diff --git a/API/API.csproj b/API/API.csproj
index ec2e97f..a565daf 100644
--- a/API/API.csproj
+++ b/API/API.csproj
@@ -15,7 +15,7 @@
     <PackageReference Include="AutoMapper" Version="14.0.0" />
     <PackageReference Include="APSIM.Graphs" Version="8.1.0" />
     <PackageReference Include="APSIM.Soils" Version="8.0.0" />
-    <PackageReference Include="APSIM.Numerics" Version="8.2.0" />
+    <PackageReference Include="APSIM.Numerics" Version="8.4.0" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/API/Services/Extensions.cs b/API/Services/Extensions.cs
index ff0611d..32e704f 100644
--- a/API/Services/Extensions.cs
+++ b/API/Services/Extensions.cs
@@ -202,7 +202,7 @@ public static Graph ToGraph(this Models.Soil soil, double[] thickness = null,
                 sw = sw.ConvertGravimetricToVolumetric(bdMapped).ToArray();
             }
             // Map water to bottom of profile.
-            sw = Soil.SWMappedTo(sw, thickness, soil.Water.Thickness, ll);
+            sw = Soil.SWMappedTo(sw, thickness, soil.Water.Thickness, soil.Water.LL15, ll, soil.Water.DUL);
 
             // Calculate plant available water.
             paw = SoilUtilities.CalcPAWC(soil.Water.Thickness, ll, sw, xf)
@@ -213,8 +213,10 @@ public static Graph ToGraph(this Models.Soil soil, double[] thickness = null,
         double pawc = SoilUtilities.CalcPAWC(soil.Water.Thickness, ll, soil.Water.DUL, Enumerable.Repeat(1.0, ll.Count).ToArray())
                                    .Multiply(soil.Water.Thickness).Sum();
 
+        // To stop the sw line crossing over ll, constrain it to ll.
+        var swConstainedToLL = sw.LowerConstraint(ll);
         return SoilGraph.Create(soil.Name, soil.Water.Thickness.ToMidPoints(), soil.Water.AirDry, soil.Water.LL15,
-                                    soil.Water.DUL, soil.Water.SAT, ll, cropName, pawc, paw, thickness?.ToMidPoints(), sw);
+                                    soil.Water.DUL, soil.Water.SAT, ll, cropName, pawc, paw, thickness?.ToMidPoints(), swConstainedToLL);
     }
 
     /// <summary>Get the crop lower limit (volumetric) for a soil.</summary>
diff --git a/API/Services/SoilServices.cs b/API/Services/SoilServices.cs
index db8ddb9..8cec9f4 100644
--- a/API/Services/SoilServices.cs
+++ b/API/Services/SoilServices.cs
@@ -188,7 +188,7 @@ public static double PAW(SoilDbContext context, string fullName, string cropName
             sw = sw.ConvertGravimetricToVolumetric(bdMapped);
         }
 
-        IReadOnlyList<double> swMapped = sw.SWMappedTo(thickness, soil.Water.Thickness, ll);
+        IReadOnlyList<double> swMapped = sw.SWMappedTo(thickness, soil.Water.Thickness, soil.Water.LL15, ll, soil.Water.DUL);
         var pawByLayer = SoilUtilities.CalcPAWC(soil.Water.Thickness, ll, swMapped, xf);
         return MathUtilities.Multiply(pawByLayer, soil.Water.Thickness).Sum();
     }
@@ -198,22 +198,18 @@ public static double PAW(SoilDbContext context, string fullName, string cropName
     /// <param name="values">The values to map.</param>
     /// <param name="thickness">The thickness to map to.</param>
     /// <returns>The mapped values.</returns>
-    public static double[] SWMappedTo(this IReadOnlyList<double> values, IReadOnlyList<double> fromThickness, IReadOnlyList<double> toThickness, IReadOnlyList<double> ll)
+    public static double[] SWMappedTo(this IReadOnlyList<double> values, IReadOnlyList<double> fromThickness, IReadOnlyList<double> toThickness, IReadOnlyList<double> ll15, IReadOnlyList<double> ll, IReadOnlyList<double> dul)
     {
         List<double> sw = values.ToList();
         List<double> thickness = fromThickness.ToList();
-        sw.Add(0.8 * values.Last());     // 1st pseudo layer below profile.
-        sw.Add(0.4 * values.Last());     // 2nd pseudo layer below profile.
-        sw.Add(0.0);                     // 3rd pseudo layer below profile.
-        thickness.Add(thickness.Last()); // 1st pseudo layer below profile.
-        thickness.Add(thickness.Last()); // 2nd pseudo layer below profile.
-        thickness.Add(3000);             // 3rd pseudo layer below profile.
-
-        var llMapped = ll.MappedTo(toThickness, thickness);
-        var swMM = sw.LowerConstraint(llMapped, startIndex: values.Count)
-                     .Multiply(thickness);
-        return SoilUtilities.MapMass(swMM, thickness.ToArray(), toThickness.ToArray())
+        sw.Add(ll15.Last());     // add a pseudo layer below profile.
+        thickness.Add(3000);
+        var swMM = sw.Multiply(thickness);
+        var swVolumetric = SoilUtilities.MapMass(swMM, thickness.ToArray(), toThickness.ToArray())
                             .Divide(toThickness);     // convert back to volumetric
+        return swVolumetric.LowerConstraint(ll15, startIndex: 0)
+                           .UpperConstraint(dul, startIndex: 0)
+                           .ToArray();
     }
 
 }
\ No newline at end of file
diff --git a/Tests/UnitTest.cs b/Tests/UnitTest.cs
index 122bfc6..d39e3d9 100644
--- a/Tests/UnitTest.cs
+++ b/Tests/UnitTest.cs
@@ -217,7 +217,7 @@ public void PAW_ShouldReturnCorrectValue()
         var paw = API.Services.Soil.PAW(context, "Clay (Kerikeri No1353)", cropName: "wheat",
                                         thickness: [ 150, 500 ],
                                         sw: [ 0.4, 0.3 ], swIsGrav: false);
-        Assert.That(paw, Is.EqualTo(19.5996).Within(0.000001));
+        Assert.That(paw, Is.EqualTo(21.72).Within(0.000001));
     }
 
 
@@ -233,7 +233,7 @@ public void PAWFromGravimetric_ShouldReturnCorrectValue()
         var paw = API.Services.Soil.PAW(context, "Clay (Kerikeri No1353)", cropName: "wheat",
                                         thickness: [ 150, 500 ],
                                         sw: [ 0.4, 0.3 ], swIsGrav: true);
-        Assert.That(paw, Is.EqualTo(22.165).Within(0.000001));
+        Assert.That(paw, Is.EqualTo(24.676).Within(0.000001));
     }
 
     [Test]