Many different approaches can be taken to budget a particular system. Consider a coastal water body which is of interest. The rate of water exchange between that system and adjacent systems is estimated by one of several procedures. The simplest procedure to describe water exchange in many coastal marine systems is the construction of combined water and salt budgets for those regions. In addition to this budget for water itself, a salt budget can also be established.
Water mixes back and forth between the system of interest and adjacent systems.
Each of the water inputs and outputs described by the water budget and described by the mixing has a characteristic salinity. Water and usually salt in a system can be assumed to have no internal sources or sinks. That is, the inputs and outputs just outlined account for the water and salt budgets. This combined water and salt budget does not provide a dynamic, quantitative understanding of the processes controlling the characteristics of water exchange in a particular system, but it is often a quick and simple way to describe the exchange. More details on the arithmetic of water and salt budgets and some examples of the procedure for describing water exchange can be found by clicking here .