How to calculate the exact water loss in cooling tower? I need with reference and proper formula.

sorry thes is not in my specialty

Actually according to my experience, every manufacturer provides the estimated evoparation loss according to his own selected model.

Very easy to calculate water evaporation loss, Here is an example.

Ex: If the water flow rate is30 GPM

Sol. W.E.L (m3/hr) =0.00085 x1.8 x water circulation rate (m3/hr) x Delta T (difference in temp)

                                                 (1 gpm =0.003785 m3/min )

                                                 (1 m3/hr =1000 lit/hr )

           (water circulation rate (30 gpm) =30 x0.003785 x60 (m3/hr) =6.813 m3/hr)

  Now, insert in above formula

                       =0.00085 x1.8 x6.813 m3/ hr x (35 c -31 c) 

                       =0.047 m3/hr is the water evaporation loss

Hope this example will help you.