An integrated system includes a desalination plant including a reverse osmosis (RO) array to produce an RO permeate blending stream and a nanofiltration (NF) array to produce an NF permeate blending stream. The integrated system also includes a blending system, a control unit, and an injection system for an injection well that penetrates an oil-bearing layer of a reservoir. The blending system is to blend the RO permeate blending stream and the NF permeate blending stream to produce a blended injection water stream. The control unit is to dynamically alter operation of the blending system to adjust amounts of at least one of the RO permeate blending stream and the NF permeate blending stream to alter the composition of the blended injection water stream from an initial composition to a target composition.