Index: wflow/reservoir_Sa.py
===================================================================
diff -u -ra9498adee6baab0a0abaa331041be8948510167b -r2d4109756d8104a5b6868028e14637fe1d03cfea
--- wflow/reservoir_Sa.py	(.../reservoir_Sa.py)	(revision a9498adee6baab0a0abaa331041be8948510167b)
+++ wflow/reservoir_Sa.py	(.../reservoir_Sa.py)	(revision 2d4109756d8104a5b6868028e14637fe1d03cfea)
@@ -14,7 +14,7 @@
 List all function versions
 """
 
-
+import pcraster as pcr
 try:
     from wflow.wf_DynamicFramework import *
 except ImportError:
@@ -746,7 +746,7 @@
     self.Fa1 = pcr.ifthenelse(
         self.SaN > 0,
         self.Fmin[k]
-        + (self.Fmax[k] - self.Fmin[k]) * e ** (-self.decF[k] * (1 - self.SaN)),
+        + (self.Fmax[k] - self.Fmin[k]) * pcr.exp((-self.decF[k] * (1 - self.SaN))),
         0,
     )