Long-term forecasting methods of dates of ice break-up and disappearance at the Dnipro Cascade Reservoirs by teleconnection indicators

Abstract

Long-term forecasting of the ice regime at the Dnipro Cascade Reservoirs is very important, first of all, for the operation of hydroelectric power stations. In addition, such forecasts also ensure the work of other sectors of the economy, namely shipping, fisheries, municipal engineering, etc. At present, the Department for hydrological forecasting of the Ukrainian Hydrometeorological Center uses techniques developedin the middle and in thesecond half of the 20th century to compile long-term forecasts and advices about the ice regimeof water bodies of Ukraine. These techniqueswere developed only for rivers;for reservoirs,they are currently lacking. The main objective of our research is to develop methods for long-term forecasting of ice break-up and disappearance at the Dnipro Cascade Reservoirs by teleconnection indicators. The research was based on the recordsfor 35 water gauges located on 6 reservoirs of the Dnipro Cascade, including the destroyed Kakhovka reservoir. The dates of the ice break-up and disappearance were used for the period from the beginning of observations at each water gauge to 2020. Moreover, the teleconnection indicators were used, namely 34 atmospheric indices, sea surface temperature indices, teleconnection indices and patterns determined by the National Weather Service (NWS) of the National Oceanic and Atmospheric Administration of United States of America (NOAA USA). Methods of the long-term forecasting of the ice break-up and disappearance at the reservoirs of the Dnipro Cascade have been developed by searching for the best correlation or regression relationship between dates and teleconnection indicators. The probable of accepted errorsof the developed methods are in the range of 62—71 %, which corresponds to satisfactory method quality that makes it possible to recommend them for use.