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Qualitative Status Analysis of the Phreatic Aquiferin the Barlad River Flood Plain

concerning the Nitrogen-Based Compounds

Rodica Macale, Doina Dragusin

National Institute of Hydrology and Water ManagementBucharest, ROMANIA

Abstract:In order to implement the 2000/60/EC Water Framework Directive in Romania, a qualitative analysisof groundwater in the Barlad River flood plain was made, because it was considered that thegroundwater body is at risk from this point of view. The normal concentrations of Ammonium ion wereexceeded in 49% of the total number of analyzed mean annual values. The used data comes from 31observation wells of the Groundwater Quality Monitoring National Subsystem, during 1997 2004.The preliminary data were statistically processsed. The results of this study are represented on GISmaps and charts.The phreatic aquifer is developing in the flood plain and terraces of the Barlad River and its tributaries.From lithological point of view the aquifer is porous-permeable, has large values of hydraulicconductivity and a poor protection of covering deposits, explaining its high vulnerability to pollution.

Key Words: Barlad River flood plain, groundwater body at risk, vulnerability to pollution.

IntroductionThe implementation of the Water Framework Directive 2000/60/EC in Romania, regardinggroundwater, assumed identification, delimitation and characterisation of groundwater bodies on thebasis of geological and hydrogeological criteria, of potential and existent anthropic influences uponthe groundwater bodies quantitative and qualitative status as well as of some water sustainablemanagement criteria.The groundwater body situated in the Barlad flood plain and terraces, presented in our study, are

developed in the eastern side of Romania, in Prut river basin (Fig.1). The area of this body is 1186km2.

Barlad river representes the left tributary of Siret river and it is in charge of Prut Water Directorate.

Figure 1. Location of study area in the Danube river basin

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Geomorphological considerationsThe Barlad Valley is like a depressionar couloir that enlarged to the south, and has a consistentcharacter both upstream of confluence with Rebricea and downstream of Crasna locality.The absolute altitude of Barlad flood plain varies between 53 m, to the south of Barlad town, and154 m to the north, in the eastern part of Bacesti locality.Accumulation relief is represented by the terraces, flood plain, alluvial fans etc.

The terraces are well developed on the Barlad valley. Beginning to Bacesti locality, on the left ofBarlad, there are developed seven terraces, having the following relative altitudes: 3-7 m, 15-20 m,60-70 m, 100-110 m, 130-135 m, 150-170 m and 190-195 m. The largest development presentterraces of 15-20 m and 60-70 m, which appear like smooth plates (Gugiuman et al., 1973).On the tributaries of Barlad river and of the lower streams of Rebricea, Vaslui, Crasna, Lohan, Similaand Tutova valleys are more developed the lower terraces (3-7 m and 15-20 m).The flood plains are the youngest and better representated accumulation forms and they aredeveloped in all valleys independent of their length. Their width is very large in comparison of river orstream bed which formed and pierced them, e.g. 1.5-4 km to Barlad and 1-2 km to Racova , Vaslui,Crasna and Elan.In Barlad flood plain are numerous microforms of relief like: levees, meanders, depressionar formswhich retain temporary or permanently meteoric water. They can create swamps and pools ofdifferent dimensions, left branches, alluvial fans and small glacis.

The main tributaries of Barlad, from Moldavian Plateau are, on the left, Fundatura, Dagata, Sacovat,Stavnic, Rebricea, Vaslui and Crasna and, on the right, Buda and Racova (Fig. 1). The lengths ofthese streams are comprised between 15 and 65 km.Downstream of confluence with Crasna, Barlad valley is orientated southeastward and receives thetributaries from Tutovei Hill, on the right: Horoiata, Simila, Valea Seaca, Tutova and Pereschivul. Thestreams Albesti, Idrici, Zorleni, Trestiana, Jeravat, Hobana and Barzota are the left tributaries ofBarlad and they move down from Falciului and Covurluiului Hills.

Geological and hydrogeological characterizationCriterium for delineation the groundwater body is the development in the Holocene porous-permeabledeposits of the shallow aquifer situated in the flood plain and terraces of the Barlad river and histributary.The lithological composition of water bearing deposits is the following: sands with gravel elements andargillaceous interbeds. The thickness of permeable deposits is about 2 5 m and it doesnt exceed 10m (Fig. 2 and 3).Barlad flood plain and terraces contain an unconfined aquifer, who was emphasize through theNational Hydrogeological Network wells.The impermeable bed of the phreatic aquifer consists of clays or marls and it was intercepted to thedepths between 5 and 20 m. In Ghidigeni area, these deposits can be seen in the cross-sectionperformed on the basis of information given by the hydrogeologic Station wells. (Fig. 4). The thicknessof porous-permeable deposits vary between 2 and 10 m. Generally, it can be observed a thicknessincreasing of these deposits from north to south, from 2-6 m at Ghidigeni zone to 12 m at Tiganestiand 17 m to Tecuci.In Barlad flood plain there were obtained yields of 0.5 2.8 l/sec./well; the aquifer is situated between7 11 m depth and it is formed from fine and coarse sands and gravels.The lower terrace of Barlad is broken and intensely drained; there are springs with yields of 0.1 0.3l/sec. to its basis. The yield of the springs that appear at the basis of medium terrace is of 0.5 0.6l/sec.In the middle basin of Barlad there are a lot of springs that catched by Valea Mare, Valea arinei andValea Seaca and, the other, from Zorleni, Fagadau and Grivia hills, that are yield of about 1l/sec.The aquifer from terraces was studied in Ghidigeni area by means of many wells. So, the well F32presents a lithological series that is constituted by an alternation of clays and marls with fine and siltysands. Below a pile of clayey marls there are a fine marly sand with iron oxides situated between12.05 and 12.95 m.In the deposits of the lower basin of Barlad there is an unconfined aquifer that has, locally, artesiancharacter (the artesian level is 1.5 2 m); these deposits are situated between 2 and 7.5 m depth andare constituted from sand and gravel.Around Barlad town, the flood plain and terraces deposits of Barlad Valley are representated by fine

coarse sands and gravels with crossing structure.The overlying stratum consists by thick impermeable deposits of clays, silts and clayey silts (2-10 mthickness).

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In many cases, due to impermeable deposits from the cover of aquifer the level is ascensional andsometimes strongly ascensional.At Ghidigeni and Tiganesti, that are situated in flood plains of Barlad river, there are an artesianaquifer at a small depth (until 30 m).Shallow aquifer recharge sources are represented by the river infiltration and precipitation (theeffective infiltration is 15 63 mm/year).

The groundwater resources from Barlad flood plain are, generally, reduced and the yields obtainedfrom the wells rarely exceed 3 5 l/sec./well. The groundwater resources from Barlad tributary aresmaller, respectively (F1 Codaesti) of 1-3 l/sec./well.The hydrogeological parameters values are: the hydraulic conductivity rarely exceed 50 m/day, thevalues are situated between 1.1 m/day (F1 Condeesti) and 35 m/day (F1 Bacaoani), due to the finegranulometry of deposits; transmissivity has values between 10 100 m

2/day (in the Barlad flood

plain the transmissivity are higher, of maximum 500 m2/day). The specific yield values are 1 5

l/sec./m, the higher values from this zone were determinated at Torcesti hidrogeological Station(3.65 l/sec./m), at Simila hidrogeological Station (4.20 l/sec./m), at Calieni hidrogeological Station(4.80 l/sec./m) and 8.70 l/sec./m in Serbanesti zone.The fine granulometry of the alluvial deposits, the lens-shaped character of the gravel and theimpermeability of the overlying stratum have a negative influence for quantity and quality of phreaticwaters, determining a higt vulnerability to pollution.

Figure 5 presents the phreatic groundwater body and the position of geological cross-sections troughtmonitoring wells.

Figure 2. Geological cross-section through the Maraseni hydrogeological Station

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Figure 3. Geological cross-section through the Sarbi hydrogeological Station

Figure 4. Geological cross-section through the Ghidigeni hydrogeological Station

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Figure 5. Groundwater body delineation into Barlad river basin

Evolution of the Nitrogen-Based Compounds ConcentrationsThe analyses of the Nitrogen-based compounds concentrations evolution from the Barladgroundwater body was based on the mean annual values provided from 31 monitoring wells for 8years interval (1997-2004). Groundwater samples from these wells were taken in order to measurethe main indicators of the drinking water, according to the Romanian Law No. 458 /2002. From thetotal number of analysed samples, 11% exceed the maximum admissible concentration for nitrates, 8% for the nitrites and 49 % for the ammonium.

0

10

20

30

40

5060

70

80

90

1997 1998 1999 2000 2001 2002 2003 2004

Period (year)

Concentration(mg/l)

DORASTI F1 DORASTI F2 DORASTI F3

DORASTI F4 DORASTI F5

Figure 6. Evolution of nitrates concentration in the wellsof the Dorasti Hydrogeological Station

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0.00

0.20

0.40

0.60

0.80

1.00

1997 1998 1999 2000 2001 2002 2003 2004

Period (year)

Concentration(mg/l)

DORASTI F2 DORASTI F3 DORASTI F5

Figure 7. Evolution of nitrites concentration in the wells of the Dorasti Hydrogeological Station

0.00

0.50

1.00

1.50

2.00

2.50

1997 1998 1999 2000 2001 2002 2003 2004

Period (year)

Concentration(mg/l)

DORASTI F1 DORASTI F2 DORASTI F3

Figure 8. Evolution of ammonium concentration in the wellsof the Dorasti Hydrogeological Station

These graphical representations denote the exceedings of the limit value, underlined by the red line(05. mg/l for nitrites and ammonium and 50 mg/l for the nitrates).

The qualitive status and trend assessment of the Nitrogen-based compounds

The Working Group which deals with the European concerning groundwater Directive in CIRCA(Communication Information Resource Centre Administrator), has proposed, in the paper entitledStatistical aspects of the identification of groundwater pollution trends, and agregation of monitoringresults (Grath et al., 2001), a methodology in order to asses the qualitative status of the groundwaterbodies.In Romania, the National Institute of Hydrology, Departament of Hydrogeology and EnvironmentalIsotopes, has applied this particular assessment methodology (Dragusin, 2004; 2005), followingseveral steps:1. To calculate the biannual and annual mean value of the nitrates, nitrites and ammonium, for eachof the 31 investigated quality monitoring wells, situated on the studied groundwater body;2. To delimitate the groundwater body, based on the ARCGIS 8.3. software;

3. To delineate the area of the groundwater body (by using the coordinates of the domain inSTEREO 70 projection and by saving the files with an *.wmf extension), using SURFER 7 soft;

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Figure 11. The previous matrix running in GWStat soft

Figure 12. Trend assessment GIS view in GWStat soft

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Figure13. The variogram and the main statistical parameters obtainedfor the ammonium mean annual concentration

Figure14. Monotonic trend assessment in GWStat soft

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Figure 15. Trend reversal assessment in GWStat soft

Conclusions

In this paper we analysed the mean annual values of the Nitrogen-based compounds (nitrates, nitritesand ammonium) for a number of 31 wells, belonging to the National Hydrogeological Network, duringthe1997-2004 period. The most significant exceedings, were registered for ammonium (49% from thetotal of 282 values).A qualitative risk assessment was made on the Barlad groundwater body, based on the registeredexceedings in ammonium. These exceedings have as a potential source the agricultural activities,although in the region an antropic pressure due to industrial activity is known.

To underline the exceedings of the above-mentioned indicators of admissible maximumconcentration, graphical interpretations were achieved. The charts, presented for the DorastiHydrogeological Station, emphasize that the Nitrogen-based compounds contents evolution ishazardously.This paper is also focused on the qualitative status assessment of the Barlad grounwater body, byusing the recommendations of the European Community Guide (Grath et al, 2001).The results of the chemical data processing provided from the 31 monitoring wells are:

The calculation of representativity index, RU, indicates the value of 21.5%, which issignificantly lower than it was recommended by the EU, respectively 80%, but that is the consequenceof the unidimensional shape of Barlad groundwater body;

The status assessment, for which we obtained the variogram and the following statisticalparameters: the arithmetic mean (AM) = 1.056 with the upper confidence limit (CL(AM)) = 1.567, theKrigging mean(KM) = 1.096 and its upper confidence limit (CL(KM)) = 2.233;

The monotonic trend assessment, which indicates a general stationary tendency; The reversal trend assessment, which indicates a general hazardous tendency.In order to achieve a complete evaluation of the qualitative status of the groundwater bodies, weconsider that some supplementary data, such as the precipitation regime, the soil structure, thetemperature values, and the evapotranspiration, should be also included. A connection between thegroundwater bodies and the surface bodies waters must be also established.

References

Dragusin, Doina, 2004:Aplicarea Ghidului metodologic de evaluare a starii calitative a corpurilor deape subterane, propus de Comunitatea Europeana, la acviferele freatice din Romania, I.N.H.G.A.Scientifical Sesion, Apa dulce pentru viitor , Bucharest, RomaniaDragusin, Doina, 2005:Evaluarea starii calitative a corpurilor de ape subterane in conformitate cu

ghidul metodologic propus de Uniunea Europeana - Aplicare la acviferele freatice din Romania,Romanian Hydrogeological Association Symposium Resursele de ape subterane din RomaniaAspecte metodologice n contextul integrarii n Uniunea Europeana, Arcalia, Romania

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