​In the absence of scientifically based environmental flow recommendations, we recommend establishing precautionary flow limits for all water bodies, so that implementation can begin as soon as possible.  Richter et al. (2012) suggested a presumptive standard of 80-90% of natural flow.  That is, flow may not be depleted by more than 10-20% without additional study showing that the standard is too restrictive for the water body in question.

Several jurisdictions have adopted this presumptive standard:
 
·         Canada uses it nationwide.
·         Tennessee issues water withdrawal permits using the 10% cumulative limit unless the applicant can prove it is too restrictive.
·         North Carolina’s Environmental Flow Science Advisory Board recommends that the ecological flow should be 80-90% of the instantaneous modeled baseline flow.
·         Florida uses a more stringent percentage as its presumptive standard.
·         Mississippi advises using the presumptive standard instead of its previously recommended 7Q10 permitting standard.