SRCLET (Soil wateR CircuLation and EvapoTranspiration software) is an open-source desktop software tool for calculating various climate parameters on a monthly basis, with a focus on evapotranspiration and soil water balance. It includes basic calculation methods and allows for customization and the creation of entirely new methods. The tool is not limited in terms of the number of years of analysis or simultaneous analyses, which is an advantage compared to other similar tools.


The software’s graphical interface is of a simple design and offers the user the option to work in either Bosnian or English language. SRCLET utilizes tabular, comma-separated, or whitespace-separated values in the columns of a text file (.txt). The calculation results can be displayed in text files or other formats, which SRCLET places in the project folder where the user specifies the path, name, and format.

SRCLET calculations are based on monthly values of various climate parameters (such as air temperature, precipitation, wind speed, etc.) that the user inputs during the initial access to the software. The data is exclusively on a monthly basis, and there should be no missing values in the dataset. SRCLET does not verify the quality of the data, so it is necessary to check the data before inputting it. The entered data must have a defined time interval, which is determined by the year and month. Since this involves climate data, it is also necessary to provide information about the location where the data was collected, including the location’s name, geographical coordinates, altitude, etc.

The data entered in this way and defined through SRCLET are base parameters (BP) and changeable parameters (CP).

The user then proceeds to create a project, names the project, and from a list of methods, which includes other methods (OM), evapotranspiration methods (ET), and soil water balance methods (WB), selects the desired calculations. Depending on the entered base parameters (BP), SRCLET will automatically offer methods and calculations that can be computed based on them. The user then checks the methods they want to calculate and export in the desired format.

As part of the project definition, depending on the selected methods, SRCLET offers the option to modify the value parameters that are part of the mathematical formulation of a specific calculation. Since this is a tool for advanced users, SRCLET automatically assigns a standard value to these parameters, which the user can modify as needed. These parameters are called changeable parameters (CP).

NameEnglish nameAbbrevationExample
NameSymbol (unit)
Bazni parametriBasic parametersBPSrednja mjesečna temperatura zrakaTmean (oC)
Promjenjivi parametriChangeable parametersCPEmpirijski koeficijent za korekciju sunčevog zračenjakRs
Druge metodeOther methodsOMSunčeva radijacija po Hargreaves-Semani (1985) Rs_HS
Metode evapotranspiracijeEvapotranspiration metodsETFAO-56 Penman-Monteith (1998)ET0 (mm/dan)
Metode vodnog bilansa tlaSoil water balance methodsWBThornthwite (1948)THOR

After preparing the project in this manner, it is possible to perform the calculations and export the data in the desired format. SRCLET allows for the simultaneous calculation of multiple sets of data over an extended period. In the case of using the soil water balance methods, the dataset must end with December of the last year.

SRCLET fundamentally has two modes of use:

  1. Using existing calculation models OM, ET, and WB.
  2. Creating custom calculation models as well as OM, ET, and WB

The earlier described procedure pertains to the first mode of use. In the case of advanced user who wishes to customize existing methods or create new ones, they can do so by using options like “Create New Base Parameter (BP)”, “Other Method (OM)”, “Evapotranspiration Method (ET)”, or “Water Balance Method (WB)”.

Choosing one of these options opens a window for creation, allowing for the definition of the method’s name, symbol, unit of measurement, and mathematical formulation (Python mathematical functions). After creating and saving it, the new method is available for calculation by selecting “Create Project”. If user wants to create a new ET or WB, they need to ensure that all variable and base parameters are available, as well as other methods if the calculation requires them. If any of these are missing, the user first creates those parameters and methods, and then the ET and WB method.

In the case of evapotranspiration (ET) calculation, it is possible to select one of the following methods:
i. FAO-PM
ii. Thornthwaite (1948)
iii. Turc (1961)
iv. Hargreaves et al. (1985)
v. Trajkovic (2007)
Within the FAO-PM method, it is possible to perform a calculation in case of insufficient climate data following the procedure provided by Allen et al. (1998).

From the soil water balance (VBT) method, the software allows you to select one of the following:
i. Thornthwaite (1948)
ii. Palmer (1965)
iii. Alley (1984)
iv. Dingman (2002)
v. McCabe i Markstrom (2007)

SRCLET is currently in the final phase of preparation, which involves method preparation. We expect the first version to be available for free download by the end of autumn 2023.