The Contracting Parties shall establish, on the basis of a harmonised methodology, domestic
water balances, as well as the general water balance of the Danube River Basin. As an input for this purpose
the Contracting Parties to the extent necessary shall provide connecting data which are sufficiently
comparable through the application of the harmonised methodology. On the same data base water balances
can also be compiled for the main tributaries of the Danube River.