Subject: Rainfall Runoff Method Posted: 11/7/2015 Viewed: 4239 times
Hello WEAP users
I would like to use the WEAP model to assess climate change impact on water resource in this region, but I have no data to use Soil Moisture Method, I just use Rainfall Runoff method (FAO). And I need to calibrate streamflow data. I do not know if I use Rainfall Runoff method, whether I can evaluate the impact of climate change after I finish my calibration process.
Does there any one have some experiences to calibrate the WEAP model in case use Rainfall Runoff method?
For the rainfall-runoff method (simplified coefficient), you can model the impact of climate change by changing the precipitation record (under the climate tab) for your catchment. Temperature is captured within the ETref variable.
Is that the method you were referring to?
Subject: Re: Rainfall Runoff Method Posted: 11/9/2015 Viewed: 4225 times
Thank you for your suggestion!
I have no enough data for Soil Moisture Method, so I just use Rainfall Runoff Method.
With rainfall runoff method, for example, if I want to assess climate change from 2015-2050 I have to calculate ETref (2015-2050) from the temperature and input result of ETref into the model, right?
You've got it - you'll calculate the ETref from the temperature and enter into the model. Remember you can do the calculations in Excel if you prefer, and enter data into WEAP using the Readfromfile Wizard and a CSV file. Good luck,
El Hassani Layla
Subject: Re: Rainfall Runoff Method Posted: 11/11/2015 Viewed: 4211 times
Could you please show me how to calculate ETref ?
Thank you : Layla.
Subject: Re: Rainfall Runoff Method Posted: 11/11/2015 Viewed: 4202 times
Definitely - I'm going to copy and paste this from the WEAP help menu. You can find the same information by searching ETReference (or Reference Evapotranspiration)
For ETref, you have two options:
1) Enter ETref directly (some climate stations provide derived ETref as data), OR
2) Calculate it using the Penman-Monteith equation. This approach has its own data requirements, with various options. Penman-Monteith requires:
a) Minimum and maximum daily temperature.
b) Relative humidity. Depending on the availability of data, different equations are used. The following are the data requirements, in decreasing order of preference.
i) Minimum and maximum daily relative humidity, OR
ii) Maximum daily relative humidity, OR
iii) Average daily relative humidity, OR
iv) If humidity data is not available, and estimate can be obtained by assuming that the dew point temperature is the same as the daily minimum temperature.
c) Solar radiation. Depending on the availability of data, different equations are used. The following are the data requirements, in decreasing order of preference.
i) Enter solar radiation data directly, OR
ii) Hours of sunshine per day, OR
iii) Cloudiness fraction, OR
iv) If neither sunshine hours nor cloudiness fraction are available, solar radiation can be estimated using the Hargreaves formula, based on minimum and maximum daily temperature and an adjustment coefficient (Krs)
d)Wind speed. (An adjustment can be made if the wind speed measurement height is known.)
e) Latitude and altitude of the climate measurement station.
(read more about the equation in the help section).
Something like ETref may also play a role in your model calibration, if you are unable to exactly calculate it for lack of complete data.
El Hassani Layla
Subject: Re: Rainfall Runoff Method Posted: 11/11/2015 Viewed: 4197 times
Thank you dear Stephanie.