Master Thesis Jeppe Eriksen [MNF680] A Field and Model Study of the Eects of Closing Haraldsborg Waterworks (Roskilde) on a Rising Water Table and Near-Surface Groundwater. Supervisors: Jens Christian Refsgaard, Torben O. Sonnenborg & Peter Engesgaard Date: 2/12/2019 Abstract The purpose of this thesis is to investigate the consequences, on the near-surface groundwater, of closing Haraldsborg waterworks in Roskilde, which is a concern for residents adjacent to it. An approximately 1200 x 1200 m hydrological model, setup with the MIKESHE code, is used as a tool to isolate the eect of abstrac- tion change from noise caused by precipitation. The model includes a geological interpretation, land use, Richard's equation and a sewer system build in MIKE11. The model is calibrated using AUTOCAL and validated on head observations in the near-surface groundwater, measured by houseowners in the area. Various sce- narios are set up to examine the consequence of closing Haraldsborg waterworks and the results are according to the model minor, between 0 to 0.1 m on the near- surface groundwater. The model is also used to simulate impact of future climate; increased precipitation and evaporation and a higher sea-level, for the years 2050 and 2100 following a worst-case scenario. The change in maximum groundwater level adjacent to Haraldsborg is by 2050 between 0 to 0.4 m and by 2100 from 0.1 to over 0.6 m. The change in mean groundwater level was by the year 2100 seen to increase less than 0.3 m and by 2050 the mean level unexpectedly fell. The results are discussed emphasizing uncertainty and model improvement, and known errors are presented. Furthermore, this study includes eld work; two wells established, one ERT prole, gamma ray logging and installation of divers. Contents 1 Introduction & Study Area 1 2 Theory 5 2.1 Gamma Ray Wireline Logging . .5 2.2 Electrical Resistivity Tomography . .5 2.3 Urban Hydrology . .5 2.4 Climate Change and Urban Flooding . .9 2.5 Hydrological Modelling . .9 3 Data Description 14 3.1 Observations . 14 3.2 Topography . 14 3.3 Climate . 14 3.4 Paved Areas . 17 3.5 Richards Equation Soil Types . 18 3.6 Drainage/Sewer System . 19 3.7 Limestone Hydraulic Head Maps . 20 4 Methods 25 4.1 Gamma Ray Logging . 25 4.2 Electrical Resistivity Tomography . 25 4.3 Geological Model . 27 4.4 Hydrological Model Setup . 27 4.5 Sensitivity Analysis, Calibration and Validation . 30 4.5.1 Sensitivity Analysis . 30 4.5.2 Inverse Calibration . 30 4.5.3 Manual Calibration . 36 4.5.4 Validation . 39 5 Results 41 5.1 Established Wells . 41 5.2 Gamma Ray Logging . 41 5.3 Electrical Resistivity Tomography . 41 5.4 Geological Model . 42 5.5 Timeseries From Divers . 47 5.6 Adding Complexity to The Model . 48 5.7 Closing Haraldsborg Waterworks Scenarios . 53 5.8 Climate Scenarios . 59 5.9 Eect of Urbanization . 62 6 Discussion 68 6.1 Fieldwork . 68 6.2 Adding Complexity to The Reference Model . 68 6.3 Closing Haraldsborg Waterworks . 69 6.3.1 Drainage . 70 6.4 Climate . 71 6.5 Uncertainty, Model Improvements and Errors . 71 6.5.1 Model improvements . 73 6.5.2 Known Errors . 74 7 Conclussion 76 References 76 8 Appendix 81 8.1 Fieldwork . 81 8.2 Calibration . 84 8.3 Timeseries from Divers . 90 8.4 Climate . 93 8.5 Eect of urbanization . 96 8.6 Discussion . 100 8.7 Timeseries from the Calibration and the Validation period . 101 List of Figures 1 Study Area . .3 2 Theoretically ERT Setup . .6 3 Eect of Urbanization on Hydrological Circle . .8 4 Components of a Fully Distributed Model . 10 5 Overland Flow Between Two Cells . 11 6 Overview of Data Location . 15 7 Topographical Map . 16 8 Precipitation . 17 9 Evapotranspiration . 17 10 Landuse Map . 18 11 UZ soil types . 19 12 Drainage System . 21 13 MIKE11 River/Drainage System . 22 14 Map of Simulated Potential Head in the Limestone . 23 15 Simulated Cone of Depression . 24 16 Electrical Resistance Tomography . 26 17 Drain Codes . 29 18 Parameter Values for the Unsaturated Zone . 29 19 Scaled Sensitivity . 31 20 Population Simplex Evolution . 34 21 Calibration Result . 35 22 Manual Calibration of n . 37 23 Manual Calibration of SZ K . 38 24 Manual Calibration Saturated Zone K Value . 39 25 Manual Calibration of Anisotropy Factor . 40 26 ERT Map . 42 27 Transect Location . 44 28 Eastwest Transect of geological interpretation . 45 29 Northsouth transect of geological interpretation . 46 30 Limestone Timeseries . 49 31 Timeseries 6 m . 50 32 Timeseries 2 m and 5 m . 51 33 Water Budget In . 52 34 Water Budget Out . 53 35 Phreatic Surface Change in Max Level . 54 36 Scenario 1 and 2, 30 and 12 m Below Surface . 56 37 Scenario 1 and 2, 6 m and 3 m Below Surface . 57 38 Timeseries of Hydraulic head in Various Depths . 58 39 Eect of an Increased Specic Storage . 60 40 Change in Mean Level of Phreatic Surface in 2100 . 63 41 Change in Max Level of Phreatic Surface in 2100 . 64 42 Change in Max Level of Phreatic Surface in 2050 . 65 43 Map Showing the Eect of The Drainage System . 66 44 Map Showing The Eect of Landuse . 67 45 Eect of Paved Areas . 75 46 Gamma Ray Log . 81 47 ERT Two Iterations . 82 48 ERT Three Iterations . 83 49 Comparison Valhalvej 41 . 84 50 Comparison Valhalvej 61 . 85 51 Comparison Haraldsborgvej 29 . 86 52 Comparison Baldersvej 10 . 87 53 Comparison Ægirsvej 7 . 88 54 Ten Best Parameter Sets . 89 55 Diver Timeseries in 12 m Below Surface on Valhalvej 55 . 90 56 Diver Timeseries 2 m Below Surface on Baldersvej . 91 57 Diver Timeseries 5 m Below Surface on Baldersvej . 91 58 Barometer Eect . 92 59 Mean Groundwater Level Change in 2100 -zoom . 93 60 Max Groundwater Level Change in 2100 -zoom . 94 61 Change in Mean Groundwater Level by 2050 . 95 62 Eect of basement upstream, 1.5 m.b.s . 96 63 Eect of basement upstream, 4.2 m.b.s . 97 64 Eect of basement downstream, 1.5 m.b.s . 98 65 Eect of basement downstream, 4.2 m.b.s . 99 66 Map of Central Heating Pipes . 100 67 Baldersvej 13 (2-3) . ..