For such a general subject, my advice is to look for a text book rather than a paper. I appreciated The Handbook of Groundwater Engineering, from Jacques W. Delleur, a thick book which covers the basic aspects of unsaturated soils hydrogeology. You will find many other resources on Google scholar, where I have found a chapter that seems to cover the subject quite well.

http://scholar.google.ca/scholar?hl=fr&q=unsaturated+soils+hydrogeology+&btnG=&lr=.

http://wwwbrr.cr.usgs.gov/projects/GW_Unsat/Unsat_Zone_Book/TindallUZChapter8.pdf

Thank alot, Serge-Étienne Parent, at your link, I got a book and one paper.

http://www.sciencedirect.com/science/article/pii/0022169488901849