EXTREME HYDROLOGICAL PHENOMENA IN THE HYDROLOGICAL BASIN OF UPPER IALOMITA, DURING 2000-2005

Ovidiu Murărescu, Petre Breţcan “Valahia” University, Faculty of Human Sciences Târgovişte, [email protected], [email protected]

Abstract

In the analysis of extreme hydrological phenomena, two distinct parameters are considered: on the one hand, the maximum flow and the high flows, which are more spectacular in point of the impact on settlements and anthropic activities, and on the other hand, the phenomena of minimum flow and drought, which are much less spectacular, but whose impact is much stronger. The maximum flow is characterized by the highest values (in percentage) during the different months of the year. Regarding the hydrographic basin of upper Ialomiţa river, where most of the hydrometric stations appeared only after 1975, we can highlight a series of territorial differences for this type of liquid flow, mainly generated by the conditions of the precipitations regime. The minimum flow represents a basic characteristic in the hydrological regime, being a parameter that is necessary in order to find out the river’s water reserves during critical periods with low flows, in order to satisfy the water demands. They appear during the periods with low quantities of precipitations or with no precipitations at all, when the alimentation takes place almost exclusively from underground resources.

Keywords: hydrographic basin, maximum flow, flood, high flood, minimum flow, hydrological drought.

1 INTRODUCTION In the hydrographic basin of upper Ialomiţa the module flow increases from upstream to downstream, in direct relation with the increase of the number of tributaries and of the alimentation basin. Along the 71 km that it covers from its sources to Târgovişte, Ialomiţa River has a module flow that grows constantly from 1.15 m3/s, at the entrance in Bolboci lake, up to 7.97 m3/s at Târgovişte. Because of the hydrotechnical arrangements along it, there appear a series of modifications in the liquid flow regime, the affluent flow module for the accumulation lakes of Bolboci, , Doiceşti being much higher than the diffluent flow, which is dictated by the need of water of the socio-economic institutions situated downstream of these lakes. These lakes have as well the role of regulating the liquid flow throughout the year, in order to lessen the high flow waves or the drought phenomena that could appear. So, if the module affluent flow in Bolboci lake is of 1.15 m m3/s, while the diffluent one is of 0.81 m3/s, increasing to 6.88 m3/s in , going down to 5.58 m3/s in Pucioasa and growing to 7.97 m3/s in Târgovişte. From the alpine area, Ialomiţa receives only one important affluent, Ialomicioara Leaotei, whose module flow is of 0.91 m3/s in . In the Subcarpathian area there are many tributaries of Ialomiţa’s, some of them reaching Ialomiţa River in this area, others in the southern plain zone. These rivers’ average module flows register values ranging from 0.17 m3/s (Slănic, in Gura Ocniţei) and 1,0 m3/s (Bizdidel, in Pucioasa). Depending on the climatic conditions, a series of extreme hydrological phenomena can develop, like the hydrological draught, or especially the floods and high floods, which occurred with a high frequency during the time period under analysis.

2 GEOGRAPHICAL SETTING

The upper hydrographic basin of Ialomiţa River is situated in the center-south of Romania. The altitude ranges from 2505 m (Omu Peak – Bucegi Mountains), the maximum limit, to the minimal level of 291 m, in Târgovişte. The average of the surface situated above the sea level is of 1398 m, which is an important indicator if we consider the fact that vertical zonality is a main element of the matter and energy flow involved in the spatial evolution of the hydrographic system under analysis. Ialomiţa River, which has its spring in Bucegi Mountains, at over 2300 m, goes through the alpine and hilly area up to Târgovişte, covering a distance of 71 km (17.03% of its total length of 417 km), going down through a level difference of about 2010 m. It forms a basin whose surface is of 686 km2 (6.62% of the total basin surface of 10,350 km2). The river has a sinuosity coefficient of 1.88 for its entire course, with slightly lower values in the alpine and hilly area (between 1 and 1.50). The density of the hydrographic networks varies between 0.100 and 0.260 km/km2. At the contact between the hills and the plain, Ialomiţa has an average flow of 7.97 mc/s (11.61 l/s/km2).

3 DATA AND METHODS

In the analysis of the liquid flow elements we used the statistic-mathematical series of data recorded at the following hydrometric stations and posts situated in the hydrographic basin of upper Ialomiţa:

Table 1. Data concerning the hydrometric posts in the hydrographic basin of upper Ialomiţa No. River Hydrometric F med. L (km) Year of Year Measurements and observations made post (km2) height creation of end H Q R Ta Fi A (m) 1. Ialomiţa Bolboci 54 1680 10,75 1990 - - x - - - - 2. Ialomiţa Moroeni 264 585 29 1954 - x x - x x x 3. Ialomiţa Pucioasa 448 296 54 1976 - - x - - - - 4. Ialomiţa Târgovişte 686 296 71 1976 - x x x x x x 5. Ialomicioara Fieni 95 903 26 1975 - x x x x - x 6. Bizdidel Pucioasa 92 654 55 1976 - x x x x x - 7. Vulcana Şotânga 105 470 18 1983 - x x - - - - 8. Slănic Gura 57 260 25 1980 - x x - - - - Ocniţei 9. Cricovul 57 260 30 1980 - x x - - - - Dulce F – surface of the hydrographic basin (corresponding to the hydrometric post); L – river length (spring – hydrometric station); H med. – average height; Q – liquid flow; R – the flow of alluvial matter in suspension; Ta – water temperature; Fi - winter phenomena; A – physico-chemical analyses

4 RESULTS

Extreme hydrological phenomena are determined by very large quantities of precipitations fallen in very short time intervals that generate high flows of great amplitude. They can also be caused by large and continuous quantities of precipitations recorded over a long time interval, corroborated to territorial differences on seasons and with favorable local factors. In the hydrographic basin under analysis, where most of the hydrometric posts were created after 1975, a series of territorial differences of the maximum liquid flow has been recorded, mainly generated by the conditions of the precipitations regime. So, the highest maximum flow recorded on Ialomiţa River so far was of 691 m3/s on June 19, 2001. High flows. In order to have a global image on the complexity of this phenomenon, we selected the characteristic high flows, with the highest water volumes. At the level of the entire geographic zone under analysis, during the interval 2000- 2005, significant high flows occurred. The history of this area recorded high flows before that as well, some of them catastrophic through their consequences, in the years 1971, 1972, 1974, 1975, 1979, 1980, 1983, 1985, 1988, 1991, 1993, 1997, 2001, 2005, which means that for every interval of 3-5 years, a large and a very large high flood occurs. The high floods can be grouped according to their size: - small high floods: 1969, 1970, 1988, under 100 m3/s: - average high floods; 1979 and 1991, under 200 m3/s; - large catastrophic high floods, in 1972, 1975, 1997, 2001, 2005, recording between 300-700 m3/s, on the large rivers, and 200-250 m3/s, on the tributaries.

High floods occur because of abundant rains, or as the snow melts, or when these two phenomena combine, the most frequent being recorded in spring (30-50%) and in summer. High floods and floods, with an accuracy of 0.5-1%, are caused mainly by large quantities of precipitations with a significant degree of torrentiality, recorded after periods when the soil moisture had increased heavily and the water absorption capacity had become low. The propagation of high flood waves is strongly modified by the anthropic activities. Uncontrolled deforestations determined an increase of the speed of concentration of the flow, as well as an intensification of the erosion, of the transport and of the depositing of the alluvial deposits and an over-heightening of the riverbeds, which increases the risk of overflow. The high flood of June 2001 represented a peak, by its size and through the participation of the whole 686 km2 basin up to Târgovişte. It recorded the highest flows for all the hydrometric stations of Ialomiţa River, upstream of Târgovişte, higher than the ones of 1975. It was generated by a front of precipitations focused for 48 hours on Ialomiţa Valley, the abundant precipitations fallen in the alpine and Subcarpathian zone summing up between 125 and 175 l/m2. Another generating factor was the humectation of the basin, namely the quantitatively insignificant precipitations that prepared the basin. The high flood started to form in the evening of June 18, and in the morning of June 19 it was present on all the tributaries. Its growth evolution is spectacular; it started from values of 5-10 m3/s and in 15-20 hours it reaches values of 200 m3/s. So, on the night of June 19, values of 196 m3/s were reached on Ialomicioara River, in Fieni, 240 m3/s on Bizdidel River, in Pucioasa, 144 m3/s on Vulcana River, in Şotânga, and 373 m3/s in Moroeni and 691 m3/s in Târgovişte, on Ialomiţa River. The high flood began to decrease on June 21. The volume of the high flood was of 5 million m3/s on Bizdidel, 7-9 million m3/s on Vulcana and on Ialomicioara, 20 million m3/s in Moroeni and 27 million m3/s in Târgovişte, on Ialomiţa River. On the rivers Slănic and Cricovul Dulce, the largest high flood occurred as well during the interval of June 18-24, 2001. On Slănic, the river flow began to increase in the morning of June 19, reaching a maximum in the evening of the same day (116 m3/s), after which the high flood begins to decrease until the day of June 22. The total volume of the high flood was of 2.4 million m3. On Cricovul Dulce, in Moreni, the high flood wave began to form in the morning of the day of June 19, and the flow increased 30 times in 12 hours, reaching the maximum value of 312 m3/s in the evening of the same day (at 20:00). The high flood wave died out in the evening of June 24, and its total volume summed up 12 million m3. In the year 2005, because of the important quantities of liquid precipitations that fell in spring, shortly the yearly quantity of precipitations went beyond all those registered before, and the river flows went far beyond the multiannual average values, recording values that went over the attention level (CA), over the inundation level (CI) and over the danger level (CP).

Table 2. Precipitations quantities and flows recorded in the months of May and June 2005 Precipitations H Q CA CI CP Data Locality Water course (l/m2) (cm) (m3/s) (cm) (cm) (cm) Târgovişte 91.4 590.0 500.0 - +40 - Ialomiţa Moroieni 46.8 254.0 29.4 - - - Fieni 81.1 Ialomicioara 338.0 17.0 +38 06-09. Runcu 77.8 II 275.2 7.3 - - - 05 70.1 101.1 5.5 - - - Bizdidel Brăneşti 67.9 412.0 150.0 +62 Şotânga 137.3 Vulcana 720.0 128.0 - - +60 Gura Ocniţei 50.0 Slănic 325.5 18.2 - - Moreni 47.9 Cricovul Dulce 310.0 181.0 - - +10 Târgovişte 29.6 208.0 28.3 - - - Ialomiţa Moroieni 32.5 236.0 16.0 - - - Fieni 25.2 Ialomicioara 244.0 3.9 - - - Runcu 32.0 II 143.5 4.1 - - - 06- Bezdead 24.0 Bizdidel 85.0 5.1 - - - 10.06 Brăneşti 23.1 Bizdidel 134.0 6.0 - - - Şotânga 23.6 Vulcana 120.1 16.3 - - - Gura Ocniţei 14.5 Slănic 130.0 4.32 - - - Moreni 18.7 Cricovul Dulce 258.0 74.8 - - -

In the time interval between 7:00 and 8:30 in the morning, 30.0 l/m2 were recorded in Brăneşti (on Bizdidel River). During the period 05-08 August, 147.7 l/m2, were recorded in Târgovişte (on Ialomiţa River). For the month of September, the normal value of the quantities of precipitations is of 70-75 l/mp, yet only for the period 19-20 September 2005 the quantities of precipitations registered were between 50-89 l/mp (Tables 2 and 3). Table 3. Precipitations quantities and flows recorded in July - September 2005 Precipitations H Q CA CI CP Date Locality Water course (l/m2) (cm) (m3/s) (cm) (cm) (cm) Târgovişte 93.1 257.5 39.9 - - - Ialomiţa Moroieni 67.2 230.0 29.0 - - - Fieni 77.0 Ialomicioara 228.5 15.3 - - - Runcu 69.9 II 187.5 4.5 - - - 4- Bezdead 102.8 124.0 6.4 - - - Bizdidel 26.07 Brăneşti 78.0 136.0 7.2 - - - Şotânga 100.0 Vulcana 486.0 94.7 - - - Gura Ocniţei 113.6 Slănic 185.2 20.5 - - - Cricovul Moreni 128.6 210.5 55.8 - - - Dulce Târgovişte 242.5 490.0 291.0 +40 - - Ialomiţa Moroieni 102.7 165.2 27.0 - - - Fieni 89.5 Ialomicioara 344.0 117.0 +44 - - Runcu 101.4 II 350.0 102.0 +50 - - 5- Bezdead 72.3 103.1 5.9 - - - Bizdidel 19.08 Brăneşti 171.5 165.2 8.5 - - - Şotânga 163.9 Vulcana 760.0 145.0 - - +100 Gura Ocniţei 88.4 Slănic 420.0 54.8 - +50 - Cricovul Moreni 102.5 400.0 234.0 - - +60 Dulce Târgovişte 176.1 594.0 500.0 - +44 - Ialomiţa Moroieni 252.3 257.0 26.3 - - - Fieni 262.1 Ialomicioara 366.0 153.0 +66 - - Runcu 340.2 II 285.1 137.2 - - - 20- Bezdead 195.5 147.5 11.9 - - - Bizdidel 21.09 Brăneşti 159.2 210.0 26.0 - - - Şotânga 121.1 Vulcana 635.0 68.6 - +25 - Gura Ocniţei 164.0 Slănic 272.0 23.4 - - - Cricovul Moreni 159.8 185.0 34.3 - - - Dulce

Regarding hydrological droughts, during the period under analysis no such case was recorded in the hydrographic basin of upper Ialomiţa. Although the year 2000 was an arid year, during the respective year no hydrological drought was recorded, given the alimentation sources and the affluent hydrographic basins.

5 CONCLUSIONS

Following the previous analysis, we can notice that during the period 2000-2005, the extreme hydrological phenomena developed in the hydrographic basin of upper Ialomiţa are related to the river’s maximum flow. These extreme phenomena occurred with a frequency of 3-4 per year, especially in the years 2001 and 2005, on the background of the penetration of certain air masses that brought in significant quantities of precipitations in a short time interval of about 48 hours. References

Diaconu, C. (1998): Râurile, de la inundaţie la secetă / Rivers, from Flood to Drought, Editura Tehnică, Bucureşti. Diaconu C. (1999): Cursuri de apă - amenajare, impact, reabilitare / Water Courses –Arrangement, Impact, Rehabilitation, Editura HGA, Bucureşti. Gâştescu P. 1990: Water resources in the Romanian Carpathians and their economic management, Rev. Roum. de géol. géophys. et géogr., Serie de Géographie, 34, Bucureşti. Murărescu O. 2001: Raportul dintre resursele de apă şi cerinţe, de la nivelul comunelor de pe valea Ialomiţei (sectorul carpatic şi subcarpatic) / The Relation between Water Sources and Water Demand, for the Communes situated on Ialomiţa Valley (the Carpathian and Subcarpathian area), Comunicări de geografie, vol. V, Editura Universităţii Bucureşti. Murărescu O. 2001: L’écoulement liquide saisonier sur les rivières de Dâmboviţa et Ialomiţa dans le secteur Carpatique et Subcarpatique - Roumanie, Annales Geogr. Series, Tome 2, Universitatea Valahia, Târgovişte. Murărescu O. (2004): Resursele de apă din spaţiul carpatic şi subcarpatic dintre Dâmboviţa şi Prahova şi valorificarea lor / Water Resources in the Carpathian and Subcarpathian area between Dâmboviţa and Prahova and their Valorization, Editura Transversal, Târgovişte. Sorocovschi V. (2002): Riscuri hidrice / Hydro Risks, in “Riscuri şi catastrofe”, vol. I, editor Sorocovschi V., Editura Casa Cărţii de Ştiinţă, Cluj-Napoca. Zăvoianu I., Podani M. 1977: Les inundations catastrophiques de l’année 1975 en Roumanie, Rev. Roum. de géol. géophys. et géogr., Serie de Géographie, 21, Bucureşti. * * * - Statistical data from the Hydrological and Meteorological Stations from Voineşti and Târgovişte.