Estimation of the flow parameters of the Irshava River under absence of hydrological data at the site

Анотація

The last decade the interest in the construction of small hydropower plants has increased in connection with the introduction of the "green tariff". In order to calculate the installed and guaranteed capacity of a small hydroelectric power station and the cost-effectiveness of investments, it is necessary to determine the hydrological parameters of the river, namely the mean annual flow, the flow in dry year and their distribution along year for the construction site. Prospective sites are located in the mountainous part of the Tisza basin of the Transcarpathian region, where hydrometric stations are unevenly located, and almost absent on small tributaries. Available specific discharge maps, regulatory documents, and regional formulas are based on the original data accumulated in 1946-1980 and need to renew and extend the rows. The methodology proposed that allows to determine the necessary hydrological parameters under absence of observation data on the example of the Irshava River, which is the right tributary of the Borzhava River basin of Tisza. To calculate the installed and guaranteed capacity, it is necessary to determine the mean annual flow and annual flow of 75% probability and their distribution in the construction sites with catchment areas of 51,1 km² and 71,4 km². There was hydrometric station downstream of Irshava River from 1955 to 1987 which could be used as an analogue for the hydrological regime estimation for the construction sites.  It is necessary to extend series of hydrological data on the Irshava hydrometric station to long-term period, which was done using data from hydrometric stations Dovhe and Shalanky. The river specific discharge depends on the elevation and the catchment area in the mountainous area. It was established relationship between the specific discharge and the average elevation of the catchment for hydrometric stations situated in the basin of the Borzhava River and adjacent basins in order to determine the hydrological parameters at the construction sites 1 and 2.  The mean annual flow of different probability were determined by the statistical parameters of the binomial asymmetric distribution curve, the coefficient of variation was calculated by the regional dependence, the coefficient of asymmetry was adopted similarly to the one at hydrometric station Irshava. The mean annual distribution of 50% probability was calculated based on the percentage distribution of the mean long-term flow at the Irshava station, the distribution in dry year is estimated using the average values in dry year of 1963 and 1983.