The present work considers the Struma River water flow on Bulgarian territory as a starting point for evalua-tion of maximum and minimum water flow using an original integral method. The risk assessment is deter-mined by specific indices like the index Mmax,i for the deviation of the maximum water flow from the calcu-lated norm of the maximum flow Qmax,0 and the index Mmin,i for the deviation of the minimum water flow from calculated norm of the minimum flow Qmin,0. The new integral approach introducing specific indicators for risk assessment like the indices Mmin,i and Mmax,i has been checked at three sampling locations of the Na-tional monitoring net along the Struma River: Pernik (in the beginning), Krupnik (in the middle) and Marino pole (at the border in Greece) for the period 1948-2006. A significant trend towards decreasing of Mmax,i in-dex is outlined for the three points. On contrary, a significant trend towards increasing of Mmin,i index is found at Krupnik and Marno pole sampling points

The present work considers the section of the Mesta River on Bulgarian territory using the integral method for evaluation of climate and anthropogenic impact on the river flow. The level of this impact is determined by the index K(i) (flow module), the coefficient C(i) for the deviation of the average annual water volume Q(i) from the flow norm Q(o) and the index h(i) for the deviation of the average annual rainfall volume H(i) from the average multi-annual rainfall volume H(o). The dynamics of the average annual flow Q(i) at two typical hydrometric stations - Yakoruda and Khadzhidimovo, as well as the dynamics of the average annual rainfall for the Yakoruda station was examined for the period 1955-2003. The data for the considered period 1955-2003 exhibit a decreasing trend of the average annual water volumes dynamics for both stations due to the impact of climate changes in the Mesta River catchment.