Hosted by Aberdeen University Plant & Soil Science:

The S.W.E.A.T. Model

Soil, Water, Energy And Transpiration

The majority of soil water and energy transport models used by agriculturalists (i) simulate water movement separately from heat flow, and therefore unreliably simulate the top 50 mm of the soil column where water vapour transfer is more significant (crucial for predictions of seedling emergence) and (ii) are coarse-scale, taking a field or larger area as their basic spatial unit, making it impossible to simulate the high variability in soil wetness over smaller spatial scales in many forest, agricultural or other ecosystems (Campbell 1985, Monteith & Unsworth 1990, Daamen & Simmonds 1994, Marshall et al. 1996). SWEAT simulates coupled water and energy fluxes in soil profiles at a fine spatial scale, which makes it particularly suitable for in situ seed germination and seedling establishment studies.
SWEAT was originally developed at ESSC Reading in 1994 with funding from the ODA (now DfID) and was based largely on the teaching program SPACTeach (see below) (the old REM website is here). Versions after 5.0 were developed with funding from NERC. You may need 7-zip to open the .zip files below.
    Download here the original version of SWEAT © 1994, University of Reading, U.K. (in Turbo Pascal, Borland® International) and associated manual (this is a scan of my personal copy: please ignore the scribbles). The manual, Daamen & Simmonds (1996) and Daamen (1997) contain between them a full description of this model. This version included a weather data manipulation program called READMET and an example input file (corresponding to Daamen & Simmonds 1994:Appx.F), which you can run by double-clicking on the "SWEAT.EXE" file (if using Windows®).
    Download here SWEAT version 3.0.3 (in Turbo Pascal, Borland® International) and associated manual from 1999 by David Pearson. ** N.B. DP does NOT offer support services for this model **. To make this run the 'Appx. F' example, upload the "METEOROL.DAT" file from SWEAT 1.0, this file "SWEAT.DAT" and the UNIX executable "sweats" onto a UNIX server and type "./sweats".
    Download here SWEAT version 4 (in Turbo Pascal, Borland® International) from 2001-04 (unfinished) by David Pearson. ** N.B. DP does NOT offer support services for this model **
    Download here SWEAT version 5.1 (in R) and associated Notes file from 2006 by Toby Marthews. Basically, the idea of SWEAT 5.1 was to go through all previous versions, get rid of any code that no longer functioned (e.g. the 'pumping' module of v4) but keep all functioning code unchanged (i.e. the actual science of v5.1 is identical to that of v3.0.3 and v4, although the input screen (all the long questions) and output format (combined into one output file) are different) and translate it all into R so that it can be run more easily. Although it has convergence problems if the soil is continually wet (Marthews et al. 2008), outside high-rainfall zones it should work fine. For the theoretical background of v5.1, please download the manual to v1.0 (above): it's still the quickest and easiest way to understand how it all works. To make this run the 'Appx. F' example, follow the steps in the notes file. R was chosen for its ease of programming not for its execution speed, by the way, so expect that SWEAT 5.1 will run significantly slower than the other SWEAT versions. ** N.B. TM does NOT offer support services for this model **.
    Download here SWEAT version 5.2 (in R) from 2006 by Toby Marthews. This is the version used in Marthews et al. (2008) to model soil drying in a tropical forest. I have a version 6.0 too, but neither v5.2 nor v6.0 are fully satisfactory because of the way the simulation doesn't converge when the soil is very wet and the soil layers are thin. The latest functioning version of SWEAT is version 5.1. ** N.B. Version 5.2 is unfinished, will NOT run as is and TM does NOT offer support services for this model **

SPACTeach is a computer-assisted learning module for exploring water movement in the Soil-Plant-Atmosphere Continuum (Simmonds et al. 1995 and there is a short description in this 2002 book; also see here and the old REM website is here). Primarily motivated by Lester Simmonds (Univ. Reading, now retired) and developed by John Schofield, it was a collaborative project between the the University of Reading, UK, and the University of Aberdeen, UK,.
    *** REQUEST *** Below are all the SPACTeach-related files I could find in 2009. I have asked everyone I can think of at Reading, CLUES and Aberdeen, but I do not have a copy of the SOURCE-CODE of SPACTeach (almost certainly written in TurboPascal so this would be a *.pas file possibly SPACTEACH.PAS) and currently (March 2015) it seems that this was not archived anywhere by anyone. Every once in a while I get asked whether I have this (and it would be useful because then we could recompile and wouldn't have to use the VirtualBox) so if YOU have a copy of the source-code, please email me and I will upload it here for everyone to use. Very many thanks! Toby. ***
    Here are the two versions I have of SPACTeach:
   Version 0.0 (1994) from University of Reading, U.K. (courtesy of Anne Verhoef in August 2009). To start SPACTeach, run the SPAC.EXE file (however n.b. this is an executable for 32 bit Windows so it won't work on Windows 64 bit - more or less anything from Vista onwards - and you'll need instead to run it within a VirtualBox environment, e.g. I use the freeware Oracle VM VirtualBox).
   Version 1.0 (1995) from University of Aberdeen, U.K. (courtesy of Chris Mullins in July 2009). Includes the two word docs GETSTART (= How to use SPACTeach) and LECTURER (= Teaching notes).
(Personally, I prefer the Reading version because it has the 'Time0' button that was taken out of the Aberdeen version). Although the meteorology is very basic, no explicit heat or vapour flow is implemented and you can only choose between 6 predefined soil types, SPACTeach is straight-forward to use with its point-and-click user interface and can give you within minutes a nice animation of soil water movement that is very good for teaching purposes. It is very good for getting a rough visual idea of how water should be moving in your soil, which you can then check against a more sophisticated model (e.g. SWEAT). Because CLUES no longer exists at University of Aberdeen, this software can presumably be used without licence.

EMERGE is a combination of SWEAT with a seedling germination and growth model called GEMA. It was a collaborative project between the University of Aberdeen, UK, the University of Reading, UK, and Sokoine University of Agriculture, Tanzania, with funding from the ODA (now DfID).
    Download here the EMERGE model © 1996, University of Aberdeen, U.K. The manual (Mullins et al. 1996) contains a full description of this model.
    Download here another version of EMERGE (in QBASIC, Microsoft®) and associated ReadMe file from 1999 by John Townend.

Contact for further information: Toby Marthews. Any extra information on this little family of models would be very welcome, by the way (does anyone have any other versions they'd like to see uploaded?). For MICRO-SWEAT, see Burke et al. (2003).

Burke EJ, Shuttleworth WJ & Harlow RC (2003). Using MICRO-SWEAT to Model Microwave Brightness Temperatures Measured during SGP97. Journal of Hydrometeorology 4:460-472.

Campbell GS (1985). Soil physics with BASIC (1st ed.). Elsevier.

Daamen CC (1997). Two source model of surface fluxes for millet fields in Niger. Agricultural and Forest Meteorology 83:205-230.

Daamen C & Simmonds L (1994). SWEAT - A numerical model of water and energy fluxes in soil profiles and sparse canopies. Manual, University of Reading, UK. *

Daamen CC & Simmonds LP (1996). Measurement of evaporation from bare soil and its estimation using surface resistance. Water Resources Research 32:1393-1402.

Marshall TJ, Holmes JW & Rose CW (1996). Soil Physics (3rd ed.). CUP.

Monteith JL & Unsworth MH (1990). Principles of Environmental Physics (2nd ed.). Edward Arnold.

Mullins CE, Townend J, Mtakwa PW, Payne CA, Cowan G, Simmonds LP, Daamen CC, Dunbabin T & Naylor REL (1996). EMERGE - A model to predict crop emergence in the semi-arid tropics. Users’ Guide, University of Aberdeen, UK.

Simmonds L, Schofield J and Mullins C (1995). SPACTeach - a computer assisted learning module exploring water movement in the soil-plant-atmosphere continuum. MERTaL Courseware, University of Aberdeen, Aberdeen.

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