Upper boundary condition

Salts that infiltrate the soil can come from several sources. Salt deposited from the atmosphere enters the soil profile with the infiltrating water from precipitation, (qin – iar). A road salt application can optionally be chosen (see switch RoadSaltApplication). In this case an additional salt input, qClroad, is added to the total infiltration during conditions when the air temperature is within a specified range determined by the parameters tsalthigh and tsaltlow. Alternatively, salt can be added to a storage pool on the road (see switch SaltRoadStorage), which emits salt resulting in a salt infiltration rate, qClRoadInf, as described in detail below. Finally, water used for irrigation of crops (see Irrigation below) may also contain salts. The total salt infiltration is calculated as:

(2.56)

where cCldep is the salt deposition concentration, qin is the total amount of infiltrated water, irate is the irrigation rate, idriprate is the irrigation rate for drip irrigation and cClirrig is the concentration of salts in the irrigation water, which can either be given as a parameter or can be read from a PG-file (see switch IrrigConcInput).

Secondly, salts are removed from the surface through surface runoff, qsurf, according to:

                                                       (2.57)

where qClroff is the removal rate of salts with runoff and CClz1 is the salt concentration in the uppermost soil layer.