The water level in lake Vänern varies essentially of the following parameters
- drainage in Göta älv
- local variations depending on wind force and direction
The ship's maximum draft is regulated partly by the general rules and partly by the so-called "Current maximum draft". The latter can vary from hour to hour.
Overall decisions aboat the maximum draft
CLO makes a so-called overall decisions on the ship's maximum draft depending on the currrent water level in lake Vänern. The decision is based on the information provided/negotiated with the production management at Vattenfall AB. Affected customers will be informed.
This over all decision are not changed daily it is fixed for a longer period of time.
Current maximum draft
The water level in Lake Vänern change from day to day depending on the catchment, drainage in Gota älv and evaporation.
Current maximum draft is decided daily.
Information on this is available from the Channel Central Trollhättan and is primarily intended for the ships discharging in ports in Vänern. Information of the current maximum draft can not be given several days in advance.
Note !!! The current maximum draft is valid only from Brinkebergskulle to and from ports in Lake Vänern.
When the Channel Central Trollhättan has given a current maximum draft is this based on the measurement station in Sjötorp ie no adjustment for wind has been made. It may therefore happen that wind strength and direction further reduces draft. The vessel will then have to wait until the water comes back.
For northbound vessels having several days trip it can be difficult to load optimally to utilize the capacity/draft. Maritime Administration can not give crossing permits in advance when deviations from the current maximum draft can occure rapidly.