Small Grants Fund project completed in Moldova
Republic of Moldova completes Ramsar Small Grants Fund project for Lower Prut Lakes
Moldova has completed its 2003 SGF project "Evaluation Study to Support Implementation of Management Plan for the Lower Prut Lakes Ramsar Site towards Wise Use and Sustainable Development".
The project was executed by the Moldavian Center for Strategic Environmental Studies ECOS in Chisinau, which undertook a range of field trips to carry out various analyses on water quality and identification of causing contaminants; of soil and soil erosion as well as sediments in the Ramsar site lakes and Cahul ponds. The parallel study of the species composition and abundance went up to the phytoplanktonian and zooplanktonian level. All these studies were linked with hydrological and topographical parameter discussions during periods of different water level in the Cahul ponds and canals connecting Beleu and Manta Lakes to the Prut River. Further focus of interest was placed on human activities such as land-use, agricultural and waste practices and how they affect the environmental conditions in the Ramsar Site (e.g. oil drilling).
Meetings and discussions on wetland issues with stakeholders accompanied the process in all stages of the project and assisted to involve them in the development of the Priority Action Plan, but also in the identification and prioritisation sources of contamination of Ramsar Lakes. Therefore the River Basin Management Planning Approach for the Lower Prut Lakes Ramsar Site from 2000 should serve as a basis.
-- Dorothea August, Ramsar
Domestic rubbish near southern bank of Manta Lake
Soil sampling near Beleu Lake for express drift assessment
Geology and Geo-Morphology Review
Prut's River terraces
Discussion with Deputy Head of Cahul Rayonal Administration and
Head of Territorial Ecological Agency "South" of actions to be taken towards rehabilitation of Manta Lake
On site discussion of Manta Lake issues with major of Pascani & Manta villages
6. Hydrological measurements in the outgoing canal Nevodului (Beleu Lake)
Land use: Private plots near Manta Lake
Access roads in operation site during inundation
In the framework of the Project "Evaluation Study to Support Implementation of Management Plan for the Lower Prut Lakes Ramsar Site towards Wise Use and Sustainable Development" supported by the Ramsar Small Grants Fund for Wetland Conservation and Wise Use (SGF), there were carried out the following studies: Surface Water Quality, Soil and Sediment Quality, Bioassessment, Hydrology, Land Use, Waste and Soil Erosion supplemented by Geology and Geo-morphology Review.
One of the main objectives of above studies was to obtain baseline data to be considered when designing the Priority Action Plan based upon the River Basin Management Planning Approach to facilitate phased and consistent implementation of Management Plan for the Lower Prut Lakes Ramsar Site compiled in 2000.
Water Quality Study. The goal of Water Quality Study was to obtain baseline data on water quality in Beleu, Manta, Brinza and Colibas Lakes, and Cahul ponds, and thereby to determine ecological status of the Ramsar Lakes, to identify likely sources of their pollution and associated environmental concerns towards developing of Priority Action Plan to control and improve water quality, and prevent and/or mitigate pollution.
Water quality was studied during high-water and low-flow periods on 3 monthly basis and assessed against both national and EU water quality standards.
The sampling was undertaken in central and littoral parts of the lakes, and water quality was studied and assessed on the following parameters: dissolved oxygen/ oxygen saturation, pH, conductivity, suspended solids, transparency, biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total phosphorus, mineral phosphorus, nitrites, nitrates, ammonium ions, total nitrogen, total inorganic nitrogen, emulsified and total (conventional) petroleum hydrocarbons, sulfates, chlorides, hydrogen carbonate, dry residue/ mineralization, sodium, calcium, potassium, magnesium, and copper and zinc in dissolved and particulate forms.
The obtained within the Study data on water quality in Beleu, Manta, Colibas and Brinza lakes can be considered as a baseline data to be used in future monitoring programs. Settling the finding on water quality against the lakes within the whole period of observation (one year on three-monthly basis), the best water quality is in Beleu Lake; then follow Manta, Brinz and Colibas lakes; settling the finding on water quality against times of sampling the best water quality in all lakes was during high-water period in 2005, i.e. during fourth sampling event.
Suspended solids were found as a major common pollutant in all Ramsar lakes during high-water period in 2004 and low-flow seasons; sources of suspended solids in the Site may include soil erosion and raw sewage.
Along with suspended solids, petroleum hydrocarbons and COD were the major pollutants in Beleu Lake during high-water and low-flow periods in 2004. Additionally, in Beleu Lake there exists a risk of extremely high sedimentation load to be occurred due to washing out of access roads built up in oil drilling operation site between oil-wells especially when they are inundated.
COD was a major pollutant in Cahul ponds, Colibas and Brinza lakes where it was found in concentrations threaten the aquatic life especially during low-flow period. Big concentrations of COD in lakes may be explained both by impact of polluted runoff from landfills and raw sewage, and also by natural and/ or man-induced active processes of dying and withering away of aquatic organisms. Low COD values detected in all lakes during high water period in 2005 can be hardly explained while comparing with data obtained in 2004 because nothing had changed in terms of likely environmental impacts since commencement of the first sampling campaign.
Ammonium appeared to be a major pollutant in Colibas Lake and in Cahul ponds where it was found in very big concentrations what indicated presence of fresh contamination entering the lakes. The most likely sources of ammonium is application in relative drainage areas such fertilizer as ammonium nitrate which is commonly used by locals in early spring and late autumn; and also livestock farming and septic drainage.
Contamination with nutrients (except sporadically occurred contamination with ammonium) and heavy metals seemed not to be an environmental problem in the area. Generally, nitrogen and phosphorus compounds were found in lakes in low concentrations what may suppose wholly satisfactory utilization of entering from adjacent territories nutrients by aquatic vegetation.
There was not revealed direct correlation between pollutants values and volume of water in the lakes.
Elevated concentration of copper and zinc in particulate forms were in line with high values of suspended solids on which these metals precipitate.
There was detected a stable presence in Beleu Lake emulsified petroleum hydrocarbons detectable in UV; in its northern part where they were found in concentrations 4,5 times exceeding national standard which was probably associated with leaks from oil wells. In other parts of the lake concentration of emulsified petroleum hydrocarbons sporadically showed 3-5-fold exceeding over national standard.
There exists an obvious risk of sudden and accidental contamination with petroleum hydrocarbons the northern part of the lake which to a great extent of probability can locally cause sporadic death of aquatic organisms. In this connection emulsified petroleum hydrocarbons values sporadically detected in Beleu Lake can be considered as disturbing one taking into consideration likely spills from wells and pipe-lines followed by increase of concentration of petroleum hydrocarbons in water what can be dangerous for aquatic organisms.
At present, according to Moldovan standard water quality in Beleu Lake in terms of petroleum hydrocarbons pollution may be considered as moderate what taking in consideration long-term pollution due to leaks from old wells may indicate sufficient self-purification capacities of Beleu Lake most likely conditioned both by presence in water micro-organisms including bottom ones which are natural consumers of petroleum hydrocarbons, and also by appropriate water exchange between lake and the Prut River.
In this regard, a special investigation on composition and abundance of aquatic (micro)-organisms including bottom ones which are potential natural consumers of petroleum hydrocarbons in Beleu Lake thereby contributing to enhancing of self-purification capacity of lake's water is required.
Due to the importance of Beleu Lake as a part of the wetland of international importance, and as a water body included in the List of Protected Areas of Moldova as one supporting biodiversity, the problem of potential contamination of the lake with petroleum hydrocarbons needs to be resolved within short-term period towards prevention of aggravation of negative processes in aquatic ecosystem.
According to ECE Standard Statistical Classification of Surface Freshwater Quality for the Maintenance of Aquatic Life and System of Classification for Ambient Surface Water Quality, water in Beleu Lake corresponded to III, V, IV and III classes of water quality determined during first, second, third and forth sampling event respectively due to increased COD values; concentration of suspended solids (210 mg/l) during high-water period in 2004 either can correspond to VI class of quality or can be considered as occasional and short-term excursion not to be taken into consideration when assessing the class of water quality and ecological status of Beleu Lake. Concentrations of other pollutants in Beleu Lake corresponded concentration of other potential pollutants mostly corresponded to I-II class of water quality.
Water in Manta Lake corresponded to IV, V, III and IV classes of water quality determined during first, second, third and forth campaigns respectively due to increased COD values; concentration of other potential pollutants mostly corresponded to I-II class of water quality
Water in Colibas Lake corresponded to V, V-VI, IV and III classes of water quality determined during first, second, third and forth events respectively due to increased COD values; concentrations of other potential pollutants corresponded to I, II and even V classes (ammonium). The similar picture was demonstrated in Brinza Lake - water quality corresponded to V, VI, IV and III classes owing to elevated COD values concentration of other potential pollutants mostly corresponded to I-II class of water quality (except suspended solids).
However, it is difficult to evaluate whether above assessments of water quality classes in Ramsar Lakes represent the facts; this can be linked with occasional manifestations of such pollutants as COD and suspended solids big values due to certain sporadic phenomena occurred in the area of concern or due to impact of seasonal variations. To assess properly water quality classes and ecological status of lakes according to EU classification the specially designed (in terms of duration, frequency and parameters) monitoring program is required. Monitoring shall be carried out to assess the magnitude and impact of all relevant significant pressures on these bodies is required.
Carrying out of such a monitoring program to assess class of water quality is especially important for Beleu Lake since its water falls under definition of protected water supporting biodiversity.
Water quality in Cahul ponds corresponded none to any class of quality due to very high concentrations of suspended solids, COD, ammonium, and pH and mineralization values. Based upon obtained data on water quality, Cahul ponds can not be considered as Ramsar water bodies anymore unless Cahul fish pond would not been rehabilitated as a water body with artificially maintained water regime.
Soil and Sediment Quality Study. The goal of the Soil and Sediment Quality Study was to obtain baseline data on Beleu, Manta, Colibas and Brinza Lakes and Cahul ponds sediments quality, and on quality of soils on relevant uplands towards determining of contaminants actually and potentially affecting water quality and aquatic organisms, and also to evaluate soil quality potential for environmentally friendly agriculture in the Ramsar Site towards developing of Priority Action Plan aimed at prevention and mitigation of relevant natural and man-induced impacts in the area of concern.
Soil quality was considered as a factor potentially affecting surface water quality; sediment quality was considered as the ability of sediment to support a healthy benthic population and as a factor potentially contributed to likely secondary pollution of surface water.
Altogether there were undertaken one soil and one sediment sampling campaigns during low-water season. Soil samples were taken in the upper horizon of the profiles at the depth 20-30 cm in the most representative spots with consideration of local relief and direction of surface run-off and assessed against national and international (German, Canadian, English) standards.
Sediment were sampled from the depth up to 30-40 cm in central parts of Beleu, Manta, Colibas and Brinza Lakes and two temporary Cahul ponds and assessed against Dutch and Canadian standards.
The quality of soil and sediment was evaluated on next parameters: pH, humus/ organic matter, conductivity, total phosphorus, inorganic phosphorus, total nitrogen, inorganic nitrogen (N-NO3 and N-NH4), calcium, magnesium, potassium, sodium, total lead, total cadmium, total and mobile copper, total and mobile zinc, petroleum hydrocarbons (in Beleu Lake), organochlorine pesticides (4-4 -DDT, 4-4 -DDD, 4-4 -DDE, -HCH, - HCH, -HCH), fluorine-containing pesticide (treflan), organophosphorus pesticides (phozalon, parathion-methyl, dimethoat, malathion).
Obtained data on sediment quality in Beleu, Manta, Colibas and Brinza lakes as well as data on soil quality on lands adjacent to the lakes can be considered as baseline data to be used in future sediment and soil quality monitoring programs.
The Soil and Sediment Quality Study demonstrated that sediments in all lakes are contaminated with DDE and DDT, especially in Manta and Colibas Lakes what possibly occurred due to long-term application of this pesticide in the past on relative drainage areas. Pesticides residues values were found in lower concentrations in downland soils as compared to relative upland soils. This might be due to the exhausting leaching capacity with stronger complexes of the pesticides residues with organic matter or different complexing agents which present in soil.
Concentrations of organochlorine and organophosphrus pesticides residues in soil complied both with moldovan and international soil quality standards.
Organochlorine and organophosphorus pesticides in sediments were found in higher concentrations as compared to relative upland soils. In spite DDT is not used in agriculture since 1972 their values still sizably exceeded HCH values;
Practically in all soil and sediment samples total heavy metal concentrations complied both with moldovan soil quality standards, and Dutch and Canadian soil and sediment quality standards. Concentrations of total copper, zinc, cadmium and lead detected in sediment may be considered as reference values of these heavy metals in sediments of Ramsar Lakes; concentrations of total copper, zinc, cadmium and lead determined in soil may be considered as background levels of heavy metals in the Ramsar Site and on adjacent territories. There was not traced an obvious correlation between trace metals concentrations in soil and sediment.
Concentrations of total metal and other micro-elements found in soil samples laid in limits of earlier determined background concentrations in the area of concern, however there is an obvious pollution of sediment with nutrients and in particular, by nitrogen compounds.
Mean concentration of total petroleum hydrocarbons in sediment sample taken in the central part of Beleu Lake was 20 mg/kg. There exist no national standards for sediment quality, and it was difficult to compare this data against available international standards elaborated for separate petroleum hydrocarbons which are parts of aromatic and other groups, and also to assess fresh contamination because baseline concentration of petroleum hydrocarbons was unknown. Such a concentration of petroleum hydrocarbons present in sediment may be considered as fairly high, and therefore one can conclude that sediment is contaminated petroleum hydrocarbons what definitely may be toxic for aquatic organisms including due to secondary pollution. The major source of this contamination is probably long-term oil leakage from old test wells that have been drilled for oil prospecting purposes during soviet times, and also leakage from currently exploited oil wells.
In soil sampled in site in immediate vicinity form Beleu Lake which during high water period is inundated concentration of petroleum hydrocarbons amounted 300 mg/kg;
Since the major potential source of contamination with petroleum hydrocarbons in immediate vicinity from Beleu Lake is a lake's water contaminated with petroleum hydrocarbons due to oil leaks from previously drilled oil wells in Beleu entering the adjacent land during inundation, and having compared above two petroleum hydrocarbons values in soil and sediment, and additionally taking into account that about 90% of petroleum hydrocarbons are accumulated in the bottom layer, the special investigation is required on presence in Beleu Lake micro-organisms including bottom ones which would be the natural consumers of petroleum hydrocarbons thereby contributing to the process of self-purification in the lake.
Organic matter content in soils in the Ramsar site varies from very high (near Cahul pond) to very low (near Brinza Lake). Organic forms of nitrogen and phosphorus prevail both in the soil and sediment. Concentrations of nutrients in soil were slightly higher as compared to potentially affected sediment what may indicate that neither sediment nor surface water are not polluted with nutrients washed out from the upland soils, what is in line with detected low concentration of nitrogen and phosphorus compounds in water in the lakes.
In future, revealed concentrations of contaminants may be used for calculation of enrichment relative to their levels as a result of likely man-made pollution and its impact to the Lower Prut and Danube basins.
It seems necessary to develop sediment quality monitoring program, and monitoring tools and methods of identification of sediment-associated pollutants in the Ramsar Site and adjacent territory; to establish natural background levels of heavy metals in sediment including those associated with different grain-size fractions, and to continue the micro-pollutants survey in research programs including potential sources of contamination and to what extent toxicants have been dispersed through the ecosystem as well as petroleum hydrocarbons survey including determining to what extent petroleum hydrocarbons are being dispersed through the system and how harmful is it for aquatic life;
Bioassessment Study. The goal of Bioassessment Study was to obtain baseline data on species composition and abundance of phytoplankton, zooplankton and benthos as well as macrophytes species occurrence and chlorophyll-a content to preliminary determine ecological status of the Ramsar Lakes and to complement water chemical survey toward the most comprehensive ecological assessment of the lakes' water quality aimed at developing of Priority Action Plan to control and maintain water quality sufficient to support diverse aquatic life.
Altogether there were undertaken three biological sampling campaigns. Biological sampling to determine phytoplankton, zooplankton, zoobenthos and chlorophyll-a content was undertaken on the same sites as water quality sampling for determining of chemical and physico-chemical parameters. Occurrence of macrophytes was studied in water bodies and along lakesides.
Within the Bioassessment Study there were determined 73 taxa of phytoplankton in Ramsar lakes and ponds belonging to classes Cyanophyte (7 taxa); Bicillariophyta (23 taxa), Euglenophyta (12 taxa), Chlorophyta (29 taxa) and Pyrrophyta (1 taxa).
The richest in a sense of phytoplankton species composition was Beleu Lake where 41 taxa were determined; out of them 32 taxa were found in spring biological samples and 14 taxa were found in autumnal biological samples. In Manta Lake there were found 35 taxa of phytoplankton; out of them 20 taxa were found in spring biological samples and 19 taxa were found in biological samples taken in autumn. In Colibas Lake there were determined 30 taxa from which 25 taxa were found in samples taken in spring and 18 taxa - in samples taken in autumn.
In Brinza Lake there were discovered 24 taxa from which 12 taxa were determined during spring sampling event and 16 taxa - during autumnal sampling event. In Cahul pond 1 there were found 33 taxa of phytoplankton; in Cahul pond 2 - 20 taxa.
There were determined 25 taxa of zooplankton in Ramsar lakes and ponds belonging to classes Rotatoria (8 taxa), and Crustacea (Cladocera -9 taxa and Copepoda -8 taxa).
From 11 taxa determined in Beleu Lake 9 taxa were found in spring, and 5 taxa - in autumnal samples. From 9 taxa determined in Manta Lake, 9 taxa were found in spring and 5 - in samples taken in autumn; in Colibas Lake there were found 9 taxa, from them 7 - were determined in spring, and 4 - in autumn. From 10 taxa found in Brinaza Lake 6 taxa were determined during spring sampling event, and 9 taxa - in biological samples taken in autumn.
In the Ramsar lakes and pond there were found 26 taxa of zoobentos belonging to classes Nematoda (1 taxa); Mollusca (5 taxa, including Gastropoda- 4 taxa); Oligohaeta (1 taxa), Crustacea (Ostracoda -1 taxa; Mysidacea - 1 taxa, Isopoda-1 taxa, Amphypoda - 2 taxa); Hirudinea (1 taxa); Insecta (Diptera -1 taxa; Heteroptera -2 taxa; Chirinomidae - 2 taxa, Ephermoroptera -1 taxa, Trichoptera - 2 taxa; Odonata -1 taxa and Coleoptera - 4 taxa). In Beleu Lake there were found 11 species of zoobenthon organisms, out of them 8 species were found in spring water samples, 7 species - in autumnal ones. In Manta Lake there were determined 6 species, from this quantity 5 species were found in spring and 5 species - in autumn. In Colibas Lake 10 zoobethon species was determined; from them 7 - were found in spring water samples, and 5 species - in autumnal samples. In Brinza Lake altogether 14 species of zoobenthos were found, 11 species - in spring, and 10 species - in autumn. In Cahul ponds 1 were found 6 taxa; in Cahul pond 2 - 8 taxa.
Altogether in Ramsar lakes and pond there were determinded 45 species of macrophytes. In Beleu Lake were found 25 species, in Manta Lake - 28 species, Colibas Lake was the poorest in this sense - 7 species, in Brinza Lake - 16 species. In Cahul pond 1 and Cahul pond 2 there were found 16 and 18 species respectively, however in two latest water bodies it was not a truly aquatic vegetation.
Phytoplankton, zooplankton and zoobenthos species diversity and abundance, and macrophytae diversity and occurrence may be considered as baseline data to be used in further biomonitoring and bioassessment programs.
The data on phytoplankton, zooplankton and zoobenthos species diversity and abundance as well as saprobic indexes, and macrophytes diversity ? occurrence obtained within study for designing the data base on species and communities inhabited in the Lower Prut Lakes wetlands.
Further detailed comparative analyses of biota and sediments is important for the further detailed mapping and assessing the effect of any likely pollutants in the Ramsar Site as well as in the Lower Prut River and Lower Danube River basins.
Species composition and cover of submerged aquatic vegetation in Brinza Lake show a high probability of entirely overgrowing of Brinza Lake what may demonstrates short- and long-term temporal changes of wetlands function and value, hydraulic dynamics and boundary fluctuations.
Results of biological assessment based on the Saprobic Index demonstrated that all Ramsar lakes may be considered as having 'moderate' ecological status. This along with low chlorophyll-a values indicating appropriate ecological status of water bodies allows to suggest that contamination of all Ramsar Lakes with COD, suspended solids and some other pollutants could be linked with seasonal variations or occasional excursions of values of these pollutants due to certain sporadic phenomena occurred in the area of concern. Again, this also allows to suggest that contamination of Beleu Lake with petroleum hydrocarbons presently does not affect inevitably aquatic organisms.
Assessment of water quality on the basis of macrophytes diversity and occurrence can be successfully used either to provide an alternative and not expensive tool for supplementary assessment of the water quality and evaluation of ecological status of the Ramsar Lakes. The saprobic index as a parameter appropriately correlated with majority of water quality parameters also can be used to complement chemical monitoring of water quality.
However, it should be mentioned that ecological status of water bodies evaluated on the basis of Saprobic Index, Oligochaeta composition and Chlorophyll-a content did not show good correlation. Besides, the saprobic index of biota determined in Cahul pond corresponded to III class of water quality what did not correlate with class of quality determined on the basis of chemical analysis of the water. This may be explained either by high degree of tolerance to adverse environmental conditions or by non-coincidence of affecting time and period of development of destructive processes in aquatic organisms. Quantities of zooplankton and zoobenthon taxa determined in all Ramsar lakes and pond were small but at approximately the same level what was probably due to moderate and poor water quality.
On the whole, results of biological assessment can indicate that occurrence of high concentrations of some water quality determinands measured within Water Quality Study could be sporadic, and on the whole they complied with admissible annual average values for these pollutants.
Hydrology Study. The goal of the Hydrology Study was to determine some baseline hydrological and topographical features of the lakes and canals connected them to the Prut River, to identify relevant impacts arising from improperly considered hydrological conditions in Beleu Lake with special regard to oil drilling, and thereupon aimed at developing of Priority Action Plan towards improvement of hydrological and ecological conditions in the Ramsar Site.
Beleu Lake. During high water period because of flood in the lower Danube, the Prut River flow amounted 40-50 m3/s, water level in Prut was 5,92 m asl while in Beleu Lake it was recorded at mark 5,50 m asl. According to estimates, surface area of Beleu Lake in that period was about 2,406 ha; minimum measured depth was 1,9 m and maximum depth - 2,61 m.
During low-water season the Prut River flow was 40m3/s, its water level at the point of entry into the feeding the Beleu Lake incoming canal was 3,9 m asl. while in Beleu Lake - 3,55 m asl. Thus, within 3 months from April to July the water level in Beleu Lake dropped on 1,95 m as compared to the flood period in the lower Danube. The surface area of Beleu Lake according to estimates was about 350-450 ha, length - 5,2 km, width - 2,75 km.
In the predominant shallow areas in Beleu Lake depths varied from 0,15 to 0,35 m; thickness of sticky silt on the lake's bottom in its southern part amounted 0,40-0,60 m. In the deepest parts of the lake measured depths reached a little more than 1 m. At the point of entry of incoming canal Manolescu into the lake the depth in Beleu reached 2 m.
Oil drilling related hydrological issues. According to project documentation, the total surface area immediately affected by oil drilling is 27,4 ha, i.e. 1,6% from the total surface area of the scientific reserve Lower Prut. However, according to expert estimate, the area exposed to drilling effect is about 50 ha. In spite such a small share, ecologically, the impact could extend far beyond the immediate area, e.g. by likely changing the hydrological regime and causing disturbance to breeding birds and other fauna by destruction of habitats, noise pollution, likely water pollution etc.
In 2004 during spring high-water period ( in mid April) the water level in the Danube River near the mouth of the Prut River reached 5,04 m asl., water level in the Prut River recorded at the fixed hydrometric station "Brinza" situated about 10 km above the origin of Beleu Lake's incoming canal was 6,34 m asl. That time the water level in Beleu Lake was 5,5 m asl. and the distance between oil wells' hatchways water surface was 0,5 m. Access roads built up between oil wells were inundated and have been washing out.
In April 2005 the water level in the Prut River near gage "Brinza" was about 6,9 m asl., near the point of the incoming canal's origin - 6,62 m asl. while in Beleu Lake it amounted 5,64 m asl., and was 14 cm as higher as compared to April 2004.
In the middle of May 2005 when the water level in the Danube River was about 6 m asl., in the Prut River (at the hydrometric station "Brinza") - 7,3 m asl, near village Slobozia Mare - 6,87 m asl, while in Beleu Lake it was 5,95 m asl. Access roads and oil platforms were fully inundated; the surface of access roads was beneath the lake's water surface by about 2 meters.
Probably such a big height of water column between lake's water level and surface of the access roads occurred because of combination of two factors: increased water level in lake conditioned both by flood and discharges from the Costesti-Stanca reservoir, and also by fast washing out of light soils from which these access roads were built up.
Since beginning of April due to forecasted flood oil drilling was halted, and cementation of ten presently exploited oil-wells was carried out in order to prevent water pollution.
According to expert estimates the heights of platforms and access roads should be raised up to the altitude about 8 m asl. what will allow to avoid their inundation even in the year of 1% probability of exccedance the hydrological values, i.e. in the year of extremely high water level in the Prut River (which hypothetically can occur once per one hundred years).
Beleu Lake canals. Beleu Lake is connected to the Prut River through four canals. Due to absence of any regulation devices on these canals the water of the Prut River freely flows through the lake having formed its hydrological regime which strongly depends on the river's water level oscillation.
The natural incoming canal Manolescu originates at the distance of 39,58 km from the Prut River's mouth and flows into Beleu Lake in its upper nort-western part. Physical parameters of the incoming canal are: total length is 3,85 km including its 1,5 km long stretch along the lake itself; width in the head is 38,5 m and depth - 4,6 m. Estimated difference in altitudes between points of canal's origin and its inflow into the Beleu Lake is 0,7 m.
During low-flow period measured surface area of incoming canal's water flow cross-section was ? - 2,075 m2, the mean water flow speed V - 0,45 m/s and water flow in canal Q - 0,95 m3/s. Full estimated capacities of incoming canal were the following: surface area of water flow cross-section was ? - 70 m2, mean water flow speed V - 0,88 m/s and water flow in canal Q - 38,4 m3/s.
There exist three outgoing canals in the lower southern part of the lake. Measured parameters of canal Nevodului are the following: width - 31 m, length - 1,4 km, depth - 1,61 m. Full estimated capacities of the canal are: surface area of water flow cross-section ? - 12 m2, mean water flow speed V - 0,5 m/s, water flow Q - 6 m3/s. Outgoing canal Girla Rotarului is heavily deformed, and at the point of Beleu Lake's water outflow into the canal, it has such a low level of weir that makes possible to lake's water to freely flow out even during low-flow period. The parameters of the canal are: width -31 m, length - 0,85 km and depth - 3,05 m. During low-flow period measured surface area of water flow cross-section was ? - 3,386 m2, mean water flow speed V - 0,5 m/s, water flow in canal Q - 1,7 m3/s. Full estimated capacities of the canal are the following: surface area of water flow cross-section ? - 22,7 m2, mean water flow speed V - 0,6 m/s, water flow in canal Q - 13,6 m3/s. Outgoing canal Popovca has the following parameters: width - 27 m, length - 0,55 km and depth - 2,25 m. Estimated full capacities of the canal are: surface area of water flow cross-section ? - 18,5 m2, mean water flow speed V - 0,6 m/s, water flow in canal Q - 11,1 m3/s.
All outgoing canals are naturally washed out, eroded and deepened both by direct water flow from Beleu Lake and by inverse water flow from the Danube River during flood.
Improper adjustments towards slowing down the speed of water outflow from Beleu Lake strongly contributed to degradation of outgoing canals.
During low-flow period through above three canals the water outflow from Beleu exceeded inflow into the lake through the incoming canal by 0,75 m3/s.
Manta Lake. During high-water season occurred because of high water in the lower Danube the Prut River water flow amounted 40-50 m3/s. In the Prut River near the point of originating of incoming canal the water level was recorded at mark 7 m asl while in Manta Lake it reached 7,90 m asl. According to estimates, the surface area of the lake's water mirror was 3000 ha. Maximum measured depth came to 1,5 m while mean depth amounted 1 m. During low-water season Prut River flow was 40m3/s; water level in Prut near its inflow into incoming canal was recorded at mark 5,42 m asl. while in Manta Lake the water level was 6,21 m asl. Length of the Manta Lake amounted 8,52 km, width - 3,4 km. According to estimation the area of water mirror was 1700 ha.
In normal conditions surface area of the lake is 2,100 ha. In the deepest places of former separate lakes the depths can reach up to 3 m even during low-flow period. At the point of canal's confluence with the lake its depth reach 2 m and more. However, in the greater shallow area of Manta Lake depths varied from 0,20 to 0,60 m. The bottom of the lake is covered with silt.
Manta Lake canals. Manta Lake is connected to the Prut River through two canals - one incoming and one outgoing. Incoming canal. During soviet times to improve water supply of Manta Lake (and Cahul fish pond) the Prut's arm originating at the distance 78,54 km from the river's mouth was reshaped into the main canal feeding the lake. Water from the Prut River enters the lake through the main canal. The substantial difference in altitudes (1,5 m) between point of originating of the canal and point of its confluence with Manta Lake ensures sufficient water inflow into the lake. The length of canal is 4 km, width in its head is 56,5 m, and maximum depth comes up 4,5 m.
During low-water season the surface area of water flow cross-section was ? - 14,4 m2; mean speed of water flow V - 0,4 m/s, and water flow in canal at the point of its entry into the lake Q - 5,76 ?3/?. When the canal operates at full capacity its parameters are next: surface area of water flow cross-section ? -109,8 m3, mean speed of water flow V - 0,63 m/s, and water flow in canal is Q - 68,7 m3/s.
In the southern part of the Manta Lake there is an outgoing canal. The canal is gradually degrading and deepening due to washing out of light soils and substrates caused by the process of natural levelling. The measured parameters of the outgoing canal are next: width in head is 51 m, length - 1 km and depth - 2 km.
During low-water season measured surface area of water flow cross-section was ? - 16,35 m2; speed of water flow was V - 0,5 m/s, and water flow in canal amounted Q - 8,15 m3/s.Estimated full capacities of outgoing canal are the following: surface area of water flow cross-section ? - 23,6 m2; speed of water flow V - 0,6 /s; water flow in canal - Q - 14,2 m3/s.
Measurements showed that during low-flow period the outflow from Manta Lake (8,15 m3/s) into the river exceeded water inflow into the lake (5,76 m3/s) at 2,38 m3/s, i.e. an intensive process of the lake's water level decrease, i.e. seasonal shallowing was to be observed. In this period water level in Manta can decreases to such marks that in a sizeable part of the lake (60-70% of its surface area) depth amounts about 30-40 cm.
Colibas and Brinza Lakes. Colibas and Brinza Lakes are not connected directly to the Prut River. They are fed by groundwaters, flood waters and rainfall run-off from drainage basin. Dimensions of the lakes oscillate and depend on probability of exceedance the hydrological values and season, and they can drastically decrease in summer time. Both lakes are shallow and overgrown with reed, especially Brinza Lake. Their predominant depths vary in limits of several tens centimeters.
In natural conditions surface area of Colibas Lake representing a complex of 3 smaller lakes may reach 22 ha. The total length of these lakes is 0,9 km, and average width comes to 0,35 km. During low-water season Colibas Lake's surface area drastically decreased and water mirror remained only in some places where probably groundwater comes into terrene. During flood in the lower Danube the estimated surface area of the lake reaches about 105 ha, length - 2,2 km, width - 0,5 km. Maximum measured depth was 0,7 m while mean depth amounted 0,3 m.
Brinza Lake represents a complex of six very small lakes overgrown with reed. In natural conditions total surface area of the lake may reach 3,84 ha. During low-water season the surface area of Brinza Lake was not measured due to high density of reed beds and uncertain contour of water body. Estimated total length of the lake was 0,6 km, average width - 0,25 km. Maximum measured depth came to 1,2 m, average depth - 0,9 m. According to estimates, during high water in the lower Danube surface area of the lake can reach 44 ha, length - 1,5 km, width- 0,3 km.
Cahul fish pond. Previously the maintenance of water level in Cahul fish pond was carried out by regulating of Prut River's water flow through the main canal by means of pumping station. At present during high-water period only two muddy and shallow ponds with total surface area of water mirror about 270 ha and average depth - 0,3 m remained at the site where probably groundwater feeding previously existed natural lakes comes into terrene. Presently drained area is used as pasture. During low water period remained two ponds are being drying out and used by locals as pastures, too.
The Hydrological Study demonstrated that hydrological features of Cahul pond do not allow to consider them as a Ramsar water body anymore unless it would not be rehabilitated.
Obtained data can be considered as baseline hydrological data to be used in future relevant surveys and research.
Incoming and outgoing canals connected Beleu and Manta Lakes to the Prut River are in low keep, rubbished, and besides, Beleu Lake outgoing canals are inappropriately modified towards slowing down the speed of water outflow from the lake;
Due to above and also because of some other reasons to be studied in detail further, during low-flow period the water outflow from Beleu and Manta lakes exceed water inflow in lakes (by 0,75 m3/s in Beleu and by 2,38 m3/s in Manta).
"Redeco"'s Oil Company oil drilling facilities as well as associated infrastructure in Beleu Lake was hydrologically improperly designed to ensure compliance with environmental protection requirements.
Taking into consideration water quality data, water exchange between lake and Prut River can be considered as still appropriate in terms of contribution to enhancing of self-purification capacities of water in Beleu Lake.
Land Use Study. The goal of Land Use Study was to identify and prioritize likely impacts on wetland ecosystems arising from land use as well as potential for surface water pollution towards developing of Priority Action Plan aimed at prevention and/or mitigation of relevant impacts.
Land ownership in the relevant part of the lower Prut basin include private lands encompassing 34182,19 ha, or 61%; public lands owned by communes - 8919,14 ha, or 16%, and public lands owned by territorial-administrative units -13333,45 ha, or 24%. A large amount of land is held in household plots, each of less than 0.3 ha. Another significant pressure related to land use practices, is the large number of animals grazing in floodplains, forested areas and slopes.
The area does have a significant history of agricultural practice. Much of the land surrounding the Lower Prut Lake site was first cleared from forest and then desiccated.
In 2003 the Land Fund in the Ramsar Site and on the territories adjacent to the Site amounted 56,235 ha. The agricultural areas made 38,843 ha including 27,440 ha of arable lands, 7,136 ha of perennial plantations and 4,228 ha of pastures. The area occupied by forests and bushes was 5,272 ha, swampy areas - 1,697 ha and by water, including lakes and ponds - 5,365 ha.
The territory used for agricultural lands is very big - about 70%. Such a big area of arable lands, perennial plantations and the small area occupied by forests do not allow to maintain properly an ecological balance between natural and anthropological ecosystems.
According to estimates, about 90% of total area of grasslands is used as pastures. These grasslands as a rule represent a land/ soil affected by factors that make possible the cultivation of field crops/plants: heavy erosion, landslides, excess of soil moisturizing, salinization. Besides, presently in the Ramsar Site the lands where previously were situated Cahul fish ponds are used as pastures, as well.
The growth number of cattle, sheep and goats in the private sector, and inappropriate land-use management as well as often distribution pastures on slopes conditioned the process of overgrazing which gradually results in decreasing of grassland biodiversity and grassland microbal contamination.
Obtained data on structure of land use in the Ramsar Site and on adjacent territories demonstrated that within last 8 years the share of arable land in the area increased by 13% at the expense of croplands while surface area of pastures decreased by 14%.
At the same time, areas occupied by forest plantations increased by 22%. The process of waterlogging in the area of concern also have a positive tendency; the surface area of swampy areas increased by 30% and presently amounts 1,697 ha. Surface area of impaired lands also increased during above period. In fact, surface area occupied by ravines increased by 270 ha, landslides - by 2 ha.
Total surface area of the Lower Prut Lakes Ramsar Site encompasses 19,152 ha. Population density in the Ramsar Site is high, and amounts about 180 persons per square kilometer (including area occupied by open water and reed-beds).
Land use and land cover within the Ramsar Site is distributed as follows: wetlands (lakes, river, ponds)-12%; reed-beeds - 23%; grasslands/ pastures - 12%; forests - 3%; agricultural lands (croplands, private vegetable gardens) - 31% and other lands (settlements, roads, argo and argo-industrial units, etc.) - 15%.
The Land Use Study demonstrated that the major part of the Ramsar Site is used for agricultural activities which mostly include grazing and farming. Grasslands used as pastures are of a low quality in terms of poor vegetation and soil quality.
The greatest potential impacts to water quality in Ramsar Lakes come from cropland, areas used for economic activities (oil drilling in Beleu Lake) and residential areas (landfills). Improper cropland tillage contribute to increase of sediment runoff into Ramsar Lakes. The forest in the Ramsar Site is of a poor quality, and area covered by floodplain forest seems insufficient to maintain properly an ecological balance between natural and anthropological ecosystems, to manage soil and appropriately prevent degradation of biodiversity that associated with this type of habitat in the Ramsar Site.
Waste Study. The goal of Waste Study was to collect and analyze information regarding assessment of impact from domestic and animal wastes, including estimation of nutrient loads into surface and groundwater, and other wastes generating in the Ramsar Site with special regard to oil drilling; identification and prioritization of sources, reasons and activities which actually and potentially affect environmental quality towards developing of Priority Action Plan aimed at prevention and/or mitigation of environmental impacts.
The principal non-point sources are from human populations served by pit latrines (non-sewered population), domestic and livestock waste, land use and also atmospheric/background loads. The waste from about the population of 33,804 served by pit latrines permeates into the soil and the nutrients are apportioned between subsurface flow to surface waters and infiltration to groundwater.
The amount of human and animal waste produced by rural households is quite large and much of this is disposed locally, certain proportion within the tiny plots of the households themselves or on adjacent farmlands.
In Ramsar Site all rural settlements except Cislita-Prut have landfills (official and unofficial). It was identified that 9 landfills can be treated as official waste dumping sites and 9 as unofficial ones. Some of official landfills (decision is usually made by the local authority) are not authorized by environmental and health authorities. The total area of official landfills is about 9 ha (with the range between 0,3 ha and 1,5 ha). Total area of unofficial landfills is about 8 ha. The average age of a landfill ranged between 10-15 years. Among landfills, placed in the Ramsar Site, 1 has age exceeding 20 years, 8 - between 10-15 years, and 9 - less than 10 years. The age of an unofficial waste sites is usually less than 10 years. Among dumping sites 10 has been allocated in the ravines, landslides areas, or were associated with quarries and 8 has been placed in more or less flat places or natural small land depressions.
Domestic Wastes. In the Ramsar Site, based on a number rural population of 33,304 equivalent to 10,514 households (with 3 persons per household) the estimated solid waste production amounts 5,210 tons per year, or about 496 kg/household/year.
Animal Wastes. Animal waste can contribute to water pollution when it is improperly stored or left uncovered near small streams and storm drains. Livestock wastes comprise slurry/ manure generated by animals within the household property boundary, grazing areas and those which are brought to waste disposal sites.
On average, domestic animals are distributed as follows: 1 cattle amounts for 6 households; 1 pig - for 2,5 households; 1 rabbit - for 6 households, 1 horse - for 8 households, 1 donkey - for 29 households. Also, on average one family keeps 3 sheep and/or goats and 22 poultry.
Total number of livestock kept in villages situated in the Ramsar Site is shared as follows: cattle - 1,808; pigs - 4,149; sheep/goats - 31,003; poultry - 234,960; rabbits - 1,714; horses - 1,362 and donkeys - 368
A small portion of animal waste is used as fertilizer by the householders However, since householders do not have equipment for spreading of manure, agricultural waste is often dumped, sometimes nearby the wells used for drinking water purposes and also near streams
Estimated distribution of waste as per type of livestock in rural households in the Ramsar Site is the following: cattle - 2.5 tons/ year; pigs - 0.4 tons/ year; horses - 1,2 tons/ year; sheep/ goats - 2,0 tons/ year; poultry - 4,7 tons/ year; donkeys - 0.2 tons/ year and rabbits - 0.03 tons/ year.
- The estimated total quantity of solid waste production from livestock in the Ramsar Site is 11 tons per year what is 0,2% from estimated total domestic waste production.
- The estimated domestic solid waste production amounts 5,210 tons per year;
- The estimated annual nutrients load into surface and ground water arising from non-seweraged population amount 99,504 kg/year for nitrogen and 13,793 kg/year for phosphorus; out of these amount 12,169 kg/year of nitrogen and 2,434 kg/year of phosphorus are estimated to be loaded into the surface waters;
- The estimated quantity of solid waste production from livestock is 11 tons per year what is 0,2% from estimated total domestic waste production;
- The estimated annual potential load of nitrogen into surface water from major livestock wastes amounts 99,317 kg, into the underground water - 151,896 kg.
- The estimated yearly potential load of phosphorus into surface water is 5,430 kg; into underground water - 181 kg;
Quantity of wastes arising from wine and eggs production process, and other small-scale economic activities, as well as quantity of hospital, mining, and construction and demolition wastes is unknown but was estimated as relatively small.
Official data on application of mineral and organic fertilizers at the arable lands in the area of concern are contradictory but nevertheless, it is obvious that current use of agro-chemicals by agricultural enterprises is minimal.
Potential for Persistent Organic Pollution includes improperly arranged disposal of out-of-use pesticides in village Cislita-Prut; old pesticide dump in village Chishmichoi situated at the distance of several kilometers from the Ramsar Site; power substation situated at the 15 km distance from the Ramsar Site; planned construction of an oil terminal, Oil Refinery, passenger and freight ports and associated infrastructure at village Giurgulesti.
Oil drilling. According to the project documentation, the total area to be used for oil drilling as well as associated facilities amounted 27,4 ha, i.e. its share is 1,6% from total surface area of Scientific Reserve, or 0,14% from the total surface area of the Ramsar Site. However, according to expert estimates the area directly affected by oil drilling and associated facilities is about 50 ha. In spite of such a small share the environmental impact arising from these activities could extend far beyond the immediate area.
In plawni between all exploited oil-wells (total number of which is planned to be 30) access road have to be built up. For that purpose the Company uses the local soil/ clay which is excavated from the open pits situated in local villages and which are easily washing out into the water thus significantly contributed to polluted sediment load into Beleu Lake.
Oil drilling operation site is not supplied with any drainage system that would collect the rain water and prevent washing out into the environmental media (soil, groundwater) technical oils and drilling mud, as well as of water used for cleaning up of such equipment as cementing pumping units. On the whole at present, the situation with liquid and solid wastes collection, disposal and treatment is not clear.
The Waste Study demonstrated that oil drilling is the major factor affecting quality of Beleu Lake and adjacent territories, and significantly contributing to deterioration of environmental conditions in the Ramsar Site.
Domestic and animal solid and liquid wastes are the major potential diffuse sources of surface water, groundwater and soil pollution in the Ramsar Site which can pose a health and environmental risk.
Domestic rubbish scattered around practically all villages but especially near villages Manta and Pascani situated near Manta Lake along with contribution to water pollution, have a great negative aesthetic impact on the Ramsar Site.
Soil Erosion Study. The goal of Soil Erosion Study was to collect and analyze information on soil erosion process in the Lower Prut Lakes watershed with special regard to assessment of soil erosion contribution into sediment load into the Ramsar Lakes, soil type and soil composition in the Ramsar Site and relevant part of the lower Prut River basin, extent of erosion evident and ongoing trends, and also to towards developing of Priority Action Plan aimed at mitigation of relevant impact on water and sediment quality, and reduction of sediment load.
Southern part of Moldova is situated on the South-Bessarabian plain (Budjac steppe), and is characterized by relatively quiet plain-wavy relief, and is the warmest and droughty region in the country. The watershed is characterized by relatively flat relief and represents the system of terraces with ledges, hillsides along small rivers and rills, gullies and Prut's floodplain.
Surface area of eroded lands in the region increased on average by 6%; the share of slightly and heavily eroded lands increased by about 15% while the share of moderately eroded lands decreased by 10%. Moreover, the share of heavily eroded lands increased on the territories adjacent to Manta, Valeni and Slobozia Mare villages, i.e. on territories the sediment runoff from which directly affect Manta and Beleu Lakes.
Generally, in the Prut River floodplain the soil of heavy granulometric composition considerably prevails. Peculiarities of geo-morphological structure of the territory and character of the deposits' surface have conditioned the steep predominance heavy-loamy soils and ordinary loamy soils in terraced part of the sub-region
Share of the soil types in the Lower Prut Lakes site was estimated as follows: loams - 27%; carbonated chernozems - 28%; meadow chernozems - 4%; alluvial soil - 29%; heavily eroded soils - 12%.
The relief in the lower Prut River basin is low-billowy and represents the system of terraces with ledges, hillsides along small rivers and rills, gullies and Prut's floodplain. On the whole, there were determined four types of drainage areas in the lower Prut River basin.
First type of drainage areas having small- and medium-size (from 20 to 500 ha)are situated on the Prut River left bank They are stretched along Prut's valley and enter the valley by a broad front of dispersed waterways. On such slopes sheet and rilling erosion dominate. These drainage areas are characterized by relatively gentle slopes with inclination up to 5-60. The major part of the territory (70-80%) occupied by such slopes has an inclination 3,50, and only lower transitional part from the slope to floodplain (in some places its width may reach up to 125 m) has an inclination more than 100. These slopes practically are not damaged by linear erosion (ravines). Only two drainage areas are damaged by linear erosion in the lower riverside. One area is situated between villages Vadu lui Isac, another - between southern border of village Valeni and central part of the village Slobozia Mare.
Second type is represented by drainage areas of a small and medium-size gullies (500-1,000 ha). They are stretched from the floodplain into the hearts of slopes (in eastern and north-eastern directions); the length of these drainage areas amounts 3-5 km; approximately the same is an average length of surface waterways. Peculiarities of these drainage areas are gentle right slopes (1-50) and steep left slopes (usually 5-100 but in separate cases inclination may reach 20-220). Besides, right slopes are eventually not damaged while damaged left slopes occur rarely. Run-off of superficial water happens by concentrated flow.
Typical representatives of these drainage areas are those of a small river Crihana (vil. Crihana), Baragina gully and Bozu gully (vil. Manta), Unguru gully (vil. Vadul lui Isac) and nameless gully northward village Colibas. Peculiarities of these drainage areas are gentle right slopes (1-50) and steep left slopes (usually 5-100 but in separate cases inclination may reach 20-220).
Third type of drainage areas is ravine-gully systems. Northern border of these areas is situated southward village Colibas while southern border is situated 1,5 km southward village Valeni. This kind is constituted by large ravines with numerous branches represented ravine systems In this section drainage areas are very damaged by linear erosion. As in a case of second type, superficial water drains by concentrated flow. The typical feature of these drainage areas is very strong terrain irregularity cut by ravines and presense of a network of small shallow gullies contributing to diversity of soil coverage. On these drainage areas the surface area of hillsides with inclination more 80 varies from 30 to 60%.
Fourth type is represented by large-scale drainage areas: Habzeu valley entering the floodplain southward village Colibas, and Tatarca gully entering directly the Prut River near the southern part of village Slobozia Mare. The surface area of Habzeu valley is 1,490 ha, length - 8 km; the surface area of Tatarca gully is 2,900 ha, length - 16 km. Within these drainage areas smaller ones can be marked out; these small drainage areas are characterized by their specific peculiarities.
One of the typical feature of above drainage areas is their meridianal stretching, gentle right slopes and gentle upper reaches of gullies whose inclination is 3-50 and more steeper left slopes with inclination 6-140. As in the drainage areas of smaller gullies of second type, right slopes are not damaged by ravines while linear erosion is manifested only by small and very small narrow gullies. Left slopes are damaged by large and small isolated ravines and also by ravine systems. Mouth parts of the drainage areas are exposed to especially strong linear erosion.
Estimation of average annual Sediment Runoff from above affecting drainage areas into the Ramsar lakes due to water erosion was determined according to Mirtzhulva's method with taking into consideration correction factors relevant to slope's shape, soil type, grading of the soil and soil erosion state.
The Soil Erosion Study showed that presently there exists no erosion control in the area, and soil erosion contributes significantly to sediment load into Ramsar Site.
- Estimated sediment load into Ramsar Lakes amounts 104,129 tons per year; total drainage area immediately affecting the Ramsar Lakes by sediment runoff is 3,008 ha.
- Estimated total sediment load into the Lower Prut Lakes floodplain amounts 278,180 tons per year; total drainage area immediately affecting the floodplain by sediment runoff is 10,650 ha. These data can be considered as a baseline ones to be used for further relevant investigations in the area.
Taking into consideration dimensions of the lakes, the greatest impact due to sediment runoff experiences Brinza Lake what is line with hydro-chemical, hydrological and bioassessment data.
The Manta Lake, especially in its southern part, is exposed to severe impact due to sediment runoff as well.
Geo-morphological and climatic conditions in the area indicate that such a tendency will remain within long period of time. Embankment of ravines and cliffs to re-orient sediment runoff directly to the Prut River and thus prevention of Ramsar lakes form over-sedimentation seems to be not reasonable (or need closer investigation) since one tone of sediment runoff contains 10-15 m3 of groundwater, and separation of runoff from the lakes may disturb/ change water regime over time.
Soils in the Prut River floodplain are characterized by heavy granulometric composition while local sub-regional chernozemes have a light granulometric composition and therefore are easily exposed to washouts even on gentle slopes; among washed out soils weakly eroded one prevail (10,3%). In the area of concern on hillsides light soil easily exposed to erosion prevails; on the tops of terraces non-eroded and weakly eroded carbonated chernozems predominate. Composing the terraces' thickness loessy loams and soil forming on them are easily exposed to destroying impact of erosion. For that reason, ravines are being formed in the area even on the slopes with low inclination.
In the terraced part of the sub-region heavy-loamy soils, ordinary loamy soil (27%) and carbonated chernozems (28%) prevail; loamy soil are on 90% full-profile, carbonated chernozem - on 50%. About 4% of the territory is covered by meadow-chernozem inwashed soils, and more than 29% belong to all categories of alluvial soils.
Geology and Geo-Morphology Review. The goal of Geology and Geo-morphology Study was to collect data on evolution through time resulted in modern geological and geo-morphological conditions in Moldova and especially in its southern part, and on associated with river structures what could represent an information potentially needed for wetland managers.
The geological structure of the area is characterized by tertiary sediments (clay, fine-grained sand, loam, and limestone), which almost everywhere reaches the surface of the slopes; often gullies and valleys occur at these locations. On the surface of interstream plateaus and slopes, the alluvium layer of tertiary rocks is found where soils have been formed.
One of the peculiarities of the geological structure of Moldova's highlands is its alternation of light sand aquifers and impermeable heavy clay layers, increasing the risk of soil erosion processes.
The terraces of the Prut River as well as most of the other rivers in the basin reach an altitude of a maximum 220 m. They are covered by quaternary loess loam. This rock is also soil forming and has a high erosion risk.
Geology. On the territory of Moldova Quaternary deposits are to be found practically everywhere. Normal thickness of Quaternary deposits consists of 2.0 - 15 m, and locally may reach more than 15 m. In fact, in the outermost southwest in the Prut's River valley the estuary-marine deposits - sands, loamy sands, and clay with thickness up to 25 m were found. Inegmentary formations in way by cloaks collide the watersheds, slopes and alluvium of rivers' terraces. In the direction from the north to the south their cross-section and thickness increase. In regions with negative neotectonic movement their thickness may reach 30 or even 50 m (as near town Cahul).
Modern alluvial formations play the vital part for water supply purposes. These formations are represented by deposits of high and low floodplains; and their thickness may reach 30 m. In the lower course of the Prut River alluvial deposits either have a thickness several meters or absent at all.
Geo-morphology. The lower Prut area site is situated in the south of Moldova and borders to the west (along Prut River) with Covurlui plane (the territory of Romania); to the south with Lower Seret low plane; to the east - with Cotlabuh low plane and Middle Cogilnic Hills, and to the north - with Tigheci Hills and Ialpug plane.
On the larger part of territory the value of a vertical partitioning rarely exceeds 70 m; to the south it slightly decreases. The ancient erosion partition in the northern and north-eastern parts does not exceed 1,8 km/km2 while in the southern part it decreases to 0,8-1,5 km/km2.
The flat watersheds are represented by alluvial late-Pliocene accumulative surface of levelling with rare outliers of eluvial-defluctional surface.
The most profoundly rivers' terraces are represented in the northern part of the area on left-bank slope of the Prut River between village Andrusul de Jos and town Cahul where all terraces revealed in the given territory (from II to XIII terraces) were discovered. Near town Cahul some terraces are eroded, most often it relates to VII and rarely - to IV terraces. In the slope section between villages Manta and Valeni II over-floodplain terrace is absent while between villages Vadul lui Isac and Valeni only isolated fragments of III, IV and V terraces are revealed. Above them Pliocene terraces are well traced already. Southward village Cislita-Prut III (lakustrine-marine), IV and V (estuary-marine) terraces were formed which along with usual for alluvial terraces sand, gravel, pebbles, boulders the presence of clay streaks is typical
On the south of Moldova the areas having altitude marks at level of VI terrace's surface (150m) as well as lower areas had been making a fire repeatedly and covered by sub-aquatic sediments. As a consequence of this, middle and lower terraces of the Prut River built of loessy loams and loess. Depressed planes in the south of Moldova the altitude of which coincides with sea level are covered by the same deposits.
Loessy loams serve as soil-generating rocks of Moldova's southern watersheds and terraces.