In order to correctly evaluate the water supply in an area it is necessary to know the natural flow conditions. As a result of human activity the degree of water usage has also risen. Many developing countries are currently faced with several water management challenges and problems that vary according to the physical, socioeconomic, and institutional context of development (Akpabio et al., 2007).
Under the circumstances, in order to find out the potential of natural water resources, it is necessary to make calculations that will eliminate the influence of human factors modifying the flow. The results obtained can be used to indicate a situation where there would not be any flow modifying factors and would allow for a quantitative analysis of water resource trends (Závoianu, 1999).
Currently, the immense water course training caused the measured discharge, namely the measured runoff, not to reflect the natural runoff as measured at most hydrometric stations. The reconstruction of natural flow started in 1980, corrections of reconstruction being made every year. The main modifying factors on the hydrologic regime in the river basins are the complex water trainings. The storage reservoirs distribute and regulate the flow during the year. During floods, they minimize the maximum discharges. That is when the reconstruction corrections have positive values (DQ > 0). During droughts, storage reservoirs compensate minimum discharges, and the values of the reconstruction corrections are negative (DQ < 0).
The river basin size has an important role in the genesis and the evolution of hydrological phenomena. In a small drainage basin, the channel flow evolution follows the rainfall depth, whereas in a significant river basin, the channel flow evolution does not follow exactly the rainfall depth. The river basin surface regulates the runoff. A wider drainage area, as it is in the Blajului and Intresecaje Tablelands, increases the flood routing speed. The river basin average altitude influences the hydrological elements. The higher drainage area elevation receives more precipitation and has more important runoff than the lower one.
The annual runoff in the Tarnava river basin is influenced by the rainfall depth, evaporation, morphometrical characteristics of the flood channel, cutoffs coefficient, and hydrogeological conditions of the drainage areas. When calculating the runoff, we should include a series of parameters that will take into account the influence of accumulations and embankments built to prevent floods. Also, other parameters can be mentioned related to the cutoff coefficient, the mor-phometrical characteristics of the flood channel, and its deposits.
There is emphasis on the practical importance of maximum runoff observation on watercourse management works. The analysis of the maximum runoff genesis as well as the distribution of the values according to genesis was based on a comparative analysis of the climatic and hydrologic variations.
The most serious floods in Tarnava river basin occurred in May 1970, July 1975, March 1981, December 1995-January 1996, and June 1998 (Sorocovschi, 2004). The flood analyses between 1970 and 2004 at Sarateni hydrometric post illustrate a great number of important floods in May 1970, July 1975, May 1978, and May 1984, followed by a period of 10 years with modest floods until 1995. The last decade presents floods in April 1999 and 2000 and May and August 2005. Floods vary according to seasons, the most numerous occurring in spring (30%-45%) and less in autumn (6%-10%). The maximum frequency is in April and March, followed by June.
The hydrotechnical works in Tarnava basin started as a result of the important damages caused by the floods in 1970 and 1975. They implied the construction of some storage reservoirs, both permanent and non-permanent, to protect different objectives within the territory. By means of redistributing the flow during the year, they created a balance in the hydrologic system, compensating for minimum discharges and decreasing the maximum ones.
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