REGIONAL GROUNDWATER FLOW AND SUBSURFACE HYDROCHEMICAL INVERSE MASS BALANCE MODELING OF LOWER BHAVANI RIVER BASIN, TAMIL NADU, INDIA

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1 REGIONAL GROUNDWATER FLOW AND SUBSURFACE HYDROCHEMICAL INVERSE MASS BALANCE MODELING OF LOWER BHAVANI RIVER BASIN, TAMIL NADU, INDIA A THESIS Submitted by S. ANANDAKUMAR in fulfilment for the award of the degree of DOCTOR OF PHILOSOPHY FACULTY OF CIVIL ENGINEERING ANNA UNIVERSITY: CHENNAI JUNE 2008

2 ii ANNA UNIVERSITY: CHENNAI BONAFIDE CERTIFICATE Certified that this thesis titled REGIONAL GROUNDWATER FLOW AND SUBSURFACE HYDROCHEMICAL INVERSE MASS BALANCE MODELING OF LOWER BHAVANI RIVER BASIN, TAMIL NADU, INDIA is the bonafide work of Mr. S. ANANDAKUMAR who carried out the research under my supervision. Certified further that to the best of my knowledge the work reported herein does not form part of any thesis or dissertation on the basis of which a degree or award was conferred on an earlier occasion on this or any other candidate. Place : Salem Dr. T. SUBRAMANI Date : (SUPERVISOR) Lecturer in Geology Department of Civil Engineering Government College of Engineering Salem

3 iii ABSTRACT Groundwater is commonly referred to as the water which lies below the surface of the earth, occupying the interstices and voids in various formations, which get annual replenishment from meteoric precipitation. The quality of groundwater is very important in evaluating its utility for agricultural, domestic and industrial purposes. Groundwater always contains some amount of chemical substances, and their concentration is a function of the initial composition, rainfall, land use, type of surrounding rocks, and the recharge processes. Variation of groundwater quality in an area is a function of physical and chemical parameters that are greatly influenced by geological formations, recharge-discharge mechanisms of groundwater and anthropogenic activities. The correlation of groundwater chemistry with hydrologic and geologic environments gives valuable information to understand the effect of these processes and to properly manage aquifer systems. Bhavani River is one of the important tributaries of Cauvery River, and originates in the Silent Valley range of Kerala State, India. The Lower Bhavani River Basin lies between N and 11 45' N latitudes and E and 77 40' E longitudes with an area of 2,475 km 2. Some of the previous studies carried out in the Lower Bhavani River Basin, Tamil Nadu, India are groundwater resources and development potentials in Erode District, groundwater level monitoring, rainfall recording, pump test analysis and

4 iv estimation of concentrations of major ions in groundwater, and a case study on groundwater quality of hard rock aquifers of Erode District. However, no systematic work has been carried out in this area to understand the spatial and seasonal variations in rainfall distribution, groundwater quality and groundwater level fluctuation. As groundwater is the major source for drinking and irrigation in the Lower Bhavani River Basin, and there has been unplanned exploitation of the groundwater resources, it is essential for an integrated study of groundwater flow and quality. Thus, a detailed study has been carried out to understand the rainfall distribution, concentrations of major and trace elements in groundwater, simulation of groundwater head, and identification of subsurface hydrochemical processes. Accordingly, data pertaining to seven years groundwater quality for 15 open wells ( ), 11 years monthly groundwater levels for 43 wells ( ), rainfall of 9 rain gauge stations ( ), borehole lithology and pump tests at 19 wells, and details regarding cropping patterns, population statistics, groundwater abstraction and irrigation were collected from reliable sources. Various thematic maps pertaining to groundwater studies were prepared with the help of Survey of India toposheets and IRS- ID-LISS III satellite imageries. Groundwater samples were collected from 43 monitoring wells during July 2006 and February 2007 for analyzing physico-chemical parameters, major anions, cations and trace elements using standard methodologies. Hydrographs were prepared for 43 wells to understand groundwater level fluctuations and recharge mechanisms. To understand spatial variations of groundwater quality, isoline and zonation

5 v maps for various major ions were prepared using Geographical Information System (GIS). Grid-based, three-dimensional digital elevation model (DEM) was also generated using GIS. Subsurface lithological variations, groundwater flow directions and groundwater quality were also included in this study. Residence time of groundwater was also considered to be an important parameter to study groundwater evolution. Rainfall and recharge analyses were carried out in detail encompassing the four seasons as categorized by the Indian Meteorological Services. These analyses include studies of seasonal and spatial rainfall variations, and regression analysis of annual and monsoon rainfall. The study indicates that increasing trends of monthly rainfall intensities are observed between January and May, and June and October, at all the rainfall stations. The basin receives more rainfall during the north-east monsoon season, which is nearly 44% of the total rainfall of the basin. Spatial variation analysis of rainfall indicates that intensity of rainfall increases towards the central and north-western parts of the basin. Regression equation (rainfall) of the basin is: Annual Rainfall = ( Monsoon Rainfall) A numerical three-dimensional groundwater flow model was developed using MODFLOW code for the Lower Bhavani River Basin with the main objectives of simulating the regional groundwater flow, and identification of the distribution of heads for improved understanding of the natural flow system in the study area. The results indicate that the aquifer system is stable under the present conditions. The model also predicts the

6 vi changes in groundwater head with changes in hydrological conditions, like drought occurring once in three years, and a normal run for another 8 years without any major changes. The groundwater of the area is fresh water, except for a few samples that represent brackish water. Most of the groundwater samples are within the maximum permissible limit for drinking as per the WHO standard, except for few samples. Heavy metal concentrations in groundwater are also well within the permissible limits for drinking. The NETPATH computer code was used to model the major subsurface processes contributing to the evolution of groundwater chemistry. The occurrence of such chemical processes as silicate weathering, carbonate dissolution, ion exchange and dilution due to rain were verified by performing inverse mass balance modeling using the same code. The net geochemical mass balance reactions between initial and final water were identified and quantified based on the flow in selected well pairs. The model output shows that dilution, ion exchange and illite precipitation are the dominant processes that control the chemistry of the groundwater along the flow paths. Calcite and NaCl dissolution are also involved to a certain extent. Reverse ion exchange process is also observed in two models.

7 vii ACKNOWLEDGEMENT The author expresses his deep sense of gratitude to his research supervisor Dr. T. Subramani, Lecturer in Geology, Government College of Engineering, Salem, for his invaluable guidance, moral support, advice and constant encouragement during all phases of this research work. The author also wishes to record his heartfelt thanks to Dr. L. Elango, Professor, Department of Geology, College of Engineering, Guindy, Anna University, and Dr. S. Thayumanavan, Principal, Dhanalakshmi Srinivasan Engineering College, Perambalur, for their continued advice and guidance throughout the course of the research work. I am immensely grateful to Dr. P. Pradeep Mujumdar, Chairman and Professor and Dr. M.S. Mohankumar, Associate Professor, Dept. of Civil Engineering, IISC, Bangalore, for their inspiring suggestions during this research as members of the doctoral committee. The author wishes to thank Prof. S.R. Damodarasamy, Principal, Government College of Engineering, Salem, for his timely help during the conduct of synopsis meeting. Dr. M. Senthilkumar, Scientist, Central Groundwater Board, Ministry of Water Resources, Ahmedabad, and Dr. R. Kannan, Scientist, Sathyabama University, Chennai, are thanked for their support in carrying out groundwater modeling work. The author wishes to thank the Management, Principal, Professors and teaching and non-teaching staff of Kongu Engineering College, Perundurai, for extending the available facilities to carryout this research work. S. ANANDAKUMAR

8 viii TABLE OF CONTENTS CHAPTER NO. TITLE PAGE NO. ABSTRACT iii LIST OF TABLES xiii LIST OF FIGURES xv LIST OF SYMBOLS AND ABBREVIATIONS xx 1 INTRODUCTION GENERAL NEED FOR THE PRESENT STUDY STRUCTURE OF THE THESIS 5 2 REVIEW OF LITERATURE GENERAL RAINFALL ANALYSIS GROUNDWATER FLOW MODELING GROUNDWATER CHEMISTRY SUBSURFACE HYDROCHEMICAL PROCESSES 12 3 METHODOLOGY GENERAL DATA COLLECTION PREPARATION OF MAPS FIELD INVESTIGATIONS AND SAMPLING 19

9 ix CHAPTER NO. TITLE PAGE NO. 3.5 SAMPLE ANALYSIS AND INTERPRETATION Determination of Trace Elements Software used for Data Interpretation MODELING OF GROUNDWATER FLOW AND QUALITY 22 4 DESCRIPTION OF THE STUDY AREA GENERAL CLIMATE AND RAINFALL TOPOGRAPHY DRAINAGE GEOLOGY HYDROGEOMORPHOLOGY LINEAMENT LAND USE SOIL 33 5 RAINFALL AND RECHARGE ANALYSIS GENERAL VARIOUS SEASONS Cold Weather Season (Winter Season) Hot Weather Season (Summer Season) South-West Monsoon Season North-East Monsoon Season (Retreating South-West Monsoon) RAIN GAUGE STATIONS 40

10 x CHAPTER NO. TITLE PAGE NO. 5.4 MONTHLY VARIATIONS OF RAINFALL SEASONAL VARIATIONS OF RAINFALL SPATIAL VARIATION PATTERNS OF RAINFALL FREQUENCY DISTRIBUTION OF RAINFALL REGRESSION ANALYSIS OF ANNUAL AND MONSOON RAINFALL DEM AND SURFACE RUNOFF MODEL RECHARGE AND WATER LEVEL FLUCTUATION RESULTS OF RAINFALL RECHARGE ANALYSIS 52 6 REGIONAL GROUNDWATER FLOW MODELING GENERAL AQUIFER CONDITION MODELING OBJECTIVES MODEL CONCEPTUALIZATION Boundary Conditions GRID DESIGN INPUT PARAMETERS Initial Groundwater Head Aquifer Characteristics Groundwater Abstraction Groundwater Recharge MODEL CALIBRATION SIMULATION RESULTS 70

11 xi CHAPTER NO. TITLE PAGE NO. 6.9 MODEL FORECAST Normal Rainfall Condition Drought (Once in Three Years) Condition RESULTS OF FLOW MODELING 75 7 GROUNDWATER CHEMISTRY AND QUALITY GENERAL GROUNDWATER CHEMISTRY DRINKING WATER QUALITY Total Dissolved Solids Total Hardness Sodium Potassium Calcium Magnesium Chloride Bicarbonate Concentration in Groundwater Carbonate Nitrate Sulfate Fluoride IRRIGATION WATER QUALITY Salinity and Alkalinity Hazard Residual Sodium Carbonate Permeability Index 104

12 xii CHAPTER NO. TITLE PAGE NO. 7.5 SEASONAL VARIATIONS OF MAJOR IONS HEAVY METALS IN GROUNDWATER SURFACE WATER QUALITY HYDROCHEMICAL INVERSE MASS BALANCE MODELING GENERAL MODEL CONSIDERATIONS MODEL RESULTS CONCLUSIONS 122 REFERENCES 124 VITAE 138

13 xiii LIST OF TABLES TABLE NO. TITLE PAGE NO. 3.1 Methods used for chemical analysis of groundwater for major ions Various seasons Average, maximum and minimum rainfall during various seasons Regression equation constants and X-variables at the nine rain gauge stations Pumping test results Minimum and maximum values of physical and chemical parameters of groundwater in the study area with statistical parameters Groundwater samples of the study area exceeding the permissible limits prescribed by WHO for drinking purposes and the consequent undesirable effect on human system Nature of groundwater based on TDS values Classification of groundwater based on hardness Quality of irrigation water based on electrical conductivity Alkalinity hazard classes of groundwater Suitability of groundwater for irrigation based on percent sodium 103

14 xiv TABLE NO. TITLE PAGE NO. 7.8 Quality of groundwater based on residual sodium carbonate Minimum and maximum values of heavy metals in groundwater with statistical parameters Minimum and maximum values of physical and chemical parameters of surface water with statistical parameters Minimum and maximum values of heavy metals in surface water with statistical parameters Results of mass balance modeling of chemical processes in the groundwater from selected wells along flow path Correlation matrix for the groundwater samples analyzed during July Correlation matrix for the groundwater samples analyzed during February

15 xv LIST OF FIGURES FIGURE NO. TITLE PAGE NO. 3.1 Flow chart showing detailed methodology Study area showing locations of PWD wells Locations of pumping test sites Study area showing locations of monitoring wells General steps involved in MODFLOW modeling Location map of the study area Elevation contour map Digital Elevation Model (DEM) of Lower Bhavani River Basin Map showing major drainages and man-made canals Drainage map of Lower Bhavani River Basin Geology map of Lower Bhavani River Basin Hydrogeomorphological map of Lower Bhavani River Basin Lineament map of Lower Bhavani River Basin Land use map of Lower Bhavani River Basin Soil map of Lower Bhavani River Basin Locations of rain gauge stations Monthly variations of rainfall pattern Seasonal variations of rainfall pattern (a) Spatial variation of average annual rainfall 45

16 xvi FIGURE NO. TITLE PAGE NO. 5.4(b) Spatial variation of average NE monsoon rainfall (c) Spatial variation of average post-monsoon rainfall (d) Spatial variation of average pre-monsoon rainfall (e) Spatial variation of average SW monsoon rainfall Frequency distribution of rainfall DEM indicating slope variation and surface runoff Hydrographs of wells located in red non-calcareous soil Hydrographs of wells located in red calcareous soil (a) Locations of boreholes in the study area (b) Borehole lithology details Spatial variation of hydraulic conductivity Spatial variation of transmissivity Grid map of groundwater table elevations Groundwater elevation model for July Groundwater table elevation model for February Discretization of the study area Initial groundwater head of the study area during January Comparison of computed and observed groundwater heads under steady state condition 70

17 xvii FIGURE NO. TITLE PAGE NO Computed and observed groundwater heads of December Simulated and observed groundwater heads of well numbers 1 and Computed groundwater head of well number 19 until 2015 under normal present conditions Computed groundwater head of well number 19 until 2015 under drought (once in three years) condition Drinking water quality of July 2006 based on TDS values Drinking water quality of February 2007 based on TDS values Drinking water quality of July 2006 based on hardness values Drinking water quality of February 2007 based on hardness values Spatial variation of sodium during July Spatial variation of sodium during February Spatial variation of potassium during July Spatial variation of potassium during February Spatial variation of calcium during July Spatial variation of calcium during February Spatial variation of magnesium during July

18 xviii FIGURE NO. TITLE PAGE NO Spatial variation of magnesium during February Spatial variation of chloride during July Spatial variation of chloride during February Spatial variation of bicarbonate during July Spatial variation of bicarbonate during February Spatial variation of carbonate during July Spatial variation of carbonate during February Spatial variation of nitrate during July Spatial variation of nitrate during February Spatial variation of sulfate during July Spatial variation of sulfate during February Fluoride concentration in groundwater during July Fluoride concentration in groundwater during February Salinity and alkalinity hazard of irrigation water in US salinity diagram Suitability of groundwater for irrigation in Wilcox Diagram Seasonal variations of major ion concentrations Long-term variations of electrical conductivity Long-term variations of major ions 108

19 xix FIGURE NO. TITLE PAGE NO Locations of surface water samples in the study area Selected flow paths for NETPATH modeling Gibbs diagram Piper Trilinear diagram 119

20 xx LIST OF SYMBOLS AND ABBREVIATIONS AAS - Atomic Absorption Spectrophotometer a.m.s.l - above mean sea level APHA - American Public Health Association AR - Annual Rainfall ASP - American Society of Photogrammetry b.g.l - below ground level C - Celsius CAI - Chloro-Alkaline Indices CGWB - Central Ground Water Board cm - Centimeter CPWD - Central Public Works Department 3D - Three-dimensional DEM - Digital Elevation Model EC - Electrical Conductivity GEC - Groundwater Estimation Committee GIS - Geographic Information System GSI - Geological Survey of India IRS -1D - Indian Remote Sensing Satellite - 1D kg - kilogram km - kilometer km 2 - square kilometer LISS-III - Linear Imaging Self scanning Sensor III S - micro-siemen m - meter meq/l - milli equivalent per liter

21 xxi mg - milligram mg/l - milligram per liter ml - milliliter mm - millimeter MSL - Mean Sea Level % Na - Sodium percentage NE - North-East PI - Permeability Index PM - Post monsoon PrM - Pre monsoon PWD - Public Works Department RSC - Residual Sodium Carbonate SAR - Sodium Absorption Ratio Sec - Second SW - South-West TDS - Total Dissolved Solids TH - Total Hardness USA - United States of America US - United States USGS - United States Geological Survey WHO - World Health Organization