My research basin located in the Canadian province of Quebec, Sherbrooke. I can't find the evapotranspiration (ET) data from the near weather stations. Where I can find the available evapotranspiration (ET) data from 2009-2015?
Dear Dr Yu, nice question, ET for a region/basin could be from various sources
1. point based observations recorded within the region by some research agency, secondary data source
2. Reference ET computations for crops for the specific region
3. Field water balance approach
4. Simple empirical approaches for ET estimates, over years and for normal weather
regards
Dear Dr Yu,
You can go through link: http://www.fao.org/docrep/x0490e/x0490e04.htm
Bests,
Ansar
1- Meteorological data
2- water balance method, it can be field base or lysimeter base
3- Via instruments such as ET guage for current work , not for past
4- Generally , mathematical models can be a useful tool.
For your case( 2009 - 2015), you can use secondary data if available
Dear Liu,
I think your main problem is the scarcity of site specific ET values for calibrating SWAT. You might try with either computing reference crop evapotranspiration (ETo) using FAO-Penman-Monteith formula or by using the data from nearby stations.
In case of using FAO model, you will then need to multiply the ETo to the crop coefficients. The values of this coefficient can be found in FAO publications and other text books.
In case of using nearby stations, jsut remember that the distance is not the main factro to be considered. You should consider the similarities based on air temperature and wind speed variations as well as altitude differences. The most the wind and temperature variations similarities, the reliable the ancillary data application.
-best,
Jalal.
daily data for swat can be downloaded from here
http://globalweather.tamu.edu/
Why not have a look at the reanalysis data, which provide long term ET data, such as GLDAS and ECMWF..
Dear Liu
Good quality of data for PET and many other meteorological data is available at CEDA, UK site follow the link. You need to register first.
http://browse.ceda.ac.uk/browse/badc/cru/data/cru_ts/cru_ts_3.21/data/pet
Hope this will help.
http://browse.ceda.ac.uk/browse/badc/cru/data/cru_ts/cru_ts_3.21/data/pet
Dear Liu
You need meteorological data from weather station closed to your research location to obtaine the evapotranspiration. There are many methods to estimate the avapotranspiration as published by FAO, but you should test which one is the most suitable method in your area before you use it. Hope will help you.
Liu, Most of the meteorological stations record the parameters those are used to calculate reference ET ( eg. Wind, RH, Temperature, Solar radiation etc.) . You can use methods proposed by FAO56, ASCE to calculate Ref. ET. Hargreaves method is also useful to calculate potential ET (Which only requires max and min temperatures as input). If the meteorological stations are equipped with the eddy covariance measurements, you may also get direct measurement of actual ET .
you can download daily data with swat format from here:
https://globalweather.tamu.edu/
these data are NCEP data. If you want to use your meteorological stations but you have limited data which can be used for Hargreaves or Priestley-Taylor methods, you can use their new revised coefficients which are given in raster format here
https://doi.pangaea.de/10.1594/PANGAEA.868808
the paper is this
http://www.earth-syst-sci-data-discuss.net/essd-2016-59/
There are many open-source database for actual and potential ET data. I recommend you to use MOD16A2 ET products. The data are 8-Day with 500 meters spatial resolution. According to Running et al. (2017), there was a validation over Canada and worldwide. Good luck!
Ref:
Running, S.W., Mu, Q., Zhao, M. and Moreno, A., 2017. MODIS Global Terrestrial Evapotranspiration (ET) Product (NASA MOD16A2/A3) NASA Earth Observing System MODIS Land Algorithm. NASA: Washington, DC, USA.
MOD16A2 data:
https://lpdaac.usgs.gov/dataset_discovery/modis/modis_products_table/mod16a2_v006
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