This study is carried out in semi-arid to arid Karkheh Basin of Iran, where massive water allocation planning is on the way, but a comprehensive knowledge on basin

hydrology and impact of these developments on different water uses and users across the basin are lacking.

Presents a theoritical outline of the techniques in the use of tritiated water (HTO) which can be used to estimate total body water, body composition, water turnover, milk intake and feed intake. Highlights its potential errors and gives a comprehensive methodology for the use of tritiated water under field conditions.