  The distribution of cold gas in dark matter haloes is driven by key processes
in galaxy formation: gas cooling, galaxy mergers, star formation and reheating
of gas by supernovae. We compare the predictions of four different galaxy
formation models for the spatial distribution of cold gas. We find that
satellite galaxies make little contribution to the abundance or clustering
strength of cold gas selected samples, and are far less important than they are
in optically selected samples. The halo occupation distribution function of
present-day central galaxies with cold gas mass > 10^9 h^-1 Msun is peaked
around a halo mass of ~ 10^11 h^-1 Msun, a scale that is set by the AGN
suppression of gas cooling. The model predictions for the projected correlation
function are in good agreement with measurements from the HI Parkes All-Sky
Survey. We compare the effective volume of possible surveys with the Square
Kilometre Array with those expected for a redshift survey in the near-infrared.
Future redshift surveys using neutral hydrogen emission will be competitive
with the most ambitious spectroscopic surveys planned in the near-infrared.

Cosmology and Nongalactic Astrophysics;Astrophysics of Galaxies