Software and mathematical (numerical) simulation models,   free downloading
Principles:   The software shown below, consisting of mathematical (numerical, computer, simulation) models, all has the same features:
-- an input menu for data handling
-- a calculation phase
-- an output menu for inspecting results including graphs
-- a possibility to make *.prn or *.txt files for spreadsheet use
Hints:   The computer programs are supposed to be self explanatory. Examples of input and output files are given.
Acknowledgement:   I acknowledge the contributions of users of the software worldwide who, through their valuable observations and suggestions, have helped to continually improve the software.                                                                                                    
Contact:   I would appreciate it to learn about your experiences. For this there is a contact form .
Click on any of the following 7 programs for more information and free downloads.
General articles
& manuals
(in Spanish,
 en Español)
reports & cases
reports & cases
& answers

CATEGORIES:             (A) Irrigation, waterlogging, salinity             (B) Drainage, runoff, drain & well spacing             (C) Statistics, frequency and regression             (D) Alternative software, calculators            
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(A) Irrigation, waterlogging, salinity


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.

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.
SaltCalc A simplified version of SaltMod with the advantage that calculations are made for shorter time steps (monthly instead of seasonally). 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 and selecting the optimal value from the range that gives model results closest to observed values.
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 automatically.
Soil salinity is not soft,
        but soil science is not hard

(B) Rainfall-runoff relations, drain and well spacing equations


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/budget 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.
A real model is not a simulation model

(C) Statistics, frequency and regression analysis, probability calculators


is meant for segmented (in splines, piecewise) cumulative frequency analysis using a breakpoint which serves for example to study discontinuous probability distributions and return periods of hydrologic factors like rainfall, river and drain discharge, water and river level, depth or level of watertable, soil salinity, hydraulic conductivity (soil permeability for water). It uses 20 different probability distributions and selects the best fitting. Preference for a certain distribution can also be expressed. An amplified version (CumFreqA), permitting to express preference for advanced composite distributions, can be made available on request.

NormDis A two-way calculator for normal probability distributions with graphics: Value => Probability, and Probability => Value. This calculator can be used for many kinds of statistical probability analysis.
SegReg can be used for segmented linear regression, i.e. regression in segments, using a breakpoint (break-point) or threshold value, which serves for example to analyse the relation between plant growth or crop production in agriculture versus soil salinity and depth of watertable in agricultural land. The software analyses 2x6 different types of models and selects the best fitting. An amplified version (SegRegA), permitting to express preference for a certain model, can be made available on request.
F-test calculator A calculator for the Fisher's F-test as used in analysis of variance (Anova). The above SegReg model uses this test for the significance of the regression. Like NormDis, this is also a two-way calculator: F-value => Probability, and Probability => F-value.
No work without errors,
      but it is difficult to do nothing

(D) An alternative extended general calculator, probability calculators

Alternative calculator

An alternative, extended calculator, originally developed by my grandson Niklas Burggraaff at 10 years of age (!). It is suitable for a long sequence of calculations as necessary in large equations. It has two input options (X and Y) and it can perform transformations of X and Y before doing the operations with X and Y. The results can be moved to X or Y to continue the next sequence of transformations and operations, or they can be stored for later use in X or Y. The record of actions is shown in a tracking table.

NormDis A two-way calculator for any normal probability distribution as also shown above under "Statistics" : Value => Probability, and Probability => Value, which can be used for many kinds of statistical probability analysis.
F-test calculator A calculator for the Fischer's F-test as used in analysis of variance (Anova). It was already introduced before under : "Statistics". The above SegReg model uses this test for the significance of the regression. Like NormDis, this is also a two-way calculator : F => Probability, and Probability => F
t-distribution calculator A two-way t-distribution calculator to perform a t-test on the significance of the difference between means (averages) of series of data using Student's t - probability distribution : t-test-value => Probability, and Probability => t-test-value.
Searching for alternatives
      is not always easy
Click on any of the above 12 programs for more information and free downloads.                                                  
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