- Author: Nathan Van Schmidt
After five years, the northern Sierra Nevadas have finally been moved out of the “severe drought” category by the US Drought monitor following a promisingly rainy start to the 2017 water year. This is not only good news for our agricultural community, but it's also good news for our wetlands, which depend on steady water flow to stay saturated and perform their ecological functions. The gold country region of the Sierra Nevadas has over 1,500 wetlands, which can provide many important benefits including water quality control and purification, runoff reduction, aesthetic value, and wildlife habitat. The Beissinger lab has been working with SFREC and local landowners to study these wetlands since 2002, originally just to track a secretive, understudied bird species: the California Black Rail (Laterallus jamaicensis coturniculus). Our recent research has expanded to study how the wetlands function as a “coupled human and natural system,” affected by both ecological processes (rainfall and natural water flows) and human processes (our irrigation infrastructure and water use).
First, we've been tracking how these wetlands changed over time with a time series of historical aerial photographs stretching back to 1947. We first made a comprehensive map of all wetlands in the region, then selected a subset of 283 wetlands and tracked them back through time. Coupled with field visits, seeing what they were like under different historic irrigation regimes allowed us to determine the water sources for each wetland. Based on that study, we estimated that nearly 9 in 10 foothill wetlands are fed by irrigation water, and roughly 2 in 3 are entirely irrigation-dependent. Some of those wetlands were intentionally created: state wildlife areas use irrigation to create new wetlands and supplement existing ones, and private landowners on the edge of the Sacramento Valley create wetland impoundments for waterfowl hunting. But over half the irrigated wetlands of the foothills are fed apparently unintentionally by excess water, forming from runoff or leaks from irrigation infrastructure.
During times of drought, these wetlands are one of the most vulnerable ecosystems because they are characterized by the presence of relatively small amounts of water saturating the surface. We were interested in figuring out how wetlands fared during the drought, and especially if irrigated wetlands and natural wetlands behaved differently. To determine this, we carried out field visits to 270 wetlands up to 12 times during the 2014 drought. At each visit our technicians walked throughout the wetland with a map and estimated the percent of the wetland surface that was saturated (either surface water or spongy mud). We found that wetlands fed by irrigation water were both wetter on average and more stable over time than natural wetlands during the drought. Natural wetlands showed strong fluctuations in saturated area, with over half drying completely at least once during the study period, compared to only a third of irrigation-only sites and only 15% of sites that had both irrigated and natural water sources. While some drying during the summer dry season is normal, this degree of seasonality was exceptional compared to what our lab had seen in pre-drought years.
Irrigation water may thus be even more important during drought for wetland species' habitat. Concurrent studies conducted by our lab have found that natural wetlands had very high levels of local extinction for California Black Rails over the course of the drought: no natural wetland occupied by the species in one breeding season remained occupied in the next, and in the last two years of the drought no California Black Rails were detected in any natural wetlands. Irrigation water use in the foothills has thus not only dramatically increased the number of wetlands in the foothills, but has increased their function by keeping them saturated year-round. This has created a unique win-win scenario where private, chiefly agricultural water use has created substantial ecosystem benefits.
However, this increased resilience to drought could lead to sudden severe impacts if drought becomes any more severe than already seen. If irrigation water is removed from the wetlands at the same time as natural water—either via cutbacks in response to more severe drought, transferring water out of the foothills, or efforts to fix leaks and reduce runoff—it may create “cliffs” where wildlife populations, bolstered by water sources resilient to mild drought, decline rapidly when faced with sudden reductions in both natural and irrigated water sources. The next step for our lab is to assess whether such dynamics might occur, using computer simulation studies to link the results of our field research together and examine how the system might respond to hypothetical scenarios.
To learn more about the Black Rail, join us on February 18th.
- Author: Nikolai Schweitzer
The Sierra Foothill Research and Extension Center in Browns Valley, CA utilizes 130 acres of summer irrigated pasture for cattle grazing. SFREC's irrigation water is supplied by a local water district via pipelines and open ditch distribution sources. The irrigation delivery system applies water through sprinklers, open ditches, and gated pipes. Each irrigated pasture at SFREC is managed for 1) Forage Production, 2) Water Quality, and 3) Soil Quality.
SFREC staff measures forage production in 15 enclosed cages throughout five different irrigated pastures. The treatments within each cage include leaving 4-6 inches of residual grass and measuring Total Forage Production (TFP). Guidelines for general irrigation and pasture management production based on past and current research recommend leaving 4 to 6 inches of residue/grass growth after each grazing period. The basis of this recommendation is to increase forage production (by leaving increased amounts of foliar surface area), improve root development, decrease weeds, cause less stress for forage grasses and increase water infiltration. Total Forage Production is measured by clipping the grass all the way to the ground. This center project is measuring the two treatments (4-6 inches & TFP) on their respective pounds/acre production. Each month (from April through October) forage is clipped from each cage, dried, and weighed (pounds/acre). After the samples are clipped, each enclosed area is leveled to its prescriptive treatment.
During the last two years of field sampling on irrigated pasture at SFREC, there was an increase in forage diversity in the Total Forage Production subplot. Clovers, birdsfoot trefoil, and filaree became increasingly abundant due to the increased sunlight and less crowding from competitive grasses. While the increase in clover and other forbes growth lends to an increase in forage quality, there is an overall decrease in forage production per acre in the TFP treatments when compared to the treatments with 4-6 inches of residual grass.
Numerous other factors can potentially impact irrigated pasture forage growth. Fertilization (rates, composition, timing), irrigation (frequency, amount, duration), grazing (stocking density, class/age of animal), species composition, physical structures (water location, loafing areas, rubbing zones, mineral location), soil properties, aspect, and slope, are other important components to manage or consider.
- Contributors: Madison Easley, Larry Forero and Nikolai Schweitzer
For this project, researchers and staff regularly monitor and assess four factors associated with the production of foothill flood irrigated pasture utilizing pipe and ditch delivery methods. These factors include the amount of water applied to the pasture, the amount of water run-off, the effectiveness of irrigation, and the production of the pasture (measured in biomass and AUM harvest).
Preliminary findings indicate that the interval between irrigations could be lengthened in the fall as the days shorten and become cooler. Fewer applications result in less water being used, saving ranchers time, money, and stress. The monitoring for this project will continue through the summer and fall, so check back for additional updates.
With July being “Smart Irrigation Month” this is the time for ranchers to explore opportunities for more efficient irrigation methods using resources like those offered in this post.
- Author: Megan G Osbourn
Adaptation to changing weather and economic conditions is fundamental to farm and ranch survival but this year's drought is pushing variable adaptation strategies to their limit. The international community is closely watching how this dire situation is progressing in California and on June 19th the Canadian Broadcast Company (CBC) visited the Sierra Foothill Research & Extension Center (SFREC) to document how ranchers are adapting to these extreme events and the implications these events have on agriculture and ultimately food production worldwide. Filming involved capturing interviews of three ranchers to explore their perspectives as well as a tour of SFREC to examine potential adaptation strategies to drought.
Joe Fischer, cattle rancher and President of the Placer County Farm Bureau, told CBC the economic impacts and emotional toll of the drought on ranching families have forced ranchers to rethink their management strategies and find innovative ways to manage the land. “Ranchers tend to be profitable if the land is productive,” Fischer said. “We have to look ahead five to ten years or more and try to be as conservative as possible with our stocking rates. Under these conditions, we have a much smaller margin for error so we have to be more precise than ever with our management strategies.”
SFREC Director Jeremy James and Livestock and Natural resource Advisor Glenn Nader used SFERC as an opportunity to demonstrate how intensive grazing management, agricultural by-products and culling strategies could be deployed to mitigate some of the impacts of drought. Many producers with limited feed sources are utilizing agricultural by-products that are available in their area in order to sustain the nutritional requirements of their livestock. Nader, pointed out that almond hulls are high in energy and have limited protein, which allows cows to more efficiently digest hay and can limit the quantity of hay they need to consume. Nader warned that the almond hulls fed must contain a low level of almond shell, in order to avoid problems with rumen digestibility. Rice straw and rice bran are more local agricultural by-products that, under the right conditions, have been utilized as dietary supplements for cattle.
To view the proceedings from the January 29th SFREC Drought Workshop, click here.
- Author: Jeremy James
The annual California Grazing Academy held at UC SFREC and led by Roger Ingram, Nevada/Placer County UCCE Director and Livestock Advisor was once again a widely attended and engaging event. Over a third of an inch of rain cooled off the 24 participants that attended the two-day event that mixed lectures and hand-on activities to explore and demonstrate key principles that drive the ability of producers to be successful grass farmers. Topics included controlled grazing principles, water and mineral cycles, pasture cell design, rest/grazing periods, nutrition and supplementation as well as grazing planning and monitoring. Each participant had the opportunity to visually estimated carrying capacity, install electric fencing, move cows with calves into their designated paddocks, and watch the cattle consume pasture grass over a period of 24 hours. This annual training has remained hugely popular across California and the West with some participants coming as far as Utah to learn from UCCE and Roger Ingram. We looked forward to another year!