UNIUNEA EUROPEAN GUVERNUL ROMNIEI MINISTERUL MUNCII FAMILIEI I

UNIUNEA EUROPEANĂ GUVERNUL ROMĂNIEI MINISTERUL MUNCII, FAMILIEI ŞI PROTECŢIEI SOCIALE AMPOSDRU Fondul Social European POS DRU 2007 -2013 Instrumente Structurale 2007 - 2013 OIPOSDRU Universitatea din Bucureşti Invest in human resources! This work was supported by project: POSDRU/88/1. 5/S/61150 “Doctoral Studies in the field of life and earth sciences”, project co-financed through Sectorial Operational Program for the Development of Human Resources 2007 -2013 from European Social Fund Particularities of the runoff in the Calmatui hydrographic basin in the Teleorman county Maria Albu Dinu 1, Lidia Sălăjan 2, Adrian Apostol 3 1, 2 University of Bucharest - Romanian 3 National Institute of Hydrology and Water Management of Bucharest - Romanian, 1

Table of Contents 1. Introduction 2. Results and discussions 3. Factors influencing the runoff regime in morphohydrographic basin – Teleorman county the Călmăţui 4. Characteristics of the runoff in the Calmatui hydrographic basin in the Teleorman county 5. Determination of the correlation curve for the minimum annual discharges in the Călmăţui hydrographic basin, according to the measurements taken at Crângu hydrometric station, over the period 1953 -2009 6. Calculation method for the correlation curves by using the Weibull, Kriţki- Menkel and Pearson’s methods 7. Conclusions: 8. References: 2

Introduction This study proposes an analysis of the runoff in the Călmăţui hydrographic basin in the Teleorman county. The main objective is to point out some specific characteristics of the basin, determined by the geographical position and its geological and geomorphological particularities. 3

Călmăţui basin is situated in the central part of the Romanian Plain 4

v From the geological point of view, the Călmăţui basin is covered by a continuous fine sediment layer (loess and loesslike deposits) dating from the mid-Pleistocene age, this are extremely permeable and friable, with a quasi-horizontal structure. These loess deposits can be found directly on the Frăteşti layers (E. Liteanu, 1961). 5 Călmăţui Basin. Map of soil parent materials

v The Boian Plain is characterized by quasi-horizontal interfluves, divided into fragments by the hydrographic network, made up of the Călmăţui River and its density of the tributaries. v The mean hydrographic network is of 0, 54 km/km 2, exceeding density of the mean hydrographic network in the Romanian Plain, which is of 0, 2 – 0, 3 km/km 2. 6

v The fragmentation density relief map reveals quite high values for a plain unit: 3 -4 km/km 2. The mean density of the hydrographic network (also taking into account the temporal hydrographic network) is of about 1, 25 km/km². The mean slope of the Călmăţui River is of about 1‰, favoring the meanders and the lateral erosion, as well as the alluvial deposits accumulation, reducing the capacity of transport of the riverbed and increasing the vulnerability to floods (Richards K. , 1985). 7

v The river slope is not constant, recording lower values (2‰) in the upper sector (between the spring and Balta Sărată) and even much lower in the middle and lower sector (0, 5‰, downstream the confluence with Calmăţuiul Sec River). The reduced slope and the alluvial flow of the Urlui River, favors the formation of significant alluvial deposits downstream the confluence and a new riverbed sector is born. v The longitudinal profile of the Călmăţui River presents a concavity in the upper reach, up to the confluence with the Călmăţuiul Sec River and a light convexity in the lower reach, indicating a rapid sinking. Geomorphologycal profile of Călmăţui valley 8

v The depth of the river in its middle sector, and particularly in the lower one, caused the formation of various springs and spring lines, through penetrating the ground water layer, at the same time preventing it from drying during the summer time Feeding of the Călmăţui River from the springs Feeding of the Urlui River from the springs 9

v The cross-cut profile of the lower sector of the Călmăţui River, points out the rapid deepening of this valley (70 m), and provides it with a unique character among other plain rivers. Cross-cut profile in the lower sector of the Călmăţui River 10

v This morphography (wide and deep valleys) favoured the construction of ponds along the main rivers. v Thus, along the Călmăţui River, 7 ponds were built, and along its tributary, the Urlui River, another 17, ressembling to a lakes necklace, able to reduce flood waves and provide the continuity of flow during droughty seasons Călmăţui River – middle sector Furculeşti pond on the Urlui River Călmăţui River – lower sector 11

v The mean annual air temperatures within the basin are of 10 110 C. The annual thermal regime presents its minimum in January ( -2…-30 C) and the maximum values are recorded in July (22 – 230 C). v The tropical heat waves determine massive warming, leading to maximum temperatures exceeding 35 -400 C (the absolute maximum temperature was of 43, 40 C, at Turnu Măgurele, in the south of the basin, on 24 July 2007) which cause a significant increase of the evapotranspiration and reduce the discharge values, thus, the drying phenomenon occurs along certain sectors. The climate graph Walter Leith at the Roşiori de Vede station Călmăţui Valley in Crăciunei village, in the summer 12

v The climate continental character influences the precipitation as well, the amounts varying within large limits in the case of the precipitation fallen within one year and from one year to another. v The mean annual precipitation amount over the period 1961 - 2010/540 mm, was of 576, 3 mm at Slatina, 515 mm at Roşiori de Vede and 528, 2 mm at Turnu Măgurele. With time, rainy years were recorded: Ex. in 2005, the precipitation reached exceptional values around 1000 mm, as well as droughty years/periods, when the precipitation amounts were below 300 mm/year in 2000. v The torrential rains have the highest frequency in the south of the country, along the sector between the Olt and Argeş Rivers, a region in which the western circulations interfere with the eastern ones. 13

v The most important precipitation amounts within one-year interval are specific to the warm semester, these rainfalls resulted from thermal convection, have a torrential character, the absolute maximum precipitation amounts in 24 hours, being of about 1/5 of the annual mean (Bogdan O, Niculescu E. , 1999). Exceptional rainy events, precipitation (max. in 24 hours) 1961 -2010 Station/ Months I II IV V VI VIII IX X XI XII Roşiori de Vede 25. 7 34. 2 38. 8 43. 1 53. 6 65. 1 82. 6 71. 3 35. 3 45. 4 43. 7 34. 4 Data (day/year) 18 / 1979 21/ 1965 30/ 1997 15/ 1970 21/ 1967 4/ 1969 11/ 1994 6/ 2005 20/ 1998 10/ 1972 20/ 1976 21/ 1969 21. 3 30 32. 4 42 50. 6 93. 2 80. 2 104, 8 37. 3 52. 4 31. 1 23. 3 Data (day/year) 1/ 2000 12/ 2009 6/ 1984 13/ 2003 7/ 2005 27/ 1998 3/ 2005 8/ 2002 6/ 2000 5/ 2008 25/ 1985 24/ 2003 Turnu Măgurele 38. 9 49. 4 42. 3 39. 4 65. 8 65. 6 132. 4 84. 8 43. 8 41. 8 37. 5 27. 5 Data (day/year) 2/ 2008 20/ 2009 6/ 1961 25/ 1961 26/ 1991 13/ 1964 5/ 1970 6/ 2005 21/ 1998 5/ 2008 20/ 1976 24/ 2003 Slatina v 14

v The lowest precipitation amounts were recorded in January, February and October. At the end of autumn and the beginning of winter, a secondary maximum amount is recorded, determined by the intensification of the Mediterranean cyclones. In comparison with the rapid summer rainfalls, which do not allow the infiltration of water in soil, in autumn, long frontal rainfalls are recorded, thus restoring the water reserve in soil. v The hydrologic factor is represented by the ground waters and the surface waters. v The ground waters include the phreatic waters and the depth waters. The most of the phreatic waters is stored in the Frăteşti layers, and the rest in the terrace deposits and in the flood plains in the Călmăţui and Urlui valleys. 15

v The aquifer horizons in the Frăteşti layers occupy the interfluve spaces and are fed by the precipitation. Due to the permeable lithology, the aquifer horizon is formed at bigger depths (15 -25 m) and point out by spring lines, where they are intersected by the deep valleys of the Călmăţui and Urlui Rivers, ensuring their permanent flow during the summer time. v As for the depth waters, can be found particularly in the Albian and Dacian sandy deposits, ascending character. with an 16

v The surface waters are represented by the Călmăţui River, occupying the 5 th rank in the Horton-Strahler hierarchical system and its tributaries (Zăvoianu, 1978). v The Călmăţui is a typical plain river, with a lot of meanders, with a total length of 139 km, a hydrographic basin surface of 1375 km², a mean annual discharge of 1. 16 m³/s, a mean flow speed of 0. 6 m/s and a mean multiannual level of 125 cm. v The sinuosity coefficient of the Călmătui River is of 1. 67, and of its tributaries varies between 1. 25 (Dragna) and 1. 65 (Urlui). v Unfortunately, lately, the natural vegetation has reduced its area, being replaced by the agricultural crops. This fact favored soil degradation through the erosion processes, as forests represent the most efficient natural shield against surface flows. 17

v The soil texture influences the flow by infiltration, and the evapotraspiration. v The soils of the southern part of the basin, which have a medium texture, presents a medium infiltration potential, the soils in the central part of the basin have a medium-to-fine one and presents a low infiltration potential, and those in the extreme north, have a fine texture and a very low infiltration potential. v The anthropogenic factor significantly contributed to the changing of the flow regime within the basin, both through massive land reclamation and through building various dams and ponds for fish breeding and irrigations. The arable fields replaced remained, the ancient which forests; contributed only to the few plots complete modification of the water circulation. Călmăţui Basin in the Teleorman county. Map of soil texture 18

Characteristics of the runoff in the Călmăţui basin v The rivers supply is mostly superficial (up to 85%), of a nivo-pluvial origin and the ground water sources have a reduced contribution (15 – 25%) (Ujvári, 1972). v The Călmăţui River has a mean multiannual discharge of 1. 3 m³/s Its mean annual discharge varied at Crângu hydrometric station over the period (1953– 2009) between 0. 5 m³/s (in 1961) and 2. 75 m³/s (in 1972). v The rivers within the basin have low discharges and are frequently affected by the drying phenomenon in the upper sector, where the water supply form ground waters is low, particularly in the second part of summer and the beginning of autumn. 19

v The interannual variability is reduced as a result of the climate conditions (lack of precipitation), corroborated with the reduced relief slopes and the high soil permeability. The multiannual variation of the mean annual discharges on the Călmăţui River at Crângu hydrometric station and the linear tendency 20

v The flow regime may vary a lot over the year, and to point out this fact, a comparison between the variation of mean monthly multiannual discharges and the maximum and minimum monthly multiannual discharges. v In the Calmatui hydrographic basin, the highest discharges are recorded over the period February – March, due to the combined effect of the water coming from snow melting and of a normal precipitation regime. v In the summer period, despite of the quite large precipitation amounts, minimum discharges are characteristic, due to the high values of the evapotranspiration. During the drought periods, the permanent flow is supplied by the ground waters, thus the complete drought being avoided and a permanent flow being ensured. 21

Comparisons between mean multiannual discharges and maximum and minimum monthly discharges v By analyzing the mean, maximum, minimum monthly multiannual discharges one can notice that, sometimes, over this basic flow (cca. 1 m 3/s), the flow fed by the summer torrential rainfalls is added, causing summer floods (Ex. July 1970, 1973, 1975, 1983 August 1957, 1959, 1962, 2005). 22

v The autumn season is characterized by long-duration rainfalls causing an increase of the runoff, under the aspect of “autumn high waters” (Ex. on the Călmăţui River, at Crângu hydrometric station, the folow rate registered in 12 th October 1972 was 42 m 3/s and after the breaking of several damps, maximum flow rate has reached the 237 m 3/s. In October 1972, the mean flow rate of 15, 6 m 3/s, is the highest mean monthly discharge over the analyzed period (1953 -2009). v During the winter season, the river has a reduced flow, this period being called “winter low waters”. Besides the fact that it is fed only by the ground waters, part of its water is stuck into ice. During the winter season, and particularly at the end of it, due to a temporary warming, snow partially melts and causes “winter floods”. 23

v A major influence upon the hydrogeomorphological dynamics is exerted by the maximum flow (Grecu, 2009). The floods are the most frequent in spring, but they may occur every season. High maximum discharges were recorded in: March 1954 (30. 4 m 3/s), March 1955 (26. 3 m 3/s), June 1970 (32. 5 m 3/s), October 1972 (237. 0 m 3/s) and March 1973 (38, 8 m 3/s) and August 2005 (53, 8 m 3/s) when the most significant floods in the Călmăţui basin occurred. v The Călmăţui River transports, in average, 0, 6 kg/s per year suspended sediments (measurements taken at Crângu hydrometric station), equivalent to a specific discharge of suspended sediments of 0, 2 t/ha/year. The most important amounts of suspended sediments are transported during the floods, There is a correlation between the maximum liquid discharges and the suspended sediments. 24

Determination of the correlation curve for the minimum annual discharges in the Călmăţui hydrographic basin, according to the measurements taken at Crângu hydrometric station, over the period 1953 -2009 v The absolute frequency is that quantitative feature representing the number of appearances of the xj value of the X statistical variable. v The sum of statistical frequencies of a statistical population or sample is called volume of the selection and represents the total number of statistical units of a sample or population. v The grouping of the statistical units into classes (intervals) is made by applying well known formulas such as Sturges or Scott’s, or by dividing the whole statistic population taking into account the rule of division norms as in the case of the numerical calculation of a Riemann interval, this algorhythm being applied for norms of the variable division till the real distribution gets a form which can be modeled by a known density of repartition. v The length of the statistical classes or of the frequency intervals can be calculated with the Sturges v and Scott’s formulas as follows: This curve is complementary to the repartition of probability, which means that F = 1 – P, as well as the distribution and repartition graphs. 25

Distribution of the absolute frequency – establishment of the interval by using the Sturges formula Repartition of probabilities –establishment of the interval 26 by using the Sturges formula

Correlation curves established through cumulating the relative frequencies in classes of intervals – intervals established by using the Sturges’ method and intervals established by 27 using the norms of division (6 intervals)

Calculation method for the correlation curves by using the Weibull, Kriţki - Menkel and Pearson’s methods v The Weibull empirical exceeding probability is given by the following empirical formula: v The coefficient is defined; in these conditions, the statistical parameters of the repartition density in the variable K, will have the following mathematical formulas: The Kriţki-Menchel theoretical probability curve with different exceeding correlations by using the Kriţki-Menkel theoretical curve can be obtained with the following formula: where the coefficient is the statistical coefficient, function of the value of and the ratio. The Pearson III theoretical probability curve is obtained by the help of the formula: where represents the deviation of the probability curve ordinate, corresponding to an exceeding probability p% 28

Correlation curves established by using the Weibull, Kriţiki-Menkel and Person III methods 29

CONCLUSIONS: v The flow is permanent, due the supply from the ground waters stored in the Frăteşti layers and to the various ponds build along these two rivers. v It can be noticed that over the year, the minimum flow values are reached during the summer, when the evapotranspiration has maximum values, but under these circumstances of “summer low waters”, (cca. 1 m 3/s), flash floods may occur and the liquid discharge is about 50 times higher (Ex. August 2005), due to the torrential rains. v Despite of this significant increase of discharges, the houses in the villages placed along these rivers are rarely affected by floods, and the damage is insignificant, due to the morphology of the valleys, these ones being much wider and deep than the water source flowing on their bottom over the year. v From the analysis made, it can be noticed that the coefficients of asymmetry and variation calculated for minimum annual discharges are almost similar. By using the three calculation methods (Sturges, Kriţiki-Menkel and Person III), as shown in the graph, it is reveled that the correlation curves overlay almost perfectly. By calculating the correlation curves, we obtained the correlation discharge 95%, called dilution discharge, which is very useful in approaching water supply problems. 30

References: C. Diaconu, Râurile României. Monografie hidrologică, Editura Serviciu Studii documentare şi publicaţii tehnice al Institutului de Meteorologie şi Hidrologie, (1971); E. Liteanu, Aspecte generale statigrafiei pleistocenului si ale geneticii reliefului din Câmpia Română, Studii tehnice şi economice, Seria E, nr. 5, pag. 41 -64, Bucureşti, (1961); Fl. Grecu, Hazarde şi riscuri naturale, Editura Universitară, Bucureşti, (2009); G. Desiderio, T. Nanni, S. Rusi, La pianura del fiume Vomano (Abruzzo): idrogeologia, antropizzatione e suoi effeti sul depauperamento della falda, Boll. Soc. Geol. It 122, (2003); I. Ujvari, Geografia apelor României, Editura Ştiinţifică, Bucureşti, (1972); I. Zăvoianu (1978), Morfometria bazinelor hidrografice, Editura Academiei, Bucuresti, (1978), L. J. , Nicolescu, M. I. , Stoka, Matematici pentru ingineri, Volumul II, Editura Tehnică Bucureşti, (1971); M. Craiu, Statistică Matematică–Teorie şi Probleme Ediţia a II-a, Editura Matrix Rom, Bucureşti, (2002); N. Florea, Câmpia cu crovuri, un stadiu de evoluţie al câmpiilor loessice, Studii tehnice şi economice, Seria C, Studii pedologie 16 (VI), pag. 339 -354, Bucureşti, (1970); O, Bogdan, E. Niculescu, Riscurile climatice din România, Institutul de Geografie, Editura Tipor Sega Internaţional, Bucureşti, (1999); P. Şerban, V. AL Stănescu, G. Andreea, Managementul Apelor Principii şi reglementări Europene, Editura Tipored, Bucureşti, 2006; R. Drobot, P. Şerban, Aplicaţii de Hidrologie şi Gospodărirea Apelor, Editura Tempus H*G*A* Bucureşt, (1999); *** Atlasul climatologic R. S. România (1966), *** Atlasul secării râurilor din România, I. M. H. şi I. G. F. C. O. T, Bucureşti, (1974); 31

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