def calculations_rain_module(basin, rain_intensity, timestep):
    """
    Calculates the volume of rain falling on a basin during 1 timestep.

    :param basin: Basin in which the rain is falling
    :param rain_intensity: amount of rain falling per hour [mm/hour]
    :param timestep: amount of seconds per timestep

    :return inflow_volume_rain:  volume of rain entering the basin in 1 timestep [m^3]
    """

    inflow_volume_rain = basin.SurfaceArea * (rain_intensity / 1000) * (timestep/3600)
    return inflow_volume_rain