To make sure that the model conserves energy and mass, energy and water imbalances appearing in a simulation will trigger errors and halt the simulation,
To accomplish energy conservation, all energy inputs at the land surface are reflected or absorbed. Absorbed energy may return to the atmosphere as sensible heat or may be emitted as terrestrial radiation, stored as soil heat, used to evaporate or transpire water, or used to melt snow and ice. Similarly, water incident on the land will evaporate, transpire through leaf stomata, run off and drain from the soil, or be stored in the soil and snow pack. The error checks for energy and water balance are contained in module BalanceCheckMod (Section A.1).
Water which runs off or drains from the soil fills river channels and flows downstream. At every model time step, the global sum of water which runs off and drains from the soil into the rivers must equal the global sum of change in river volume. This is because the global sum of water flowing out of grid cells must cancel the global sum of water flowing into grid cells from upstream. This error check is contained in module RtmMod (Section A.26).