Re: The Effects of UV light

Several factors affect the penetration of ultraviolet radiation (UVR) into 
water. Pure water attenuates very little UVR and therefore it will very 
easily penetrate the typical water volume of a pool. However, 10-25 % of 
UVR is reflected (scattered) off the surface of the pool and never enters 
the water volume. Impurities in the water will have different attenuation 
characteristics than pure water but would probably be negligible in a 
typical swimming pool. I think that the bottom of the pool will absorb 
most of the UVR; of course this will depend upon the scattering 
characteristics of the material. 

When a formula is considered the impurities in a water volume must be 
considered and thus complicates the process. Much research on the 
penetration of UVR into water bodies has been performed to study the 
effects on biological systems. I would suggest a search into this area of 
research for a comprehensive treatment of this topic.

[note added by MadSci Admin:  Check this reference for the
absorption characteristics of water:
http://www.lsbu.ac.uk/water/vibrat.html]