Index: wflow-py/wflow/wflow_sbm.py
===================================================================
diff -u -r210a8f89dcdbdf34d06ab44039da2bac7119fe41 -r3ff1d3324fd887832271fe5576ea4103c4d5450f
--- wflow-py/wflow/wflow_sbm.py	(.../wflow_sbm.py)	(revision 210a8f89dcdbdf34d06ab44039da2bac7119fe41)
+++ wflow-py/wflow/wflow_sbm.py	(.../wflow_sbm.py)	(revision 3ff1d3324fd887832271fe5576ea4103c4d5450f)
@@ -1192,10 +1192,11 @@
 
         #self.Inwater = self.Inwater + self.Inflow   # Add abstractions/inflows in m^3/sec
         # Check if we do not try to abstract more runoff then present
-        self.SurfaceWaterSupply = ifthenelse (self.Inflow < 0.0 , max(-1.0 * self.Inwater,self.SurfaceRunoff), self.ZeroMap)
-        self.Inwater = ifthenelse(self.SurfaceRunoff + self.Inwater < 0.0, -1.0 * self.SurfaceRunoff, self.Inwater)
+        MaxExtract = self.SurfaceRunoff + self.Inwater
+        self.SurfaceWaterSupply = ifthenelse (self.Inflow < 0.0 , min(MaxExtract,-1.0 * self.Inflow), self.ZeroMap)
+        self.Inwater = self.Inwater + ifthenelse(self.SurfaceWaterSupply> 0, -1.0 * self.SurfaceWaterSupply,self.Inflow)
 
-        #self.Inwater = self.Inwater + self.Inflow  # Add abstractions/inflows in m^3/sec
+
         ##########################################################################
         # Runoff calculation via Kinematic wave ##################################
         ##########################################################################
@@ -1207,7 +1208,8 @@
         self.SurfaceRunoffMM = self.SurfaceRunoff * self.QMMConv  # SurfaceRunoffMM (mm) from SurfaceRunoff (m3/s)
         self.updateRunOff()
         self.InflowKinWaveCell = upstream(self.TopoLdd, self.SurfaceRunoff)
-        self.MassBalKinWave = (-self.KinWaveVolume + self.OldKinWaveVolume) / self.timestepsecs + self.InflowKinWaveCell + self.Inwater - self.SurfaceRunoff
+        self.MassBalKinWave = (-self.KinWaveVolume + self.OldKinWaveVolume) / self.timestepsecs +\
+                              self.InflowKinWaveCell + self.Inwater - self.SurfaceRunoff
 
         Runoff = self.SurfaceRunoff