Quantifying how the gas content depends on galaxy properties and their environment is of paramount importance for constraining models of galaxy formation. Equally important is to perform such studies on large and unbiased samples of galaxies, in order to obtain results that are truly representative of the local population.
I will present results based on the recently completed GALEX Arecibo SDSS Survey (GASS), which was designed to provide such a representative sample for massive galaxies. I will discuss how the atomic hydrogen (HI) content of massive systems depends on their structural and star formation properties, as well as on their environment, and will point out the relevance of these findings for the future surveys that will be carried out with the Square Kilometer Array and its pathfinders.