Hi María, in my humble opinion there are some of the best lectures in PDEs:
1) PDEs and introduction, by Walter Strauss (quite good !!!)
2) Partial Differential Equations. Modeling, Analysis, Computation. by R. M. M. Mattheij S. W. Rienstra, J. H. M. ten Thije Boonkkamp, edited by SIAM. is another interesting choise.
3) There are a tree volume edition of Partial Differential Equations I by Michael E. Taylor, which is a reference work.
4) Partial Differential Equations in Action From Modelling t o Theory by Sandro Salsa,in another good one.
5) Partial Differential Equations Analytical and Numerical Methods
Mark S. Gockenbach. Edited by siam
6) One of my favourites is Equations of the Physical Mathematics, by Godunov, and other classic is the work of Tijonov and Samarki with a similar title.
You have two ways to proceed as your needs. As I saw you were a student of the department of irrigation engineering nd hydraulics, assumed it was focused on the Hydraulic , if this is the case I reaffirm my indication because the cited text would be more appropriate, but if you are a student of other areas suggest look the other proposals, especially the classic text Godounov, as indicated by Legnani.