Evapotranspiration

All evapotranspiration methods inherit from ETBase. class.

class ai4water.et.et_methods.ETBase(input_df: pandas.core.frame.DataFrame, units: dict, constants: dict, **kwargs)[source]

This is the base class for evapotranspiration calculation. It calculates etp according to Jensen and Haise method. Any new ETP calculation must inherit from it and must implement the __call__ method.

class ai4water.et.et_methods.Abtew(input_df: pandas.core.frame.DataFrame, units: dict, constants: dict, **kwargs)[source]

daily etp using equation 3 in Abtew 1996. k is a dimentionless coefficient.

uses: , k=0.52, a_s=0.23, b_s=0.5

:param k coefficient, default value taken from [1] :param a_s fraction of extraterrestrial radiation reaching earth on sunless days :param b_s difference between fracion of extraterrestrial radiation reaching full-sun days

and that on sunless days.

class ai4water.et.et_methods.Albrecht(input_df: pandas.core.frame.DataFrame, units: dict, constants: dict, **kwargs)[source]

Developed in Germany by Albrecht, 1950. Djaman et al., 2016 Wrote the formula as

eto = (0.1005 + 0.297 * u2) * (es - ea)

class ai4water.et.et_methods.BlaneyCriddle(input_df: pandas.core.frame.DataFrame, units: dict, constants: dict, **kwargs)[source]

using formulation of Blaney-Criddle for daily reference crop ETP using monthly mean tmin and tmax. Inaccurate under extreme climates. underestimates in windy, dry and sunny conditions and overestimates under calm, humid and clouded conditions.

Doorenbos, J., & Pruitt, W. O. (1977). Crop water requirements, FAO Irrigation and Drainage. Paper 24, 2a ed., Roma, Italy.

class ai4water.et.et_methods.BrutsaertStrickler(input_df: pandas.core.frame.DataFrame, units: dict, constants: dict, **kwargs)[source]

using formulation given by BrutsaertStrickler

:param alpha_pt Priestley-Taylor coefficient = 1.26 for Priestley-Taylor

model (Priestley and Taylor, 1972)

:param a_s fraction of extraterrestrial radiation reaching earth on sunless days :param b_s difference between fracion of extraterrestrial radiation reaching full-sun days

and that on sunless days.

:param albedo Any numeric value between 0 and 1 (dimensionless), albedo of the evaporative surface

representing the portion of the incident radiation that is reflected back at the surface. Default is 0.23 for surface covered with short reference crop.

Returns

et

class ai4water.et.et_methods.Camargo(input_df: pandas.core.frame.DataFrame, units: dict, constants: dict, **kwargs)[source]

Originally presented by Camargo, 1971. Following formula is presented in Fernandes et al., 2012 quoting Sedyiama et al., 1997.

eto = f * Tmean * ra * nd

Gurski et al., 2018 has not written nd in formula. He expressed formula to convert extra-terresterial radiation into equivalent mm/day as

ra[mm/day] = ra[MegaJoulePerMeterSquare PerDay] / 2.45 where 2.45 is constant.

eto: reference etp in mm/day. f: an empircal factor taken as 0.01 ra: extraterrestrial radiation expressed as mm/day nd: length of time interval