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:   1. - The computer programs are supposed to be self explanatory. Examples of input and output files are given.
            2. - Since 06-03-1961 the source code of the software was made available for free download on the source code page.

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 15 programs for more information and free downloads.
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CATEGORIES:             (A) Irrigation, drainage, waterlogging,
& soil salinity
           
(B) Drainage, runoff, drain &
well spacing
           
(C) Statistics, frequency & regression             (D) Alternative software, in   development            
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(A) Irrigation, drainage, waterlogging, salinity
SaltMod 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 water-table, capillary rise and deep percolation. 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.

SahysMod This is 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 This is 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.

PolySalt 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".

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
RainOff This helps in modelling effective rainfall, recharge, and water storage. It calculates runoff, drainage and discharge relations in hydrological catchment areas (watersheds) using the concept of a nonlinear reservoir.
EnDrain This model does calculations on horizontal subsurface drainage systems in agriculture, hydraulic head, as well as depth and level of water-table in agricultural land. It comes up with a 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. All is applicable to pipe/tile drains (drain pipes) and open ditches.

WellDrain This model 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
CumFreq
This model 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. It can anlyse hydrologic factors like rainfall, river and drain discharge, water and river level. Also the depth or level of watertable, soil salinity, and the hydraulic conductivity (i.e. soil permeability for water) can be sudied. The software 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 This is a two-way calculator for normal probability distributions with graphics: Value => Probability, and Probability => Value. The calculator can be used for many kinds of statistical probability analysis.

SegReg This model 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 This is 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, it is also a two-way calculator: F-value => Probability, and Probability => F-value.

PartReg This software is similar to SegReg but it emphasizes the horizontal part in Type 3 and Type 4 relations with the aim to define crop tolerance levels more precisely. Further explanation is given on the PartReg page.

t-distribution calculator This is 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.

Simulation models are
      software

(D) Software and apps in development
Alternative calculator
This ia 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.
LeachSalt & SaltSim
The model LeachSalt is in development. It is an amplification of LeachMod permitting two neighboring areas with different irrigation treatments so that the salt balance in one area may influence the balance of the other. For example it simulates the capillary rise in one area with limited irrigation supply induced by the percolation from the second area with ample irrigation.
            Also, a simplification of LeachMod (SaltSim) is on the way in which the underground water movement and the subsurface drainage are eliminated. This model is applicable for experiments in lysimeters or in controlled field experiments with saline irrigation water.
            Check with the sitemaster for more info.

soil salinity and
      statistics are not always easy
Click on any of the above 15 programs for more information and free downloads.                                                  
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crop yield and soil salinity
This data set of crop yield and soil salinity needs an analysis by segmented regression to determine the response and salt tolerance of the potato.

Here, the soil salinity is expressed in terms of electric conductivity (EC) of an extract (e) from a saturated soil paste ==> ECe

If the relation shows a not descending line in the first stretch of ECe values, e.g. from ECe=0 to ECe=7, then this is a stretch of "no effect", and the tolerance level can be set at ECe=7 beyond which value the yields start to decline due to negative influence of the saline soil.

For more explanation see this lecture note on segmented regression
 

crop yield and soil salinity
This data set of annually maximum 1-day rainfalls needs an analysis by probability distribution fitting to determine the frequency of occurrence of extreme values and the cumulative frequency.

Such an analysis can be done with the SegReg model which also gives a histogram as well as the correlation between predicted and observed values. The applicability of the probabity distribution is expressed in terms of goodness of fit.

For more explanation see this lecture note on frequency analysis