| File Name | Description |
|---|---|
| calculated_evaporation_test.inp | SWMM 5 Input File |
| MinMax.dat | Temperature File |
You need to be a member of SWMM 5 or SWMM or EPASWMM and SWMM5 in ICM_SWMM to add comments!
| File Name | Description |
|---|---|
| calculated_evaporation_test.inp | SWMM 5 Input File |
| MinMax.dat | Temperature File |
You need to be a member of SWMM 5 or SWMM or EPASWMM and SWMM5 in ICM_SWMM to add comments!
Comments
Hi! It's from the equation you provided me
It looks like a lambda greek character, i need some more context.
Hi! Could you please tell me what does
represent here?
Thank you so much! Now I'm clear.
No, it is the Hargreaves equation
As an alternative when solar radiation data, relative humidity data and/or wind speed data are missing, reference evapotranspiration, ET0 (mm d-1), can be estimated using the Hargreaves equation (Hargreaves and Samani, 1985). The FAO-56 Hargreaves equation (Allen et al., 1998) for daily computation is given by:
where Tmax(°C) is the maximum daily air temperature, Tmin(°C) is the minimum daily air temperature, Ra (MJ m-2 d-1) is the extra-terrestrial solar radiation. The parameters a (mm d-1) and b are calibrated coefficients, determined on a monthly or yearly basis by regression analysis or visual fitting. An unadjusted version of Hargreaves equation (given by default) is given with a=0 and b=1.
In addition, is this Penman-Monteith equation?
Hi! Thanks for your quick reply! Which kind of evaporation get from SWMM 5? Only soil evaporation or both soil evaporation and evaporation from tree leaves?
This is the code for the temperature calculations, if you want to estimate evaporation from temperature, however, you can also enter the pan evaporation or lake evaporation directly
double getTempEvap(int day)
//
// Input: day = day of year
// Output: returns evaporation rate in in/day
// Purpose: uses Hargreaves method to compute daily evaporation rate
// from daily min/max temperatures and Julian day.
//
{
double a = 2.0*PI/365.0;
double ta = (Tave - 32.0)*5.0/9.0; //average temperature (deg C)
double tr = (Tmax - Tmin)*5.0/9.0; //temperature range (deg C)
double lamda = 2.50 - 0.002361 * ta; //latent heat of vaporization
double dr = 1.0 + 0.033*cos(a*day); //relative earth-sun distance
double phi = Temp.anglat*2.0*PI/360.0; //latitude angle (rad)
double del = 0.4093*sin(a*(284+day)); //solar declination angle (rad)
double omega = acos(-tan(phi)*tan(del)); //sunset hour angle (rad)
double ra = 37.6*dr* //extraterrestrial radiation
(omega*sin(phi)*sin(del) +
cos(phi)*cos(del)*sin(omega));
double e = 0.0023*ra/lamda*sqrt(tr)*(ta+17.8); //evap. rate (mm/day)
if ( e < 0.0 ) e = 0.0; //(5.0.019 - LR)
if ( UnitSystem == US ) e /= MMperINCH;
return e;
}
What method does SWMM 5 use to calculate evaporation? Which kind of equations?