RESEARCH ON POSSIBLE CHANGES IN THE DISTRIBUTION OF SALINE SEEPAGE IN THE NETHERLANDS COPYRIGHT @BY CENTRAL ORGANIZATION FOR APPLIED SCIENTIFIC RESEARCH IN THE NETHERLANDS TNO, 1980 COMMISSIE VOOR HYDROLOGISCH ONDERZOEK TNO COMMITTEE FOR HYDROLOGICAL RESEARCH TNO Verslagen en Mededelingen No. 26 Proceedings and Informations No. 26 RESEARCH ON POSSIBLE CHANGES IN THE DISTRIBUTION OF SALINE SEEPAGE IN THE NETHERLANDS PROCEEDINGS OF TECHNICAL MEETIh'G 36 (March 1979) VERSL. MEDED. COMM. HYDROL. ONDERZ. TNO 26 - THE HAGUE - 1980 CONTENTS 1. Introduction and problem formulation. J.C. VAN DAM .................... 9 Summary................................................ 9 1. Introduction ........................................... 9 2 . Problem formulation ....................................... 9 3 . State of the art .......................................... 11 4 . Programme of the meeting ................................... 13 References .............................................. 14 2 . Saline seepage in the Netherlands. occurrence and magnitude. J .WESSELING ....... 17 Summary ............................................... 17 1. Introduction ........................................... 17 2 . Geohydrological conditions ................................... 21 3 . The seepage problem ....................................... 25 4 . The magnitude of the saline seepage .............................. 30 References .............................................. 32 3 . Physical fundamentals of the flow problem. W.H.C. TEN HOORN .............. 34 Summary ............................................... 34 1. Introduction ........................................... 34 2. Flow through porous media ................................... 34 3. Flow of groundwater with gradually varying density .................... 38 4 . Flow of fresh and salme groundwater. in case of a sharp interface.................. 38 5. Schematization .......................................... 40 6 . Conclusions ............................................ 42 References ............................................. 43 4 . Notes on calculation methods for groundwater flow. P. VAN DER VEER .......... 44 Summary ............................................... 44 1. Introduction ........................................... 44 2 . Analytic calculation methods .................................. 45 2.1. One-dimensional ...................................... 45 2.2. Twodimensional ...................................... 46 S 2.3. Note on the simultaneous flow of several fluids .................... 46 3 . Numerical methods ....................................... 47 3.1. Methods having an analytical character ......................... 47 3.2. Semi-analytical methods .................................. 48 3.3. Discretization methods .................................. 48 References .............................................. 48 5 . Some results obtained with a finite difference method . D . PEREBOOM ............ 50 Summary ............................................... 50 1. Introduction ........................................... 50 2 . Models ............................................... 51 2.1.Modell ........................................... 51 2.2.Model2 ........................................... 52 3 . Equations and boundary values ................................. 52 4 . The implicit finite difference method ............................. 53 5 . Results ............................................... 55 5.1.Modell ........................................... 55 5.2.Model2 ........................................... 60 6 . Conclusions and recommendations ............................... References .............................................. Annex1 .............................................. Annex11 .............................................. Annex111 ............................................. 6 . Some results obtained with an analytical solution in a radial symmetric profie. G.L.MOLENKAMP ......................................... Summary ............................................... 1. Introduction ........................................... 2 . Calculation of the real roots of simultaneous non-linear equations ................. 3. An approxirnative solution method. APSOM. to solve integrals .............. 3.1. Modification of the equations that describe the groundwater flow .......... 3.2. APSOM applied to a mathematical example ...................... 3.3. APSOM applied to groundwater flow .......................... 4 . Conclusions ............................................ References .............................................. Annex1 .............................................. Annex11 .............................................. Annex111 ............................................. AnnexIV ............................................. AnnexV .............................................. 7 . The finite element method in freshlsaline groundwater. J . SCHONEVELD .......... Summary ............................................... 1. Introduction ........................................... 2 . Equations ............................................ 3. Introduction of elements .................................... 4 . A one-dimensiond example ................................... 5 . A two-dimensional example ................................... 6 . Transient stages .......................................... 7 . Conclusions ............................................ References .............................................. 8 . Some results obtained with a boundary element method. R . AWATER ............ Summary ............................................... l . Introduction ........................................... 2 . Analytical function method (AFM) .............................. 3 . Original intention ........................................ 4 . Problem definition ........................................ 5 . Geohydrological schernatization ................................ 6 . Model schematization ...................................... 7 . Results ............................................... 8. Conclusions ............................................ 9. Recommendations ........................................ References .............................................. 9. Results of a geo-electrical survey to the depth of the fresh water .salt water interface in the polder Groot Mijdrecht. J.D. LEENEN .......................... Summary ............................................... 1. Introduction ........................................... 2. Geological situation and its implications ........................... 3 . Results ............................................... 4 . Conclusions and recommendations ............................... References ............................................. 10. Accuracy and verification of groundwater flow models. C.R. MEINARDI and A.N.M.OBDAM ........................................... Summary ............................................... 1. The relation between verification and accuracy of model results .............. 2 . Accuracy of model parameters ................................. 2.1.Geometry .......................................... 2.2. Transmissivity and horizontal permeability ....................... 2.3. Vertical permeability ................................... 2.4 Hydraulic resistance .................................... 3 . Boundary and initial conditions ................................ 3.1. Groundwater heads and surface water levels ...................... 3.2. Salt and density distribution in the underground .................... 4 . Accuracy of results of two models concerning fresh and brackish groundwater ..... 4.1. An analytical model for the position of a sharp interface ............... 4.2. A numerical model neglecting density differences ................... 5 . Conclusions ............................................ References ............................................ 11. Conclusions. J.C. VAN DAM .................................... 12. Recommendations. J.C. VAN DAM ............................... APPENDIX A: Review of literature on fresh and saline groundwater. F.C. VAN GEER .... 1. Introduction .................................... 2. Principles and basic equations .......................... 3 . The occurence of brackish and salme groundwater ............... 4 . Steady flow problems in which diffusion and dispersion are allowed to be neglected ................................... 5 . Non-steady flow problems in which diffusion and dispersion are allowed to be neglected ................................... 6 . Groundwater in which diffusion and dispersion are taken into account ... References ....................................... APPENDIX B: Fresh water .salt water relationships. J.C. VAN DAM .............. List of symbols ..................................... 1. Confined groundwater ............................... 2. Phreatic groundwater ............................... 3 . Semi-confined groundwater ............................ AUTHORS Prof. dr. ir. J.C. VAN DAM Delft University of Technology, Delft Dr. ir. J. WESSELING Institute for Land and Water Management Research, Wageningen 11. W.H.C. TEN HOORN Delft University of Technology, Delft Dr. ir. P. VAN DER VEER Rijkswaterstaat, Data Processing Division, Rijswijk D. PEREBOOM* Delft University of Technology, Delft 11. G.L. MOLENKAMP Delft University of Technology, Delft J. SCHONEVELD* Delft University of Technology, Delft Ir. R.