What term describes systems operated or affected by water or fluids of low viscosity?

The term that describes systems operated or affected by water or fluids of low viscosity is hydraulic. Hydraulic systems utilize the properties of liquids to transmit power and perform work, making them effective in applications such as lifting, pressing, and shaping materials. Water and other low-viscosity fluids can be easily moved through pipes and reservoirs, allowing for efficient energy transfer and operation of hydraulic machinery.

In contrast, pneumatic systems operate using gases under pressure, which is not applicable in this context since the question specifically refers to fluids with low viscosity. Thermal systems are focused on heat transfer and temperature control, while mechanical systems broadly incorporate the physical movement or force application through various components, which includes but does not specifically relate to the characteristics of fluids. Hydraulic is the best fit for describing the specific operation with low-viscosity fluids.