The Drainage Basin Hydrological Cycle: The Water Balance.

(Precipitation = runoff + evapotranspiration + change in storage)

Drainage basin = area of land that is drained by a river and its tributaries.

Water can be stored in:

1. Leaves or branches of vegetation (by interception).

2. The surface as puddles, either on impermeable or waterlogged ground.

3. In vegetation, depending on type and season.

4. In soil.

5. In porous rocks (aquifers).

6. In the river channel.

Water can move by:

1. Throughfall (dripping from leaves to the ground), or stemflow (flow down stems or trunks). 

2. Infiltration (water sinking into the soil). If the infiltration rate is exceeded by that of throughfall/stemflow, water travels across the ground in overland flow, usually to a river. Otherwise, the water travels more slowly to the nearest river by throughflow. This is aided by root channels in the soil, meaning a higher amount of vegetation leads to quicker flow.

3. Transpiration through leaves.

4. Percolation into the rocks below. Rate of this depends on permeability of the rock.

5. These all lead to a river or groundwater store. The water is transported in the river by channel flow. The amount of water that leaves the drainage basin in this way is called runoff.

6. Evaporation.