The Detroit lake of Oregon receives the orographic type of rainfall where the Gateway region of Oregon is falling in the rain shadow region. So Detroit receives a huge more amount of rainfall as compared to Gateway region.
Step-by-step explanation:
The orographic type of rainfall is dependent on the landform of a region. As a mountain lies by the side of a huge lake or sea, the moisture laden wind that is coming from the sea or the lake rises along the mountain. As it ascends, the temperature of the atmosphere cools, which condenses the water vapour and the rain is precipitated on the same side of the mountain. As the wind reaches the opposite side of the mountain, it's already dry again, so very little amount of precipitation is seen there.
Same is the case with Detroit and Gateway where the Detroit lies between the Pacific ocean and Rocky mountains whereas the Gateway lies on the opposite side of Rocky mountains and doesn't get the rainfall.