Evaluating the impact of neogene sediments on the river runoff formation

Abstract

Due to the recently increasing frequency of extreme changes in river runoff regime, scientific literature has dealt with the characteristics of runoff formation. Studies have been carried out on analyzing climate change and a lot of attention has fallen on land-use structures. Migration of precipitation through the river basin is influenced by the lithological composition of sediments. Its structure is determined by analyzing geological and geomorphological maps and by drilling boreholes in the selected area. With the help of boreholes the level of groundwater and lithological composition of sediments can be assessed. An installed system of lysimeters and piezometers in the borehole allows us to monitor the change of groundwater level and the amount of water moving through the unsaturated zone of sediments over time. The set of lysimeter boreholes allows us to capture and map the spacial change of these parameters. Following thorough analysis of the lithological structure of river basins in separate costal zones, this article aims at evaluating river runoff formation characteristics. The basin lithological factor was calculated based on large-scale maps using ArcGis software. In order to cany out more thorough analysis of the influence of lithology in given territories, sections of 0-50 m. 50-200 m, 200-500 m, 500-800 m, 800-1000 m. and >1000 m were established, calculating the distance in meters from the riverbank. Eight river basins of typical lithological structure (sandy, loamy, argillaceous) were selected and examined. The period of the year 1960-2013 was analyzed as this period and the relationship between the runoff and precipitation with conelation of 0.72-0.83 was established, as well as that with the lithological structure, established following the derivation of a hydromodule.