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DSD-INT 2019 Groundwater Flow Model for parts of the Federal State of Hesse - Prein

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Presentation by Angela Prein, Hessisches Landesamt für Naturschutz, Umwelt und Geologie, at the iMOD - User Day, during Delft Software Days - Edition 2019. Tuesday, 12 November 2019, Delft.

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DSD-INT 2019 Groundwater Flow Model for parts of the Federal State of Hesse - Prein

  1. 1. The Hessian Reed as a strongly structured and heavily used catchment area - How to deal with a complex river system using SFR package in iMOD - Dr. Angela Prein Hessisches Landesamt für Naturschutz Umwelt und Geologie 12. November 2019 iMOD User Day Groundwater Flow Model for parts of the Federal State of Hesse
  2. 2. 2 Hessisches Landesamt für Naturschutz, Umwelt und Geologie Groundwater Flow Model Federal states Germany Hesse Foto: Digitalel/Heibel
  3. 3. 3 Hessisches Landesamt für Naturschutz, Umwelt und Geologie Groundwater Flow Model Hydrogeological areas BedrockaquiferPoreaquifer Karte: Hydrogeologische Großräume, BGR Hannover
  4. 4. 4 3 Upper Rhine Graben with Mainz Basin and Northern Hessian Tertiary Basin The hydrogeological area of the Upper Rhine Graben with the Mainz Basin and North Hessian Tertiary Basin marks the active, Cenozoic loose sediments filled the subsidence zone of the Rhine Valley and the sedimentation areas of tertiary marine distribution. The pore aquifers contain rich groundwater resources. Karte: Hydrogeologische Großräume, BGR Hannover Hesse Hessisches Landesamt für Naturschutz, Umwelt und Geologie Groundwater Flow Model Hydrogeological areas
  5. 5. 5 Hessisches Landesamt für Naturschutz, Umwelt und Geologie Groundwater Flow Model South of Hesse
  6. 6. 6 Model area Hessisches Landesamt für Naturschutz, Umwelt und Geologie - is oriented to the hydrogeological areas - green area: appr. 2.300 km² - yellow area: tributary catchment areas
  7. 7. 7 Water balance Hessisches Landesamt für Naturschutz, Umwelt und Geologie Components of Water balance Influx Groundwater Streams Groundwater recharge Discharges from wastewater treatment plants Groundwater enrichments by infiltration
  8. 8. 8 Water balance Hessisches Landesamt für Naturschutz, Umwelt und Geologie Components of Water balance Outflux Streams Lakes and ponds Groundwater extractions for water supply Extraction for irrigation for agriculture Extraction for industry
  9. 9. 9 Water balance Hessisches Landesamt für Naturschutz, Umwelt und Geologie Outflux to outside the model streams Two selected components of Water balance: Influx from outside the model streams This components are reflecting the interaction between stream and aquifer. In iMOD this data is taken into account via the package SFR - Surface water flow routing package -
  10. 10. 10 River system Hessisches Landesamt für Naturschutz, Umwelt und Geologie Green area: - Rivers and creeks (red) (approximately 20.000 segments) - Small ditches (green) (approximately 8.000 segments)
  11. 11. 11 River system Hessisches Landesamt für Naturschutz, Umwelt und Geologie Purple dashes: available profile data of streams
  12. 12. 12 River system and weirs and gauges Hessisches Landesamt für Naturschutz, Umwelt und Geologie - Weirs at the rivers Main and Nidda - Gauges Various conditions have to be taken into account in the SFR Surface water flow routing package.
  13. 13. 13 River system and wastewater treatment plants There are about 50 wastewater treatment plants and their discharges into the river system. Some streams carry only discharges from wastewater treatmend plants. Discharges are timevariant over the year and over the years. Hessisches Landesamt für Naturschutz, Umwelt und Geologie
  14. 14. 14 River system and lakes There are 45 lakes and ponds, which are partly connected to the streams. 9 oxbow rivers are considered as connected lakes because usually the river is deeper than the oxbow river. Hessisches Landesamt für Naturschutz, Umwelt und Geologie Oxbow river V
  15. 15. 15 System of ditches - small-sized streams - no bottom level are known - often very low gradient - flow direction frequently not known Hessisches Landesamt für Naturschutz, Umwelt und Geologie
  16. 16. 16 1. Some streams have groundwater inflow. For the bottom level the situation has to be doublechecked in very dry years, when the groundwater surface is known. 2. Sometimes pipework replaces the ditches. 3. Some streams carry only discharge from wastewater treatment plants. In this case the flux only shows information about the bed permeability. 4. There is a large system of streams and ditches. The required gradient has to fit to the surface level (digital elevation model). 5. SFR package requires a decreasing gradient of the river bed. Most streams naturally have irregular gradients. 6. Removing segments led to confusion in the allocation of segments to the individual streams. 7. The flow direction has to be defined in the model. In some parts the gradient is very low and the flow direction is various or hard to predict. This leads to inconsistencies and incorrect results in the model. Collection of special features and challenges in the implementation of the river system using SFR in iMOD Hessisches Landesamt für Naturschutz, Umwelt und Geologie
  17. 17. 17 1. Some streams (without profile data) have fluxes generated by groundwater. For these the situation has to be doublechecked for very dry years (e.g. 1976), for which a dry stream bed is known and a guess of bottom level is possible. Stream bottom level Hessisches Landesamt für Naturschutz, Umwelt und Geologie In this case, the bottom level of the stream has to be higher then the lowest measured groundwater level.
  18. 18. 18 2. Sometimes pipework replaces the ditches. Pipework Hessisches Landesamt für Naturschutz, Umwelt und Geologie This requires historical research or research using aerial photographs.
  19. 19. 19 3. Some streams have fluxes coming exclusively from wastewater treatment plants. Timevariant data of about 50 wastewater treatment plants are to be addressed in iMOD. Each timevariant discharge shall be addressed to one specific stream segment. Discharges from wastewater treatment plants Hessisches Landesamt für Naturschutz, Umwelt und Geologie
  20. 20. 20 Gradient of stream bottom Hessisches Landesamt für Naturschutz, Umwelt und Geologie 4. There is a large system of ditches. The required gradient has to fit the surface level (digital elevation model). SFR package offers a gradient value of min. 0,001 m in a segment for missing gradients at the bottom level. If the ground surface is almost flat, there will be a conflict with the needed gradient required by the SFR package.
  21. 21. 21 SFR doesn‘t work with energy level of the water in the river (Bernoulli). Hessisches Landesamt für Naturschutz, Umwelt und Geologie 5. SFR package requires a descreasing gradient of the river bed. Most streams naturally have an irregular gradient. Decreasing gradient of stream bottom v V V
  22. 22. 22 6. Removing segments leads to confusion in the allocation of segments to the individual streams. Example: Segments outside the model area are not nesessary. If segments are removed, ID numbers are reallocated and lose their original ID. Remove stream segments Hessisches Landesamt für Naturschutz, Umwelt und Geologie
  23. 23. 23 7. The flow direction has to be defined in SFR package. The model area has some flat parts. There the flow directions of streams are indifferent. If it is not possible to determine the flow direction by topography or on-site, the direction is forced on the model. Change flow direction Hessisches Landesamt für Naturschutz, Umwelt und Geologie
  24. 24. 24 Issue with the datafile structure regarding ISG-file Hessisches Landesamt für Naturschutz, Umwelt und Geologie ▪ Deleting segments in the ISG-file - Segments have serial numbers in the ISG-file and segments are referenced by these IDs for imports. - Deleting a segment leads to reassignment of IDs. All following segments from the one deleted are altered. ▪ Adding data into ISG-file - There are specific data for a few specific segments like discharges. These data are prepared and edited and have to be imported. - If the initial segment-IDs were changed because of deleting segments, the preprocessed mass import data lose their usability This can lead to an import / adding of data to the wrong segments.
  25. 25. 25 Issue with the datafile structure regarding ISG-file Hessisches Landesamt für Naturschutz, Umwelt und Geologie ▪ Merging ISG-Files − The validity-loss of extern mass data waiting to be added (or later modified) especially is critical if two ISG-files are merged. At least one ISG-file completely looses the original IDs. This is a challenge when working with external tools for editing the data. ❖ Summary: ➢ For a specific segment the associated data in other files are referenced only by the main ISG file by, again, serial numbers. ➢ The changeability of IDs causes an issue for mass data that has to be imported later to the finished ISG-file, inbetween versions, or after merging of different ISGs. ➢ Right now it is imposible to edit relevant data with mass operations quickly and consistently.
  26. 26. 26 Hessisches Landesamt für Naturschutz, Umwelt und Geologie Each application of the SFR package in iMOD points out possibilities and also brings new questions and consequently also answers for the developers and improvements for the user.
  27. 27. 27 Thank you for your attention to the report about “disentangling” of the river system Hessisches Landesamt für Naturschutz, Umwelt und Geologie

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