Index: src/Deltares.DSoilModel.Forms/SosSoilLayer1DControl.Designer.cs
===================================================================
diff -u -r6 -r954
--- src/Deltares.DSoilModel.Forms/SosSoilLayer1DControl.Designer.cs	(.../SosSoilLayer1DControl.Designer.cs)	(revision 6)
+++ src/Deltares.DSoilModel.Forms/SosSoilLayer1DControl.Designer.cs	(.../SosSoilLayer1DControl.Designer.cs)	(revision 954)
@@ -44,6 +44,8 @@
             this.BottomEdit = new DevExpress.XtraEditors.SpinEdit();
             this.TopEdit = new DevExpress.XtraEditors.SpinEdit();
             this.BottomLabel = new DevExpress.XtraEditors.LabelControl();
+            this.InterPolationMethodLabel = new DevExpress.XtraEditors.LabelControl();
+            this.InterpolationMethodEdit = new DevExpress.XtraEditors.ComboBoxEdit();
             ((System.ComponentModel.ISupportInitialize)(this.LayerGroupControl)).BeginInit();
             this.LayerGroupControl.SuspendLayout();
             ((System.ComponentModel.ISupportInitialize)(this.RemarkTopLevelEdit.Properties)).BeginInit();
@@ -54,10 +56,13 @@
             ((System.ComponentModel.ISupportInitialize)(this.HeightEdit.Properties)).BeginInit();
             ((System.ComponentModel.ISupportInitialize)(this.BottomEdit.Properties)).BeginInit();
             ((System.ComponentModel.ISupportInitialize)(this.TopEdit.Properties)).BeginInit();
+            ((System.ComponentModel.ISupportInitialize)(this.InterpolationMethodEdit.Properties)).BeginInit();
             this.SuspendLayout();
             // 
             // LayerGroupControl
             // 
+            this.LayerGroupControl.Controls.Add(this.InterPolationMethodLabel);
+            this.LayerGroupControl.Controls.Add(this.InterpolationMethodEdit);
             this.LayerGroupControl.Controls.Add(this.RemarkTopLevelEdit);
             this.LayerGroupControl.Controls.Add(this.RemarkTopLevelLabel);
             this.LayerGroupControl.Controls.Add(this.MinDepthTopLevelEdit);
@@ -159,7 +164,7 @@
             // AquiferCheckEdit
             // 
             this.AquiferCheckEdit.AutoSizeInLayoutControl = true;
-            this.AquiferCheckEdit.Location = new System.Drawing.Point(19, 265);
+            this.AquiferCheckEdit.Location = new System.Drawing.Point(19, 235);
             this.AquiferCheckEdit.Margin = new System.Windows.Forms.Padding(4);
             this.AquiferCheckEdit.Name = "AquiferCheckEdit";
             this.AquiferCheckEdit.Properties.Caption = "Is aquifer";
@@ -272,6 +277,27 @@
             this.BottomLabel.TabIndex = 8;
             this.BottomLabel.Text = "Bottom";
             // 
+            // InterPolationMethodLabel
+            // 
+            this.InterPolationMethodLabel.Location = new System.Drawing.Point(20, 263);
+            this.InterPolationMethodLabel.Margin = new System.Windows.Forms.Padding(4);
+            this.InterPolationMethodLabel.Name = "InterPolationMethodLabel";
+            this.InterPolationMethodLabel.Size = new System.Drawing.Size(21, 16);
+            this.InterPolationMethodLabel.TabIndex = 71;
+            this.InterPolationMethodLabel.Text = "Soil";
+            // 
+            // InterpolationMethodEdit
+            // 
+            this.InterpolationMethodEdit.Anchor = ((System.Windows.Forms.AnchorStyles)((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Right)));
+            this.InterpolationMethodEdit.Location = new System.Drawing.Point(180, 259);
+            this.InterpolationMethodEdit.Margin = new System.Windows.Forms.Padding(4);
+            this.InterpolationMethodEdit.Name = "InterpolationMethodEdit";
+            this.InterpolationMethodEdit.Properties.Buttons.AddRange(new DevExpress.XtraEditors.Controls.EditorButton[] {
+            new DevExpress.XtraEditors.Controls.EditorButton(DevExpress.XtraEditors.Controls.ButtonPredefines.Combo)});
+            this.InterpolationMethodEdit.Properties.TextEditStyle = DevExpress.XtraEditors.Controls.TextEditStyles.DisableTextEditor;
+            this.InterpolationMethodEdit.Size = new System.Drawing.Size(100, 22);
+            this.InterpolationMethodEdit.TabIndex = 70;
+            // 
             // SosSoilLayer1DControl
             // 
             this.AutoScaleDimensions = new System.Drawing.SizeF(8F, 16F);
@@ -290,6 +316,7 @@
             ((System.ComponentModel.ISupportInitialize)(this.HeightEdit.Properties)).EndInit();
             ((System.ComponentModel.ISupportInitialize)(this.BottomEdit.Properties)).EndInit();
             ((System.ComponentModel.ISupportInitialize)(this.TopEdit.Properties)).EndInit();
+            ((System.ComponentModel.ISupportInitialize)(this.InterpolationMethodEdit.Properties)).EndInit();
             this.ResumeLayout(false);
 
         }
@@ -312,5 +339,7 @@
         private DevExpress.XtraEditors.SpinEdit MinDepthTopLevelEdit;
         private DevExpress.XtraEditors.LabelControl MinDepthTopLevelLabel;
         private DevExpress.XtraEditors.TextEdit RemarkTopLevelEdit;
+        private DevExpress.XtraEditors.LabelControl InterPolationMethodLabel;
+        private DevExpress.XtraEditors.ComboBoxEdit InterpolationMethodEdit;
     }
 }
Index: src/Deltares.DSoilModel.Data.Tests/SosSoilLayer1DTest.cs
===================================================================
diff -u -r883 -r954
--- src/Deltares.DSoilModel.Data.Tests/SosSoilLayer1DTest.cs	(.../SosSoilLayer1DTest.cs)	(revision 883)
+++ src/Deltares.DSoilModel.Data.Tests/SosSoilLayer1DTest.cs	(.../SosSoilLayer1DTest.cs)	(revision 954)
@@ -72,6 +72,7 @@
             Assert.IsNull(sosLayer.Soil);
             Assert.IsFalse(sosLayer.IsAquifer);
             Assert.AreEqual(0, sosLayer.TopLevel);
+            Assert.AreEqual(WaterpressureInterpolationModel.Automatic, sosLayer.WaterpressureInterpolationModel);
         }
 
         [Test]
@@ -115,7 +116,8 @@
                 MaximumTopLevel = -9,
                 MinimumTopLevel = -11,
                 RemarkTopLevel = "remark testSos1",
-                Soil = new Soil("TestSoil1", Color.Beige)
+                Soil = new Soil("TestSoil1", Color.Beige),
+                WaterpressureInterpolationModel = WaterpressureInterpolationModel.Hydrostatic
             };
             sosProfile.Layers.Add(sosLayer);
             sosLayer = new SosSoilLayer1D
@@ -147,7 +149,7 @@
                 {
                     "Id", "Name", "Soil", "Color", "SetCoordinate", "ChangeLog"
                 };
-            var result = co.Compare(sosProfilesCopy, sosProfiles);
+            var result = co.Compare(sosProfiles, sosProfilesCopy);
             Assert.AreEqual(0, result.Differences.Count, "SOSProfileLayer1D fails comparison: " + result.DifferencesString);
         }
 
@@ -267,7 +269,8 @@
                 MaximumTopLevel = 12,
                 MinimumTopLevel = 13,
                 RemarkTopLevel = "remark testSos1",
-                Soil = new Soil("TestSoil1", Color.Beige)
+                Soil = new Soil("TestSoil1", Color.Beige),
+                WaterpressureInterpolationModel = WaterpressureInterpolationModel.Hydrostatic
             };
 
             var sosLayer1DClone = sosLayer1D.Clone();
@@ -291,7 +294,8 @@
                 TopLevel = 11,
                 MaximumTopLevel = 12,
                 MinimumTopLevel = 13,
-                RemarkTopLevel = "remark testSos1"
+                RemarkTopLevel = "remark testSos1",
+                WaterpressureInterpolationModel = WaterpressureInterpolationModel.Hydrostatic
             };
 
             var sosLayer2 = new SosSoilLayer1D()
@@ -308,6 +312,7 @@
             Assert.AreEqual("remark testSos1", sosLayer2.RemarkTopLevel);
             Assert.AreEqual(13, sosLayer2.MinimumTopLevel);
             Assert.AreEqual(12, sosLayer2.MaximumTopLevel);
+            Assert.AreEqual(WaterpressureInterpolationModel.Hydrostatic, sosLayer2.WaterpressureInterpolationModel);
         }
     }
 }
\ No newline at end of file
Index: src/Deltares.DSoilModel.Forms/SosSoilLayer1DControl.cs
===================================================================
diff -u -r883 -r954
--- src/Deltares.DSoilModel.Forms/SosSoilLayer1DControl.cs	(.../SosSoilLayer1DControl.cs)	(revision 883)
+++ src/Deltares.DSoilModel.Forms/SosSoilLayer1DControl.cs	(.../SosSoilLayer1DControl.cs)	(revision 954)
@@ -42,8 +42,8 @@
             BindSupport.BindTextValueAndUnit<SosSoilLayer1D>(this, MaxDepthTopLevelLabel, MaxDepthTopLevelEdit, l => l.MaximumTopLevel);
             BindSupport.BindTextValueAndUnit<SosSoilLayer1D>(this, MinDepthTopLevelLabel, MinDepthTopLevelEdit, l => l.MinimumTopLevel);
             BindSupport.BindTextAndValue<SosSoilLayer1D>(this, RemarkTopLevelLabel, RemarkTopLevelEdit, l => l.RemarkTopLevel);
-
             BindSupport.Bind<SosSoilLayer1D>(this, AquiferCheckEdit, l => l.IsAquifer, BindingType.LabelAndValue);
+            BindSupport.BindTextAndValue<SosSoilLayer1D>(this, InterPolationMethodLabel, InterpolationMethodEdit, l => l.WaterpressureInterpolationModel);
 
             LocalizationSupport.Register(typeof(SoilLayerControl), LayerGroupControl);