Hydrologie II, part II

macropores: due to biological activity, roots, animals. usually close to the surface

fingering flows: unstable wetting fronts due to persistent flow patterns created by soil heterogenity

i) close to surface, between organic and mineral soil

ii) deeper, at interface between bedrock and soil

equivalent infiltration capacity infiltration excess runoff

bucket model, saturation excess runoff

equivalent infiltration capacity + initial abstraction

φ method

assumes infiltration excess runoff

for long-term events and large catchments

R = P-K^

based on saturation excess runoff

for relatively wet catchments and topographic controlled streamflows

S_max = Z_soil*(θ_sat-θ_r)

its a combination of equivalent infiltration cap and bucket model.

first saturation excess is used (bucket), then infiltration excess

R = (P-I_a)-K^

a percentage of rainfall is used to generate runoff

for short events and small catchment areas,used for design small hydraulic structures

R=φ*P

topmodel

vic model

pdm model

overland flow occurs when the water table crosses the topographic surface thus determining a saturated area which contributes to the overland flow. its a topographically controlled model.

when topography is very distinctive or no data is available (except a DEM)

there is a saturated zone in equilibrium with a steady state recharge rate over an upslope contributing area "a". qi = P*ai

water table is parallel to the surface auch that the effective hydraulic gradiant is equal to the slope of the local surface qo=T(zi)*tan(ßi)

only gravity, no capillarity

stationary conditions qo=qi

hydraulic conductivity decreases exp with depth

depth of bedrock Z is much larger than depth of water table zi

variable infiltration capacity model

runoff Q = Rainfall - added storage DS

added storage is calculated based on the initial storage at wt

.

non linear

time varying

distributed in space

characterized by heterogenities, anisotropies....

"randomly" varying in time and space

linearity: I1(t)*e -> o1(t)*e, I1+I2->o1+o2

time invariance: I1(t)->o1,I2(t+tau)->o2

lumped description

-> linear model, conceptual and lumped describtion of basin response

evapotranspiration

water availability, hydrograph shape and peaks

I₀=1366 W/m2

delta= 23.45°

Ri = Rr + Ra + Rt

incoming = reflection + absorbtion + transmission

scattering of incoming radiation

Rsw = Rdir + Rdif

Rsw = I₀/4 = 342 W/m2 (due to shape and night)

surface = 188 W/m2

R1/a1=R2/a2 or R1/e1=R2/e2

a: absorptivity, e: emissivity

"a good reflector is a bad emitter"

a=1 -> black body

R= R(lambda, T),

Rtot = integral from 0 to infinity over R(lambda)d_lambda

lambda_max = b/T

b: wiens konstant = 2898 um/K

describs the displacement of the wavelength with max radiation depending on the Temperature

Rtot = sigma * T⁴

radiation as a function of Temperature

alpha = Rr/Ri

alpha = alpha(lambda)

Rn = Rsw(1-alpha) + R_LW_in - _{R_LW_out}

Rn = reflected + atmos - surface

R_{LW_in} = e_cs*K*sigma*T_A⁴

R_{LW_out} = e_s*K*sigma*T_s⁴

K is funct of cloud cover

e is frunct of vapour presure and temp

Rn - lambda*E - H - G -Lp*Fp + A_H = dU/dt

net radiation - latent heat - sensible heat - ground heat flux - energy from carbon fluxes (photosynthesis) + energy advection = energy stored in the system

Rn - lambda*E -H -G =0