CONJUNCTIVE USE OF SURFACE AND GROUNDWATER TO IMPROVE FOOD PRODUCTIVITY IN A RESTRICTED AREA Degree of Doctor of Philosophy By Saravanamuttu. Subramaniam. Sivakumar. University of Moratuwa Sri Lanka May 2008   CONJUNCTIVE USE OF SURFACE AND GROUNDWATER TO IMPROVE FOOD PRODUCTIVITY IN A RESTRICTED AREA Thesis submitted for the award of the Degree of Doctor of Philosophy Submitted by Saravanamuttu. Subramaniam. Sivakumar. BSc. (Eng) University of Peradeniya Sri Lanka. MSc. (Water Resource Development) University of Roorkee, India Irrigation Department, Mullaitivu, Sri Lanka Supervised by Professor D.C.H.Senarath May 2008 Department of Civil Engineering Faculty of Engineering University of Moratuwa Sri Lanka i Abstract This thesis presents alternate policy decisions based on technical strategies to operate minor and medium irrigation schemes with integrated conjunctive use of surface and groundwater to improve groundwater systems in a restricted area for the economic pumping for agricultural and domestic water use, by optimizing the use of groundwater and surface water. A groundwater simulation model was formulated using integrated finite difference method to carryout this research. Unlike finite difference method the integrated finite difference method can be formulated to any shape of catchment by connecting perpendicular bisectors of the observation points through out the catchment. An electronic spread sheet model was developed for groundwater system in integrated finite difference method and was applied to a selected restricted catchment area of about 185.23 km2 in Vavuniya, for testing its validity after calibration. Forty one domestic dug wells were identified as observation wells among the available domestic/agro wells within the study area of 185.23 km2, to represent the aquifer. This study area was divided into forty one Thiessen polygons by connecting the perpendicular bisectors of adjoining observation wells. A groundwater simulation model was formulated for this polygonal net work using integrated finite difference method in spreadsheet. The model was calibrated for the period 1997 to 2001 having eight seasons. The recharging period of eight months was taken as from 1st October to 31st May of the following year and discharging period of four months was taken as from 1st June to 30th September. By this calibration the hydro geological stress parameters such as Transmissibility, Storage coefficient, Recharge coefficients for irrigation tank, irrigation field, rainfall and the Withdrawal factor for agro and domestic pumping were found using an optimization technique. A complete water balance study for each polygon for each season was carried out. Forty one error models have been prepared for the water balance, for each polygon for all the seasons. To avoid the negative and positive errors getting cancelled, the squares of all seasonal errors were added and minimized with suitable constraint. Practicable ranges for Transmissibility, Storage coefficient, Recharge coefficients and Withdrawal factor were given during minimization as constraint. MATCAD2000 was used for this optimization. This model in spreadsheet, calibrated by error optimization technique, validated and recalibrated was used to predict the system behavior for various operational policies of the selected restricted groundwater catchment. Water levels were predicted for changes in operational policy of minor and medium irrigation schemes by forgoing certain percentage of cultivation, boundary treatment to reduce the transmissibility in steps, and combination of both. The economic feasibility was analyzed by taking the energy saved in pumping of raised groundwater as a benefit and boundary treatment cost and income loss due to change in operational policy of minor and medium irrigation schemes by forgoing certain percentage of cultivation as cost. The present worth of benefit and cost for various interest rate and project life period were calculated and compared. Change in operational policy of minor and medium irrigation schemes by forgoing one third of the cultivation under them or keeping one fourth of the storage of minor and medium irrigation schemes at any time together with 40% - 50% reduction in boundary permeability will recover an average of 60% to 70% of the loss of water table in any consecutive season in almost 95% of the area under consideration. ii Acknowledgement I would like to thank a great many people who have helped me for the successful completion of this thesis. My supervisor Prof.D.C.H.Senarath for the kind support and guidance over the years, even after retirement from active service. I thank him from the bottom of my heart for his encouragement, qualified discussions, and positive attitude towards my work and making me think twice before commencing anything. I wish to thank the Head of the Department of Civil Engineering and the Director of Post Graduate Studies and the research Co-ordinator Prof S.A.S.Kulathilaka for their great commitment to provide necessary facilities and coordinate the research activities. The Director General, Irrigation Department Colombo, Director, Irrigation Department North East Province Trincomalee and Director, Irrigation Department Northern Province Trincomalee kindly gave me permission to use departmental facilities for this research work. I thank all of them and their staff for giving direct and indirect encouragement and moral support in this research work and for providing the necessary facilities. Even though this research effort is a self financed one, University of Moratuwa waived 80% of its tuition fees and the Irrigation Department Colombo, the Irrigation Department North East Province and the Irrigation Department, Northern Province paid for the balance cost. My sincere gratitude to the University of Moratuwa for the waiver of 80% payment of the tuition fee. I express my gratitude to the staff of the Irrigation Department Colombo, the Irrigation Department NEPC Trincomalee and the Irrigation Department NPC Trincomalee for their cooperation in data collection and other activities relevant to this research. I shall not forget Eng.G.T.Dharmasena who was the Director of Specialised service and later the Director General of Irrigation for his keen involvement in encouraging my first research publication in the seminar on IRRIGATION for the centenary programme of the Irrigation Department held on 15th and 16th of February 2001 at BMICH, Colombo, which lead to my enrolment at the University of Moratuwa as a PhD candidate. I thank him very much for his whole hearted encouragement. I have to specially thank Irrigation Department Colombo for the financial support through Irrigation Research Management Unit (IRMU) for the pumping test in one of the observation well. My sincere thanks to Eng V Regunathan former, Secretary Ministry of Irrigation Housing and Construction NEPC Trincomalee, Director Irrigation (Plan Implementation) Colombo, Secretary Ministry of Rehabilitation and Hindu Culture Colombo and presently the Project Director of PEACE project, for his earnest encouragements in perusing this research work and for correcting the virgin script of this thesis. Finally I would like to thank all the staff in the offices of the Regional Director of Irrigation Vavuniya, Deputy Director of Irrigation Mullaitivu and Deputy Project Director NEIAP Mullaitivu for giving their fullest support in data collection, documentation and much other direct and indirect support in connection with the research throughout the period from 2001 to 2007. I also like to thank any others whom I may not have mentioned specifically by their names, who have helped me in many other ways to complete this research work. iii Dedication To my 86 year old dear mother Mrs.Rasamani Subramaniam of Point Pedro for her dedicated determination to turn her third son also to complete his PhD by exerting continuous encouragement and moral support to complete this research. and also To my wife Logeswari Sivakumar, daughter Jananie Sivakumar and son Sivakumar Janen for their utmost support in completing this research project. iv Declaration I hereby declare that the research reported here, is an authentic record of my own work carried out during the period from October 2001 to May 2008, for the PhD degree under the guidance of Prof.D.C.H.Senarath, Senior Professor, Department of Civil Engineering, Faculty of Engineering, University of Moratuwa, Sri Lanka. The matters embodied in this research thesis have not been submitted for award of any other degree to any other institution. Date: Eng.S.S.Sivakumar Irrigation Department Mullaitivu Sri Lanka Certification I certify that, this thesis is the bonafide work of Eng.S.S.Sivakumar, who carried out this research under my supervision. I certify further that to the best of my knowledge, the work reported herein does not form part of any other thesis on the basis of which a degree or award was conferred on an earlier occasion on this or to any other candidates. Date: Professor D.C.H.Senareth Research supervisor v Table of Content Abstract…….…………………………………………………………………………………………………i Acknowledgement.............................................................................................................................ii Dedication…………………….............................................................................................................iii Declaration……………………………………………………………………………….............................iv Table of content.................................................................................................................................v List of Tables.....................................................................................................................................x List of Figures…………………………………………………………………………..............................xii Abbreviations ……………….............................................................................................................xiii List of Annexure...............................................................................................................................xiii Chapter 1 – Introduction……………….…..……………………………………………………………...1 1.1 Problem Statement ....................................................................................................... 2 1.1.1 Water scarcity ............................................................................................... 2 1.1.2 Water resources ............................................................................................ 2 1.1.3 Equilibrium of groundwater ............................................................................ 3 1.1.4 Groundwater flow problems .......................................................................... 4 1.2 Thesis Statement .......................................................................................................... 4 1.2.1 Objective of the research .............................................................................. 4 1.2.2 Research methodology ................................................................................. 5 1.3 Thesis Structure ............................................................................................................ 6 Chapter 2 – Literature Review on Relevant Aspects of Groundwater and Modelling .............. 8 2.1 Hydrology ...................................................................................................................... 8 2.1.1 Types of soil water and distribution ............................................................... 8 2.1.1.1 Hygroscopic water ......................................................................... 8 2.1.1.2 Capillary water ............................................................................... 8 2.1.1.3 Gravitational water ......................................................................... 8 2.1.2 Soil moisture budgeting ................................................................................. 8 2.1.3 Groundwater movement ................................................................................ 9 2.1.4 Darcy’s law .................................................................................................... 9 2.1.5 Groundwater flow equation ........................................................................... 9 2.2 Groundwater Modelling ................................................................................................. 10 2.2.1 Objectives of groundwater modelling ............................................................ 11 vi 2.2.2 Data required for developing a groundwater model ....................................... 11 2.2.2.1 Topography ................................................................................... 12 2.2.2.2 Geology ......................................................................................... 12 2.2.2.3 Type of aquifers ............................................................................. 12 2.2.2.4 Unconfined aquifer ........................................................................ 12 2.2.2.5 Confined aquifer ............................................................................ 13 2.2.2.6 Aquifer thickness and lateral extent ............................................... 13 2.2.2.7 Aquifer boundaries ........................................................................ 13 2.2.2.8 Aquifer characteristics ................................................................... 15 2.2.3 Type and extent of recharge areas ................................................................ 15 2.2.3.1 Rate of recharge ............................................................................ 16 2.2.3.2 Main recharge sources .................................................................. 16 2.2.3.3 Methods for recharge estimation ................................................... 16 2.2.3.4 Direct recharge .............................................................................. 17 2.2.3.5 Estimating direct recharge ............................................................. 17 2.2.3.6 Evapotranspiration ......................................................................... 18 2.2.3.7 Indirect recharge............................................................................ 18 2.2.3.8 Recharge from irrigation canals. .................................................... 18 2.2.3.9 Recharge from irrigated fields ........................................................ 19 2.2.3.10 Recharge from irrigation storages ................................................ 19 2.2.3.11 Rate of discharge ........................................................................ 19 2.3 Model Calibration .......................................................................................................... 19 2.4 Model Validation ........................................................................................................... 20 2.5 Model Prediction ........................................................................................................... 20 2.5.1 Introduction of prediction ............................................................................... 20 2.5.2 Data requirement…………………………………………….………………….….21 2.6 Conjunctive use and management of surface water and groundwater ......................... 21 2.6.1 Advantages of conjunctive use of surface and groundwater ......................... 23 2.6.2 Disadvantages of conjunctive use of surface and groundwater…………...… 24 Chapter 3 – Mathematical Model .................................................................................................. 25 3.1 Systems and Modelling Concepts ................................................................................. 25 3.1.1 Numerical models ......................................................................................... 26 3.1.2 Finite difference method (FDM) ..................................................................... 26 vii 3.1.3 Integrated finite difference method (IFDM) .................................................... 26 3.1.4 Polygonal network. ........................................................................................ 26 3.2 Models for Management and Conjunctive Use .............................................................. 28 3.2.1 Optimisation models ...................................................................................... 29 3.2.1.1 Linear programming ...................................................................... 29 3.2.1.2 Dynamic programming .................................................................. 29 3.2.1.3 Non linear programming ................................................................ 30 3.3 Aquifer Simulation Model and Inverse Modelling Technique ......................................... 30 3.3.1 Determination of aquifer parameters. ............................................................ 30 3.3.2 Regional aquifer parameters ......................................................................... 30 3.3.3 Optimal set of aquifer parameters ................................................................ 31 Chapter 4 – Model Formulation .................................................................................................... 32 4.1 Description of the model and assumption........................................................................32 4.1. 1 Hydraulic assumptions.......................................................................32 4.1.2 Operational assumptions....................................................................32 4.1.3 Economic assumptions.......................................................................33 4.2 Study area .................................................................................................................... 33 4.2.1 Location and size .......................................................................................... 34 4.2.2 Climate .......................................................................................................... 39 4.2.3 Soil and groundwater .................................................................................... 40 4.2.4 Agriculture…………………………………………………………………..………41 4.3 Nodal Network and Polygon Geometry...........................................................................41 4.3.1 Selection of time step.....................................................................................48 4.3.2 Tolerance level................................................................................................48 4.3.3 Nodal coordinate.............................................................................................48 4.3.4 Water level data ............................................................................................ 48 4.3.5 Hydraulic stress parameters of aquifer............................................................48 4.3.5.1 Specific yield and storage coefficient ............................................. 48 4.3.5.2 Transmissibility ............................................................................. 50 4.3.5.3 Field pumping test to find T, S by WRB…..…………………............50 4.3.6 Recharge coefficients……………………………………………………..……….50 4.3.6.1 Rainfall recharge values ................................................................ 51 4.3.6.2 Recharge from canal seepage ....................................................... 51 viii 4.3.6.3 Recharge from irrigation fields ...................................................... 51 4.3.6.4 Recharge from irrigation schemes ................................................. 51 4.3.7 Data collection……………..………………………………………………..….…..53 4.3.8 Withdrawal from groundwater reservoir...........................................................54 4.4 Calibration ..................................................................................................................... 54 4.4.1 General ......................................................................................................... 54 4.4.2 Source of errors ........................................................................................... 54 4.4.3 Calibration procedure .................................................................................... 55 4.4.3.1 Model calibration using optimizer GINO or MATCAD 2000….…....55 Chapter 5– Model Formulation in Spreadsheet /MATCAD for Calibration and Prediction…....63 5.1 Spreadsheet Model Formulation for Calibration 5.1.1 Data entry in spreadsheet………………………………………………………...63 5.1.1.1 Selection of season…………………………………..………….….....63 5.1.1.2 Nodal connectivity matrix………………………….………….……….63 5.1.1.3 Seasonal water level matrix………………………………....….…….63 5.1.1.4 Conductance factor (J/L) matrix……………………………..…...…..63 5.1.2 Model Calculation in Spreadsheet………………………………………………………63 5.1.2.1 Intermediate calculations……………………………………….…….....64 5.1.2.1.1 Water level matrix for the season………………………...64 5.1.2.1.2 Head difference matrix for the season ...........................64 5.1.2.2 Final calculation…………………………………………………….…..64 5.1.2.2.1 Matrix of lateral flow divided by T....................................64 5.1.2.2.2 Change in storage divided by specific yield....................64 5.2 Error Optimization Model Formulation for Calibration in “GINO” / “MATCAD 2000”…..65 5.2.1 Optimization (minimization) by “GINO”…………………….…………………....65 5.2.2 Optimization (minimization) by “MATCAD 2000”…..…………………..……...65 5.3 Predictions Model in Spreadsheet..................................................................................69 5.4 Model Validation………………………………………………………..….……………….….69 5.5 Model Recalibration………………………………………………………............................70 5.6 Model revalidation……………………………………………………..….……………….…..70 Chapter 6– Model Predictions for Various Operational Policy and Economic Analysis.……..75 6.1 Behavior of Aquifer with Various Operational Policies of Irrigation Schemes………..…75 ix 6.2 Behavior of Aquifer with Decrease in Transmissibility……..….…………………………...78 6.2.1 Effect on outer boundary nodes……………………..……………………....……81 6.2.2 Effect on nodes within treated boundary……………..…………………..……...81 6.3 Behavior of Aquifer with Various Operational Policies of Irrigation Schemes with Boundary Treatment…………………………….…..……….………………………………..81 6.4 Economic Analysis of Research Finding…………………..…..……………………….…...82 6.4.1 Economic performance Indices……………………….…………………….……82 6.4.1.1 The present worth method………………………………..…………..82 6.4.1.2 The rate of return method………………….…………….…………...83 6.4.1.3 The benefit cost ratio method …………………………..……………83 6.4.1.4 The annual cost method…………………………………….………...83 6.4.2 Benefits and costs……………………………..…………..….…………….…….83 6.4.3 Impact of economic analysis on outcome of this research……………………85 6.4.3.1 Economic analysis for the change in operational policy of minor / medium irrigation schemes…………. …..………………. ...86 6.4.3.2 Economic analysis for boundary treatment ……………..….……….88 6.4.3.3 Economic analysis for the change in operational policy of minor / medium irrigation schemes and boundary treatment………………90 Chapter 7– Discussion Generalization Conclusions Limitation and Recommendations for Future Study.........................................................................................….…………......91 7.1 Discussion………………………………………………………………………………………91 7.1.1 Summary of operational research…………………………………..……….......91 7.1.2 Summary of economic analysis of the operation research.….…...................93 7.2 Summary of Research Finding and Implementation ……..…….…………………..........93 7.3 Generalization…………………………………………………………………………………94 7.4 Conclusion …………………………………………….………………….………..…..……..94 7.5 Limitations of the Research Findings…………………………………………….…………95 7.6 Area of Future Study…….……………………………………………………….…...….......96 Reference ……….……………………………………………………………………………….………....97 Bibliography....................................................................................................................................101 Annexure…………………………………………………………………………….……..……………….104 x List of Tables Table 4.1 Monthly water levels - 2004 Table 4.2 Monthly water levels - 2005 Table 4.3 GN Division within study area and their number Table 4.4 Name of minor and medium irrigation schemes within the study area Table 4.5 Addresses of all the observation wells Table 4.6 Average seasonal rain fall Table 4.7 Observed seasonal water levels from May1998 to Sept. 2004 for all the observation wells Table 4.8 Polygonal parameters of all the 41 polygons of the study area Table 4.9 Coordinates of all the observation wells Table 4.10 GN Division falling within the polygons Table 4.11 Seasonal water levels in m MSL Table 4.12 Parameters of irrigation schemes within polygons Table 4.13 Seasonal data of OFC cultivation in Medium Irrigation Scheme Table 4.14 GN Division wise population, cultivation, NWS&DB withdrawal Table 4.15 Seasonal capacity of water stored in irrigation schemes Table 4.16 Seasonal quantum of water issued for cultivation from Irrigation Schemes Table 4.17 Seasonal pumping from domestic wells Table 4.18 Seasonal pumping from agro wells Table 4.19 Seasonal rainfall volume Table 5.1 Calibrated optimized polygonal parameters - S, a, b, c, d, q Table 5.2 Calibrated optimized polygonal parameters- Transmissibility Table 5.3 Comparison of predicted water levels Table 5.4 Recalibrated optimized polygonal parameters - S, a, b, c, d, q Table 5.5 Recalibrated optimized polygonal parameters- Transmissibility Table 6.1 Trial operational policy of minor and medium irrigation schemes Table 6.2 Predicted water levels for various operational policy of minor and medium irrigation schemes season 9 Table 6.3 Predicted water levels for various operational policy of minor and medium irrigation schemes season 10 Table 6.4 Boundary treatment steps of Transmissibility Table 6.5 Predicted water levels for boundary treatment season 10 xi Table 6.6 Average increase in water level for each step of reduction in permeability during boundary treatment Table 6.7 Average increases in water level for each step of operational policy of minor and medium irrigation schemes Table 6.8 Summary of maximum water level change in ft. for various options Table 6.9 Total water availability and utilization within study area Table 6.10 Present worth of cost incurred for boundary treatment Table 6.11 Electricity saving for pumping season 10 Table 6.12 Present worth of return by saving energy cost Season 10 Table 6.13 Benefit cost ratio for the boundary treatment for season 10 Table 6.14 Electricity saving from pumping for various operational policy of minor and medium irrigation schemes Season 9 Table 6.15 Benefit cost ratio for various operational policy of minor and medium irrigation schemes Season 9 Table6.16 Electricity saving from pumping for various operational policy of minor and medium irrigation schemes Season 10 Table 6.17 Benefit cost ratio for various operational policy of minor and medium irrigation schemes Season 10 Table 6.18 Summary of benefit/cost ratio greater than unity option and steps xii List of Figures Figure 1.1 Schematic diagram of hydraulic equilibrium Figure 1.2 Study area map from one inch to one mile topo sheet Figure 2.1 Schematic diagrams of soil moisture types Figure 2.2 Conceptual diagram of soil moisture budgeting Figure 2.3 Four types of aquifer boundaries Figure 3.1 Schematic representation of conceptual modelling technique Figure 3.2 Typical polygonal nodes Figure 4.1 Study area with observation well numbers Figure 4.2 Monthly groundwater level fluctuation in observation well 4 - 10 Figure 4.3 Monthly groundwater level fluctuation in observation well 30, 35, 41 Figure 4.4 Average seasonal rain fall Figure 4.5 Maximum groundwater levels at the end of recharge period Figure 4.6 Nodal net work of the study area Figure 4.7 Seepage losses and recharge factors of an aquifer system Figure 5.1 Validation of groundwater levels May 2005 Figure 5.2 Validation of groundwater levels September 2005 Figure 6.1 Map showing the peripheral treatment area boundary xiii Abbreviations ac Acres ac.ft Acre-Foot APC Agrarian Production Centre ASC Agrarian Service Centre CEB Ceylon Electricity Board DAC DOA District Agriculture Committee Department of Agriculture DP Dynamic Programming DS Divisional Secretary ET Evopotranspiration FDM Finite Difference Method FSL Full Supply Level GDP Gross Domestic Product GN Grama Nilathari GNP Gross National Product IFDM Integrated Finite Difference Method k Permeability K Hydraulic Conductivity MSL Mean Sea Level NGO NEPC Non Governmental Organization North East Provincial Council NWSDB National Water Supply and Drainage Board OFC Other Food Crop RE Recharge RF Rain Fall S Storage Coefficient/ Storability of the Aquifer SLAAS Sri Lanka Association for Advancement of Science SMD Soil Moisture Deficit sq.mls Square Miles Ss Specific Storage Coefficient T Transmissibility WRB Water Resources Board List of Annexure Annexure 1 Calculation of net return from cultivation 2007 Annexure 2 Pro rata calculation for savings of power Annexure 3 Pro rata calculation for clay cut off Annexure 4 Electricity tariff 2007 of CEB