The hydrologic cycle over land includes interception of water by plant foliage and wood, throughfall and stemflow, infiltration, runoff, soil water, and snow. These are directly linked to the biogeophysics and also affect temperature, precipitation, and runoff. Total runoff (surface and sub-surface runoff) are routed downstream to oceans using a river routing model. A river transport model (RTM) is synchronously coupled to the Community Land Model (CLM) for hydrological applications as well as for improved land-ocean-sea ice-atmosphere coupling in the Community Climate System Model (CCSM).