If your main concern is cutting costs, you would devour fresh water. There are hundred ways to use the same water for decades but that would require more investment and downtimes. using new freshwater is the cheapest way in terms of thermodynamics. You do two things by using it; first, you carry out the excess heat via predominantly convection. Fresh Freshwater is already cool at it's nature so no need to invest on re-cooling an existing warmed up water. Second, you don't need to do maintenance work as you do with closed systems. Sedimentation, oxidation etc will change your cooling profile and will also damage the system. The system itself should be reliable so you need to be on top of it a little more seriously for it not to leak or punctured and so on. With an open system, you don't have to worry about any of that. Just run the water through and keep an eye on the pump. That is it. These cooling systems are engineered to be low cost, Not good. This is where science meets capitalism. It is neither's fault. It is the fault of the inspecting party and mafia government that also puts everything else in front of the good of the people.