Characteristics of the winter minimum runoff of the rivers of the Lake Sevan basin and their spatial and temporal fluctuations

Abstract

The purpose of this study is to assess the ongoing changes in the winter minimum runoff characteristics of rivers in the Lake Sevan basin, as well as the possibility of effectively considering them in assessments and forecasts under climate change. The study used available long-term observations of average daily and urgent minimum water discharges from the main rivers of the study area, provided by the hydrological observation network of the Center for Hydrometeorology and Monitoring (SNCO, Ministry of Environment of the Republic of Armenia) up to and including 2021, along with research materials and other publicly available sources. Methods of statistical data analysis, mathematical modeling, and hydrological calculations were applied. We performed analysis and reconstruction of observation series, and assessed the spatial and temporal variability of winter minimum runoff characteristics. Quantitative characteristics of minimum water discharges during winter low water were determined for the main rivers. The analyzed minimum runoff characteristics included daily minimum water discharges, long-term average values (norms) of daily minima, minimum 30-day water discharges, long-term average values of average monthly minima, and absolute (urgent) minima. It is shown that the spatial distribution of winter minimum water discharges is highly uneven across the Lake Sevan basin. The average values of the minimum 30-day water discharge during winter low water were calculated. Correlations were obtained between these values, average daily minima, and absolute (urgent) minima. To confirm the representativeness of the calculation period for river sections with century-long observation records, normalized difference integral curves were constructed, and total (integral) curves were used to test the homogeneity of hydrological series. For the majority of the studied rivers, there is a stable trend (67%) toward increasing winter minimum water discharges, which should be taken into account in developing water management schemes. These significant changes cover large areas and are explained by regional climatic shifts. The results obtained are of great scientific and practical importance, especially given current spatio-temporal fluctuations in minimum runoff; predictive estimates are of particular value. Based on these findings, a comprehensive analysis of spatio-temporal variations in winter minimum runoff can be carried out. Contribution of the authors: Margaryan V.G. - main idea and overview, reduction and generalization of materials. Gaidukova E.V. - conducting out calculations, conclusions based on the results of calculations. Vershinin D.A. - conducting out trend calculations, conclusions based on the results of trend calculations. The authors declare no conflicts of interests.