Water is vital, not only for drinking but also in food production. However, changes in climate affect the overall water cycle and availability of water resources, threatening the whole agricultural sector. 

The objective of the hydrology model of MOSAICC is to estimate water resources under different climate change scenarios. The tool is based on STREAM ("Spatial Tools for River Basins and Environment and Analysis of Management Options"), a gridded rainfall runoff model simulating flow rates in water catchment areas.

STREAM can have several applications. At the scale of a watershed, STREAM can be used to estimate the water availability for irrigation schemes under different climate change scenarios. At country level, the model can be used to assess total actual renewable water resources.

The main output of this component is simulated volumes of monthly stream flows in the future driven by localized climate projections.