The operation of an ASP-15 stationary deep-water measuring complex located in the south part of Lake Baikal is analyzed. The complex conducts all-the-year-round measurements of hydrooptical characteristics at 1000-1200-m depths. The method of determining the water absorptivity is based on measuring the decay rate of irradiance from an isotropic emitter as the distance between the source and the receiver changes. Based on numerical modeling of the light field, the method accuracy is estimated and possible causes of anomalous range dependences of the irradiance are determined. The experimental data obtained in recent years with the ASP-15 complex are presented.