Index: DamClients/DamUI/trunk/src/Dam/Tests/DamEngineIo/FillXmlInputFromDamUiTests.cs
===================================================================
diff -u -r2468 -r2510
--- DamClients/DamUI/trunk/src/Dam/Tests/DamEngineIo/FillXmlInputFromDamUiTests.cs	(.../FillXmlInputFromDamUiTests.cs)	(revision 2468)
+++ DamClients/DamUI/trunk/src/Dam/Tests/DamEngineIo/FillXmlInputFromDamUiTests.cs	(.../FillXmlInputFromDamUiTests.cs)	(revision 2510)
@@ -617,7 +617,27 @@
             Assert.AreEqual(0, result.Differences.Count, "Differences found read/write Input object");
 
         }
-    }
 
+        [Test]
+        [ExpectedException(typeof(NullReferenceException), ExpectedMessage = "Location 'Location 1', scenario '1' has no river level")]
+        public void RaiseExceptionWhenRiverLevelIsMissing()
+        {
+            // Given DataSet with undefined riverlevel
+            DamProjectData expectedDamProjectData = CreateExampleDamProjectData();
+            var scenario = expectedDamProjectData.WaterBoard.Dikes[0].Locations[0].Scenarios[0];
+            scenario.RiverLevel = null;
+
+            // When Writing Xml
+            string xmlString;
+            Input input = FillXmlInputFromDamUi.CreateInput(expectedDamProjectData);
+            xmlString = DamXmlSerialization.SaveInputAsXmlString(input);
+
+            // Then Raise Exception With Clear Message()
+            input = DamXmlSerialization.LoadInputFromXmlString(xmlString);
+            DamProjectData actualDamProjectData = FillDamUiFromXmlInput.CreateDamProjectData(input);
+            CompareDamProjectData(actualDamProjectData, expectedDamProjectData);
+
+        }
+    }
 }
 
Index: DamClients/DamUI/trunk/src/DamClientsLibrary/Deltares.Dam.Data/DamEngineIo/FillXmlInputFromDamUi.cs
===================================================================
diff -u -r2422 -r2510
--- DamClients/DamUI/trunk/src/DamClientsLibrary/Deltares.Dam.Data/DamEngineIo/FillXmlInputFromDamUi.cs	(.../FillXmlInputFromDamUi.cs)	(revision 2422)
+++ DamClients/DamUI/trunk/src/DamClientsLibrary/Deltares.Dam.Data/DamEngineIo/FillXmlInputFromDamUi.cs	(.../FillXmlInputFromDamUi.cs)	(revision 2510)
@@ -409,6 +409,17 @@
                 {
                     throw new NullReferenceException("No scenarios defined in location");
                 }
+                else
+                {
+                    foreach (var scenario in location.Scenarios)
+                    {
+                        if (scenario.RiverLevel == null)
+                        {
+                            throw new NullReferenceException(string.Format("Location '{0}', scenario '{1}' has no river level", 
+                                location.Name, scenario.LocationScenarioID));
+                        }
+                    }
+                }
             }
             if (dike.SurfaceLines2 == null)
             {
@@ -587,7 +598,7 @@
                 {
                     var designScenario = location.Scenarios[j];
                     var inputDesignScenario = new LocationDesignScenario();
-                    inputDesignScenario.RiverLevel = designScenario.RiverLevel ?? 0.0;
+                    inputDesignScenario.RiverLevel = designScenario.RiverLevel.Value;
 
                     inputDesignScenario.Id = designScenario.LocationScenarioID;
                     inputDesignScenario.RiverLevelLowSpecified = designScenario.RiverLevelLow.HasValue;