Intra-Annual Dynamics Dissolved Solids and Suspended Sediment in the Extreme Hidrological Events – Case Study Nišava River

Abstract

Dynamics of totall dissolved solids (TDS) and suspended sediment concentrations (SSC) were monitored on the river Nišava at the hydrological station Dimitrovgrad. Water samples were collected each day in the period from 01.01.2010–31.12.2010. TDS concentration followed a seasonal pattern imposed by the availability of water, with higher concentrations recorded in low-flow periods and lower concentration in the highflow period. SSC was extremely variable and dominate mainly with specific high-flow events. Mean annual discharge (Q=6.68 m3/s, q=13.9 l/s/km2) over the year was 3.3 times higher than the average for the period of 50 years. In the study period, the annual transport dissolved load (Qd) was 36962.8 t (specific load Qds=76.7 t/km2/yr) and suspended sediment load (Qs) was 98861.9 t (specific load Qss=205.1 t/km2/yr). The transport of dissolved load and suspended sediment load shows temporal variations in different seasons. The analysis revealed that the maximum loads was transferred during the winter (Qd=43.3% and Qs=56.8% of the annual transport) and spring season (Qd=37.9% and Qs=38.9% of the annual transport). A comparative analysis of Q, Qd, and Qs show that the suspended sediment shows greater variability and exponential pattern of transport. For instance, 90% of the time was required to export 65% of the total water and transported 77% of the total dissolved load and only 22% total suspended sediment load. The most extreme precipitation episodes and extreme temperatures events was recorded in February 2010. The floods in February contributed by 44.8% of the total Qs transport over the study period. These findings have important implications for water resource management in the context of sediments mobilization, erosion, channel management, water quality and ecological functions.