The fluvial transport in upper Crnica catchment

Abstract

Upper Crnica catechment is positioned in the middle part of Serbia. Mountainous, eastern part of it, is built of limestone (60 %) and western part of Permian red sandstone (40 %). The rivers begin in the contact of limestone and sandstone, from numerous springs, and this water never filling. Average annual precipitation is 800 - 950 mm and annual run-off is 171 mm. Magnitude and frequency characteristic of suspended and dissolved solids transport in the upper Crnica catechment have been determined over a period of 5 years. Each day sample of water have been analyzed in voice to determine concentration of dissolved and suspended solids. Analyses of the water show that the average concentrations of dissolved solids (271 mg SQR(dm,-3)) are more than two times greater then the concentration of suspended solids (112 mg*SQR(dm,-3)). The relationship between discharge and concentration of suspended solid is unusual; the greatest discharges are the lower concentration of silt is (Tab. 2). This phenomenon is due to the large part of 'flat' morphology consisting of limestone. Analyses of variance, with concentration of tilt as a factor, show that is no differences between alt months except May. Namely, the maximum concentration of suspended solids were recorded during the May, when some day's concentrations were more than 3 g*SQR(dm,-3) ! After this conditions, therefore the average transport of dissolved solids (41,77 t*SQR(km,-2)*SQR(yr,-1)) is greater then the sediment removal (24,991*SQR(km,-2)*SQR(yr,-1)). The largest part of dissolved solids originated from limestone, while the almost all part of suspended material is from sandstone. A range of discharges close to baneful level carries more suspended sediment then the dissolved solids. During only four days in May 1987. year, from upper Crnica catechment was carried out more suspended solids (27921) then for the sum of rest four years (27661)! The reason for this enormity high erosion was coincidence of several factors: snowmelt, heavy rain and poor cover of soil with vegetation beginning of vegetation period). The probability for the transport of suspended malarial more than 100 t*SQR(day,-1) (1,3 t*SQR(km,-2)*SQR(yr,-1)) is 0,82 % e.g. 3 days over the year.

Na osnovu svakodnevih petogodišnjih merenja koncentracije suspendovanog i hemijski rastvorenog materijala, utvrđen je obim i dinamika pronosa dva najvažnija dela rečnog nanosa. U odnosu na transport hemijski rastvorenog nanosa, pronos slita je manji, podložan je naglim promenama i pod velikim je uticajem klimatskih, vegetacionih i antropogenih faktora. Ukupna specifična erozija iznosi 66,7 t SQR(km,-2)*SQR(god,-1), pri čemu pronos hemijski rastvorenih mineralnih materija iznosi 41,771*SQR(km,-2)*SQR(god,-1) a silta 24,991*SQR(km,-2)*SQR(god,-1) .