The Characteristics of the Chemical Flow Within the Motru

Cent. Eur. J. Geosci. • 3(1) • 2011 • 39-43 DOI: 10.2478/s13533-011-0006-6

Central European Journal of Geosciences

The characteristics of the chemical ﬂow within the Motru catchment area, south – west Romania

Communication

Oana Ionuș∗

University of Craiova, Geography Department, A. I. Cuza Street, No.13, Code: 200585, Romania

Received 19 November 2010; accepted 11 January 2011

Abstract: The present paper, with reference to the Motru catchment area, contributes to the hydrochemical studies at an international level and to the completion of the characteristics regarding the chemical flow in Romania. In this regard, it emphasizes once again the dependence between the content of dissolved salts (fixed residue - mg/l) on the one hand and the lithological conditions, human activity, flow and the surface of the catchments on the other hand. The calculation and the analysis of the chemical flow for the Motru catchment area (located in the south-west of Romania) was performed on the basis of two parameters: the average flow of dissolved chemical substances (mg/s) and specific average chemical flow (t/kmp year) recorded at the monitoring stations on the Motru River and its tributaries during the period 2005-2009. The values obtained (for example: 2.63 mg/s and 47.7 t/km2 year, at the Fata Motrului station, on the Motru River, in 2009) confirm the importance of the areal factors of natural background in the analysis of chemical flow as a morpho-dynamic process and implicitly for the chemical quality of surface waters. Keywords: fixed residue • average flow of dissolved chemical substances • specific average chemical flow • chemical flow © Versita Sp. z o.o.

1. Introduction age flow or drainage of dissolved substances. The studies give at the same time, the first regional information regarding this hydrochemical parameter. The terminology The chemical flow is defined by Trufaș V. [1] as “the flow of is widely diversified: analysis and chemical values (the dissolved solved substances which can be analyzed as the chemistry of the rivers [1]); hydrological characteristics value of the ionic flow or as a ratio between the ionic flow (the physical and chemical transport for the surface wa- and the surface unit – specific ionic flow”. All these values ters [2]; the content, the concentration and the specific form the hydrochemical regime that is set up based on flow of dissolved solid substances from the waters trans- the annual characteristic values (average, maximum and ported by the rivers [1]) and geomorphological estimations minimum) for the total content of dissolved salts (fixed (the erosion and chemical denudation [3]). residue). The international research of the theoretical, methodolog- In the national studies from the middle of the 20th century ical and practical issues in water erosion and nutrient the notion of chemical flow also refer to the specific aver- transport takes a multidisciplinary and integrative ap- proach. “The interactions between landscape pattern and ∗E-mail: [email protected] nutrient transport processes and spatiotemporal scale and

39 The characteristics of the chemical ﬂow within the Motru catchment area, south – west Romania

scaling are the two central themes of reflection in method- Given the vertical zoning of the catchment area on a relief ological integration [4]”. level difference of approximately 1 700 m (between 102 m at the confluence with the Jiu River and approximately According to Tardy Y. [5] “the chemical erosion (which 1 800 m at the bottom of the Orlea peak), the variety of ge- precedes the mechanical erosion) correspond to the rock omorphological units leaves its footprint on the character- weathering by hydrolysis or dissolution, modifying the in- istics of the surface water drainage. In its basin, the Motru ternal horizons of the alteration profiles, with a conse- River receives 13 tributaries on the right side (Scarisoara, quent transport to the rivers, as dissolved chemical sub- Motrul Sec, Brebina, Crainici, Peșteana, Gârdoaia, Lupșa, stances”. Coșuștea, Jirov, Cotoroia, Hușniţa, Slatinic˘ and Tal˘ apan)˘ The relation between the chemical erosion rates and the and 3 tributaries on the left side (Lupoaia, Ploștina and characteristics of catchment areas is described for the Hi- Stângaceaua).˘ malaya and the Indian regions by Tripathy G. R. & Singh K. S. [6] (...“the chemical erosion rates in the river basins could be due to intense physical erosion caused by their higher relief and runoff”...) and respectively by Bikshama- 2. Material and methods iah G.& Subramanian V. [7] (...“while geology is a control- ling factor from a quality point of view, discharge and ele- The determination of the characteristics of the chemical vation control quantitatively the annual mass transfer”...). flow in the Motru catchment area was based on the correlation between the flows of dissolved substances and the Taking into consideration the fact that the chemical flow water flows. The following formula proposed by Trufaș is a subject of international interest, strongly debated in V. [3] was used : Romania in the ‘70s and ‘80s (with only one study in the Rc = Q x (Rf / 103); Siret catchment area, in the east of Romania), the present Rc (mg/s) – the average flow of dissolved chemical sub- paper will underpin the importance of this parameter as stances ; an element for expressing the chemical quality of rivers. Q (m3/s) – the average liquid flow ; The study area is the Motru catchment area (1 895 km2) Rf (mg/l) – the average value of the fixed residue . which covers several geomorphological units: the moun- The specific average chemical flow of dissolved salts is tain, the Subcarpathian sector and the piedmont ( Fig- another way of expression for chemical flows proposed by ure 1). Trufaș and it is defined as “the amount of salts that flows in the time unit per area unit (surface of the catchment area) and it is expressed in kg/km2 s, t/km2, t/hectares year [1]”: p (t/km2 year) = P (kg/s) 31,56 ·106 / F (km2) 1000 p – the specific average chemical flow ; (the average amount of salt that flows in a year on a km2); P – the multi-annual average flow which flows through every section in the time unit ; F – the catchment area; 31,56 ·106 – the number of seconds in a year.

The scientiﬁc research is based on the application of the two calculation formula and the temporal and spatial analysis of the results. Therefore, for the analysed period (2005-2009), data on hydrometric activity supplied by the Jiu Water Branch of the Romanian’s National Water Ad- ministration (6 hydrometric stations: Cloșani, Broșteni, Faţa Motrului, Baia de Arama,˘ Corcova and Strehaia) has been correlated with data from the monitoring activity of the surface waters (7 monitoring stations: Cloșani, Figure 1. The hypsometry of the Motru catchment area and the lo- Brošteni, Faţa Motrului, Gura Motru, Baia de Arama,˘ Cor- cation of the monitoring and hydrometric stations. cova and Strehaia).

40 Oana Ionuș

3. Results and discussions

In order to calculate the chemical flow in the Motru catchment area, the main calculation source used was the value of fixed residue (Rf, mg/l). It is the concentration of dissolved solids in rivers, recorded at 7 stations within the monitoring network (4 stations on the Motru River and 3 stations on its main tributaries – the Brebina River, the Coșuștea River and the Hușniţa River) on a 5 year period, 2005-2009. Thus, the concentration values of dissolved salts from the recorded rivers fall in the interval of 51–447 mg/l for the monitoring stations Cloșani (2006) and Strehaia (2007) respectively, thus falling in the interval of 37–8000 mg/l given by Varduca A. [2] for running surface waters in Ro- mania. By comparing the annual average values of fixed residue with the values of specific average chemical flow at Faţa Motrului station in the 2005–2009 period, there is a dis- crepancy in 2007 (a decrease of the liquid flows and an increase of the dissolved salts due to the high tempera- ture and severe drought in summer). It reflects the special role that climatic factors play in the process of flow and Figure 2. The seasonal variation of the fixed residue values at the chemical flow – carrying the salts from the soil surface monitoring station in the Motru catchment area (2009). and conditioning their passage towards the river beds [8]. The seasonal distribution of dissolved salts concentration at the Faţa Motrului station in 2009 is similar to the liquid frequently exceeded at the level of the entire region ana- flow, with the lowest values in autumn (23%) and winter lyzed, the years with the highest values being 2000, 2003, (22%) and the highest in summer (28%) and spring (27%) and 2007 [10]”. (Figure 2). These values can be compared to the val- The intensity of the dissolved substances transport per ues calculated by Trufaș V. for the Siret catchment area: unit area is due to the specific average chemical flows spring (35-45%) and autumn (13-16%) [9]. The differences calculated according to the second calculation method. are not only the result of changes in the annual flow dis- While for the entire area of the country the specific chem- tribution but also of the prevalence of different supplying ical average flow equals 100 t/km2year [11], in the Motru sources for the rivers in the two catchment areas. catchment area the values of specific average chemical By applying the first calculation method mentioned above, flows (the Brebina catchment area – 119.27 t/km2 year, the a variation of the average flow of solved chemical sub- Coșuștea catchment area – 66.5 t/km2 year, the Hușniţa stances is found, depending on the location of the moni- catchment area – 26.77 t/ km2year and the Motru catch- toring station along the watercourse, source – river mouth. ment area – 47.7 t/km2 year) (Figure 3) are situated in For instance, the Cloșani station presents low values due the intervals calculated by Trufaș V. and correlated with to its location in the upper Motru catchement area, down- the major relief units: <50 t/km2 year, 50-100 t/km2.year, stream to Valea Mare reservoir and the Faţa Motrului sta- 100-200 t/km2year and >200 t/km2 year [3]. tion presents high values due to its location in the lower The highest value during the analysed period of time Motru catchment area with the highest values of flow and was registered in 2005, at the Faţa Motrului station the anthropogenic sources of pollution (the Broșteni and (115.17 t/km2 year). The year 2005 is an important year the Strehaia stations, which are located downstream from from the point of view of the extreme hydrological phe- the discharge of untreated sewerage from the Motru and nomena, with the value of the flow of 12 988 l/s km2 [8]”. Strehaia towns, record high values). For the annual variation of the average flow of dissolved Given the fact that ”during the year, the flow and concen- substances, the year 2007 is recorded at most stations tration regime of dissolved substances comes under the in- because of the decrease of the flow values, the climatic fluence of soil washing processes and rocks [9]” and of ge- factor being the most important: “the 22oC threshold was ological diversity among the areas related to the gauging

41 The characteristics of the chemical ﬂow within the Motru catchment area, south – west Romania

Figure 3. The distribution of the speciﬁc average chemical ﬂow in the Motru catchment area (2005-2009).

42 Oana Ionuș

References stations and the flows of dissolved substances, a unique connection is not yet possible. The large amounts of the specific average chemical flow in the Brebina catchment [1] Trufaș V., Trufaș C., Hidrochimie [Hydrochemistry]. area (119 t/km2year) is largely due to the lithological Bucharest University Publishing House, Bucharest, formation predominantly of karst and they can be com- 1975 (in Romanian) pared to the values given by Trufaș V. for Banat Moun- [2] Varduca A., Hidrochimie și poluarea chimica˘ a apelor tains (where the carbonate rocks also occupy considerable [Hydrochemistry and chemical water pollution]. Tem- areas). pus Collection, H.G.A. Publishing, Bucharest, 1977 However, in terms of specific flows of dissolved solids ”val- (in Romanian) ues are approximate because each square km (ha) from the [3] Trufaș V., Popescu N., Patroescu˘ Maria, Eroziunea surface of a river basin does not contribute in an equal way și denudașia chimica˘ pe teritoriul României [Chemi- to the formation of the flows of dissolved substances [1]”. cal erosions and denudation in Romania’s territory]. Probleme de Geomorfologia României, 1988, 2, 97- 106 (in Romanian) 4. Conclusions [4] Lü Y., Fu B., Chen L., Liu G., Wei W., Nutrient transport associated with water erosion: progress and The importance of the present paper lies in the fact that by prospect. Prog. Phys. Geog., 2007, 31, 607-620 analysing the chemical flow in the Motru catchment area [5] Tardy Y., Erosion. In: Encyclopedia Universalis, Uni- (the concentration of the dissolved salts, the average flow versalis Editons, Paris, 1990, 8, 615-627 of dissolved chemical substances and the specific chemical [6] Tripathy G. R., Singh K. S., Chemical erosion rates average flow) we can: of river basins of the Ganga system in the Himalaya. Geochem. Geoph. Geosy., 2010, 24, 1159–1171 • compare the values obtained with values from pre- [7] Bikshamaiah G., Subramanian V., Chemical and sed- vious specific papers: the values of dissolved salts iment mass transfer in the Godavari River basin in from the recorded rivers are situated in the inter- India. J. Hydrol., 1980, 46, 331-342 val of 51- 447 mg/l, a sequence on the interval [8] Ionuș O., Drainage Evolution Determined by the Dy- 37 – 8000 mg/l given by Varduca A. [2]; the val- namics of Forest Areas within the Motru Hydro- ues for the specific chemical flow from 2009 (the graphic Basin. Geographical Phorum, 2009, 8, 97- Brebina catchment area – 119.27 t/km2 year, the 103 Coșuștea catchment area – 66.5 t/km2 year, the [9] Trufaș V. Chimismul apei râurilor [Rivers chemistry]. Hușniţa catchment area - 26.77 t/ km2 year and In: Badea L., Gâștescu P., Velcea V. (Eds.), Geografia the Motru catchment area - 47.7 t/ km2 year) fall României, Geografie fizica˘ [Geography of Romania, within the intervals calculated by Trufaș V. [1] and Physical Geography]. Publishing House of the Ro- correlated with the major relief units; manian Academy, Bucharest, 1983, 341-345 (in Ro- manian) • use the analysis to emphasise the correlation be- [10] Vladuţ˘ A., Ecoclimatic indexes within the Oltenia tween the content of dissolved salts and the flow, Plain. Geographical Phorum, 2010, 9, 49-56 the surface of the catchment areas and the litho- [11] Trufaș V., Patroescu˘ M., Caracterizarea fizico-chimica˘ logical contents, confirming at the same time that a apei râurilor [The physicochemical characteristics of these chemical elements have a natural origin, thus the rivers]. In: Trufaș V. (Ed.), Chimismul apei râurilor they do not indicate pollution [12]. din bazinul hidrografic al Siretului [Rivers chemistry within the Siret catchment area]. Bucharest Univer- sity Publishing House, Bucharest, 1980 (in Roma- Acknowledgements nian) [12] Ministerul Mediului si Gospodaririi Apelor (The The research was achieved within the framework of a Ministry of Environment and Water Management), grant offered by the Simion Mehedinţi Doctoral School Normativului privind clasificarea calitaţii˘ apelor de (Faculty of Geography, University of Bucharest), project suprafaţa˘ în vederea stabilirii starii˘ ecologice a cor- co-financed through the Sectoral Operational Programme purilor de apa,˘ Ordin nr. 161/2006 [The Standard re- for Human Resources Development 2007-2013, POS- garding the classification of the surface waters qual- DRU/6/1.5/S/24/7546 Contract. ity in order to establish the ecological status of the water bodies], Order no 161/2006, Official Gazette, no. 511 of 06.13.2006 (in Romanian)