4.1.2—Hydrological cycle

Draw stores as boxes and flows as labelled arrows from source to destination, then state the system boundary.

At global scale, water matter is approximately closed: it changes state and location. Energy crosses the boundary as solar input and heat loss, so the system is open to energy.

A diagram can show ocean → evaporation → atmosphere → precipitation → river → ocean, with each arrow named.

The boundary determines which inputs and outputs count; a catchment is open even when the global cycle is nearly closed.

A store is an amount, not a process; flows need direction and often a rate.