Identifying optimized structure and uncertainty analysis of monthly water balance model

Monthly water balance models (monthly Rainfall-Runoff models) are considered as the main tools in the evaluation and long-term planning of water resources. The main structure of these models included continuity equations for soil moisture storage, subsurface water and sometimes groundwater. Variables considered in the modelling of water catchments consist of surface runoff, precipitation, evaporation, and in some of cases, monthly average temperatures. Since there are too many unknown parameters in the monthly water balance equation used in the modelling process, using auxiliary relations is inevitable. These equations are usually empirical and recommended as default in the models. In this paper, the used relations in the structure of the Budyko model for estimating the contribution of groundwater in base flow, soil moisture and evaporation were optimized. The uncertainty of the result in both traditional and optimized models was evaluated using GLUE method. The results indicated an improvement in the optimized model performance and uncertainty compared to the common traditional model in three different watersheds.