Canadian Nicole Walker and Atout des Trambles were edged by Jessica Springsteen by just one-tenth of a second in the large class of 68.
The victory came aboard the mare Greya, deflecting a strong challenge from Christian Kukuk and his Olympic gold medal partner Checker 47.
This week the Belgian pulled out Katanga V/H Dingeshof, a speedy 15-year-old mare, for the first time this season.
One of the most successful equestrian nations of all time, Germany continues to be a dominant force on the global stage.
The American and the speedy mare won the $340,000 Longines FEI Jumping World Cup in Thermal, CA, his second WC victory this season.
The WEC Grand Arena was the scene for a contest between 12 nations; Canadian Tiffany Foster placed sixth riding Electrique.
The German rider won the lion's share of the $215,000 purse in the MARS Equestrian CSI4* Grand Prix on the grass field.
The Belgian rider won his second Cup round; Canadian Mario Deslauriers placed 7th riding S&L Quatro van de Meerputhoeve.
Fresh off an Olympic gold medal, the Team GB will rely on their determination, skill, and a stellar support staff this season.
The Olympic champions took on a tough international field of 45 over Canadian Peter Grant's course, edging Ben Maher and Nina Mallevaey.