A fundamental way of approach must be to identify minimum criteria or “bottom lines” for ecosystems and their functions, terrestrial as well as aquatic. When balancing upstream against downstream interests one has to work from the downstream end after identifying bottom lines for the aquatic ecosystems there in terms of uncommitted environmental flows and minimum water quality. The approach then, has to be to move segment-wise upstream (cf., Box 7). A particular challenge here is to identify resilience determinants to avoid ecosystem collapses.