The water reservoir for much of Washington is the snow pack that accumulates in the mountains over the winter. People watch that carefully since an extremely low annual snowfall can lead to water restrictions — even today.
Then there is the population gains the state has been seeing and the fact that when you look at climate change impacts, Washington could have even more significant gains from people looking to escape the more extremes of climate change in other states. More people means more water demand.
The following article comes from the Seattle Times. There is some science in the article but it is more of a direct observation by people who climb glaciers frequently and are observing the rapid changes.
“In North Cascades, researchers, climbers watch Washington’s snowpack quickly melt, exposing glaciers’ retreat”