Calculation of water volume in step wells for cyclopicide application and its eco-epidemiological implication: mathematical validation of some theoretical considerations.

Chemical treatment of step wells to kill cyclopoid vectors of guinea worm by temephos (50 per cent E. C.) at the dose of 1 ppm is now an important activity of the guineaworm eradication programme in India. Calculation of correct volume of water in step wells, to determine the exact quantity of temephos to be applied, therefore, deserves adequate attention to prevent over and underdosing of stepwells by the chemical. The prescribed method of calculation of water volume includes two formulae; pi r2h and 1 x b x h (where h = mean depth for uneven bottoms and is a single depth measurement for almost even bottoms). Field observations revealed that in many stepwells there were marked variations in depth within the same well. These differences in depth ranged from small to very large in some wells. Since these depth variations would lead to miscalculation of water volume by existing method and the dose of temephos to be applied, with eco-epidemiological consequences, new formulae have therefore been deduced for conceivable patterns of depth variations by geometrical and algebric applications. The new formulae will permit calculation of, nearest to, exact quantity of temephos required for application. These formulae have been validated by an example.