The studies about groundwater system began since post-war period, when the basis of hydrological network was implemented. Increase in need to supply the localities with underground water and the industry development cause the necessity for retrofitting the control methods and groundwater monitoring.
The purpose of the works are to study the system and elements of groundwater balance and to appraisal the status of the exploitable reserves and prognosis resources, research of exploitable wells, the determination of physical and chemical variation of groundwater under the influence of natural factors. In this way, the activities will be realized in order to use reasonable the groundwater and protect it from pollution and exhaustion.
- To emphasize physical and geographical conditions that affects the formation of the aquifer system.
- Analysis of studied problem mirrored in published works, thematic reports etc.
- Description of the geological structure and analysis of hydrogeological condition in order to determine their status for setting up the aquifer system.
- To emphasize the importance of aquifer system monitoring.
- The analysis and collection of the existing geological information, completing the data base and fixing hydrogeological objects.
- The analysis of quantity and quality parameters.
- The evincing of GIS technology capacity for identification and characteristic of groundwater bodies.
This project contains the basic tendencies of groundwater system in scantily deflected conditions, data about the prognosis of average annual level, minimum of spring, autumn and winter, also the summer maximum of groundwater. At the same time, it includes a terse characteristic about scantily deflected groundwater system of RM (depth of the location, temperature and chemical composition of groundwater).
The observations about meadow regime of groundwater are effectuated in the vales of big and small rivers. In coast areas, these are influenced by the stream regime, which starts up during the flooding and in time of episodic, seasonal rising and decreasing.
Seeing that on the RM territory for water supplying of population is used aquifer systems, these represent one of the most important duties for a hydrogeological study.
Groundwater regime forecasts performing the following works:
• The study of groundwater regime in scantily deflected conditions and deflected (under exploit influence).
• The study of chemical composition of groundwater in deflected regime.
• The setting up of groundwater maps of quality.
The objects of study are the aquifer systems and horizons, which are characterized by: hydric balance, the extending, thickness, configuration, the potential for storage and debiting, hydraulic conductivity, transmissivity, diffusivity hydraulic coefficient, efficacious storage and the refueling of aquifers, drain possibility, druse or cracking, the permeability of aquifer rocks, the capacity to retain or cede water, pressure load and the chemical composition.
The Artesian Moldavian Basin belongs to Artesian Black Sea Basin and includes the whole territory of RM, then it extends to the north-east and south on the Ukraine territory. The main hydrological subdivisions are the aquifer systems and horizons, scantily aquifers and impermeable differentiated by type and permeability coefficient.
The observation network contains 182 exploitable drills, of which 122 are in deflected regime and the other 60 in weak deflected regime. The existent monitoring network is situated in 33 posts (fig.1). The location of observation drills in public network performed on the strength of hydrological preliminary partition of the RM territory, taking into acount the specific of the observation regime. (Balina A.I. an.1977).
Below are described in short the aquifer systems and horizons of Artesian Moldavian Basin.
Aquifer horizon Aluvial-Deluvial (аА3)
Water sediments of aluvial-deluvial are prevalent and used to supply with potable water the population of RM (by wells). According to the forming conditions of the water stocked rocks, we can distinguish:
a) aquifer horizon of aluvial sediments;
b)aquifer horizon of the flood plain terrace liable to inundation with lower and upper holocenic age;
c) aquifer horizon of sediments with diverse genesis.
Aquifer system Badenian-Sarmatian (N1b-S1)
It extends almost whole the territory of RM, with the exception of the narrow bands from vales of Prut and Nistru rivers. Also, it excludes a sector from south-weast margin of territory. It is the unique hydraulic aquifer system and in the north side connects the Sarmatian and the lower Badenian, at the central and south side connects the lower and medium Sarmatian. Aquifer rocks are the limestones that in some zones are stratified by shales and sands. Water abundance of Sarmatian-Badenian system differs for each territory, so, in the north side, the flow of research drills specify a value about 0,1 - 2,2 l/sec (Donduşeni and Ocniţa district), inthe center side: 0,0 - 2,2 l/sec (Teleneşti district). The smallest water abundance of the system records in Glodeni and Făleşti districts, where the debit from drills is 0,1 – 0,3 l/sec.
The upper Meotian-Sarmatian system (N1S3-m).
The upper Meotian Sarmatian system extends in the center and south side of Moldavian Artesian Basin. The thickness of aquifer rocks is unevenly and point about20.0-300m (in the south side). The aquifer rocks are in the sands with a fine small granulation, aleurolites with interpolation by limestones, clays and grit-stones with the thickness about 2-28 m. The basic rocks are represented by sediments of clay-sands distributed on the layers at the level of Middle Codru.
Groundwaters from this system don’t have pressure but whown the sediments immerse to the south, these acquire a high pressure about 65-100m.
Even if the water quality don’t meet the sanitary requirements, these are used to supply the localities with potable water. Groundwater resources are achieved by the infiltration of rainfalls and the flow of water from the aquifer horizons and systems.
The aquifer horizon of middle Sarmatian (Congerian) (N1S2)
This aquifer horizon includes congerian sands of middle sarmatian and extends in the south-weast side, on the territorybetween Nistru and Prut rivers. Aquifer rocks are the sands with small and fine granulation that stratify with clays, limestones and grit-stones. The thickness of aquifer horizon is about 5-15m to 20-30m, in the south side can touch 40-50m. The smallest value of horizon’s thickness records in Batir, Taraclia, Troitcoe, Stoianovca and Cebolaccia villages.
The water abundance of congerian sands in unevenly. The debit of drills is about 0,7 - 1,6 l/sec. In other zones, this value can vary Cazanjic v. - 5,7 l/sec, Cecur-Minjir v. - 2,2 l/sec, Comrat t.- 3,3 l/sec,Beşalma v.- 3-7 l-sec, Cebolaccia v.- 2,9 l/sec and Stoianovca v. - 2,6 - 9,0 l/sec. Groundwater resources are achieved by the infiltration of rainfalls and the flow of water from the aquifer horizons and systems.
Ponţian aquifer horizon
Pontian aquifer horizon extends in the south side of RM. Aquifer rocks are sediments of novorosiisk sub-stage, represented by granular sands with content of limestone mould in the lower side of section. Some zones have intercalations of sands (about 4), studied like aquifer horizons which have pressure and specific level (intercalation from 3-5 cm to 25 cm, the total thickness – 80-100m).
The groundwater level of pontian aquifer horizon records at a depth of 1-5m (Giurgiulesti village), 5-10m along Prut river (Slobozia-Mare and Suvorova villages). The observations about groundwater level show that it stays unchanged, in this way, the exploitation don’t affect the groundwater regime.
Aquifer system Cretacic - Silurian (К2-S)
This system includes aquifer sediments of lower silurian and cenomanian. The south limit of cretacico-silurian resources is the band along Leova, Ceadîr-Lunga and Taraclia.
From Transnistria direction to Rîbnița district, the aquifer rocks are represented by limestones with the thickness about 10m. To the south side, these are represented by grind-stones. It thickness grows from 1…20m to 60…70m and in the vale of Prut river it is about 35-40m
The groundwater from this system have pressure. The water abundance depends of territory. The biggest debit values is 1.4 l/sec, rarely 0.1-0.3 l/sec. In Criva and Șireuți villages, the debit of drills is 0,2-2,7 l/sec, Edineț and Bratușeni villages q=0.1-0.3 l/sec, Drochia t.-3.9 l/sec.
Following the fluor contain, the groundwater of the system don’t meet the requirements of GOST 2874-82. Therefore, these groundwaters are not recommended for supplying the population with potable water.
According with the results of described studies, the conclusions are:
• The groundwaters of these aquifer systems and horizons depends of water quantity that were extracted, at the same time there is no stability for position of hollow areas, caused by growing or lowering of water consumption.
• Evaluating the chemical conditions, we point aut the unevenly spreading of macro and micro-elements, that can be noticed in obtained maps of mineralization spreading. So, the groundwater’s chemical conditions are not very good and need implementations of measures to reduce the pollution of potable water resources.
• The chemical composition shows that there is no aggravation of groundwater quality. Comparing with previously years, the chemical composition of basic aquifer systems and horizons are stable.