In their mission to efficiently and responsibly produce an asset, today’s completions engineers must balance several competing factors regarding mixwater.  Freshwater costs, disposal costs for accumulated produced water, and logistical elements of the pad location need to be considered in light of the effects of water quality on completion quality, particularly when highly saline water is considered.  Historically, optimum costs have been difficult to model because decisions made on one of the interrelated factors affect several other factors simultaneously and in different ways. This talk presents an overview of a reservoir-centric model that helps with decision-making, including logistics, frac fluid quality, and impact on the producing reservoir.  A preliminary case study demonstrating successful fracturing operations in a horizontal well using a robust gelled fluid based on standard underivatized guar in ~300,000 ppm TDS mixwater of variable quality will be presented. This may represent a critical step in delivering the best completion engineering at reasonable cost.