There is a GREAT book around if you look on Amazon called
How to select and install TURBOCHARGERS by Hugh McInnes, circa 1971! (the genuine & by far the best FIRST book on turbocharging).
It is excellent for Turbo historians and enthusiasts, though probably boring to some it has real pioneers contributing to it in the early days of turbocharging and some real awesome projections and insights into turbocharging and its effect on the modern performance world, racing to street cars.
You will find in it excellent paragraph on water injection and also contributions from people who are the god fathers of this stuff, there is also quotes to testing of this exact topic as well
....... there is other super interesting items on real HP and how to measure it! just to name a few. Take a look around there are not many copies of it available anymore and its easily confused for later version, its pretty expensive a but a real good read on this topic alone.