Depending on a couple factors such as ingenuity and whether or not you are considering the land needed to hunt game to be included in the total land area needed, i think it could easily be done on two acres or less. There are many stories of people growing enormous amounts of food on small suburban plots of land.
Here are three examples of extreme productivity on very little land:
- Growing Power – On a 2-acre urban lot in Milwaukee, Will Allen grows over a million
pounds of food every year, including thousands of fish, and a livestock inventory of chickens, goats, and bees.
- The Urban Homestead – A family of four produces most of their own food and $60,000 a year on just a fifth of an acre.
- Singing Frogs Farm – Just 3 harvested acres on this farm bring in over $100,000 an acre, using low water methods that sequester carbon and generate topsoil.
Using techniques and principles in the resources below, you can potentially grow all your food on as little as a quarter of an acre!
One of the biggest concerns with growing a lot of food is the necessary water to do, so but in your question you have specified it would be plentiful.
The following info-graphic also shows that two acres would be plenty for both produce, meat and dairy.
Andrew Mateskon, from Polycultures also writes:
The earth feeds 7 billion people on 3.8 billion acres of arable and permanent cropland. You can more than triple this figure if you include rangeland for meat. This is about 0.5 acres of cropland per person, or over 1.5 acres per person if we include rangeland. Some systems are vastly more efficient than others. If there were no "externalized" inputs, industrial monocropping would be the most efficient system ever seen. However, some other systems are able to feed many people with much smaller negative impact. Traditional and contemporary Chinese Agroforestry provides some of the best techniques. China imports an incredibly small amount of food, yet feeds their people to the tune of around 20 per acre. They grow carp in the ditches under fruit and nut trees with crops and herbs between trees and chickens running around. An ancient polyculture of carp, rice, and ducks is practiced in some areas. This increases the yield of the rice, plus adds two more yields to the equation, plus reduces inputs of fertilizer and pesticide.
With this example i would say it is more than reasonably to think that you could grow enough food for a family of 4 to survive on roughly 2 acres if the land was used wisely.