The recent identification in the Northern sky of more than 12 sources of gamma rays with energies up to the PeV opens a new era. To extend such observations to the Southern Hemisphere, a large wide-field gamma-ray observatory, covering a large surface and able to attain high background rejection factors, has to be built. In this seminar, it is shown that the quantification of the azimuthal non-uniformity in the pattern of the shower at the ground as a function of the distance to the shower core, might be a way to access the intrinsic differences in the development of electromagnetic and hadronic showers without implementing any costly strategy to absorb the electromagnetic component of the shower. Such a scenario is then explored for an observatory composed of small, single-layer water Cherenkov detectors, with photomultiplier tubes (PMT) placed at their bottom. This work has been carried out in the context of a possible proposal for the future Southern Wide-field Gamma-ray Observatory (SWGO).