Recharge Period Parameters

Period length (TPER): [T]. Length of the recharge period

Initial time Step (DELT): [T]. Length of the first time step in the recharge period

Time step multiplier (TMLT): The length of the time step is multiplied by this value after every step. The value for TMLT must be greater than or equal to 1. If it is equal to 1. then time step size will not be increased.

Maximum time step (DLTMX): [T]. If time step multiplier is greater than 1, then time step length will be successively increased until this value is reached, after which the time step length remains constant.

Minimum time step (DLTMIN): [T]. Time step length will not be reduced below this value.

Time step reduction factor (TRED): Factor by which time step length is reduced if convergence is not obtained after maximum iterations per time step is reached. The value of TRED must be between 0 and 1. Values between 0.1 and 0.5 are usually used. If TRED equals 0 or 1 then no reduction in time step size occurs.

Maximum head change (DSMAX): [L]. Maximum allowed change in head between successive time steps for this period.

Steady state head criterion (STERR): [L]. When maximum change in head between successive time steps is less than this value, the program assumes that steady state has been reached for this period.

Maximum height of ponding (POND): [L]. The meaning of this parameter depends on its sign (see figure). If POND is positive, then the surface of maximum ponded water height has the same shape as the land surface and is situated a distance of POND above the land surface. This setting is reasonable if the land surface is flat or uniformly sloping (cases A and B in figure) but is unrealistic if the land surface includes a furrow or depression (case C in figure). In case C, water would drain by overland runoff into the depression, where it might accumulate to some significant depth (case D of figure). This situation is simulated by specifying a negative value for POND. The negative value refers to the distance from the highest point of land surface to the surface of maximum ponded water height, which is always flat when POND is negative.

Print results (PRINT): Select this option to write output variables to main output file (vs2dh.out) for each time step in this period. Deselect this option to write output variables at output times and at end of the period. See: Output Options and How to Control VS2DH 3.0 output. If this option is selected the user should be warned that an excessive amount of output may be produced.

Simulate evaporation (EVAP): Select this option to simulate evaporation (over bare soil) in this period. (Not shown if evaporation is not simulated.)

Simulate transpiration (PLANT): Select this option to simulate transpiration (plant root extraction) in this period. (Not shown if transpiration is not simulated.)