STATISTICAL ANALYSIS OF YANTRA RIVER FLOW

Abstract

The study is focused on statistical analysis of river discharges. The registered river flow regime and hydrological characteristics of Yantra River are investigated. Yantra watershed is situated in North Bulgaria and belongs to Danube river basin Directorate. The current study is focused on the low flows. Thirteen hydrometrics stations located in the watershed are available for the investigation. Data used are from monitoring network of the National institute of meteorology and hydrology, Bulgaria. The flow duration analysis was carried out for each gauged river within watershed. Flow duration analysis provides information on the percentage of time that flows are equalled or exceeded. Some baseflow indices were calculated in order to estimate the relative contribution of groundwater or baseflow. The obtained results clearly show a significant contribution of subsurface inflow to surface river runoff. The time of occurrence of minimum daily discharges (by month) were extracted from database and values were analysed. The minimum daily water discharge has the greatest frequency in the four summer months based on the performed analysis. In second place are the winter months when we work with three seasons each with four months duration. The magnitude of the low flow event was studied using frequency analysis. The probability of occurrence of different flows was calculated. Regional regression analysis was applied. Regionalization scheme and regression curves are presented and discussed. The obtained results show that the most of the rivers from the watershed have a similar behaviour at low flow. This study is focused on flow metrics that best describe the flow regime and the hydrological characteristics of Yantra river. Furthermore, hydrological studies are important for all types of environmental investigations � fish habitat, water intakes, stream productivity, etc. In the recent years we are dealing with co-called ecological flow. Particularly the low flow statistical analysis is crucial for determination of ecological flows in the sense of European water framework directive.