helps in modelling effective rainfall, recharge, water
storage, runoff, drainage and discharge relations in
hydrological catchment areas (watersheds) using

the concept of a nonlinear reservoir.

EnDrain

does calculations on horizontal subsurface drainage
systems in agriculture, hydraulic head, depth and level
of water-table in agricultural land, and drain spacing
using the energy balance of groundwater flow but also
the Darcy and continuity equation (mass balance of
water). It includes drain entrance resistance and soil
anisotropy of hydraulic conductivity (soil permeability
for water), i.e. the horizontal and vertical hydraulic
conductivity are different. Applicable to pipe/tile
drains (drain pipes) and open ditches.

WellDrain

Calculates the spacing of wells, the shape, depth, and
level of the watertable in vertical drainage systems
using pumped wells. Like EnDrain, it permits aquifers
with various different properties and, in addition,
fully/partially penetrating wells.

SaltMod

a mathematical, numerical simulation model describing
the relations between agriculture, crop rotation,
irrigation, rainfall, potential and actual,
evaporation (evapotranspiration), climate,
hydrology, depth and level
of water-table, capillary rise, deep percolation, soil
salinity and subsurface drainage by drains or wells, and
reuse (conjunctive use) of ground and drain water from
wells. It includes farmers' responses to water logging
and soil salinity.

SaltCalc

A simplified version of SaltMod with the advantage that
calculations can be made for shorter time steps (e.g.
weekly or monthly). SaltCalc can be used when field
observations of irrigation, water table and soil
salinity have been made and one wishes to develop a
model for that situation. Normally, calibration of
unknown values must be done using a range of values of
the corresponding variable, running the model
repeatedly for a number of time steps, and
selecting from the range
the value giving model results closest to observed
values as the optimal value.

LeachMod

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.

SahysMod

a combination of Saltmod with a 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.