California Snow Packs: The Hidden Reservoir
If you have been following my blog series on California water, you know I have spent a lot of time looking at our reservoir data. But there is another reservoir that does not sit behind a dam – the Sierra Nevada snowpack.
The snowpack acts as a natural reservoir. Each winter, snow accumulates in the Sierra Nevada and other mountain ranges across the state. Come spring, that snow melts and flows into our rivers and reservoirs. Roughly 30% of California’s water supply originates as Sierra Nevada snowmelt1. When you think about it, the snowpack is one of the largest “reservoirs” we have – and it costs us nothing to build or maintain.
The chart above shows the total SWE across California’s snow courses. The CDEC maintains a network of over 100 snow sensors throughout the state that report conditions electronically, supplemented by manual snow course surveys conducted monthly during winter and spring2.
Comparing snow years tells us a lot. The driest snow years align closely with our worst drought years, and the wettest snow years often correspond to the floods that follow. This is the fundamental challenge of California water management: feast or famine, with snowpack as the leading indicator.
Climate change is making this harder. As temperatures rise, the snow line moves higher in elevation, more precipitation falls as rain instead of snow, and the snowpack melts earlier in the season3. This means less natural storage and more pressure on our built reservoirs to capture runoff that arrives faster and earlier than it used to.
The data above summarizes key snow year statistics. I encourage you to compare these numbers with the reservoir data from earlier posts in this series – you will see how tightly coupled snowpack and reservoir storage really are.
Snowpack monitoring is something I think most Californians take for granted. But without it, we would be flying blind on water supply forecasting. Here is to the people who trek up to those snow courses every month to take measurements, and to the sensors that report around the clock.