ENVIR SCI 1A03 February 12, 2014
Hydrologic Cycle and Water Balance
What is the Hydrosphere?
• All of Earth’s water.
• Ocean – 97% of all water, freshwater – most in glaciers and ice caps,
surface freshwater are in streams or lakes.
• Hydrologic Cycle
o Over the ocean – 86% evaporation, clouds will form and cloud will
move from over ocean to land and the transfer between land and
atmosphere are going to be balanced.
o The movement on the land by slopes balances the net transfer
between the atmosphere and the land.
Where does Rainwater go on Land?
• Water can be absorbed by plants or evaporated = evapotranspiration
• Can infiltrate the ground and percolate downward and fill pore spaces and
recharge water table and form water table
• Move at the surface – runoff as overland flows, inter flow is just beneath
the ground surface
What is a Water Balance?
• Represents: hydrological cycle at the local state
• Accounts for interactions with the available energy and moisture at the
• Take into account moisture and latent heat
• Take a look at all the energy the system provides – output, input and
What is the Water Balance Equation?