Over the Water Years

By Ryan Ferrell, Research Scientist

At Pepperwood we have several meteorological station that track various climate and weather metrics. Our longest running station, which we fondly call “Grass MET,” has been active since 2010. These stations are part of our Sentinel Site and long term monitoring. We’ve been collecting a myriad of climatic, soil, vegetation, and wildlife data since 2010, giving us an ever-evolving long term picture of this landscape. Each data stream is like its own lens, allowing us to see how the land and its inhabitants are responding to a changing climate as well as different extreme weather events like wildfire and drought. These data also help center our stewardship actions in science, allowing us to adapt and change as needed. If you ask me, each data stream deserves its own blog, at least. So for this blog I’m going to focus on precipitation – so you can see where we’re at water-wise as we head into the drier months of summer and fall. Below is a basic map of Pepperwood with each of our meteorological stations marked with a green circle. The corresponding measurement shows how much precipitation each has received to date in this water year (water years are measured from Oct. 1st through Sept. 30th and are named for the year in which they end).

Map of Pepperwood showing topography and meteorological stations with corresponding amount of precipitation received at each station.

The topographical map indicates the locations of precipitation measurements at Pepperwood. But notice the difference in totals over short spatial areas. These differences suggest there are topographic and directional effects impacting the distribution of rainfall across the landscape. The “station of record” named Grass MET, is our longest running weather station (est. 2010) located at the Bechtel house. So how much rainfall does this mean we’ve received in total (at Pepperwood) as we round the bend into summer this week?

The graph above shows the current 2023 water year, which is depicted in dark blue with daily precipitation noted in bars of light blue. Our long-term (12-year average) is depicted in dashed red. We are currently 13.48” above average and will likely maintain this through the end of the water year. The bulk of this year’s precipitation was derived from two large storm windows: late December though mid-January and the entire month of March. Both storm windows brought a series of atmospheric rivers. However, unlike previous years these atmospheric rivers were spaced out enough to avoid major flooding events in communities lower in the Russian River watershed. Now let’s compare the water year we’re in with previous water years.

What does this mean for our aquifers? Well, this is a fantastic bump in the right direction. This winter’s storms likely did a lot to recharge our chronically depleted aquifers. However, it’s important to understand that our aquifers are deep and took years, decades, millennia! to develop and fill. It can take a long time for rain water to travel through the subsurface and reach these aquifers. I would hesitate to say “we’re good to go, we’ve got all our water back.” We certainly have full reservoirs and flowing creeks at the moment, but I think longer term. What might our late summer conditions look like? What’s this year’s baseflow, or the portion of the streamflow that is sustained between precipitation events and fed to streams by delayed pathways? Are we going to have water running in our creeks all summer long?

These are important questions when it comes to human use and the suitability of these headwater stream environments for many aquatic species including young steelhead and salmon that typically need cool running water to survive as they grow and mature before entering the ocean. Recently, and as seen in our short 12 year record, one year to the next can produce vastly different amounts of water. In 2021 for example we only received ~14” of precipitation, two years later here we are at 40+”. Regardless of the amount of water we get one year to the next its going to be important to plan, prepare, and adapt for the extremes, whether it’s long multiyear droughts or flood events.

 

Comment(1)

  1. Mike Winter says:

    Excellent post. The data you collect and the work you do to maintain the collection systems are so very important. Keep the articles coming!

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