paper: Add a sentence for stricklers list.

doc/paper/2023/simhydro/paper.txt

@@ -53,7 +53,7 @@ Figure 3: Edition window of the boundary conditions hydrograph for the Saar rive
 3.1.3	Lateral contribution
 The user interface for lateral contributions is similar to that for boundary conditions, except that it applies to a part of a reach between two KP, and not to a node.
 3.1.4	Friction
-Friction editing is linked to a reach, a friction coefficient is defined and then applied to a portion of the reach between two KP (Figure 4). Friction is defined by two Strickler coefficients, one for the river's main channel and one for the flood plain.
+Friction editing is linked to a reach, a friction coefficient is defined and then applied to a portion of the reach between two KP (Figure 4). Friction is defined by two Strickler coefficients, one for the river's main channel and one for the flood plain. The list of available Strickler coefficients is defined at the study level.