Abstract: A gel-forming composition is provided comprising a PVA based substance selected from the group consisting of a polyvinyl alcohol, a polyvinyl alcohol copolymer, and mixtures thereof, aldehyde, and water. The gel-forming compositions are preheated to effect a predetermined amount of partial crosslinking of the PVA based substance and the aldehyde thereby enabling a lower aldehyde concentration to be used which in turn produces a more stable gel. The gel-forming compositions are useful for retarding the flow of fluids in subterranean formations. For example, for retarding the flow of water in high permeability channels in oil reservoirs. The gels and method of use herein provided are particularly useful in waterflood operations to increase the sweep efficiency of the oil recovery process.