Every cooling system operates under stress. As stress varies, the potential for scale corrosion and fouling changes. The ability to monitor the changing potential for these operational problems, detect upsets and take appropriate corrective action becomes increasingly important as systems are pushed harder to reduce total cost of operation. Over the pas two years, new methods of managing open industrial cooling water systems based on the actual stresses placed upon them have been developed in and evaluated in the field. This paper will discuss three applications where variation in system stress presented potential for scale, corrosion, and microbial fouling. Operational data will be presented explaining how these stresses were managed using a comprehensive treatment, monitoring and control strategy.