eutrophication is accelerated as a result of human activities near or in a body of water that generate residential wastes, untreated or partially treated sewage, agricultural runoff, urban pollutants and so forth. Sewage or residential waste, consisting largely of phosphate containing detergents, is a major source of nutrients in water bodies. The U. S. Environmental Protection Agency (1976) suggested that for phosphate, 0.08 ppm was the critical level for the occurrence of eutrophication in lakes and reservoirs. The flow of nutrients in the water may over stimulate the growth of algae. This creates conditions that interfere with the recreational use of lakes and adversely affect the diversity of indigenous fish, plant and animal populations.
16 Lathrop (1988) studied present trends in the summer levels of phosphorous, chlorophyll and water clarity in the Yahare lake from 1976-1988. These three interrelated parameters are indices of lake trophic state (degree to fertility). Phosphorous is generally the nutrient causing lake eutrophication. Chlorophyll-a, the primary photosynthetic pigment, is a direct measure of algal biomass, Secchi disk transparency readings represent an easily understood measure of the water quality of the lake of how ‘green’ the lakes are perceived. Savita et. al. (2005) conducted study on nutrient overloading of Shahpura lake, a fresh water lake of Bhopal. High phosphate content in the lake water revealed that nutrient load in the lake was very high and hyper eutrophic conditions were prevailing. The phosphate concentration in the water is very high as compared to the standard guidelines. This condition was accompanied by a gradual filling up of the water body, which became shallower from the accumulation of plants and sediments on the bottom and also became smaller due to the invasion of shore vegetation. The extinction of the lake can result because of enrichment, productivity, decay and sedimentation. Yateesh Kandi.et.al reports that water quality in inland lakes is often described in terms of tropic state (nutritional state). A lake with increased growth of phytoplankton is called a “Eutrophic Lake”. The main reason for eutrophication in most lakes is phosphorus loading. Because the different broad classes of algae have somewhat different spectral response patterns, aerial and space imaging can distinguish them. By spectral response, we mean the response of an object to the incident wavelength upon it. Each object responds differently to the different wavelengths. This is described by its unique response called Spectral Signature. The data collected from various sources (Aerial Photographs, Satellite Images, Field Surveys and stored databases) will be integrated and analyzed in a GIS to provide useful spatial information and temporal changes over large geographic areas affecting the structure and function of lakes. Sheela (2006) conducted study on the downstream stretch of the river Karamana. 14 samples from this stretch starting from Thiruvallom were collected and analyzed. The variation in water quality with respect to each 18 water quality parameters was shown on a map using the monitoring results with the help of Kirging method in the geostatistical tool. Variation in water quality index in the stretch was also presented using GIS. This
17 will assist the concerned authority in analyzing the spatial distribution of ‘Eutrophication level’ in a lake. This will help them in taking decisions regarding ‘usage of lake for different purposes’ and also take countermeasures to ‘control pollution level’ of the water bodies. Robert E. Carlson developed a numerical trophic state index for lakes that incorporates most lakes in a scale of 0 to 100. Each major division (10, 20, 30, etc.) represents a doubling in algal biomass. The index number can be calculated from any of several parameters, including Secchi disk transparency, chlorophyll, and total phosphorus. K. Muniz1, A. studied a dataset comprising 12 oceanographic cruises (from 1979 to 1983), covering two regions in the Northwestern Mediterranean Sea (Gulf of Lyon and Catalan Sea), was statistically analyzed for nitrate and phosphate relationships with silicate, salinity and depth. This analysis provided a preliminary assessment of the data’s quality, as well as a predictor model of these nutrients below the surface layer. Results from the statistical analysis showed no significant difference (P = 0.05), between the regression equations (nitrate-depth and phosphate-salinity) of most cruises in the Gulf of Lyon, indicating that these relationships do not change in this area, particularly in summer and autumn. A significant relationship between nitrate and phosphate with salinity and depth (multiple regressions) was observed, suggesting that nitrate and phosphate distribution in the intermediate level are significantly related to the mixture of the water masses and the degradation of organic matter. The phosphate data showed a wide variance and a bias, probably due to procedural problems in the chemical analysis. Below the Intermediate Levantine Water, results from the ANOVA showed no significant variation of the phosphate and nitrate concentrations in the water column. However, a spatial and temporal variation was observed in this level. Sunil S. Shaha et.al characterized lakes as dynamic ecosystems that reflect their specific characteristics, variations in climate, and biological components. The size of the lake basin, its depth and volume, the size of the watershed and the quantity and quality of water that enters the lake are important considerations. Lake management activities are implemented on the basis of this information, including surface use regulations, aeration, native and exotic aquatic plant management. Lake management issues related to the
18 physical characteristics of the lake will require data on the surface area, shape, depth and volume of the lake. The inlet and outlet characteristics and bottom types are also important. A detailed study and project reports are prepared for conservation and revival of Rankala Lake at Kolhapur, Mahalaxmi Lake at Vadagaon and Mansi Ganga Lake at Govardhan. The general methodology included Reconnaissance survey of lake and its catchments, detailed survey of the lake area, gathering present and historical information. The objective is to emulate a natural, self-regulating system that is integrated ecologically with the landscape in which it occurs. Management towards this end should emphasize the long-term sustenance of historical and natural functions as well as values. The preliminary step that is proposed in restoring lake for their long-term sustenance. Muraleedharan Nair et.al.(1998) conducted various physical and chemical studies in the water and sediment quality parameters and concluded that for most part of the year, the lake as a whole is in a highly degraded state. The study revealed that the chief sources of pollutants to this lacustrine system are from the municipal and domestic sewage and untreated or partially treated industrial effluent discharged in to the system. Lack of natural flushing, elevated values of nutrient content and near-fresh water conditions of the lake aids in the prolific growth of aquatic weeds, especially the water hyacinth. It was recommended to take coordinated approach for salvaging and sustaining this lake system by involving planners, scientists, environmentalists, technocrats and administrators.
CHAPTER 3 METHODOLOGY
19 3.1 GENERAL The knowledge on the physico-chemical parameters of a lacustrine system is of great importance while attempting to characterize its general features, distribution pattern of various pollutants, salinity intrusion, abundance of nutrients, etc. Its essential to analyze various sediment and water quality parameters to assess the health of a lacustrine system. Hydrographic features such as temperature, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), salinity, nutrients, etc., of the lake are greatly influenced by topographic, climatic and anthropogenic factors. Sediments act as sinks to various pollutants introduced into the water body.
3.2 WATER QUALITY ANALYSIS
The study area, Akkulam lake is situated in Thiruvananthapuram District of Kerala, India. For the present investigation to study the degradation of the lake, six sets of samples from February to July 2008 were collected from ten selected locations. Water samples were collected with utmost care. As far as possible samples were taken from the same place at the same time of the day. Water samples were collected in sterilized plastic bottles. The collections were made during the day time. The temperature of the water samples were examined at the spot by means of a good grade Celsius thermometer. Maximum care was taken for the collection of samples, their preservation and storage as per the APHA standards. The physico-chemical characteristics of the water samples were analyzed using the standard methods (APHA. et al., 1995). The parameters analyzed are pH, Electrical conductivity, Turbidity, Secchi Distance, Chemical Oxygen Demand, Suspended solids, Total dissolved solids, Dissolved Oxygen, Biological oxygen demand, Ammoniacal Nitrogen, Nitrite, Nitrate, Sulphate, Phosphate, Total Phosphorous, Chlorophyll (may), Chloride, Total Coliform and Fecal Coliform.
3.3 SEDIMENT ANALYSIS
20 Sedimentation is a spontaneous natural process and the analysis of the sediments has greater attention in the world due to the growing awareness of environmental pollution and its impact on the ecosystem. Four sampling stations were selected for investigation. Sediments were scooped up from the sampling locations by using a Van Veen Grab. A part of the sediment samples was oven dried at 100 – 105 C overnight and finely powdered. The organic carbon content of the sediment was estimated by the method of El-Wakeel and Riley(1957). The pH and conductivity of the sediment samples were determined using the pH meter and conductivity meter. Textural Analysis of the sediment samples was done using the Wet sieving and Pipette method.
3.4 DISPLAY WATER QUALITY INDEX
Water quality index serves as a tool to examine trends, to highlight specific water quality conditions. National Sanitation Foundation Water Quality Index (NSF WQI) is used for the study. Table 3.1 Equations for Water Quality Parameters (NSF WQI) Water Quality Range Equation Correlation Parameter Applicable Coefficient Percentage Saturation 0 – 40% DO`= 0.18+0.66x(% saturation 0.99 DO DO) 40 – 100% DO`= -13.5+1.17x(% saturation 0.99 DO) 100 – 140% DO`= 163.34-0.62x(% saturation -0.99 DO) BOD(mg/L) 0 – 10 BOD`= 96.67-7.00x(BOD) -0.99 10 – 30 BOD`= 38.90-1.23x(BOD) -0.95 pH 2 – 5 pH`= 16.10+ 7.35x (pH) 0.925 5 – 7.3 pH`= -142.67- 33.5x (pH) 0.99 7.3 – 10 pH`= 316.96- 29.85x (pH) -0.98 10 – 12 pH`= 96.17- 8.00x (pH) -0.93 Fecal 1 – 103 Coli`= 97.20-26.80xlog(FC) -0.99 Coliforms(No/100mL) 103-105 Coli`= 42.33-7.75xlog(FC) -0.98 105 Coli`= 2 - (Source: Water Quality Analysis Statistical CPCB )
21 It has been calculated on the basis of water quality parameters namely dissolved oxygen, fecal coliforms, pH and BOD. In order to facilitate easy computation of the sub indices, mathematical equations could be fitted. Table 3.1 lists the regression equations for the four water quality parameters of concern. The variation of NSF WQI can be shown in a map as mentioned above. The variation can be described on the basis of the following descriptor words suggested for reporting the NSFWQI.
Table 3.2 Descriptor words for reporting NSF WQI NSF WQI Descriptor words 0-25 Very bad 26-50 Bad 51-70 Medium 71-90 good 91-100 Excellent (Source: Water Quality Analysis Statistical CPCB )
3.5 CREATING THEMATIC MAPS USING GIS
GIS is a tool, which will help the designers for storing and retrieving the required information with ease and work in a systematic manner. Spatial data is obtained from topological maps of the study area (scale 1:50, 000) were obtained from CED. 58D14 and 58D15 are the topo sheets of the study area. Location of water sampling stations was obtained using Geographic Positioning System available with the CED. The study area has every chance of developments in near future. Thus it needs a very careful thought and well-documented studies of various aspects of the project area. The details of topography, road network and effect of various water qualities are also important parameters. The first step in a GIS project is to create a digital map database. Now that the database is complete, the analysis phase of the project begins. Spatial analysis will identify the intensity of various water quality parameters.
3.5.1 Map Projection
22 Georeferencing is the method by which a relationship can be established between the map coordinates and the corresponding real world coordinates. This process requires high level of accuracy. Map was georefernced. The spherically undulating nature of the earth surface, when represented on two- dimensional maps, result in some distortions unless a curved surface is used to represent it. Map projection is defined as “a mathematical formula for representing the curved surface of the earth on a flat surface of a map”. It defines the relationship between the map co-ordinates and the corresponding real world co-ordinates. The map projection used in this work is GCS_WGS-1984.
3.5.2 Integrating data – map Overlay The ability to integrate data from two sources using map overlay is perhaps the key GIS analysis function. Using GIS it is possible to take different thematic map layers of the same area and overlay them one on top of the other to form a new layer. The technique of GIS map overlay may be linked to sieve mapping, to overlaying of tracing of paper maps on a light table. Map overlay has many applications. As one layer it can be used for the visual comparison of data layers. Overlays where new spatial data sets are created involve the merging of data from two or more input data layers to create a new output data layer.
3.5.3 Spatial Interpolation Spatial interpolation is the procedure of estimating the values of properties at un sampled sites with an area covered by existing observations. A common application of interpolation is for the construction of height contours. Kriging is an interpolation technique in which the surrounding measured values are weighted to derive a prediction for an unmeasured location. Weights are based on the distance between the measured points, the prediction locations, and the overall spatial arrangement among the measured points. Kriging is based on regionalized variable theory, which assumes that the spatial variation in the data being modeled is statistically homogeneous throughout the surface. That is, the same pattern of variation can be observed at all locations on the surface.
23 A GIS offers many options for creating customized maps and reports. ARC MAP is used for the mapping needs, and INFO to generate the final report. The map contains a series of themes or coverage’s and descriptive information to interpret the information on the map.
3.6 CARLSON WATER QUALITY INDEX
Carlson trophic state index was developed for use with lakes that have few rooted aquatic plants and little non-algal turbidity. Use of the index with lakes that do not have these characteristics is not appropriate.
The formulas for calculating the Carlson Trophic State Index values for Secchi disk, chlorophyll a, and total phosphorus are given below:
TSI = 60 - 14.41 ln Secchi disk (meters) TSI = 9.81 ln Chlorophyll a (ug/L) + 30.6 TSI = 14.42 ln Total phosphorus (ug/L) + 4.15 where TSI = Carlson trophic state index ln = natural logarithm Ranges of trophic state index values are often grouped into trophic state classifications. The range between 40 and 50 is usually associated with mesotrophy (moderate productivity). Index values greater than 50 are associated with eutrophy (high productivity). Values less than 40 are associated with oligotrophy (low productivity).
Carlson's index uses a log transformation of Secchi disk values as a measure of algal biomass on a scale from 0 - 110. Each increase of ten units on the scale represents a doubling of algal biomass. Because chlorophyll a and total phosphorus are usually closely correlated to Secchi disk measurements, these parameters can also be assigned trophic state index values. The Carlson trophic state index is useful for comparing lakes within a region and for assessing changes in trophic status over time.
24 Secchi depth is often the only variable that can be inexpensively measured. Priority is given to chlorophyll, because this variable is the most accurate of the three at predicting algal biomass. According to Carlson, total phosphorous may be better than chlorophyll at predicting summer trophic state from winter samples and transparency should be used if there are no better methods available.
The possible interpretations of deviations of the index values are given below:
Table 3.3 Relationship between TSI Variables
Relationship Between TSI Variables Conditions TSI(Chl) = TSI(TP) = TSI(SD) Algae dominate light attenuation; TN/TP ~ 33:1 Large particulates, such as Aphanizomenon flakes, TSI(Chl) > TSI(SD) dominate Non-algal particulates or color dominate light TSI(TP) = TSI(SD) > TSI(CHL) attenuation TSI(SD) = TSI(CHL) > TSI(TP) Phosphorus limits algal biomass (TN/TP >33:1) Algae dominate light attenuation but some factor TSI(TP) >TSI(CHL) = TSI(SD) such as nitrogen limitation, zooplankton grazing or toxics limit algal biomass.
3.7 STATISTICAL ANALYSIS OF WATER QUALITY PARAMETERS
Data from 10 Stations from February to July 2008 were statistically analyzed and relationship of each station with Ammoniacal Nitrogen, nitrite, nitrate and phosphate were examined. The statistical analysis conducted in this study had an objective to establish a predictive model by observing which of all the regression relations from all various stations did not vary throughout the period. Samples were collected at each station and nutrient analyses were performed on untreated samples. Correlation and regression help in developing and interpreting relationship between water quality parameters and rationalizing monitoring network. Comparisons among the set of
25 regression equations for all stations were made. From these linear regression equations, a predictor was defined for each nutrient based on two criteria: adjusted R2 (the highest); root mean square error (sqrtMS) (the lowest). Those criteria were used to choose the predictive model. From them, and because this resulting regression best illustrated the distribution of the nutrients in the lake (> R2), we were able to select a regression relation that was constant in time and space.
CHAPTER 4 RESULTS AND DISCUSSIONS 4.1 GENERAL As industrialization and urbanization progressed the aquatic ecosystem became loaded with enormous quantities of nutrients, sediments and toxic materials. For the
26 assessment of the environmental quality and protection, monitoring of pollutants present in the environment is highly essential. The unique feature of the Lake permits sea-lake relation and interaction leading to large scale exchange of water and sediments.
4.2 WATER QUALITY ANALYSIS The present study was carried out for six months from February to July 2008. Values of various physico-chemical parameters for the ten stations; Near Amayizhanchan thodu, Before Boat Club, After Boat club, Centre of Akkulam Lake, Manakkunnu, Oruvathilkotta, Near T. S. Canal, Near English Indian Clays, Near SIFFS and Near Sea from February to July 2008 was plotted. Data for the month of February 2008 are shown in Appendix I
4.2.1 pH When pH is outside the range of 5.5 to 8.5, most aquatic organisms become stressed and populations of some species can become depressed or disappear entirely.
27 28 Fig 4.1. Seasonal Variation of pH Raw sewage reaches the Akkulam lake through Amayizhanchan thodu. At this point, pH is having a minimum of 6.2 in February. The minimum value of pH 6.16 was recorded at station after this point (beyond boat club) in February. Then it was increased to 6.68 at the centre of Akkulam lake. At the point where T. S. canal meets the Veli lake, pH is 6.74 and near sea, its value is 6.79. This may be due to nearness to the sea. Increase in pH was observed in April, May and June due to rain. Occasional breaching of the sand bar during rainy season results in intrusion of sea water having pH so that Veli side of the lake water has higher pH values during monsoon.
4.2.2 Turbidity Turbidity in water is caused by the presence of suspended matter, such as clay, silt colloidal organic particles, Plankton and other microscopic organisms. Turbidity is an expression of certain light scattering and light-absorbing properties of water. Turbidity is an important parameter for characterizing the water quality.
29 Fig 4.2 Seasonal Variation of Turbidity
30 Raw sewage enters the Akkulam lake through Amayizhanchan thodu. Maximum turbidity (33.8 NTU) was observed in February at this point and this may be due to the turbid particles in sewage. A maximum value of 49.8 NTU (March) was observed near the sea. It is seen that turbidity increases during the monsoon periods at all stations.
4.2.3 Electrical conductivity Conductivity is a measure of the ability of water to conduct an electric current, which is dependent upon the concentration of charged particles (ions) dissolved in the water. Minimum value of 100microSiemens was observed and a maximum value of 5100micro Siemens was observed during July.
31 Fig 4.3. Seasonal Variation of Electrical conductivity
In Akkulam lake where sewage enters the water body, electrical conductivity is less as less inorganic ions are present in sewage. It ranges from 380 to300 micro siemens. It is seen that the conductivity increases towards sea and the conductivity is maximum at 2100 micro siemens near sea at Veli lake in June.
32 4.2.4 Dissolved oxygen and biological oxygen demand Oxygen in the dissolved form is essential to maintain biological life in water. . Dissolved Oxygen concentration is an important gauge of existing water quality and the ability of a water body to support well balanced aerobic conditions.
33
Fig 4.4 Seasonal variations of DO and BOD
The main sources of dissolved oxygen in water are the atmosphere and aquatic plants. In Akkulam lake where sewage enters through Amayizhanchan thodu, lower value of dissolved oxygen was observed. It is nil in May. In the centre of the Akkulam lake, its value is zero in March and April. Very low values in DO content is observed in stations located in the Akkulam side of the lake system. The organic pollution is the main reason for the depletion of dissolved oxygen in the lake. The Kannammoola Thodu and Chakka Thodu bring in organic rich land drainage and sewage. There is improvement in the quality of water Veli lake towards the sea.
34 Biological Oxygen Demand indicates the amount of oxygen required for the biological oxidation of organic matter. BOD has an inverse relationship with the DO and direct relation with the phytoplankton. The minimum value of Biological Oxygen Demand was recorded at the centre of the Aakkulam lake, 0.6mg/l (March) and maximum value was recorded at the point were Amayizhanchan thodu meets the Aakkulam lake, 25.8mg/l (February). Lower BOD values can be observed near the sea.
4.2.5 Chloride Chloride occurs naturally in all types of fresh water. Chloride is a “mobile ion,” meaning it is not removed by chemical or biological processes in soil or water. Many products associated with human activities contain chloride (e.g., de-icing salts, water softener salts, and bleach). Although most fish are not affected until chloride concentrations exceed 750 PPM, increasing chloride concentrations are indicative of other pollutants associated with human activity (such as automotive fluids from roads or nutrients / bacteria from septic systems) reaching our waterways.
35 Fig 4.5. Seasonal variation of Chloride The chloride concentration in the present study ranged having a maximum of 1450mg/L in July and having a minimum of 27mg/L in April. It’s usually seen that higher values are observed near the Veli side of the lake due to also of the intrusion of sea water along with the drainage from land and sewage. In the present study chloride concentration is heavy due to sewage disposal (BIS. 1996, 250mg/l) and industrial pollution.
36 4.2.6 Ammoniacal Nitrogen, Nitrite and Nitrate Nutrients play an important role in an aquatic environment, which mainly governs the phytoplankton growth and diversity. Nitrates are the end products of decomposition of organic matter and indicate that organic matter is fully oxidized.
37 Fig 4.6 Seasonal variations of Ammonia cal Nitrogen, nitrite and nitrate
In present study maximum concentration of ammoniacal nitrogen is found at station where Amayizhanchan thodu meets Akkulam Lake and it is also maximum at the station where T. S. canal meets Veli lake. It is seen that the input of sewage into the lake has a profound effect in summer. Nitrites are the products obtained by the oxidation of ammonia. Nitrates are the fully oxidized form of ammoniacal compounds.
4.2.7 Phosphate Phosphate is a vital nutrient for the growth of phytoplankton. Maximum concentration of 1.01mg/L was observed in February which may be due to eutrophication and a minimum of 0.032mg/L in July near the Pozhi. Phosphate concentration above 2mg/l is considered as an indication of high pollution.
38 39 Fig 4.7. Seasonal Variation of Phosphate
The excessive weed growth in the Akkulam –Veli Lake has resulted in impairment of many of the lake related activities. In addition, phosphorous is contributed to the water body by domestic sewage, industrial effluent and drainage from agricultural lands where excess phosphatic fertilizers are used.
4.2.8 Total Hardness Hard water forms precipitates on boiling or when soap is added to it. Hardness is due to the presence of calcium, magnesium or ferrous (iron salts) as chloride, sulphate or
bicarbonates. The degree of hardness is equivalent to CaCO3 concentration and designated as soft (0-60 mg/1), medium hard (60-120 mg/1), hard (120-180 mg/1), very hard (>180 mg/1).
40 Fig 4.8 Seasonal Variation of Total Hardness
41 Higher values of total hardness are found near the Pozhi. Its value varies from 138 to 296 mg/l in this area. This may be due to nearness to the sea. The values of total hardness are 56 mg/l at Oruvathilkotta and 296 mg/l near sea.
4.3 SEDIMENT ANALYSIS Lakes display a wide variety of geological and physiographic characteristics. Samples were collected from four stations for analysis during December 2007, April 2008 and July 2008. Hydrogen ion concentration of soil depends largely on relative amounts of the absorbed hydrogen and metallic ions. Hydrogen ion concentration of sediments samples get drastically changed due to disposal of industrial waste sewage etc. The four stations selected are the following given below Where Station1 – Amayizhanchan thodu Station 2 – Akkulam_Centre Station 3 – Veli_TS canal Station 4 – Veli_near sea shore
4.3.1 pH and Electrical Conductivity pH of sediments ranged from 3.58-7.29 and conductivity from 500 – 4940mS/cm. At Station 3 there may be a contamination from the English India clay Ltd causing a lowering of pH of 3.58 at April 2008. A high conductivity of 4940mS/cm is observed at station 2 due to eutrophication during December 2007.
Table 4.1 pH of sediment samples Location December 2007 April 2008 Station 1 5.35 5.40 Station 2 5.37 5.42 Station 3 5.68 3.58 Station 4 7.29 5.78
Table 4.2 Conductivity (mS/cm) of sediment samples
42 Location December 2007 April 2008 Station 1 1038 1015 Station 2 4940 2550 Station 3 2680 3340 Station 4 500 460
4.3.2 Texture Texture of the sediment samples showed that the silt content was greater near the Amayizhanchan thodu ie. the upper reaches of the lake and sand and clay was greater near the sea station. Table 4.3 Texture of sediment samples Location December 2007 April 2008 Sand% Silt% Clay% Sand% Silt% Clay% Station 7.7 92.14 0.16 1 Station 9.8 88.8 1.4 0.165 50.48 49.59 2 Station 45.4 53.57 1.03 11.38 25.95 62.67 3 Station 71.1 27.4 1.5 50 45.43 4.57 4
4.3.3 Organic Carbon Suspended organic matter received by the lake through land run off, sewage etc settle and forms part of bottom sediments. Dead aquatic plants and organisms also contribute much to the organic content of the sediments. Enriched with organic matter, the sediments acts as good reservoir of nutrients.
Table 4.4 Percentage organic carbon of sediment samples
Location December 2007 April 2008 Station 1 2.032% 1.978
43 Station 2 7.5% 7.112% Station 3 7.15% 6.5% Station 4 0 0.226%
Maximum value of 7.5% was recorded at station 2 during December 2007 and minimum value of 0 was observed at station 4 during December 2007. The sediments at Akkulam part comprise of silty clay while that in the Veli part is sandy. Contribution by Kannammoola Thodu and debris of aquatic weeds are also more at Akkulam part of the lake.
4.4 WATER QUALITY INDEX Water quality index serves as a tool to examine trends, to highlight specific water quality conditions. National Sanitation Foundation Water Quality Index is used for the study. It has been calculated on the basis of water quality parameters namely dissolved oxygen, fecal coliform, pH and BOD. The variation can be described on the basis of the following descriptor words suggested for reporting the NSF WQI. These codes could be effectively used to classify the water quality while preparing the water quality maps. This information could be then readily used to take suitable control actions for water quality restoration or improvement. Table 4.5 NSF WQI for the Summer and Monsoon Period Stations Summer Monsoon Amayizhanchan Thodu 34.21 36.64 After Boat Club 37.08 36.90 Manakkunnu 29.57 39.72 TS Canal 33.87 39.92 SIFFS 41.74 40.23
Variation of water quality index along the Lake is seen above in Table 4.5. Water Quality of the lake is described to be “bad” according to NSF WQI. Water quality index is 29.57 at Manakkunnu indicating water quality is bad at this point mainly due to low mixing. Water quality indices at TS Canal and SIFFS are ranging from 33.87 to 41.74 respectively indicating quality of water is bad at these points due to the land drainages.
44 4.5 CREATION OF THEMATIC MAPS USING GIS
The result of geographic analysis can be communicated by maps (a graphical representation of data), reports ( a written description of the results) or both. The final product should relate directly to the objectives of the project. The Thiruvananthapuram corporation is digitized. The details of the major existing roads have been delineated from 1:50,000 scale Survey of India Topographical sheets. A base map is a general topological map that covers the lake and includes important features of the area such as: 1. Road layout maps 2. Streams and tributaries contributing towards the lake 3. Variation of different water quality parameters in the lake for prediction of values at any point in the lake. 4. To evaluate potential sources of contamination to the Lake. Determination susceptibility to contaminant source inventoried within source. The GPS Unit Trimble Geoexplorer 3 was used to collect information about the actual point source. The most common sources of contaminants found were the sewage pumping stations, medical institutions, industries etc. The stations from where different water samples are taken for the analysis are the following
I. Akkulam Lake 1. Near Amayizhanchan thodu
2. Before Boat Club
3 After Boat club
4. Centre of Akkulam Lake
5. Manakkunnu
6. Oruvathilkotta
II. Veli Lake
7. Near T. S. Canal
45 8. Near English Indian Clays
9. Near SIFFS
10. Near Sea
46 Fig 4.9 Thematic map showing sample points
47 Fig 4.10 Thematic map showing road and railway network
48 Fig 4.11 Thematic map showing Lake, stream and tributaries
49
Fig 4.12 Thematic map showing BOD variation
Fig 4.12 shows BOD is higher towards the Veli lake causing a profound effect on the SIFFS station.
50 Fig 4.13. Thematic map showing DO variation Fig 4.13 shows DO is very low in Akkulam lake due to the drains from the Amayizhanchan Thodu and Parvathy Puthenar. Whereas DO increases as it moves towards the sea due to the intrusion from the sea
51 Fig 4.14 Thematic map showing COD variation Fig 4.14 shows COD is very much higher towards the Veli lake and at some stations of the Akkulam lake because COD is mainly contributed due to the drains from the land drainage and industrial effluents
52 Fig 4.15 Thematic map showing pH variation Fig 4.15 show pH is higher at English India Clay Ltd station due to the contamination from the industry. Whereas the station where Amayizhanchan Thodu meets the Akkulam lake has lower pH due to acidic sewage draining from the Thodu.
53 Fig 4.16 Thematic map showing Sources of contamination Fig 4.16 shows the contamination sources in the Thiruvananthapuram corporation contributing towards the Akkulam – Veli lake causing the deterioration of the lake. Contamination mainly occurs due to the overflows from the pumping stations, sewage farm, boat club, English India clay ltd and land drainages.
54 Fig 4.17 Overflow from Pattoor Pumping Station
Fig 4.18 Overflow from Plamood Pumping Station
55 Fig 4.19 Overflow from Murinjapalam Pumping Station
Fig 4.20 Overflow from Kannamoola Pumping Station
56 Fig 4.21 Thematic map showing Contour layout
Fig 4.21 shows the digital elevation model of the Thiruvananthapuram Corporation. Most of the land drains flows directly into the lake due to gravity flow.
57 4.6 ASSESSMENT OF EUTROPHIC CONDITION OF THE LAKE The Trophic Status Index can serve as a standard of trophic measurement against which comparisons can be made between the many chemical and biological components of the lake system that are related to trophic status. The result could be a more complete and dynamic picture of how these components relate to one another and to the lake ecosystem as a whole. TSI values for the month of May are plotted in fig 4.22. The Total Phosphorous and Secchi Disk TSI values remained higher than the Chlorophyll TSI values. Chlorophyll or total phosphorus is not considered as the basis of a definition of trophic state but only as indicators of a more broadly defined concept. The best indicator of trophic status may vary from lake to lake and also seasonally. The lake was receiving most of its phosphorous from sewage effluent and their was noticeable deterioration of water quality near the boat club and centre of Akkulam Lake. Heavy algal blooms are possible throughout the summer with dense macrophyte beds, but extent limited by light penetration. Often its classified as hypereutrophic.
Fig 4.22 Tropic status index of the lake Fig 4.22 shows that the TSI values of chlorophyll lies in the range of 30-50 i.e in the mesotrophic state. TSI values of total phosphorous and Secchi distance lies in the range of 70-90i.e in the hypereutrohic state. According to the relation non algal particulates or colour dominate light attenuation.
58 Fig 4.23 TSI of Phosphorous Fig 4.23 shows that the high TSI value of phosphorous is seen in the Akkulam lake due to high eutrophication.
59 When chlorophyll values are converted to TSI, however, they can be seen to be responding rapidly to enrichment, and the changes parallel those in the TSI values based
Fig 4.24 TSI of Secchi Disk
60 on transparency. Lakes will become anoxic in the hypolimnion during the summer.
61 Fig 4.24 shows that high TSI value of Secchi distance is observed at station after boat club due to eutrophication.
62
Fig 4.25 TSI of Chlorophyll
The index can be used for regional classification of all surface waters, including streams and rivers. Any body of water could be classified using the total phosphorus index, which is essentially a predictor of potential algal biomass
63 4.7 STATISTICAL ANALYSIS The simple linear regression was determined for the ten stations from February to July 2008, using the variables ammoniacal nitrogen, nitrite, nitrate and phosphate. From the correlation matrix given in Table 4.6, it is seen that a strong linear relationship exists at certain stations.
Ammoniacal Station Nitrite-N Nitrate-N Phosphate nitrogen Akkulam Lake 1. Amayizhanchan (5.232-0.248x) 0.078 0.221 (4.928-4.398x) Thodu 0.782 0.826 2. Beyond boat (5.422-0.307x) 0.346 0.307 (5.448-10.95x) club 0.782 0.617 3. After Boat club 0.197 (4.823-26.91x) 0.158 (5.419-10x) 0.714 0.626 4. Centre of (4.94-0.337x) (4.64-8.29x) 0.243 0.167 Akkulam Lake 0.623 0.677 5. Manakkunnu 0.367 (5.06-10.74x) (3.95-0.42x) 0.173 0.694 0.616 6. Oruvathilkotta (4.99-0.317x) 0.071 0 0.164 0.692
64 Veli Lake 7. TS Canal 0.434 0.383 0.465 0 8. English India (5.101-0.512x) (4.69-11.62x) 0.297 (5.618-12.54x) Clay Ltd 0.675 0.782 0.666 9. SIFFS 0.414 (5.73-17.38x) 0.265 (5.695-14.55x) 0.863 0.691 10. Veli near sea 0.332 (5.27-24.82x) 0.187 (4.823-6.43x) 0.759 0.809 Table 4.6 Correlation significance of ammoniacal nitrogen, nitrite, nitrate and phosphate with stations Sampling stations indicate that the ammoniacal nitrogen samples drawn near the Amayizhanchan Thodu (Station 1) have higher scores compared to other Stations. This is clearly due to the fact that Station 1 is influenced by the inflow of sewage from the Amayizhanchan Thodu which also brings in the nutrients, especially phosphate. Whereas nitrate rises toward the Manakkunnu as complete oxidation of ammonium takes place and is the final oxidation stage. At station 1,2 and 6 the sewage is input into the lake through the Amayizhanchan Thodu and Parvathy Puthenar causes an increase in ammoniacal nitrogen which gives a high relationship with those stations. Whereas the nitrite and nitrate has lower values as decomposition of the organic matter is yet to be started at those stations. Sewage is relatively rich in phosphorous compounds also which causes a high relation at station 1 and 10 due to the sewage input from Amayizhanchan Thodu and due to the intrusion from sea. The stations included in this predictive model for ammoniacal nitrogen are: Amayizhanchan Thodu, beyond boat club, centre of Akkulam lake, Oruvathilkotta and English India Clay Ltd. The general predictive model is: Y= 18.820 – 0.692x (Y = Station and x = Ammoniacal Nitrogen) The general predictive equation for nitrite includes station After Boat club, Centre of Akkulam lake, Manakkunnu, English India clay ltd, SIFFS and Veli near sea: Y = 16.129 – 0.312x (Y = Station and x = nitrite). The general predictive equation for nitrate includes station Manakkunnu: Y = 3.95-0.42x (Y = Station and x = nitrate). The general predictive equation for phosphate includes station Amayizhanchan Thodu, after boat club, beyond boat club, English India clay ltd, SIFFS and Veli near sea:
65 Y = 21.762 – 16.198x (Y = Station and x = nitrate).
CHAPTER 5 CONCLUSIONS
Water is more prone to pollution than air. The surface water bodies like lakes, rivers and streams are more prone to pollution. Thus regular monitoring of hydrological parameters is a prerequisite for the proper evaluation. The present paper analyzes the lake water quality data collected from the Akkulam Lake. Important water quality issues include the biological productivity of a lake (trophic state), water chemistry profiles, nutrient concentrations, specific pollutants and historical trends.
• Comparatively lower pH is observed during monsoon season. Saline water intrusion due to occasional breaching of sand bar during monsoon months contributes to spikes in pH value in Veli side of the Lake water • Increase in BOD values, nutrients and decrease in DO content are due to input from the domestic sewage and industrial effluents. Lack of natural flushing, elevated values of nutrients content and near fresh water condition help prolific growth of aquatic weeds. • In the present study it was revealed that the most polluted stations are in the upper reaches of the lake resulting in lower dissolved oxygen and a high amount of biological oxygen demand. • Sediments are mud dominated in the Akkulam part and enriched in sand towards the Veli side. The Akkulam part is slowly silted up due to drains from Kannammoola Thodu, dispersed sources and debris from aquatic weeds
66 • Water Quality Index shows that water quality is very bad at Manakkunnu. A large quantity of sewage generated in the Thiruvananthapuram city reaches the lake through the Amayizhanchan Thodu and Parvathy Puthenar and that is the main reason for the deterioration of water quality. The problem can be solved only by the installation of adequate treatment plant for the sewage generated especially in the Corporation area. • Thematic maps were prepared, showing the variation of different water quality parameters hence able to predict the values at various points and also the sources of pollution into the Lake. • Assessment using Trophic Status Index indicates that the Lake lies in the Hypereutrophic state as the index is used for regional classification of all surface waters, including streams and rivers based on the biological productivity. • Statistical model has been constructed, which explains the relationships between the various physico–chemical variables that have been monitored and the environmental conditions. Ammoniacal nitrogen and phosphate concentration has higher relation with respect to those stations were the sewage input is received from Amayizhanchan Thodu and Parvathy Puthenar. Nitrite and nitrate has lower relation at those stations as oxidation of organic matter has not yet started.
This may harmfully affect the water quality and the flora and fauna, which lead to the ecological imbalance of our environment. Hence it is highly essential to control the anthropogenic activities in and around the lake so as to exploit these resources sustainably for domestic as well as economic purposes.
67 CHAPTER 6 SUGGESTIONS
Lakes are hub for the socio economic activities of the country besides being a major attraction for the tourists from distant places. The sewerage system in Thiruvananthapuram city was commissioned in 1945. The system was designed in such a way that the overflow i.e. excess sewage above the holding capacity in the pumping stations due to pumping breakdown caused by power failure, break down of pump sets etc., should reach the nearest canal/rivers. Now the population and the number of houses in the City have increased many folds and the inflow into the sewage pumping stations also has increased. The system has exceeded its designed capacity resulting in the discharge of a large quantity of raw sewage as overflow into the Akkulam Lake through the Amayizhanchan Thodu and Parvathy Puthenar. Only some part of the total quantity of sewage reaches the sewage farm. The sewage farm which is in use since 1940 can take care of a small quantity of sewage. A large quantity of rain/seepage enters the system during rainy season although the sewerage scheme is designed for disposal of sewage and sullage. A large quantity of sewage goes as overflow at many places such as through manholes, sump wells in the pumping stations reaches the Akkulam Lake through T. S. Canal, Amayizhancan thodu and Parvathy puthenar due to the inadequacy of the existing system and negligence of some of the pump operators. The conservation and protection of lake involves not only buffering lake from direct human pressures but also maintaining important natural processes that operate on the lake from outside, which may be altered by human activities. The preliminary step that is proposed in restoring lake for their long-term sustenance includes pollution
68 impediment, removal of algae, floating and submerged aquatic weeds, dilution and flushing, desiltation (wet dredging), chemical remediation / bioremediation and catchments treatment. The living conditions of the local inhabitants are highly deplorable. It is estimated that Akkulam Lake is degraded due to the input of 21 mld of sewage from the drains inflowing in to the lake. The oxygen demand level of the water body is too high, indicating unfair situation for the growth of biological and aquatic species. First and foremost is to treat the inflow in to the lake to have desired level of quality, and to control the sewage inlet to the canal and inflow of domestic effluents. Badly damaged reaches of the canal need to be protected. Sewage treatment plants are to be energized. Sewage Treatment Plants have to be installed at various places. These plants should be positioned so that polluted water can be treated before discharge into the lake. Both secondary treatment and tertiary treatment are important. This is a very expensive process. Decentralized sewage treatment system has been suggested. FAB (fluidized aerobic bio-reactor) technology has been found suitable due to land scarcity and low power requirement The sewage from the treatment plant will be used to produce 150 kilo watt of hydel power. The simplest way to manage weed problem is to harvest it and utilize it for useful products like utilization in animal feed, biogas generation, handicrafts, paper industries, etc. In some parts of India it is also used as a medicinal plant. The main problem of utilization and management of water hyacinth is its high cost of transportation to the disposable site or factories. To overcome this problem a mechanical system was developed at College of Technology and Engineering, Udaipur, India which chops and crushes water hyacinth simultaneously in a single pass and reduces its volume. Hence such a system can be adopted. Processes of supplementing the flushing system are to be ensured. Providing groynes at the mouth of the inlets to the sea will be helpful in ensuring free flow of water from the stream to the sea. Proper investigation and studies are to be carried out before designing the system. The entire length of thodu bed should be desilted and the unwanted vegetative growths will be removed so as to ensure free flow of surface water. Canal fencing has been recommended in the thickly populated areas near the thodu to avoid solid waste
69 dumping. Provision is also made for the construction of foot bridges. Silt traps and drains should be constructed wherever required along the periphery. Desilted sludge should be removed from the banks of the lake as soon as possible. The desilted sludge can be taken for land filling and if organic carbon is low, could be used for making bricks. Sanitation of the local residents by the side of Parvathy Puthanar is to be improved considerably. Most of the households have simply kept the outlets of their toilets and latrines direct to the canal for economic reasons. The drainage connections to the Parvathy Puthanar canal and to all public water bodies are necessarily to be cut off and covered septic tanks to be provided for all the houses. Protection works are required at Vazhavila to Akkulam, fencing the canal to prevent pollution and Renovation of Poonthura to Akkulam reach of Parvathy Puthanar. Contamination of water is yet another problem faced by the lake. The fertilizers and pesticides used for agricultural activities in the nearby area get intruded into the lake, for which necessary barriers need to be constructed. Desiltation of the lake is also necessary for increasing its capacity. Desiltation and removal of age old wastes & rubbish thrown into it will reduce the BOD level of water, thus helping to enhance the aquatic life in it. Fish cultivation may also be started along with this, which in turn will be an added benefit to the society. Construction of boundary in pucca form and proper fencing to safeguard against dumping of solid wastes is required. A walkway on its outer periphery to enjoy its beauty and for enabling maintenance in future is also required. Awareness campaign throughout the city is to be held quite frequently and all possible measures resorted to save as much water as possible and keep the surroundings and the lake clean.
70 REFERENCE
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