RainOff :   a conceptual rainfall-runoff simulation model with a nonlinear reservoir
Totally free download of software

The RainOff computer program, or simulation model, calculates runoff from rainfall on watersheds (hydrologic catchment areas) whose extension is limited by the condition that the rainfall can be assumed evenly distributed over the area. The program can be freely downloaded, it is free shareware in the public domain.
      The rainfall is converted into recharge by routing through a retention reservoir from which water escapes depending on predetermined characteristcs as storage capacity, initial storage and maximum rate of escape (representing evaporation or subsurface drainage). This first reservoir gives the recharge (rainfall excess) as overflow.
      The recharge is routed through a second, non-linear, reservoir with a reaction factor whose value depends on the storage level. Thus, the conversion (transformation) of rain into runoff (surface drainage) and flooding is produced.
      Modelling with RainOff gives the opportunity of predicting the hydrology of the watershed (catchmnent) and of flood forecasting.

The reaction (response) factor can be determined from recorded rainfall-runoff data. The program uses various reservoir functions and selects the optimal function. Alternatively, it is possible to introduce the reservoir function, together with rainfall data, and the program will calculate the runoff.
      On 12 December 2010 an extra graph was provided for the recorded rainfall-runoff statistics and trends, thanks to a suggestion by Mr. Juan Victoria.
      On 27 August 2012 the program was updated to include a quadratic reservoir function and on 1 december 2012 a Help function and an observed-calculated graph was added.
      More details are given in the program itself.

The program starts giving clicking on RainOff.Exe.
More information is given in the program itself.

A lecture note ("Data Analysis") on drainage research with examples of RainOff applications is found on the articles page.
              An example of the application of the Curve Number Method for the design of a surface drainage system for sugar cane plantations in a humid tropical coastal area can be found in a chapter ("Agricultural Drainage Criteria"), also on the articles page.


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introduction to rainfall-
           runoff software Introduction screen of RainOff program
The RainOff simulation program converts rainfall into
runoff depending on the characteristics of the
watershed or catchment area.
The software uses a reservoir model with inflow
creating storage of water and outflow.
The model can also be used for surface drainage.
rainfall-runoff simulation Example of RainOff application
The software model gives output graphics.
Here is an example of a fairly close fit
of the observed and simulated discharge of the
stream in a small valley.