Adhesion. The water molecules are attracted to the surface of the structure by adhesive forces. This means that when the water molecules are away from the stru

Adhesion. The water molecules are attracted to the surface of the structure by adhesive forces. This means that when the water molecules are away from the structure, there is "potential adhesive energy". As the water moves closer to the surface, the "potential adhesive energy" is reduced and turns into gravitational potential energy -- until at some point an equilibrium is reached. The more surface area the liquid can adhere to, the higher it can rise. If this is hard to understand, think of two strong magnets, one lying on a table, and one mounted at a point somewhere above the table. When the two magnets are not touching, there is potential magnetic energy. If you bring the top magnet low enough, at some point the bottom magnet will be pulled up towards the other magnet until it touches, increasing it's potential gravitational energy and minimizing its potential magnetic energy.