Water Balance

Water balance analysis (hydrologic budget) attempts to understand the role of water within the Merrimack and its subwatersheds. The hydrologic cycle is a natural machine, a constantly running generator and pump.
The sun, which supplies heat energy, along with the force of gravity, keeps the water moving: from the earth to the atmosphere as evaporation and transpiration (evapotranspiration), from the atmosphere to the earth as condensation and precipitation, and on the earth as stream flow and groundwater flow, and then to the ocean.
The components of the hydrologic cycle can be summarized as precipitation (rainfall, snowfall, hail, sleet, dew, drizzle, fog, etc.), evapotranspiration, runoff (surface runoff, subsurface runoff, and groundwater runoff or baseflow), infiltration, percolation, and deep seepage.
Stream flow in a river is derived from the hydrological balance of its watershed. If one focuses on the hydrology cycle of a watershed, precipitation, evapotranspiration, surface runoff, infiltration, and baseflow are dominant processes that circulate water, as shown in Figure 2.

 

 

 

 

 

 

 

 

 

Figure 2 - Water Balance