Hook gauge

Range : Hook gauge

A Hook gauge evaporimeter is a precision instrument used to measure changes in water levels due to evaporation. It is used to precisely measure the level of a free water surface as an evaporation pan.


It’s inserted into a Stilwell to avoid any disturbance from water waves when readings are taken.


  • It features a sharply pointed “”U”” shaped hook attached to a calibrated stem and a micrometer dial.
  • Measurements are made by placing the hook gauge into an evaporation pan and on top of a stilling well.
  • The micrometer dial is rotated until the point at the end of the hook pierces the water’s surface from below. As the water evaporates, the hook point is moved to the new surface position.
  • Adjustments to the hook’s point are made daily and the new dial reading is recorded to determine the amount of water loss.



  • Span: 3″ or 7 cm
  • Graduations, stem:
    • Major divisions 1″ or 1 cm
    • Minor divisions 0.1″ or 0.1 cm (1 mm)
  • Graduations, dial:
    • Major divisions 0.01″ or 0.1 mm
    • Minor divisions 0.002″ or .02 mm
  • Size: 7″ L x 5.25″ Dia (178 mm x 133 mm)
  • Weight/shipping: 1 lb/3 lbs (0.5 kg/1.4 kg)