Least Sounded Depth (MGD)
This is a service from the Dutch government that reports the actually measured channel depth in the marked fairway, as the depth below OLR (which is actually an international agreement that is thus simply being violated) is not maintained. Its practical use is often seen as limited, much like the guaranteed depth below GlW or OLR, because it does not specify the exact locations of the shallow spots. For example, in the spring of 2025, a shallow was discovered on the Waal in the fairway. The Least Sounded Depth was immediately adjusted by 70 centimeters, while the remaining width of the channel was still more than sufficient. However, this also means that valuable information, such as the depth at the dangerous shallow hard layer near Nijmegen, is lost. This makes it more of a tool to shift responsibility onto the skipper. Dutch regulations are such that a captain can get into legal trouble if they load deeper than the published MGD and subsequently run aground, even if that was caused by someone else's fault and even if they were to adhere to the guaranteed depth below OLR with a 30cm margin, just like in Germany. The peculiar thing, however, is that no safety margin is recommended: as long as you are not loaded deeper than the MGD, it is considered acceptable, which in practice does not really make sense, since a ship always experiences squat. A grounding is therefore still theoretically possible when navigating a stretch that is no deeper than the MGD.
This is also the case on the Boven-IJssel. Experienced skippers know they can often increase their draft by another 15 cm on top of the published MGD, while still maintaining a safe margin to the actual shallows in the deepest gully. This brings the actual draft more in line with the 250 cm channel depth at OLR that Rijkswaterstaat aims for. To do this, however, one must be well aware of the shallows and possibly use the bow thruster regularly to navigate through the deeper outer bend, in addition to waiting for downstream traffic below bends where there is officially no ban on meeting. Ultimately, this is also possible because less channel width is needed at low water than what follows from standard calculations for waterway dimensioning. With an empty ship, you need more space again, but in that case, the shallow inner bends are less of a problem. But here too, loading deeper than the MGD remains a risk, as the depths of the crossings between the bends are not published (the actual shallows), and in the event of a grounding, the captain will be held liable.