The contractor started on the site near Waltham Cross in Hertfordshire in July 2009 and came in on budget on the £31m project.
The centre was officially unveiled yesterday by HRH The Princess Royal.
The Lee Valley White Water Centre has a 300m competition course for Olympic canoe slalom events and a 160m intermediate course.
More than 150,000 cubic metres of material was put in place to form the canoe course embankments and the venue landscaping.
Before and after 2012, the Lee Valley Regional Park Authority (LVRPA) will own and operate the venue as a sporting and leisure facility for canoeing and white water rafting, as well as a major competition and training venue. The centre will open to the public for rafting and canoeing in April 2011.
Olympic Delivery Authority DA Chairman John Armitt said: ‘The completion of the White Water Centre – on budget and over 18 months before the Games – is a huge milestone. As the first brand new 2012 venue we have finished, it is a clear sign of the early legacy the Games are already delivering.
‘Seeing canoeists and rafters use the courses for the first time gives us a glimpse of the excitement we can expect here in 2012 and the world-class new facilities that people of all ages and abilities will be able to use for many years to come.’
Campbell Walsh, Olympic silver medallist in canoe slalom, said: 'It’s hugely exciting to test the rapids at the new Lee Valley White Water Centre for the first time. The course looks great and I'm sure it will make a spectacle of a race for the Olympic Games.'
Paul Owen, chief executive British Canoe Union, said: 'We now have in Britain the best white water stadium in the world and we look forward providing a sensational event for the 2012 Olympic Games in a venue with a lasting legacy.'
Morrison Construction is also constructing the Olympics’ enhanced rowing and canoe sprint facilities on Dorney Lake at Eton College, near Slough.