Using meteorological data for reconstruction of annual runoff series over an ungauged area: Empirical orthogonal function approach to Moldova–Southwest Ukraine region

The water-management transformation of runoff and the prospective change of global climate necessitate studying the climate forcing associated with runoff processes. This paper presents some quantitative estimations for the role of climatic factors in this process on an example of the Moldova–Southwest Ukraine region. Using empirical orthogonal functions, we establish the contribution of the annual evaporation, annual precipitation, and warm- and cold-season precipitation to the annual runoff for arid-zone rivers. An efficient approach for the reconstruction of natural annual runoff time series is developed and tested. The problems relating to (i) the estimation of annual runoff for rivers with lacking or deficient observational data, (ii) the definition of climate forcing for natural runoff parameters, and (iii) the modelling of annual runoff time series are solved.