That doesn't follow because rain fills reservoirs the same as snow. One difference, though, is that snow releases as it melts during the spring/summer.
Snow is localised and melts into captured streams. It gets refilled because high alt + low temp preferentially causes rainfall/fog that replenishes the snowpack.
If fewer rain cloud condense on the peak then it just rains more dispersed which leads to much less efficient capture (some absorbed by the ground, some rains over ocean, evaporation is faster when you have water spread over large area so fraction of time spent in liquid form is smaller, etc).
It makes a big difference. Imagine watering your favourite plant once per month with 4 litres of water, vs watering weekly with 1 litre of water. The snowpack melt cycle allows for gradual watering of the surrounding areas. Not directly answering the question for reservoirs, but the rapid loss of snowpack and glaciers has a massive impact on the environment.
Right. Snowpack is a form of massive reservoir. Snowmelt through the course of the year allows us to constantly release water from human-made reservoirs while their levels stay the same. There is still snow in the Sierra today, and in a typical year snow stops falling in April.
Rainfall is much, much harder to capture, and the release curve is completely different; you can very quickly go from flooding to bone-dry.
But more rain doesn't necessarily equate to more ground level water supply. Rain more easily evaporates, and can then be transported elsewhere. Snowpack historically is critical to water supplies in the West because it slowly melts and provides a steady source of water throughout the dry season. A mega storm with no way to capture the water AND prevent it from evaporating in the dry season can still provide far less water than an equivalent amount of snowpack.
> "The root of the problem is an ongoing, 23-year drought, the worst stretch for the region in more than a millennium. Snowpack in the mountains that feed the 1,450-mile river has been steadily diminishing as the climate warms. Ever-drier soils absorb runoff before it can reach reservoirs, and more frequent extreme heat hastens evaporation."
