Vibrational relaxation of the OH stretching and bending modes of water monomers in acetonitrile is studied by two-color pump-probe experiments in a frequency range from 1400 to 3800 cm(-1). Measurements with resonant infrared excitation reveal vibrational lifetimes of 6.4 +/- 1.0 ps of the OH stretching modes and 4.0 +/- 0.5 ps of the OH bending mode. After OH stretching excitation, the OH bending mode shows an instantaneous response, a hallmark of the anharmonic coupling of stretching and bending modes, and a delayed population buildup by relaxation of the stretching via the bending mode. The relaxation steps are discussed within the framework of current theoretical pictures of water's vibrational relaxation. (C) 2016 Elsevier B.V. All rights reserved.