with the aim of determining the HI mass () of large numbers of galaxies, such as the Arecibo Dual Beam Survey (ADBS, Rosenberg & Schneider 2000), the HI Parkes All-Sky Survey (HIPASS, Barnes et al. 2001) and the HI Jodrell All-Sky Survey (HIJASS, Lang et al. 2003). Most recently, the Arecibo Legacy Fast Arecibo L-band Feed Array (ALFALFA) survey has provided a wide area, moderate depth (log /M$_{\odot} >$8.5), blind survey of HI in the local ($z<0.06$) universe (Giovanelli et al. 2005). Due to the broad inverse correlation between gas fraction and stellar mass, relatively few massive galaxies are included in the ALFALFA detections. To complement the strategy of ALFALFA, the GALEX Arecibo SDSS Survey (GASS) has therefore performed deep 21 cm observations of $\sim$ 1000 massive (log M$_{\star}$/M$_{\odot} >
10$) galaxies down to a fixed gas fraction limit (Catinella et al. 2010, 2013). Coupled with multi-wavelength data from other large surveys, these large HI surveys have provided unprecedented insight into the connections between global gas properties and environment, nuclear activity, star formation and chemical enrichment (Cortese et al. 2011; Fabello et al. 2011; Bothwell et al. 2013; Lara-Lopez et al. 2013; Hughes et al. 2013).

Despite the tremendous efforts 