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Lecture GB - Prac 11 Modeling packages tools

3 important questions on Lecture GB - Prac 11 Modeling packages tools

What is conductance and what is the formula?

Conductance = NOT conductivity (conductivity is part of the conductance)
Has to do with resistance

Formula: lwk*( (Hdrn - Haqfr)/b )

l: length of drain
w: width of drain
k: Hydraulic conductivity of sediments
b: Thickness of sediments (that's where potentail diff between Hdrn and Haqfr occurs)
Hdrn: head drainage
Haqfr: head aquifer

Formula: Cond(uctance) = (l*w)/Centr = l*0.8/5 = l*0.16
Centrance = entrance resistance
inverse of k/b = entrance resistance(???)

Unit of conductance: (m2/d)/m when putting it in DRN package (bc it automatically calculates the *l [m]). Thus eventually conductance has units m2/d

STR: stream(?) package

Not only Cauchy, but also including its own water budget and flow eq, Manning equation

Outflow and inflow flow (open water flow visible) = open water flow (Manning)
Flow into aquifer = GW interaction
Head in stream are calculated, NOT fixed (advantage to RIV or DRN where you need to fix this)

Stream has its own water budget

Explicit vs. Diffuse(=upscaled) situation

Explicit: Havg = 2/3(Hmax-Hditch)

Diffuse(upscaled): not indicated where real head build-up is and where ditches are, but take an average for this and first calculate the upscale affect of the ditch distance (L^2) and of the hydraulic properties of the subsoil (kD).

Cdrn = L^2/12kD [d]
Cond(uctance per cell) = (dx*dy*k)/dz = (dx*dy)/Cdrn = area/Cdrn [m^2/d]

Result from explicit and diffuse should on average be (approx) the same!

The question on the page originate from the summary of the following study material:

Advanced Hydrological Systems Analysis

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