- Author: Dan Macon
Looking back at more than 20 years of precipitation data I've collected since my family moved to Auburn, I can't say that we've ever had an “average” year – that is, we've never had exactly 32.68 inches of rain. Some years, like 2016-17, we measure quite a bit more than average (62.96 inches, to be exact); other years, like 2020-21, we measure less (just 19 inches). Since I started keeping track in 2003, we've had 12 years with less than our average, and 6 years with more than average (the balance – 3 years – have been close to what I would call "normal"). Since 2007, we've experienced several 2-4 year stretches of below average rainfall – including the memorable droughts of 2012-2015 and 2020-2022. Interestingly, though, the trendline on my data suggests that our “average” precipitation has increased slightly since I started keeping track in 2003.
But as anyone who manages livestock on our annual rangelands will tell you, the amount of rainfall we receive is only part of the story when it comes to grass growth – timing and temperature (both soil and air temperature) are key drivers in rangeland forage production. The last two years have provided a stark example!
Think back to mid-March 2022. After an exceptionally wet start to the water year (in October 2021, I measured more than 10 inches of rain), our rangeland forages got off to a great start – they'd germinated in late October and had grown through early December. But in January 2022, the faucet shut off – we received less than 2.5 inches from January 1 through March 31. By some accounts, it was the driest January-March on record. I recall checking soil moisture on the rangelands where our sheep were grazing in mid-March 2022, and finding that we had less than 25% moisture – more like May conditions in the root zone of our rangeland plants.
Despite these dry conditions, however, the UC Sierra Foothill Research and Education Center (SFREC) measured 1,412 pounds of forage per acre on March 1, 2022 (187% of “average” for the date). Rain returned in April 2022, and total forage production at SFREC ended up being 122% of the long term average (just over 3,800 pounds per acre).
In the autumn of 2022, our germinating rain came nearly a month later than the year before – which meant the rangeland forage didn't have much time to grow before the short days and cold temperatures of December forced it into dormancy. A wet and cold December was followed by a wetter (if somewhat warmer) January 2023. While February was slightly drier than “average,” March turned wet and cold again. As of this writing (March 29), we've measured exactly 28 inches of rain at our home place in Auburn since New Year's Day!
Even with all of this moisture, however, forage production at SFREC is lagging significantly behind last year. On March 1, SFREC measured just 619 pounds per acre (less than the long term average for that date of 750 pounds - and less than half of what we had a year ago at this time). As you might expect, soil temperatures followed the cooler air temperatures in late February; cold soils mean little or no forage growth.
Stated another way, we were in a precipitation drought on this date last year – and we had more forage than “average.” This year is shaping up to be one of the wetter years since I've worked in the foothills – and we're short on feed at the moment (a grass drought). With long days and warmer temperatures coming, I suspect the forage will explode in April, but for now, feed conditions in the foothills are tight!
So how do we manage through this kind of uncertainty? As ranchers, how can we set our stocking rates and production calendars given these wide swings in conditions? During our Working Rangelands Wednesdays webinar series last year, Dr. Leslie Roche (our Cooperative Extension Specialist in Rangeland Management) suggested that while the total amount and seasonable distribution of precipitation are the biggest drivers for annual forage production, specific timing is also critical. November and April precipitation are especially important, based on Dr. Roche's analysis. A statewide collaborative effort is ground-truthing remote sensing technology that will hopefully provide real-time forage production data without needing an army of range technicians clipping plots on a weekly basis.
All of this information will help ranchers make decisions about seasonal and annual adjustments to our stocking rates, but good management will always require careful planning and on-the-fly adjustment to the current year's conditions. While While my colleague Grace Woodmansee (Siskiyou County Livestock and Natural Resources Advisor) developed our Drought Decision Support Tool with drought in mind, I'm realizing there's value in putting together a 12-month forage plan regardless of the conditions! There's no such thing as an average year!
- Author: Dan Macon
I've kept daily weather records since we moved to Auburn (nineteen years this week, in fact). During that time, we've experienced some exceptionally wet years (2016-17 comes to mind, when we measured almost 63 inches of precipitation), as well as some exceptionally dry years (like 2006-07, when we received just under 20 inches). Other years and specific months stand out, too - like the 14.5 inches we measured in January 2017, or the 0.5 inches we received in December 2013. Unfortunately, February 2020 will go down as one of those stand-out months - we measured a measly 0.03 inches of rain for the entire month.
The current water year (which started in October) was preceded by a wetter-than-normal September (at least here in Auburn). We received better than 2 inches - enough to germinate the grass on our annual rangelands. As often happens when we get early rain, though, we didn't get much to follow up the promising start. From October 1 through November 30, we measured just 0.71 inches. We got back on track in December (with more than 8 inches), but 2020 has been disappointing so far. Through the end of February, the season total was just 56 percent of our long-term average for the date. The March 3 version of the U.S. Drought Map puts all of Placer, Nevada, and Yuba Counties, as well as the eastern portion of Sutter County, in the Moderate Drought category. And the most recent drought outlook from the National Weather Service (see below) suggests that drought will persist or develop in the northern two-thirds of California.
Looking ahead to summer irrigation season, we're fortunate that most of our local water agencies went into the winter with more holdover in their reservoirs than normal. Even so, the latest Sierra snow pack numbers for our region are more depressing than the lack of rain. The central Sierra snow pack is only 38 percent of normal for this date.
I'm not a weather forecaster by any stretch of the imagination, but I am a weather geek. This morning, I looked at the long term average precipitation for March through June in my weather records, which didn't provide much reassurance. Even if we get 75 percent of our average rainfall for the next four months, we'll end the water year with less than 20 inches total. Even with 150 percent of average - a miracle March (and April, May, and June) - we'll end the water year well below our long-term average.
We've definitely seen an impact on the annual rangeland where we winter our sheep west of Auburn. The February 1 forage supply at the Sierra Foothill Research and Extension Center in the Yuba County foothills was about 69 percent of normal. I suspect the March 1 measurement won't be much better. While the lack of moisture is concerning, the warm February temperatures have pushed many of the blue oaks to leaf out 3-4 weeks earlier than normal. Last Thursday (before the brief storm over the weekend), I walked through one of the pastures we hadn't grazed yet. The grass was short generally, but I was especially surprised to see the vegetation beneath the oaks starting to wither and die - in the first week of March! This Sunday, after we'd received roughly a third of an inch of rain the day before, I dug a six inch hole to check soil moisture at the root zone of our annual grasses. I'd estimate moisture levels to be at around 25 percent of field capacity - in other words, incredibly dry for early March. No wonder the creeks aren't running!
Most of us will likely have enough grass to get buy this spring, although a lack of stock water could be problematic. I'm more concerned about the potential lack of fall feed. Short grass this spring means we're covering more ground with our sheep. This could mean less dry feed to return to with our sheep after the summer irrigation season ends in October. Our plan is to cull our older and less productive ewes at shearing or weaning. We may even consider selling some of the replacement ewe lambs we'd normally keep.
These conditions call for drastic measures, obviously - and so we've scheduled drought workshops in Grass Valley and Yuba City! Over the last six years, I've attended or helped to organize four or five drought workshops - and it's rained every time!
In all seriousness, in light of the ongoing coronavirus outbreak, we are scheduling a Drought Planning for Rangeland Livestock Producers webinar (rather than an in-person workshop) in late March or early April. Stay tuned for details! We'll share results from our 2016 post-drought rancher interviews, feature panel discussions with ranchers and other experts, and discuss ranch-specific goal setting - all focused on coping with what is shaping up to be another drought year.
If you'd like to receive notice of this webinar (and future workshops), contact me at dmacon@ucanr.edu.