The answer is a qualified "yes." REF-ETw will read and process all DEF files that were created with older versions of the program. However, there are now more parameters that are used and created by REF-ET and that are saved to the definition file.

Therefore, when "old" DEF files are read into REF-ET, the user needs to carefully review the definition "screens" and fill in or modify some of the parameters. For example, REF-ET now keeps track of the specific ET equations that are calculated and printed.

REF-ET can only read data from ASCII (text) data files. However, the data can be in a wide variety of formats and values can be separated by spaces, tabs, or commas. However, an ASCII file can be created from a spreadsheet fairly easily.

If data are in a spreadsheet, an ASCII data file (.dat) can be created for the weather data by pasting the spreadsheet data into WordPad and then saving it as a text file. This is done by loading the spreadsheet file into the spreadsheet program (for example, QuattroPro or Excel), then marking the block of data columns that include all of the information that needs to be read by REF-ET (for example, date or day of year, maximum and minimum air temperature, etc.). It is OK to include column headings in the block since these can be ignored when the file is read by REF-ET. Once the block has been highlighted (marked) in the spreadsheet, select Edit Copy from the menu bar of the spreadsheet to temporarily copy the block into the Windows clipboard. Then, open the Windows WordPad editor (by pressing the Windows Start button and selecting Programs and then Accessories and then WordPad). Once WordPad is open, you can select Edit Paste from the menu bar of WordPad to paste the weather data into WordPad.

After the weather data have been pasted into WordPad, the new data file is created by selecting File SaveAs from the menu bar of WordPad. After selecting the folder into which to place the data, the name of the data file should be specified as ---------.dat where "--------" is to be filled in by the user. In addition, the "Save as type" window should be selected so that the file type is "Text Document". The "Text Document" file type is the same as ASCII. Then press the "Save" button.

After the "ASCII" data file has been created using WordPad, it can be read by REF-ET as a data file. All columns in the spreadsheet will be presented in the new file as "tab delimited" data. In other words, all values will be separated by tabs. Therefore, when the REF-ET definition file is created, as described in the next section, no beginning or ending column numbers need to be specified by the user, since REF-ET will recognize that the data are separated by tabs. Any "blank" columns in the spreadsheet will be represented in the WordPad data file as an extra tab. However, REF-ET will ignore this extra tab, and will go on to the next data item. Therefore, the process just described will essentially delete empty columns that were in the spreadsheet as far as REF-ET is concerned. The user will need to experiment to insure that the .dat file that is created is read properly by REF-ET. This can be done by viewing the ".IN1" intermediate file that can be created by REF-ET as described in a later section. The IN1 file contains an "echo" of the data as read in by REF-ET. This is all covered later.

There is currently no help information that is built directly into REF-ET for Windows version 2.0. However, you should be able to find help on a number of topics by viewing the REF-ET manual that is on this site.

Future versions of REF-ET will contain extensive help. We apologize for this inconvenience at the present time.

REF-ET is programmed in MicroSoft Visual Basic version 6.0
The Visual Basic source code for REF-ET is not available for distribution. Distribution is restricted so as to insure protection of the "integrity" of the software and to insure that the standardized calculation of parameters remains true to name.
Any questions concerning how a particular parameter or condition was coded into REF-ET can be submitted to the discussion group. Registered users of REF-ET can submit questions concerning the implementation of equations via the special Email address made available upon registration

The "read past end of file" error is probably caused by the "format" of the data file or definition file. The various "lines" of the file may only use a "line feed" character (ASCII code 10) to separate themselves.

REF-ET, when it reads a line of data or a line from the definition file, expects each line to be separated by both a "carriage return" character (ASCII code 13) and the line feed character. This latter combination is "standard" practice for text or ASCII files.

When only the line feed is present, REF-ET tries to read the entire file as a single line of data until it runs out of memory. It then quits and issues the error. Sometimes this problem occurs when files are sent across the internet in Email attachments. Some Email programs may modify how lines are delineated.

The carriage return and line feed characters are invisible in most editors, so it is difficult to know what has been used. However, if you get the Error #62, or if you see your data in the "peek" window on the first definition file screen appear to all be on a single line, you can suspect that carriage returns are missing.

Fortunately, this problem is fairly easy to fix. Generally, if you open the data or definition file in a standard "text" editor, for example, MicroSoft WordPad, and then save it, the text editor will automatically insert the required carriage return characters. Be careful that you don't use a word processor such as Word, since these processors prefer to save the file in their own format with all kinds of junk characters that will drive REF-ET nuts. If you do use a word processor make sure that you 1) use a small enough font size so that all data lines are on the same line and do not "wrap." 2) you save the file as a "text" file (use the "File Save As" command). It is recommended that you use WordPad, which on most Windows machines you can find by selecting "Start" and then "Programs" and then "Accessories" and then "WordPad."

The typical way to calculate ET for other crops (ETc) is to use the crop coefficient (Kc) method, where ETc = Kco ETo or ETc = Kcr ETr where ETo is grass reference ET and Kco is a crop coefficient intended for use with grass reference ETo.

Unfortunately, REF-ET does not calculate Kc's or ETc. This can be a relatively complicated process due to the large number of crops and derived Kc curves around the world, the various means of expressing the Kc curves vs. time or vs. energy units, the method for estimating evaporation from wet soil, etc. Therefore, REF-ET does not attempt to make these calculations.

The user is referred to publications that describe how to apply Kc curves and that include tables of Kc values. In addition, many local universities and research centers often have locally derived or fitted Kc information.

There are also a number of computer programs available that can assist in calculating ETc using the crop coefficient method. Some of these include

the IWR model by NRCS at
http://www.wcc.nrcs.usda.gov/nrcsirrig/Water_Management_Models/water_management_models.html

CROPWAT - FAO Program for Irrigation Planning and Management at
http://www.fao.org/WAICENT/FaoInfo/Agricult/agl/lwris.HTM

and, in the western US, from the WaterRight web site:
http://www.wateright.org/
 

Publications that list typical values for Kc include the following:

Doorenbos, J. and W.O. Pruitt, 1975, 1977. Guidelines for predicting crop water Requirements, Irrigation and Drainage Paper 24, (1st and 2nd ed)., Food and Agriculture Organization of the United Nations, Rome, 179 and 156 p.

Jensen, M.E., R.D. Burman, and R.G. Allen (ed). 1990. Evapotranspiration and Irrigation Water Requirements. American Society of Civil Engineers, Engrg Pract. Manual No. 70. 332 p.

Allen, R.G., Pruitt, W.O., Businger, J.A., Fritschen, L.J, Jensen, M.E., and Quinn, F.H. (1996). "Evaporation and Transpiration." Chapter 4, p. 125-252 in: Wootton et al. (Ed.), ASCE Handbook of Hydrology. New York, NY.

Allen, R.G., L.S. Pereira, D. Raes, and M. Smith. 1998. Crop Evapotranspiration: Guidelines for computing crop water requirements. Irrigation and Drainage Paper 56, Food and Agriculture Organization of the United Nations, Rome, 300 p.

Doorenbos, J. and Kassam, A.H. (1979). "Yield response to water." FAO Irrig. and Drain. Paper No. 33, FAO, Rome, Italy. 193 pp.

Wright, J.L. 1982. New Evapotranspiration Crop Coefficients. Journal of Irrigation and Drainage Division, ASCE, 108:57-74.

Feddes, R. A. 1987. Crop factors in relation to Makkink reference crop evapotranspiration. Tech. Bull. Inst. for Land and Water Management Research. No. 67, pp. 33-45.

Fereres, E., (1981). (ed.) "Drip irrigation management." Cooperative Extension, Univ. California, Berkeley, CA, Leaflet No. 21259.

Grattan, S. R., W. Bowers, A. Dong, R. L. Snyder, J. J. Carroll, and W. George. 1998. New crop coefficients estimate water use of vegetables, row crops. California Agriculture 52 (1): 16-21.

Howell, T. A., D. A. Bucks, D. A. Goldhamer, and J. M. Lima. 1986. "Management Principles: 4.1 Irrigation Scheduling.", in Trickle Irrigation for Crop Production: Design, Operation and Management (F. S. Nakayama and D. A. Bucks (ed)). Elsevier.

Howell, T. A., Steiner, J. L., Schneider, A. D., and Evett, S. R. 1995. Evapotranspiration of irrigated winter wheat - southern high plains. Trans. ASAE 38 (3): 745-759.

Neale, C. M. U., W. C. Bausch and D. F. Heerman. 1989. Development of reflectance-based crop coefficients for corn. Trans. ASAE 32 (6): 1891-1899.

Snyder, R. L., Lanini, B. J., Shaw, D. A., and Pruitt, W. O. 1989a. Using reference evapotranspiration (ETo) and crop coefficients to estimate crop evapotranspiration (ETc) for agronomic crops, grasses, and vegetable crops. Cooperative Extension, Univ. California, Berkeley, CA, Leaflet No. 21427, 12 p.

Snyder, R. L., Lanini, B. J., Shaw, D. A., and Pruitt, W. O. 1989b. Using reference evapotranspiration (ETo) and crop coefficients to estimate crop evapotranspiration (ETc) for trees and vines. Cooperative Extension, Univ. California, Berkeley, CA, Leaflet No. 21428, 8 p.

There are example spreadsheets available for applying the FAO-56 Kc curves on the www.FAO.org web site (note these are not available yet, but soon will be).

Generally when this happens, REF-ET is able to read the first part of the file and show the first screen in the file definition portion of the program. However, when the user presses the continue key to advance to the second screen, REF-ET quits and displays the error.

The problem is in the def files that were created by version 2.0 or older of the DOS version of REF-ET (before about mid 1991). This version did not include a place for station longitude. REF-ET for Windows assumes that longitude (or a value of 0) will be in the definition file. When it is missing, REF-ET reads the next parameter (in this case day-night wind ratio) as longitude and then becomes off one "cog". It ultimately runs out of data in the definition file or attempts to read a string as a numeric value, hence the Run-time error 13, Type mismatch.

The problem can be fixed by opening the definition file using a text editor, and inserting a zero (0) after the entry for latitude. This will normally be on the second or third line of the file. You don't need a real value for longitude if you are making daily calculations, since longitude is used only for hourly computations. However, it still demands a place in the definition file. Don't worry about preserving the exact format of the edited line. REF-ET is able to find the values as long as they are in the correct order. However, it is important that you don't delete any lines in the definition file, since REF-ET uses the number of lines and beginning characters to confirm where it is at.

If you use a text editor or word processor to open and edit the definition file, be careful to save it as a standard text (i.e., ASCII) type of file so that no word processing characters are imbedded.

Users installing REF-ET on computers having Windows 2000 may encounter the following problem during installation:

A prompt may be displayed saying that the installation needs to update files on the computer. These are various .dll and .ocx files related to Visual Basic and updating these files should not cause any problem with the computer. You should allow the installer to update the files. The installation will then ask you to restart the computer.

If, after restarting the computer and reinitiating the REF-ET installation, you receive the same message, then this indicates that an updated "service pack" is needed for your Windows 2000 installation. At least "Service Pack 2" should be on your computer. The latest service pack for Windows 2000 can be found at: http://www.microsoft.com/windows2000/downloads/servicepacks/

After downloading and installing the new service pack from Microsoft, you should be able to install REF-ET. You might receive an error message during REF-ET installation about problems in copying a system file named "DBGRID32.OCX." If this message occurs, click on "Ignore" and REF-ET will load normally.

We apologize for this defect by William Gates.