Water Stops Flowing

Created a canal between the sea and pre-existing clay pit. Water starts to flow into the clay pit but then stops at an arbitrary point.

Steps to reproduce:

  1. Create channel between sea and existing pit
  2. Water starts to flow but then stops

Expected Results:
Pit to be completely filled with water.

Actual Results:
Water stops flowing.

Version Number and Mods in use:
Release-687 (x64)

System Information:
Windows 10