diff --git a/appl/lecture/mhs/groundwater/external_interface.hh b/appl/lecture/mhs/groundwater/external_interface.hh
index cad3cff335c104768886bbcc18924764aae1229f..9b20bf54ad0a52d14289c9c6320a5634f4bacbc9 100644
--- a/appl/lecture/mhs/groundwater/external_interface.hh
+++ b/appl/lecture/mhs/groundwater/external_interface.hh
@@ -62,7 +62,8 @@ public:
     //Initialization of ISP Parameters
     {
         using namespace std;
-        double viscosity, density;
+        double viscosity=0.001;
+        double density=1000;
 
         std::cout << std::endl
                 << "-----> ISP: Interface Soil Properties Initialization ...\n";