The Welshman has had one operation and will have another this week after fracturing his tibia and fibula.
Rowe, 27, concedes his lay-off might be even longer than a year.
"It was a freak accident. It wasn't like I was swinging from the roof tops drunk, but there is only one person to blame," Rowe told BBC Wales Sport.
Rowe, Team Sky's road captain, broke a rib in a crash on the opening stage of this year's Tour de France but rode on to help Chris Froome win the title.
Rowe, who says he has no regrets about attending his brother's stag-do, jumped into a shallow section of water while rafting and landed on rocks.
I knew straight away how serious it was, it was excruciating pain and there are quite a few broken bones. It was a case of trying to get out of the water as quickly as possible and into an ambulance.
I've broken a fair few bones in my career but this was significantly worse than any of them. It was double the pain - add the pain of a few broken bones together.
I lifted my leg, but my foot stayed still, it was kind of hanging off, limp. The bone didn't break the skin, but it is pretty scary when you look down and see that when you are on the side of a riverbank.
It was a freak accident but it was a mistake. The water clearly wasn't deep enough to jump into, but hindsight is a beautiful thing. Other people were jumping with no problems, but I hit a rock.
I knew straight away the implications of what I had done and how long it would take to come back.
Rowe told Team Sky he was going on the stag-do and they flew a doctor out to Prague to immediately accompany him back to Cardiff for the first of what could be several surgeries.
The leg is in a bad way and recovery is a bit of an unknown at the moment. It will be a long road back but I won't back down and I want to get back to where I was.
Some people react to the operations and treatment really well but it is hard to predict a race, a point in the season or even a year when I will be able to come back.
I've been asking the doctors time and time again. When can I train? When can I walk? When can I get back on a bike?
The first questions I asked were for dates because you get impatient. But essentially the doctors are all telling me the same thing. We do know that operation by operation, scan by scan, it will get better. But the timescale? We just don't know that.
It's a moment in your career where your back is against the wall and you really need to roll your sleeves up. It's going to be a tough few months for me and it could be up to 9-12 months - that's realistic.
I have to live my life. I'll be on crutches at my brother's wedding in seven weeks' time and I don't think I will be spending much time on the dance floor."
Team Sky's Luke Rowe says he "could be out for up to a year" after breaking his right leg while white-water rafting on his brother's stag party in Prague.