diff --git a/core/src/parameter.jl b/core/src/parameter.jl
index 479a45442..e3742808e 100644
--- a/core/src/parameter.jl
+++ b/core/src/parameter.jl
@@ -162,6 +162,8 @@ end
 """
 struct Basin{T, C, V1, V2, V3} <: AbstractParameterNode
     node_id::Indices{NodeID}
+    inflow_ids::Vector{Vector{NodeID}}
+    outflow_ids::Vector{Vector{NodeID}}
     # Vertical fluxes
     vertical_flux_from_input::V1
     vertical_flux::V2
@@ -182,6 +184,8 @@ struct Basin{T, C, V1, V2, V3} <: AbstractParameterNode
 
     function Basin(
         node_id,
+        inflow_ids,
+        outflow_ids,
         vertical_flux_from_input::V1,
         vertical_flux::V2,
         vertical_flux_prev::V3,
@@ -199,6 +203,8 @@ struct Basin{T, C, V1, V2, V3} <: AbstractParameterNode
         is_valid || error("Invalid Basin / profile table.")
         return new{T, C, V1, V2, V3}(
             node_id,
+            inflow_ids,
+            outflow_ids,
             vertical_flux_from_input,
             vertical_flux,
             vertical_flux_prev,
diff --git a/core/src/read.jl b/core/src/read.jl
index f2efc9050..00a17b895 100644
--- a/core/src/read.jl
+++ b/core/src/read.jl
@@ -490,7 +490,7 @@ function Terminal(db::DB, config::Config)::Terminal
     return Terminal(NodeID.(NodeType.Terminal, static.node_id))
 end
 
-function Basin(db::DB, config::Config, chunk_sizes::Vector{Int})::Basin
+function Basin(db::DB, config::Config, graph::MetaGraph, chunk_sizes::Vector{Int})::Basin
     node_id = get_ids(db, "Basin")
     n = length(node_id)
     current_level = zeros(n)
@@ -533,8 +533,12 @@ function Basin(db::DB, config::Config, chunk_sizes::Vector{Int})::Basin
 
     demand = zeros(length(node_id))
 
+    node_id = NodeID.(NodeType.Basin, node_id)
+
     return Basin(
-        Indices(NodeID.(NodeType.Basin, node_id)),
+        Indices(node_id),
+        [collect(inflow_ids(graph, id)) for id in node_id],
+        [collect(outflow_ids(graph, id)) for id in node_id],
         vertical_flux_from_input,
         vertical_flux,
         vertical_flux_prev,
@@ -1053,7 +1057,7 @@ function Parameters(db::DB, config::Config)::Parameters
     level_demand = LevelDemand(db, config)
     flow_demand = FlowDemand(db, config)
 
-    basin = Basin(db, config, chunk_sizes)
+    basin = Basin(db, config, graph, chunk_sizes)
     subgrid_level = Subgrid(db, config, basin)
 
     p = Parameters(
diff --git a/core/src/solve.jl b/core/src/solve.jl
index 160d00718..96ec3b6f5 100644
--- a/core/src/solve.jl
+++ b/core/src/solve.jl
@@ -607,10 +607,10 @@ function formulate_du!(
     # subtract all outgoing flows
     # add all ingoing flows
     for (i, basin_id) in enumerate(basin.node_id)
-        for inflow_id in inflow_ids(graph, basin_id)
+        for inflow_id in basin.inflow_ids[i]
             du[i] += get_flow(graph, inflow_id, basin_id, storage)
         end
-        for outflow_id in outflow_ids(graph, basin_id)
+        for outflow_id in basin.outflow_ids[i]
             du[i] -= get_flow(graph, basin_id, outflow_id, storage)
         end
     end
diff --git a/core/test/utils_test.jl b/core/test/utils_test.jl
index e6dadb501..fab1b3ab1 100644
--- a/core/test/utils_test.jl
+++ b/core/test/utils_test.jl
@@ -38,6 +38,8 @@ end
     demand = zeros(2)
     basin = Ribasim.Basin(
         Indices(NodeID.(:Basin, [5, 7])),
+        [NodeID[]],
+        [NodeID[]],
         [2.0, 3.0],
         [2.0, 3.0],
         [2.0, 3.0],
@@ -92,6 +94,8 @@ end
     demand = zeros(1)
     basin = Ribasim.Basin(
         Indices(NodeID.(:Basin, [1])),
+        [NodeID[]],
+        [NodeID[]],
         zeros(1),
         zeros(1),
         zeros(1),