Index: wflow-py/wflow/wflow_lib.py
===================================================================
diff -u -r74c9106bc711c80b9496353805ce09ae7e90f317 -r1ac2ebed745d166f0cb0b082c0dc883b2078f0ce
--- wflow-py/wflow/wflow_lib.py	(.../wflow_lib.py)	(revision 74c9106bc711c80b9496353805ce09ae7e90f317)
+++ wflow-py/wflow/wflow_lib.py	(.../wflow_lib.py)	(revision 1ac2ebed745d166f0cb0b082c0dc883b2078f0ce)
@@ -175,6 +175,63 @@
     return storage, outflow, percfull, prec_av, pet_av, demandRelease / timestepsecs
 
 
+def simplereservoir_routing(
+    storage,
+    inflow,
+    ResArea,
+    maxstorage,
+    target_perc_full,
+    maximum_Q,
+    demand,
+    minimum_full_perc,
+    ReserVoirLocs,
+    ReservoirSimpleAreas,
+    timestepsecs=86400,
+):
+    """
+    Adjusted simplereservoirs function for routing 
+    (or when precip and evap are not available as input)
+    
+    :param storage: initial storage m^3
+    :param inflow: inflow m^3/s
+    :param maxstorage: maximum storage (above which water is spilled) m^3
+    :param target_perc_full: target fraction full (of max storage) -
+    :param maximum_Q: maximum Q to release m^3/s if below spillway
+    :param demand: water demand (all combined) m^3/s
+    :param minimum_full_perc: target minimum full fraction (of max storage) -
+    :param ReserVoirLocs: map with reservoir locations
+    :param timestepsecs: timestep of the model in seconds (default = 86400)
+    :return: storage (m^3), outflow (m^3/s), PercentageFull (0-1), Release (m^3/sec)
+    """
+
+    inflow = ifthen(boolean(ReserVoirLocs), inflow)
+
+    oldstorage = storage
+    storage = (
+        storage
+        + (inflow * timestepsecs)
+    )
+
+    percfull = ((storage + oldstorage) * 0.5) / maxstorage
+    # first determine minimum (environmental) flow using a simple sigmoid curve to scale for target level
+    fac = sCurve(percfull, a=minimum_full_perc, c=30.0)
+    demandRelease = min(fac * demand * timestepsecs, storage)
+    storage = storage - demandRelease
+
+    # Re-determine percfull
+    percfull = ((storage + oldstorage) * 0.5) / maxstorage
+
+    wantrel = max(0.0, storage - (maxstorage * target_perc_full))
+    # Assume extra maximum Q if spilling
+    overflowQ = (percfull - 1.0) * (storage - maxstorage)
+    torelease = min(wantrel, overflowQ + maximum_Q * timestepsecs)
+    storage = storage - torelease
+    outflow = (torelease + demandRelease) / timestepsecs
+    percfull = storage / maxstorage
+
+    return storage, outflow, percfull, demandRelease / timestepsecs
+
+
 def lookupResRegMatr(ReserVoirLocs, values, hq, JDOY):
 
     np_res_ids = pcr2numpy(ReserVoirLocs, 0)