LEC 11: WATER CYCLE AND RESOURCES

Surface Balance = Supply – Demand ± Surplus/Deficit

The balance between how much of something is available (supply) and how much is needed or used (demand).

Effects of Water Surpluses

• Recharge soil moisture

• Recharge deeper groundwater

• Become runoff

1. Supply: Precipitation

atmosphere to oceans/land

2. Demand: Evaporation

oceans/land to atmosphere

3. Demand: Transpiration

plants to atmosphere

4. Surplus: Runoff

land to oceans

Potential Evapotranspiration (PET)

Maximum amount of water that could evaporate from the ground and be released by plants

Actual Evapotranspiration (AET)

Amount of water that actually evaporates from the ground and is released by plants

Precipitation (P)

Water that falls from the atmosphere

Evapotranspiration (ET)

Water that returns to atmosphere

→ Evaporation from surfaces, Transpiration from plants

Percolation

Gravitational pull of water downwards through pore space in soil and rock

Porosity

Amount of pore space in rock or sediments

Permeability

Degree of connectedness among pores

Groundwater Mining

Removing water faster than nature can replace it