One-way Head Dependent Source/Sink

What is it?

One-way head dependent flux allows water to leave the aquifer system in the case that the hydraulic head exceeds the top aquifer elevation, but water may not enter the aquifer system.

How to use it:

Check the radio box next to ‘One-way’. The drop-down menu next to ‘Name’ provides different naming options for the zone feature that will be used in displaying results, e.g., when performing water balance analyses. The stage of the water sink can be assigned as:

- a constant value that does not change with time – select the radio button next to ‘Const:’ and enter the desired value)
- the aquifer top elevation minus some prescribed value; by default, the stage is set to the aquifer top elevation, as indicated by the value of zero in the text box next to ‘Top E’.

Leakance

Use the text box next to ‘Leakance:’ to enter a value . The leakage rate per unit area for a leaky polygon or lake = leakance x DH, where DH is the head difference across the bed sediment thickness The leakance for a lake (or leaky polygon) is defined as a ratio: bed sediment conductivity / bed sediment thickness with a dimension of [1/T or 1/day]. Leakance = leakage rate per unit area per unit head difference across the sediment.