The book is the first part of the proceedings of the 26th Congress of SIL held in Sao Paulo, Brazil in 1995. The 15 plenary papers by well known specialists cover a wide range of important topics such as limits on life in lake ecosystems, renewal of badplain forests along rivers, saline lake problems, river water quality issues, water resource and scarcity in India, ecosystem theory and biogeochemical cycles in large rivers to name a few.