It's hydrological balance between rainfall plus irrigation to that of changes in soil moisture, evaporation, percolation and runoff.
The accounting of water input and output and change in storage of the various components of the hydrologic cycle .
Balance of the water resources of a region, comparing precipitation and inflow with outflow, evaporation, and accumulation.
Water that has a pH of 7.4 to 7.6, a total alkalinity of 80 to 140 ppm, Calcium Hardness of 200 to 400 ppm, and a TDS of less than 2500 ppm. The water is said to be "in balance" when the water is within these parameters.
A state of equilibrium when rainfall or irrigation water in a landscape is accounted for by the sum of run-off, plant water use, evaporation, recharge and changes in soil moisture content.
In hydrology, the water balance is an equation which describes how water can be accounted for within a drainage basin.