Tomas Saks, Aija Dēliņa, Konrāds
Popovs, Jānis Jātnieks, Andis Kalvāns
INVESTING IN YOUR FUTURE

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

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

Area - 484000 km 2
Volume - 579000 km 3
Average thickness- 1.2 km
Basin scale groundwater model

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

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:
1.No-flow conditions are defined for the side boundaries.
2.No-flow boundary conditions were applied on the bottom of the model.
3.Infiltration conditions are applied on the surface (derived from regional climate model data)
4.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 (S s
) values for each layer, determined during the calibration
S s
 h ( t )
 t
  

K
 h ( t )

 q ( t )

Infiltration
Precipitation, mm/year
Data from regional climate models (RCM) from
ENSEMBLES project for 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
Groundwater flows are mainly determined by infiltration in large closed basins.
Evaporation, mm/year

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

• In total 38325 boreholes reaching the bedrock surface
• 2306 in paleoincisions

• Boreholes as a source data
• Probably 4 genetic types
– Burried gullies
– Burried fluvial channels
– N channels
– N channels in old fluvial channels

Groundwater mineralization (TDS in g/l) in Middle and Lower
Devonian multiaquifer.
6550000
6500000
6450000
6400000
6350000
6300000
6250000
6200000
6150000
6100000
6050000
6000000
100000 200000 300000 400000 500000 600000 700000 800000
-1100
-1300
-1500
-1700
-1900
-2100
-2300
-2500
-2700
-2900
-3100
-3300
-3500
500
300
100
-100
-300
-500
-700
-900
5
2
20
10
1
0.5
0.2
0.1
100
50
The impact of the Burried valleys on the groundwater flow

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

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

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

• 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