Reports state the inland oil tanker Tanya was detained on the Mittelland Canal near Lohnde, Germany, after a passing boater noticed a track of oil in the water.   The boater had alerted the master of the Tanya who contacted the authorities.   The local fire department responded and deployed an oil boom to keep the diesel fuel spreading into the channel.   Divers inspected the hull of the Tanya and discovered a 15 centimeter crack along the hull.   A special type of plaster was placed into the gap as a temporary repair to prevent further leaking.  The master of the Tanya reported that he had grounded the vessel earlier when he steered the vessel closer to shore to allow a passing motor vessel to go by.   Reports state 150 liters of diesel has been released.   The authorities have charged the master of the Tanya for water pollution.