In the meantime, we suggest you try searching with Google, restricting the results to this website.
soil leaching site:czo-archive.criticalzone.org
flux tower site:czo-archive.criticalzone.org/sierra/
manganese site:criticalzone.org/shale-hills/
The first search covers all of the archived CZO website, whereas the latter two are restricted to a specific observatory.
Because dataset listings have moved to CUAHSI HydroShare, your best option is to start there.
But if you do want to search the archived CZO website, use Google searches like:
groundwater depth data site:criticalzone.org/calhoun/data/