Ann: BFS Presentation, page-3

Presumably the side walls of the pit are paleochannel sediments, some of which have compacted by years of mine access.
These sediments have been assigned a very low specific yield of 3%, I guess they won't give up much brine at the best of times.
The lake bed, top sequence, sediments have a relatively low yield of 11% and presumably there is a significant surface dry patch around the lake perimeter.

You have to admit that the pit has been great for marketing. By comparison RWD pumped over 1/10th of the pit volume during the last batch to trench trials with nothing visually to show for it. These guys have a glossy image that surpasses the trial ponds built by KLL (that were actually trial ponds rather than ramp up ponds).

But plenty of significant mining investors on the register, clearly doing something right! All progress is good for the sector.