  The survey speed of ASKAP makes it a prime instrument with which to survey
the HI universe, enabling it to carry out both wide surveys of the entire sky,
as well as deep surveys covering cosmologically representative volumes. Here,
the use of ASKAP to study deep HI fields is discussed as proposed by the Deep
Investigation of Neutral Gas Origins (DINGO) survey. This ASKAP science survey
project anticipates observing in excess of 10^5 sources out to redshift z~0.4.
Key science goals include: Omega_HI and its evolution, the cosmic web as traced
by distributions such as the HI mass function and the 2pt correlation function,
and the formation and evolution of galaxies. Science returns are maximised by
targeting the GAMA survey regions, enabling the HI content of galaxies to be
studied and understood in full context with all the major galactic constituents
over the past 4 Gyr.
