  We analyse the properties of circumgalactic gas around simulated galaxies in
the redshift range z >= 3, utilising a new sample of cosmological zoom
simulations. These simulations are intended to be representative of the
observed samples of Lyman-alpha emitters recently obtained with the MUSE
instrument (halo masses ~10^10-10^11 solar masses). We show that supernova
feedback has a significant impact on both the inflowing and outflowing
circumgalactic medium by driving outflows, reducing diffuse inflow rates, and
by increasing the neutral fraction of inflowing gas. By temporally stacking
simulation outputs we find that significant net mass exchange occurs between
inflowing and outflowing phases: none of the phases are mass-conserving. In
particular, we find that the mass in neutral outflowing hydrogen declines
exponentially with radius as gas flows outwards from the halo centre. This is
likely caused by a combination of both fountain-like cycling processes and
gradual photo/collisional ionization of outflowing gas. Our simulations do not
predict the presence of fast-moving neutral outflows in the CGM. Neutral
outflows instead move with modest radial velocities (~ 50 kms^-1), and the
majority of the kinetic energy is associated with tangential rather than radial
motion.
