WaSim - Water balance model

Title: WaSim - Water balance model


Dr Tim Hess

Email: t.hess@cranfield.ac.uk

Client/Sponsor: Department for International Development (DFID)

Partner Organisations:  HR Wallingford

The model:

Developed by HR Wallingford and Cranfield University (with support from DFID), WaSim is a computer-based training package for the teaching and demonstration of issues involved in irrigation, drainage and salinity management. WaSim simulates the soil water salinity relationships in response to different management strategies (e.g. drainage designs and water management practices) and environmental scenarios (e.g. weather data, soil types, cropping patterns).


  • WaSim runs on a daily time-step using historical rainfall and reference evapotranspiration data
  • Simulations of up to 30 years in duration can be undertaken
  • Up to 3 crops (+ fallow) can be specified in rotation
  • Soil characteristics for a single layered soil can be specified
  • Irrigation can be scheduled according to ‘rules’ or specified for particular dates
  • WaSim simulates drainage to sub-surface tile (pipe) drains
  • WaSim can also be run as an unsaturated water balance simulation model, with drainage/watertable and salinity options switched off
  • WaSim incorporates comprehensive on-line help, and is accompanied by Users and Technical manuals.

Accompanying modules:

The DRAINSPACE module can be used to design drain spacing.

The WaSim-ET module is provided to calculate reference evapotranspiration from weather station data.


  • Soil water balance simulation
  • Calculation of irrigation requirements
  • Testing of water management scenarios
  • Watertable simulation in drained / un-drained environments
  • Evaluating the medium-term salinity build-up in the soil under different water management systems.
  • Downloads:

Download the WaSim software package

Download the WaSim software package

Download the WaSim software manuals


  1. Hess, T.M, and Counsell, C. (2000) A water balance simulation model for teaching and learning - WaSim. Paper presented at the ICID British Section Irrigation and Drainage Research Day, 29 March 2000. HR Wallingford.
  2. Graves, A.R., Hess, T., Matthews, R.B., Stephens, W., Mason, T. (2002). Crop simulation models as tools in computer laboratory and classroom-based education. Journal of Natural Resources and Life Sciences Education. Vol. 31:48-54.

Published applications:

  1. Depeweg, H. and Fabiola Otero, M (2004) Optimization of water management in the RUT Irrigation District, Colombia. Irrigation and Drainage, Volume 53, Issue 1 , Pages 55 – 67.
  2. Dongyi, Chen (2003) Analysis and Control of Salinity in Liyuanhe Irrigation District (LID), Gansu Province, China. Thesis HE 138, April 2003. IHE, Delft.
  3. Meenakshi Hirekhan, S.K. Gupta and K.L. Mishra, (2007) Application of WaSim to assess performance of a subsurface drainage system under semi-arid monsoon climate, Agricultural Water Management, Volume 88, Issues 1-3, 16 March 2007, Pages 224-234. ()
  4. Stephens, William, Hess, T.M. and Knox, J.W., (2001) The effect of energy crops on hydrology. Aspects of Applied Biology, 65:101-108. 

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