M_HI – redshift parameter space, showing where MIGHTEE-HI and LADUMA are sensitive to galaxies, divided into cells of size Δz = 0.01 and Δ log(M_HI) = 0.1. Light, medium, and dark grey shading indicates where at least one, 10, and 25 galaxies are expected per cell. Light, medium, and dark red shading shows where at least one, four, and eight galaxies are expected per cell. The horizontal dotted line indicates the z = 0 characteristic H I mass from the HIMF. The hatched region corresponds to the redshift range 0.09 <  z <  0.22 most affected by RFI.