### Using Hydrus 2D to Output Vertical Velocity Profile

Posted:

**Tue Jun 05, 2018 8:22 pm**Hello,

I am working on a 2D simulation of a cross section of a micro-catchment (200 cm across x 35 cm deep) using a time varying varying head boundary to simulate the measured water level within the catchment. I am interested in predicting the infiltration rate of a complex catchment with 5 separate soil layers (see img) during different water levels during the simulation. To accomplish this, my logic was to create a Velocity profile across the boundary of the catchment, which could be multiplied by surface area of a micro-catchment to calculate the discharge at any given timestep. This velocity profile could approximate flow out of catchments of varied geometry given an accurate stage to volume of each catchment. I am converting the boundary.out file for my atmospheric boundary that also simulates the water level when h is positive to this velocity profile, but had some questions about the output file.

The boundary.out file has a Q value with the listed units of [V/T]. I am unclear what this Q value is used for, and why is does not have units of [L^2/T]? It also can not calculate this Q values by multiplying the velocity by the node length.

I have been using the v [L/T] columns for my boundary to create the vertical velocity profile. I wanted to make sure that the output velocity of the water would not need to be multiplied by the volumetric water content in order to calculate a flux.

My initial simulations under-predicted the total infiltration rate out of 7 microcatchments by 25-60%. I am also curious if there is any documentation on translation from 2D simulations to 3D application where radial flow from the catchment comes into play.

Thanks for reading my lengthy question! I'm happy to provide any additional details.

I am working on a 2D simulation of a cross section of a micro-catchment (200 cm across x 35 cm deep) using a time varying varying head boundary to simulate the measured water level within the catchment. I am interested in predicting the infiltration rate of a complex catchment with 5 separate soil layers (see img) during different water levels during the simulation. To accomplish this, my logic was to create a Velocity profile across the boundary of the catchment, which could be multiplied by surface area of a micro-catchment to calculate the discharge at any given timestep. This velocity profile could approximate flow out of catchments of varied geometry given an accurate stage to volume of each catchment. I am converting the boundary.out file for my atmospheric boundary that also simulates the water level when h is positive to this velocity profile, but had some questions about the output file.

The boundary.out file has a Q value with the listed units of [V/T]. I am unclear what this Q value is used for, and why is does not have units of [L^2/T]? It also can not calculate this Q values by multiplying the velocity by the node length.

I have been using the v [L/T] columns for my boundary to create the vertical velocity profile. I wanted to make sure that the output velocity of the water would not need to be multiplied by the volumetric water content in order to calculate a flux.

My initial simulations under-predicted the total infiltration rate out of 7 microcatchments by 25-60%. I am also curious if there is any documentation on translation from 2D simulations to 3D application where radial flow from the catchment comes into play.

Thanks for reading my lengthy question! I'm happy to provide any additional details.