Groundwater
Lithuania is situated in the Baltic artesian basin, a square of which is 460 th. km2. Part of it, ~200 th. km2 lies under the Baltic Sea. A basin is related with a large structure of Eastern Europe platform – Baltic syneclyzis. There are 3 structural parts of the Baltic artesian basin – central, bottom of it lies at the depth from 500 to 5000m, the Northern and North – Southern slopes of basin, where crystalline bedding lies closer than 500 m. Crystalline bedding is covered by layered sedimentary rocks of different filtration properties.
There are found layers of 3 different hydrogeological stage: a) Cenozoic – Mesozoic; b) Upper Paleozoic; c) Lower Paleozoic – Upper Proterozoic. They are separated by confining Triassic and Silurian – Ordovician aquitards. Paleozoic hydrogeological stage is divided in two parts by Devonian Narva aquitard.
The Baltic artesian basin:
1. – fracture lines; 2. – isoline of Crystalline bedding depth; 3. – Crystal sheet; 4. - Paleozoic bedding boundary; 5. – boundary of artesian basin; 6. - Byelorussian – Mozurian anteclyzis; 7. – Northern and North Western slope of artesian basin, 8 – central part of artesian basin A depth of crystalline bedding, m: 9. - <500, 10. – 500 – 1000, 11. – 1000 – 2000, 12. – 2000 – 3000, 13. – 3000 – 4000, 14. – 4000 – 5000, 15. ->5000.
At the Upper part of artesian basin, a zone of fresh water is found, thickness of which is changing from 50 to 450 m. At the lower part of basin aquitards are more compact, a vertical circulation is minor. High salt concentration and a wide chemical composition, a higher temperature is present here. There is an intermediate zone between Upper – and Lower – ones. Therefore the Baltic artesian basin has structure consisting of three zones. There aquifers and impermeable layers lies smoothly, but many tectonic fractures with different vertical amplitude – from ten to some hundred meters, complicates order. In such areas a continuous groundwater flow is broken. Because of a high pressured mineralized groundwater is rising from lower zone to surface through tectonic fissures. This is a reason of mineral water springs and hydrochemical anomalies in upper aquifers.
Groundwater zone of bicarbonates is spread on the entire country and is used for drinking water supply. Thickness of it is changing from 200 – 400 m at Baltija and Žemaičiai highland, to 50 – 150 m at the Nemunas lowland. Despite differences of chemical composition and mineralization in various aquifers or parts of them, the ions of bicarbonate and calcium prevails.
A groundwater of sulfate, chloride–sulfate and chloride hydrochemical zones is used or could be used in future for balneologic and industrial purposes. (Both can be active in future).
Investigations of drinking water resources in Lithuania were performed apace and during 30 years were approved sufficient amount of resources to satisfy drinking water demand. Totally 103 groundwater bodies were explored, with evaluated groundwater resources of 2023.1 th. m3/day.
Distribution of explored groundwater resources
|
Aquifer |
Geological index |
Amount of approved resources |
|
|
No. of well fieldsi |
thous. m3/d |
||
| 1. Aliuvinis 2. Kvartero tarpmoreniniai 3. Viršutinės kreidos 4. Viršutinės–apatinės kreidos(smėlis) 5. Viršutinės juros 6. Permo ir permo–viršutinio devono 7. Žagarės 8. Stipinų 9. Šventosios–Upninkų |
aIV, mIV agIII, agIII–II,agII–I, agI, fgIII K2 K2+1cm+alb J3 D3žg |
13 40 7 4 2 11 |
310,4 768,1 55,7 50,2 13 150 |
|
Totally |
103 | 2 023,1 | |
Groundwater bodies
In order to manage water resources, including groundwater, more efficiently according general principles of European Union, Lithuania made steps in fulfilling requirements of Water Framework Directive. All aquifers, containing fresh groundwater were assigned to 6 major groundwater bodies (basins). A separate groundwater body has set of aquifers or aquifer complexes with similar recharge, transit and discharge areas and has in depended balance of groundwater resources formation. Initial characterization of groundwater resources was performed for all groundwater bodies; their quantitative and chemical status was evaluated.
Water extraction from groundwater bodies
|
Groundwater bodies(GWB) |
|
Available groundwater resources, thous. m3/d |
Water extaction in 2005 |
|
|
thous. m3/p |
% from available resources |
|||
| Pietryčių Lietuvos kvartero (Q-1); | aIV, mIV, agIII, agIII-II, agII-I, agI, fgIII | 2100 | 195,2 | 9,3 |
| Vakarų žemaičių kvartero (Q-2) | aIV, mIV, agIII, agIII-II, agII-I, agI, fgIII | 61,7 | 11,3 | 18,3 |
| Kainozojaus-Mezozojaus (Kz-Mz) | K2, K2+1, J | 433,9 | 46,1 | 10,6 |
| Permo – viršutinio devono (P2-D3) | P2, P2+D3kr, D3kr, D3žg | 177,4 | 26,7 | 15,0 |
| Viršutinio devono stipinų (D3st) | D3st | 118,3 | 21,5 | 18,1 |
| Viršutinio – vidurinio devono (D3-D2) | D3šv+D2up, D3 kp-s, D3 įs-t | 706,9 | 49,4 | 76,9 |
Groundwater extraction for public water supply in Lithuania
A groundwater in Lithuania is extracted mostly from Quarternary aquifers (206.5 th. m3/d) – it comprises more than 58% of total volume of extracted fresh drinking water in country. Compared with available prognostic resources, the Quarternary aquifers were exploited the most intensively. The least amount of groundwater is extracted from of Upper Devonian, Stipinai groundwater body.
Groundwater extraction for public water supply in Lithuania
Lyginant turimus požeminio vandens prognozinius eksploatacinius išteklius (prognozinių eksploatacinių išteklių kiekis įvertintas pagal požeminio vandens eksploatacinių išteklių modulių pasiskirstymą plote ir regioninio išteklių įvertinimo ataskaitų rezultatus) ir išgauto vandens kiekį 2005 metais, matyti, kad vandens gavyba skirtinguose požeminio vandens baseinuose svyruoja nuo 6,9 iki 18,3 %. Vidutiniškai tai sudaro 9,8 % visų prognozinių požeminio vandens išteklių.