Only curve I has no leakage. II is leakage without storage in a finite semipervious layer, III is leakage with storage in an infinite semipervious layer, and IV is leakage with storage in a finite semipervious layer. The top curve demonstrates no leakage and the bottom curve demonstrates leakage. The difference is a result of leakage across one part of the aquifer vs. fully confined for the other part. So after 1 day the drawdown would be 5.7 m, not 2.7 m. 4.
Diffusion processes can operate in the absence of groundwater flow.
The process needs a concentration gradient.