कᴂद्रीय भूमि जल बो셍ड जल संसाधन, नदी विकास और गंगा संरक्षण विभाग, जल शक्ति मंत्रालय भारत सरकार Central Ground Water Board Department of Water Resources, River Development and Ganga Rejuvenation, Ministry of Jal Shakti Government of India AQUIFER MAPPING AND MANAGEMENT OF GROUND WATER RESOURCES THIRUVANANTHAPURAM DISTRICT, KERALA केरल क्षेत्र, वत셁िनंतपुरम Kerala Region, Thiruvananthapuram भारत सरकार GOVERNMENT OF INDIA जल संसाधन, नदी विकास और गंगा संरक्षण मंत्रालय MINISTRY OF WATER RESOURCES, RIVER DEVELOPMENT & GANGA REJUVENATION के न्द्रीय भूममजल बो셍ड CENTRAL GROUND WATER BOARD AQUIFER MAPPING AND MANAGEMENT PLAN OF THE HARD ROCK AREA OF THIRUVANANTHAPURAM DISTRICT, KERALA (AAP 2017-18) KERALA REGION Thiruvananthapuram January 2019 3 Preface The National Project on Aquifer Management (NAQUIM) is an initiative of the Ministry of Water Resources, Government of India, for mapping and managing the entire aquifer systems in the country. The aquifer systems in Kerala are being mapped as part of this Programme and this report pertains to aquifer mapping of the hard rock terrains of Thiruvananthapuram district. The target scale of investigation is 1:50,000 and envisages detailed study of the aquifer systems up to 200 m depth, to ascertain their resource, water quality, sustainability, and finally evolve an aquifer management plan. The report titled Aquifer Mapping and Management Plan of Hard Rock Area of Thiruvananthapuram district, Kerala gives a complete and detailed scientific account of the various aspects of the hard rock aquifers in the area including its vertical and horizontal dimensions, flow directions, quantum and quality of the resources, of both - the shallow and deeper zones of the hard rock aquifers. Voluminous data were generated consequent to hydrogeological studies, ground water regime monitoring studies, exploratory drilling, geophysical studies etc carried out in the district, and incorporated in the report. The information is further supplemented by various data collected from State departments. It portrays the various ground water issues pertaining to the area along with recommendation for suitable interventions and remedial measures. Thus, it provides a total and holistic solution to the water security problems in Thiruvananthapuram district. This document has been prepared under the guidance of Dr. N. Vinayachandran, Scientist D & Nodal Officer, and Smt. Mini Chandran, Scientist D &Team leader. The painstaking efforts of field hydrogeologist Smt. Anisha K, Scientist B in carrying out the aquifer mapping are well appreciated. Dr. K.R. Sooryanarayana, Suptdg. Hydrogeologist and Dr. V.S. Joji, Scientist D deserves appreciation for their meticulous scrutiny of this report before printing. I am also thankful to the Chairman, Members and officers of CGWB, Faridabad for their valuable guidance in finalizing this document. Thanks, are also due to various organizations of Government of Kerala and Government of India for providing data required for the compilation of this document. I hope this compilation will be of help to the planners, administrators and stakeholders in the water sector in Kerala and will serve as a useful guide for the optimal and sustainable management of ground water resources in Thiruvananthapuram district. Thiruvananthapuram, January 2019. (V. Kunhambu) Regional Director Table of Contents 1.Introduction ...................................................................................................................................... 1 1. 1 Approach and Methodology ........................................................................................................ 1 1.2 About the Area ............................................................................................................................. 1 1.3 Climate ......................................................................................................................................... 2 1.4 Soil ................................................................................................................................................ 3 1.5 Geomorphology ............................................................................................................................ 3 1.6 Agriculture & Land use ................................................................................................................ 3 1.7 Drainage and Drainage Characteristics ....................................................................................... 7 1. 8 Geology of the Area ................................................................................................................... 12 1.9 Previous Work............................................................................................................................ 13 2 DATA COLLECTION, GENERATION AND INTERPRETATION ...................................................... 15 2.1 Data collection and Data Gap Analysis ....................................................................................... 15 2.2 Data Generation and Integration ............................................................................................... 21 3. AQUIFER MAPPING ........................................................................................................................ 30 3.1Weathered zone with associated shallow fractures ................................................................... 30 3.2 The fracture aquifer system ....................................................................................................... 51 3.3. Ground Water Resource Estimation ......................................................................................... 67 3.4 Ground Water related problems ................................................................................................ 70 3.5 Aquifer map ................................................................................................................................ 71 4. Ground Water Management ......................................................................................................... 74 5. Thiruvananthapuram Urban Area .............................................................................................. 80 List of Figures Fig.1.1: Location map of the study area ................................................................................................. 2 Fig.1.2: Soil Map ..................................................................................................................................... 4 Fig.1.3: Geomorphology Map ................................................................................................................. 5 Fig.1.4: Drainage pattern in the study area ........................................................................................... 9 Fig.1.5: Geology of the area .................................................................................................................. 14 Fig.2.1: Graph showing Annual Average rainfall ................................................................................. 18 Fig.2.2: Isohyetal Map of rainfall in the area .................................................................................. Fig.2.3: Graphical Representation of Mean Monthly Rainfall .............................................................. 19 Fig.2.4: Normal Monthly rainfall of IMD stations in the study area .................................................... 20 Fig.2.5: Location of Exploratory wells ................................................................................................. 22 Fig.2.6: Location of VES........................................................................................................................ 23 Fig.2.7: Location of Water Quality monitoring stations ...................................................................... 24 Fig.3.1: Spatial variation of weathered zone thickness in the area ..................................................... 31 Fig.3.2:Pre-monsoon Water level map of Phreatic aquifer ................................................................. 37 Fig.3.3: Post Monsoon Water level map of Phreatic aquifer ............................................................... 38 Fig.3.4: Water level Fluctuation map of Phreatic aquifer .................................................................... 39 Fig.3.5 Water table elevation contour map of Phreatic aquifer. ......................................................... 40 Fig.3.6 Pre- Monsoon Saturated thickness of Phreatic aquifer ........................................................... 41 Fig.3.7: Post- Monsoon Saturated thickness of Phreatic aquifer......................................................... 42 Fig.3.8: Hydrographs of some wells .................................................................................................... 46 Fig.3.9: Piper Diagram of phreatic Aquifer .......................................................................................... 48 Fig.3.10: Gibbs Diagram of phreatic aquifer ........................................................................................ 49 Fig.3.11: Lineament map of the area ................................................................................................... 52 Fig.3.12: Cross section along AA’, B-B’ and C-C’ .................................................................................. 53 Fig.3.13: Panel Diagram ......................................................................................................................