Assessment of the Water Budget from GLDAS Model

According to the EU Water Framework Directive every country is obliged to monitor the groundwater level, which is essential for the country's water management. Among others, the groundwater is a very important source of drinking water and a significant element of the agricultural economy. Water budget (balance), a basic quantity of hydrology, is used to assess the amount of water in the ground needed for consumption. This is the reason why the water budget must also be calculated, even if the basic purpose is the groundwater level determination from GRACE data. Water budget computations are based on evapotranspiration and land surface hydrosphere state. The quantities required to calculate it can be obtained from land data assimilation systems, like American GLDAS (Global Land Assimilation System). In this paper, all the components of the water budget, like precipitation, surface run-off and evapotranspiration, are studied over the area of Poland. The resultant water budget is determined, interpreted and presented graphically.