Soil Water Balance Components and Methods for Calculation PhD Student: Željko Vasilić Project TR37010: Urban Drainage Systems as Key Infrastructure in Cities and Towns Belgrade, Mentor: Miloš Stanić

Outline: Introduction Soil water balance Evapotranspiration Infiltration Conclusions

About project TR „Urban Drainage Systems as Key Infrastructure in Cities and Towns“ Funded by Ministry of Science Experimental catchments for investigation of urban runoff

About project TR Experimental catchment – Belgrade Parking areaOil separatorInfiltration tank

About project TR Experimental catchment – Belgrade

Soil Water Balance Water balance components (for unsaturated soil) P saturated unsaturated ET E GWR Q surf P-Pint INF Evapotranspiration Infiltration Process of water penetrating from the ground surface into the soil.

Evapotranspiration modelling Factors driving the process 1. Energy 2.Meteorological factors (T, Humidity, Wind speed..) ETp – potential ET0 – Reference Ea – actual Other factors affecting Ea 1.Soil characteristics and conditions 2.Vegetation characteristics 3.Environmental conditions

Evapotranspiration modelling Methods for measuring Ea 1. Evaporation pan – direct measurement 2. Lysimetry – indirect measurement of evapotranspiration by measuring all other components of soil water balance Evaporation pan Source: Wikipedia Lysimeter ( Source:.llansadwrn-wx.co.uk)

Evapotranspiration modelling Methods for calculation 1. Energy balance method 2.Aerodynamic method 3.Combined method Methods for calculation of ETp 1. Blaney – Cridle eq. 2.Pristley – Taylor eq. 3.Penman – Monteith eq.

Penman Monteith method

– Assumes horizontal surface. – Modification (Allen,2006):

Penman Monteith method Results data from meteo station Smederevska Palanka Lat 44 o 22’N ; Lon 20 o 57’ E; Altitude m Orientation NorthOrientation South Total annual ET

Inflitration modelling Basic equation for unsaturated flow Continuity equation (z direction): Momentum equation: Combination gives (Richard’s eq.):

Infiltration modelling Other methods 1.Simple methods a)Horton equation b)Philips Equation 2.Based on approximate theory a)Green Ampt method (k=const.,sharp boundary wetting front,semi-infinitive domain…) f(t) (mm/h) fo fc α 2 >α 1 α1α1 t(h) Horton’s method Darcy’s law: Continuity eq.: Combined:

Inflitration modelling Implementation of Simplified Green Ampt model Darcy’s law: Continuity eq.: Combined (with assumptions):

Conclusions and future work Slope and orientation of the surface can significantly affect evapotranspiration Infiltration can be calculated using methods of different complexity After the measured data from the experimental catchments are obtained all methods will be tested

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