Final answer:
A rain shadow is created when moist air rises up a mountain, condenses and precipitates, resulting in dry air on the other side. The Sierra Nevada mountains contribute to the rain shadow effect, affecting the flow of the Colorado River.
Step-by-step explanation:
A rain shadow is created when prevailing winds carrying moisture rise quickly in elevation up a mountainside, where the air cools and condenses to precipitate out its moisture in the form of rain or snow. By the time the air mass hits the top of the mountain, its moisture is reduced. The dried air rushes down the other side of the mountain range, where it increases in temperature. The warm, dry air coming off the mountains continues to pull moisture out of the land, resulting in arid climate conditions.
The Sierra Nevada mountains contribute to the rain shadow effect, affecting the flow of the Colorado River. As wet air masses move from the Pacific Ocean over the North American continent, they encounter the Sierra Nevada mountain range. The Sierra Nevada acts as a barrier, preventing the moisture from falling on the leeward side of the mountains. As a result, the regions east of the Sierra Nevada experience a semi-arid climate, with less precipitation. This reduction in water flow affects the Colorado River, as it receives less water from the Sierra Nevada region.