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Modelling as a tool for groundwater protection

INVESTING IN YOUR FUTURE. Modelling as a tool for groundwater protection. Tomas Saks, Aija Dēliņa, Konrāds Popovs, Jānis Jātnieks, Andis Kalvāns. Outline. MOSYS modelling system (PUMA project) Buried valleys of Latvia and Estonia Modelling examples.

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Modelling as a tool for groundwater protection

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  1. INVESTING IN YOUR FUTURE Modelling as a tool for groundwater protection Tomas Saks, Aija Dēliņa, Konrāds Popovs, Jānis Jātnieks, Andis Kalvāns

  2. Outline • MOSYS modelling system (PUMA project) • Buried valleys of Latvia and Estonia • Modelling examples

  3. Scheme of integrated model system development Information base Geometry model Hydrogeological model • 3D mesh • equations • numerical method • boundary conditions • calibration • solutions Geological data Monitoring data Closed 3D spatial model, which includes geological structure and properties of geological materials • input • update • storage • access • remote access(web) • Objects(layers, faults, materials) • Automatic mesh generation • Stratigraphy (hronological generation) • Result: groundwater flow in BAB

  4. The Baltic Basin Basin scale groundwater model Area - 484000 km2 Volume - 579000 km3 Average thickness- 1.2 km

  5. Geometry generation – automated scripting The construction of the geometric mesh is implemented by specially developed script in Python. Scripting has several advantages: flexibility in choosing ways to build the structure; parallelization in developing/updating of different structure elements; documented and repeatable structure building path; possibility to rebuild the structure with slight or significant modifications at any time; possibility to build, and maintain several structures of different complexity simultaneously; extension to the next stages of the model development – calculation of groundwater flows and mass transport and model [auto]calibration.

  6. Groundwater flow modelling Steady state and transient groundwater flow models.The result of the model is spatial distribution of groundwater head (h(t)) and spatial distribution of groundwater flow (derived from the groundwater head field). Boundary conditions: No-flow conditions are defined for the sideboundaries. No-flow boundary conditions were applied on the bottom of the model. Infiltration conditions are applied on the surface(derived from regional climate model data) Mean or time-dependent discharge values are applied for the water abstraction wells (where data was available) Material properties are constant horizontal and vertical hydraulic conductivity (K) and specific storage (Ss)values for each layer, determined during the calibration

  7. Infiltration Data from regional climate models (RCM) from ENSEMBLES projectfor time period 1961-2010 with spatial resolution of 25 km was used. Spatially varying, time-averaged infiltration distribution was applied proportional to run-off from RCM models (employing empirical calibration constant). Where infiltration amount results in heads above surface level, remaining water are considered not infilrating. Run-off, mm/year Precipitation, mm/year Groundwater flows are mainly determined by infiltration in large closed basins. Evaporation, mm/year

  8. Examples of results Vilnius Rīga Kohtla-Järve Height ASL, m Upper layers Lower Devonian aquifers Regional aquiclude D2nr Distance, km O-S Cm-V Distribution of head, schematic flow arrows

  9. Burried valleys of Latvia and Estonia • In total 38325 boreholes reaching the bedrock surface • 2306 in paleoincisions

  10. Burried valleys of Latvia and Estonia • Boreholes as a source data • Probably 4 genetic types • Burried gullies • Burried fluvial channels • N channels • N channels in old fluvial channels

  11. Modelling example Groundwatermineralization (TDS in g/l) in Middle and Lower Devonian multi-aquifer. The impact of the Burried valleys on the groundwater flow

  12. Modelling example • Stable dO18 Isotopes in the Middle and Lower Devonian multi-aquifer The impact of the Burried valleys on the groundwater flow

  13. Modelling example • Groundwater flow beneath the Scandinavian Ice sheet (LGM) and residense time in the Middle and Lower Devonian multi-aquifer without Burried valleys

  14. Modelling example • Groundwater flow beneath the Scandinavian Ice sheet and residense time in the Middle and Lower Devonian multi-aquifer with Burried valleys

  15. Summary • Basin scale modelling is a start for an operational model • Burried valleys are potentially a connecting conduid for aquifers and also a potentional recharge sites for the glacial meltwater intrusion into the deep aquifer systems • Therefore good knowledge of distribution and depth of these erosional features are essential not only for groundwater safety, but also assessment of the resources

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