FLOODS AND DROUGHT - HYDROCLIMATIC RISKS IN SUHA RIVER BASIN TÎRNOVAN ALINA1, ROMANESCU GH.1, COJOC MARIA GIANINA1 ABSTRACT. Floods and drought-hydroclimatic risks in Suha basin. Suha is a right tributary of Moldova River, and presents a typical discharge for the geographical unit of Obcinele Bucovinei. Data used in the paper have been taken from Siret Basin Water Administration, Bacău, and represent a time sequence of 40 years. The most significant floods occurred in 1975, 1981, 1984, 1991, 2005, 2006, 2007 and 2008. The most obvious droughts occurred in 1969, 1974, 1978, 1983, 1987 and 2001. It was observed that the evolution of hydrological risk phenomena is closely linked to climatic changes. Increasing population and the need to extend the building design must take into account the extreme values of river flow over time, water resources also being important. Because extreme events occur more often, considering preventive plans against floods is needed. For this reason are analyzed the temperatures, rainfalls and discharge rates. Keywords: flood, drought, river catchment, hydroclimatic risk 1. INTRODUCTION The growing concentration of population in Suha watershed drew out the attention on its protection against flooding and ensuring water demands. Currently, in this drainage basin are eight hydrometrical stations for daily monitoring river levels. Identification of hydroclimatic risk phenomena in the Suha basin was based on monthly and annual analysis of average discharge values, average temperatures and rainfalls over a period of 30-40 years, with data recorded at three of the eight gauging stations in the basin, considered representative: Stulpicani (on Suha River), Gemenea 2 (on Gemenea River) and Gemenea 5 (on Slătioara River). The present paper examines hydroclimatic risk phenomena manifested in Suha river basin. 2. GEOGRAPHICAL POSITION Suha is a tributary of Moldova River (Fig. 1). Aspects regarding the flow rates on the river have been previously highlighted by Diaconu, 1988; Olariu, 1992; Romanescu, 2005, 2009, etc. 1 Alexandru Ioan Cuza University, Faculty of Geography, Iaşi, Romania e-mail: [email protected], [email protected], [email protected] 188 Fig. 1. Geographical position of the Suha river basin and gauging stations location Suha basin is located in the flysch area of the Eastern Carpathians. Only Gemenea, a left tributary, springs from the crystalline Mesozoic area of Rarău Mountains. It has an area of 368 km2 and an average altitude of 876 m. The main collector is Suha, with tributaries on both right and left side. It is characterized by an almost circular shape, the value of C being equal to 1.42. The rivers’ slopes in the basin have values between 23 and 84%. The existence of small depressions at Negrileasa, Gemenea and Stulpicani gives the basin the character of an amphitheatre, which generates a rapid concentration of major floods. Another factor that influences river flow is the large sediment transportation and deposition, especially in the medium and lower sectors of the main watercourses: Suha, Gemenea, Slătioara, Negrileasa (Siret Basin Water Administration, Bacău, 2013; I.N.M.H., 1971). From a climatic point of view, Suha basin is located in the temperate- continental area, mountain-climate type. Rainfalls are relatively low because the basin is located in an area with a slight foehn manifestation. 189 3. DATABASE AND WORKING METHODS The data analyzed were collected from Siret Basin Water Direction, Bacau. The methods used in the analysis and interpretation of data are specific to hydro- meteorological analysis, statistical analysis, comparison and data interpretation. For a clearer understanding have been used charts and tabular data. For the geographical localization of Suha basin was used the digital terrain model, scaled 1:5000. Mean monthly and annual values were compared with the multi-annual average. 4. RESULTS AND DISCUSSIONS The liquid discharge in the Suha river basin between 1973- 2012 Multi-annual average discharge defines the hydrological potential of a watercourse (Romanescu and Nistor, 2011). From the analysis of data can be separated some periods of liquid discharge (Fig. 2, 3, 4, 5): - 1973-1983, with high flow rates; - 1984-1996, with the average annual values of very low flows, the only exception being the year 1991, which has an average annual flow rate much higher than the multi0annual mean value; - 1997-2008, with discharges that exceed the multi-annual average values; - 2001-2012, with discharge rates that are starting to fall gradually. 3.5 3.0 2.5 2.0 mm 1.5 1.0 0.5 0.0 2010 2011 2012 2007 2008 2009 2003 2004 2005 2006 2000 2001 2002 1997 1998 1999 1993 1994 1995 1996 1990 1991 1992 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 Year Hydrometrical station Stulpicani Hydrometrical station Gemenea 2 Hydrometrical station Slătioara 3 The multiannual average precipitation Fig. 2. Average annual rainfall in Suha river basin (1979-2012) 3.500 3.000 2.500 2.000 Qmc/s 1.500 1.000 0.500 0.000 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2011 2012 Year The annual average flow The multiannual average flow Fig. 3. Average annual discharge at Stulpicani hydrometric station (1979-2012) 190 annual decreased respectively and average the high, reasons for justifying and discharge, temperature precipitation, a clear between of relation 9). the These give picture graphs in 1981(Fig. rainfall gr monthly the monthly multi the monthly multi the constructed was area hydro the of some that be seen can it recent years In phenomena. hydrological of behavior the understanding in point starting a is quantities rainfall of evolution the of Analysis evaporation. high by or year the of periods some in precipitation 2. 10, 5and 20, of insurances flood reached have These 5(1991, discharges 2006,2008). and Gemenea 2008) 2(2006, Gemenea 2008); 2005, 2006,2007, 1984, 1981, (1975, Stulpicani in stations hydrometrical the at recorded floods largest The the 30 1.000 1.200 Qmc/s 0.000 0.200 0.400 Qmc/s0.600 0.800 0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 Fig. 5. Average annual discharge at Gemenea Gemenea at discharge annual Average 5. Fig. Fig. 4. Average annual discharge at Gemenea 2 hydrometric station (1979 station 2hydrometric Gemenea at discharge annual Average 4. Fig. logical events can be assimilated with climate changes. For Suha river basin basin river Suha For changes. climate with assimilated be can events logical - 40 years with records, under the direct influence of the rainfall quantities. quantities. rainfall of the the influence under direct with40 years records, Temperatures influence the discharge rates by reducing the reducing by rates discharge the influence Temperatures during flows of frequent oscillations by characterized is basin Suha River 1973 1973 1974 1974 1975 1975 The annual average flow The average annual The annual average flow The average annual 1976 1976 1977 1977 aph in 1981 (Fig. 8) and the annual monthly average flow chart flow chart average monthly annual the 8) and (Fig. in1981 aph 1978 - 1978 annual average rainfall chart (Fig. 7), the annual average average annual the 7), (Fig. chart rainfall average annual 1979 1979 1980 1980 1981 1981 1982 1982 1983 1983 - 1984 1984 annual average monthly temperatures chart (Fig. 6), 6), (Fig. chart temperatures monthly average annual 1985 1985 1986 1986 flows. 1987 1987 1988 1988 191 1989 1989 Year 1990 1990 1991 Year 1991 1992 1992 1993 5 hydrometric station (1979 station 5 hydrometric 1993 1994 1994 1995 1995 The multiannual average flowl average multiannual The The multiannual average flow average multiannual The 1996 1996 1997 1997 1998 1998 1999 1999 2000 2000 2001 2001 the basin wereat 2002 2002 2003 2003 2004 2004 2005 2005 2006 2006 intake of of intake 2012) 2012) - 2007 - 2007 2008 2008 2009 2009 2011 2011 2012 2012 18.0 12.0 6.0 0.0 Celsius degrees Celsius I II III IV V VI VII VIII IX X XI XII -6.0 -12.0 Month Rarău meteorological station Câmpulung Moldovenesc meteorological station The annual average temperature Fig. 6. Average multi-annual monthly temperature variation 160 140 120 100 80 mm 60 40 20 0 I II III IV V VI VII VIII IX X XI XII Month Rarău Stulpicani Gemenea 2 Gemenea 5 Frasin Fig. 7. Average monthly multi-annual precipitation 7.0 6.0 5.0 4.0 mm 3.0 2.0 1.0 0.0 I II III IV V VI VII VIII IX X XI XII Month The annual average precipitation Fig. 8. Average monthly precipitation at Stulpicani hydrometric station, 1981 9 8 7 6 5 Qmc/s 4 3 2 1 0 I II III IV V VI VII VIII IX X XI XII Month The monthly average flow Fig. 9. Monthly average discharge rates at Stulpicani hydrometric station, 1981 During January, February, March, November and December, when temperatures and rainfall quantities are very low, their contribution to the flow rates is very weak. Starting with April temperatures begin to rise and also do rainfall values (according to the monthly multi-annual trend). The flow dynamics copies the 192 same dynamics. The quantities and distribution of rainfall in time and space gives the area the characteristics of a moderately humid continental climate, with average values of 903.4 l/m2 in Rarău Mountains, 743.2 l/m2 in Stulpicani commune, 788.0 l/m2 at Gemenea 2 hydrometric station, 824.6 l/m2 at Gemenea 5 hydrometric station, and 782.2 l/m2 at Frasin.