  We use weak lensing observations to make the first measurement of the
characteristic depletion radius, one of the three radii that characterize the
region where matter is being depleted by growing haloes. The lenses are taken
from the halo catalog produced by the extended halo-based group/cluster finder
applied to DESI Legacy Imaging Surveys DR9, while the sources are extracted
from the DECaLS DR8 imaging data with the Fourier_Quad pipeline. We study halo
masses $12 < \log ( M_{\rm grp} ~[{\rm M_{\odot}}/h] ) \leq 15.3$ within
redshifts $0.2 \leq z \leq 0.3$. The virial and splashback radii are also
measured and used to test the original findings on the depletion region. When
binning haloes by mass, we find consistency between most of our measurements
and predictions from the CosmicGrowth simulation, with exceptions to the lowest
mass bins. The characteristic depletion radius is found to be roughly $2.5$
times the virial radius and $1.7 - 3$ times the splashback radius, in line with
an approximately universal outer density profile, and the average enclosed
density within the characteristic depletion radius is found to be roughly $29$
times the mean matter density of the Universe in our sample. When binning
haloes by both mass and a proxy for halo concentration, we do not detect a
significant variation of the depletion radius with concentration, on which the
simulation prediction is also sensitive to the choice of concentration proxy.
We also confirm that the measured splashback radius varies with concentration
differently from simulation predictions.
