diff --git a/src/MizurouteV1.jl b/src/MizurouteV1.jl
index 45d0e23..7326c40 100644
--- a/src/MizurouteV1.jl
+++ b/src/MizurouteV1.jl
@@ -12,6 +12,8 @@ function MizurouteHillslope{FT}() where {FT <: AbstractFloat}
     return MizurouteHillslope(shape,timescale)
 end
 
+function update_state_from_hillslope!(river_state, hillslope_model, environment)
+end
 
 struct MizurouteChannelV1{FT <: AbstractFloat} <: AbstractChannelModel 
     "Wave velocity, C [m/day]"
@@ -26,3 +28,9 @@ function MizurouteChannel{FT}() where {FT <: AbstractFloat}
     return MizurouteHillslope(wave_velocity, diffusivity)
 end
 
+
+function update_state_from_channel!(river_state, hillslope_model, environment)
+end
+
+
+
diff --git a/src/RiverModels.jl b/src/RiverModels.jl
index ac864f7..3652c3f 100644
--- a/src/RiverModels.jl
+++ b/src/RiverModels.jl
@@ -8,11 +8,26 @@ abstract type AbstractRiverModel end
 abstract type AbstractHillslopeModel end
 abstract type AbstractChannelModel end
 
-struct HillslopeChannelRiverModel{HS <: AbstractHillslopeModel, CH <: AbstractChannelModel} <: RiverModel
+struct HillslopeChannelModel{HS <: AbstractHillslopeModel, CH <: AbstractChannelModel} <: RiverModel
     hillslope_model::HS
     channel_model::CH
 end 
 
+
+function calculate_streamflow!(
+    river_state::RS,
+    river_model::HCM,
+    environment::E,
+    ) where {
+        RS <:RiverState,
+        HCM <: HillslopeChannelModel,
+        E <: Environment,
+    }
+    
+    update_state_from_hillslope!(river_state, river_model.hillslope_model, environment)
+    update_state_from_channel!(river_state, river_model.channel_model, environment)
+    return calculate_streamflow(river_state)
+end
 # Specific hillslope-channel models loaded here:
 include("MizurouteV1.jl")