Monitoring of optical properties of deep lake water

We present the results of the one year monitoring of absorption and scattering lengths of light with wavelength 375–532 nm within the effective volume of the deep underwater neutrino telescope Baikal-GVD, which were measured by a device «BAIKAL-5D». The «BAIKAL-5D» was installed during the 2020 winter expedition at a depth of 1250 m. To carry out the optical measurements, we use a device with a shaded point-like isotropic light source having a spectral resolution of about 3 nm. A wide angle light receiver is moved by a stepper motor so that the distance between the receiver and the light source can vary from 0.9 m to 7.4 m. The absorption and scattering lengths were measured every week in 6 spectral points. The short-time variation of absorption length was estimated.