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 This is a mathematical, numerical simulation model describing the relations between agriculture, crop rotation, and irrigation. Factors like rainfall, potential and actual evaporation (evapotranspiration), climate, and hydrology play also a role. The model calculates depth and level of shallow water-table, capillary rise and deep percolation as well as the salt balance in the soil It gives graphs of soil salinity and subsurface drainage by drains or wells. There is ample attention regarding the reuse (conjunctive use) of ground and drain water from wells. Finally, the model includes farmers' responses to water logging and soil salinity. This is a combination of Saltmod with a hydrologic model of ground water flow and hydraulics to account for large spatial variation through a network of polygons. It includes phreatic (unconfined) aquifers as well as soil layers with slow vertical hydraulic conductivity (soil permeability for water) resulting in semiconfined (leaky) aquifers. This is simplified version of SaltMod with the advantage that calculations are made for shorter time steps (monthly instead of seasonally or even daily). SaltCalc can be used when field observations of irrigation, sahallow water table and soil salinity have been made and one wishes to develop a model for that situation and for the maintenance of the salt balance in the soil. Normally, calibration of unknown values must be done using a range of values of the corresponding variable, running the model repeatedly and selecting the optimal value from the range that gives model results closest to observed values. This is simplified version of SahysMod with the advantage that calculations are made for shorter time steps (monthly instead of seasonally). The application principles are similar as those described before under "SaltCalc". This model is somewhat similar to SaltCalc. On the one hand the water management options are fewer (e.g. re-use of drainage or well water for irrigation do not feature here), but the model is more modern in the sense that the variable input for each time step is given in a table so that the calculations over all the time steps are done in one go. Moreover, by inserting the observed values of soil salinity in the data table, the model optimizes the leaching efficiency of the soil automatically so that the optimal salt balance can be found.