The cantonal authorities may lay down lower minimum residual flow rates in the following circumstances:

a.²⁵

if the flow rate Q₃₄₇ of the body of water is lower than 50 l/s: over a 1,000 m long stretch below a point of withdrawal from a body of water situated at an altitude higher than 1,700 m above sea level or from a body of water not suitable as a habitat for fish and situated at an altitude between 1,500 and 1,700 m above sea level;

b.

in the case of water withdrawals from bodies of water not suitable as habitats for fish provided that the residual rate of flow represents at least 35 per cent of the flow rate Q₃₄₇;

b^bis.²⁶

on a 1000 m long stretch below a place of withdrawal in sections with negligible ecological potential, provided the natural functions of the body of water are not substantially impaired;

c.

in the framework of a protection and utilisation planning for a limited area forming a topographical whole, in so far as an appropriate balance can be achieved in the same area by specific measures such as refraining from further withdrawals; such protection and utilisation plan shall require the approval of the Federal Council;

d.

in cases of necessity, for withdrawals limited in time, in particular for the supply of drinking water, for fire-fighting or for agricultural irrigation.