Index: examples/wflow_rhine_sbm/wflow_sbm.ini
===================================================================
diff -u -rd2c0c4e94f1d2839aac6127be3347248dc05cdfd -r0a7244d3fd5a8ff367e028431f5c372bd6643b4a
--- examples/wflow_rhine_sbm/wflow_sbm.ini	(.../wflow_sbm.ini)	(revision d2c0c4e94f1d2839aac6127be3347248dc05cdfd)
+++ examples/wflow_rhine_sbm/wflow_sbm.ini	(.../wflow_sbm.ini)	(revision 0a7244d3fd5a8ff367e028431f5c372bd6643b4a)
@@ -77,13 +77,14 @@
 
 
 [outputmaps]
-#self.Inflow=iflow
+self.zi=zi
 self.SurfaceRunoff=run
 #self.SubCellFrac=scf
 #self.Inwater=inw
 #self.DistToUpdPt=dist
 #self.SnowMelt=sno
-#self.FirstZoneFlux=fzf
+self.FirstZoneDepth=fzd
+
 #self.TopoLdd=ldd
 self.InwaterMM=iwm
 #self.watbal=wat
Index: wflow-py/wflow/wflow_sbm.py
===================================================================
diff -u -r4c161912050329621df4a8ea3b626227fc54f60a -r0a7244d3fd5a8ff367e028431f5c372bd6643b4a
--- wflow-py/wflow/wflow_sbm.py	(.../wflow_sbm.py)	(revision 4c161912050329621df4a8ea3b626227fc54f60a)
+++ wflow-py/wflow/wflow_sbm.py	(.../wflow_sbm.py)	(revision 0a7244d3fd5a8ff367e028431f5c372bd6643b4a)
@@ -1039,8 +1039,10 @@
 
         # Start with the soil calculations
         # --------------------------------
+        #self.zi = max(0.0, self.FirstZoneThickness - self.FirstZoneDepth / (self.thetaS - self.thetaR))
+        self.zi = min(self.zi, self.FirstZoneThickness)
+        self.FirstZoneDepth = (self.thetaS - self.thetaR) * (self.FirstZoneThickness - self.zi)
 
-
         self.AvailableForInfiltration = ThroughFall + StemFlow
         UStoreCapacity = self.FirstZoneCapacity - self.FirstZoneDepth - self.UStoreDepth