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. 

The way rainfall is translated to runoff and streamflow in rivers depends on many complex, interconnected processes in the landscape. Rain falling onto hillslopes, meadows, or forests is either infiltrating into soils or flowing as runoff on the surface of soils. Either way, the moving water is often mobilizing solutes, pollutants, or nutrients along its pathway, which have the potential to contaminate streams and impair water quality. Knowing where these flow pathways occur in the landscape is crucial to prevent pollutants (e.g. excess nitrogen from fertilizer or manure, pesticides, pathogens) from being transported to rivers and lakes, where they can cause algae blooms. Observation of and understanding where and when runoff is occurring in the landscape and how the moving water is transporting pollutants to streams has been at the heart of hydrological research for many decades and has triggered the Clean Water Act in 1972.

For many years, hydrologists (e.g. water scientists) have used hydrologic measurements such as streamflow hydrographs (e.g. graphs of streamflow vs time) to characterize hydrologic- and associated transport-flow pathways, however, these methods do not allow for identifying specific pollutant sources and individual flowpaths of concern in the landscape. In recent years, chemical tracers like bromide or chloride and dyes (blue, red, yellow fluorescent colored dyes) have been used to obtain more information, but the variety of unique tracers available from each type is extremely small, thus limiting the identification of multiple flowpaths at the same time. Additionally, once introduced into the system, it is often problematic to reuse the same tracer because of uncertainty in whether old or new tracers are being detected. 

To overcome the problems that have plagued traditional tracer studies we have developed a new tracer concept that utilizes bio-molecular nanotechnology. We use short, artificially made DNA sequences that are wrapped into a safe, biodegradable polymer composed of polylactic acid (PLA) to protect the DNA from being eaten by microbes during the transport process.  Because DNA is made of the four basic building blocks adenine (A), thymine (T), guanine (G) and cytosine (C) (Fig. 1), which can be combined in any random order, our unique DNA-based tracers allow, in theory, fabrication of an enormous number of unique tracers (approximately 1.61 x 10⁶⁰) with identical transport properties. Because of their unique DNA sequence the tracers have unique IDs, thus, we can use multiple tracers at the same time in the same watershed. The amount of tracer present in a streamwater sample can be estimated with real-time quantitative polymerase chain reaction (qPCR), a method commonly used in molecular biology, which determines the number of DNA copies present in a sample. Finally, during the tracer fabrication process, we can alter the size of the tracer particles to anything from 200 nanometers (size of a virus) to 1 micrometer (size of colloids or bacteria), which helps mimicking the physical transport properties of the pollutant of interest.

In the next two years we will test differently sized DNA tracers in a well-studied, small experimental watershed at SFREC to test their use for identifying hydrologic flow pathways. This study will provide invaluable information for the understanding of processes in hydrologic systems that can be used to improve hydrological and biogeochmical models used to predict transport of pollutants from hillslopes to streams. To achieve this broader goal, we will distribute 5 different DNA tracers at 5 different locations at incrementally increasing distances from a trenched hillslope at SFREC and measure the tracer breakthrough curves in a runoff collection system and the watershed outlet. The injection locations will be chosen to represent a range of specific soil-landscape characteristics such as places with relatively deep soils, shallow soils and areas where flow visually concentrates in the landscape. With the tracer experiments we also hope to quantify preferential flow pathways (e.g. macropore flow) in the watershed. Preferential flow is hypothesized to lead to shorter travel times of water and pollutants through soils and the vadose zone. Because of the variable size of our DNA tracers (0.1-0.4 µm) they could be particularly useful for quantifying macropore and preferential flow because we expect that a small fraction of the tracers will be filtered out in the soil matrix while the majority of the DNA tracers will move along the most rapid flow pathways. The results from these experiments, if successful, will provide improved estimates of the time it takes for water and solutes to travel through the soil to streams, which will allow us to more accurately predict the risk of pollution of streams and surface water bodies during storm events.

In mid November, SFREC partnered with Grass Valley Charter School and Twin Ridges Home Study by bringing students to the center to catch a glimpse of salmon spawning in the Lower Yuba River. The opportunity to observe salmon spawn is a way for students to see the last stage of the unique salmon life cycle and learn about the important habitat that our local waterways provide to this species.

Kindergarteners from GVCS visited over two days for a fun-filled science field day. Students were able to hunt for benthic macroinvertebrates, look at decaying salmon carcasses, search for salmon redds (the nests that they build to lay their eggs), and understand the challenging lives that salmon have by acting out the stages of their life cycle. Students loved their field day, saying they "couldn't choose a favorite thing, it was all so fun!" Another student noted that "I am happy to be a human. Being a salmon seems hard."

Students of all ages from Twin Ridges Home Study visited on another field day. They were led on an interpretive hike where they learned not only about salmon, but about the history of the land around the river. This includes looking at the gravel piles created by historic mining and learning about how the land is now used for grazing cattle.

The opportunity to see these natural wonders first hand can have a lasting impact on student learning. SFREC is dedicated to increasing the number of hands-on science field days it offers to local students. This spring we will be offering field science trips for 4th and 5th graders where they will learn about a variety of science concepts and field science techniques. For more information about these field science days please contact Ali Stefancich at astefancich@ucanr.edu. 

Last month, teachers and educators from around Northern California came together for a weekend to learn about best practices for science education with a Forestry Institute for Teachers+ (FIT+) workshop. FIT+ is a new professional development program from the Northern California Society of American Foresters and UC Cooperative Extension Project Learning Tree. This workshop is an extension of the Forestry Institute for Teachers, which focuses on curriculum from Project Learning Tree and Project Wild. The Forestry Institute for Teachers also hosts lectures from foresters about best practices and lesson plan development using the program's curriculum guides. FIT+ on the other hand, concentrates more on the Project WET curriculum and hosts guest speakers that talk about all varieties of ecology.

The educators had a fun-filled, well-rounded, educational weekend. They connected with one another and practiced the Project WET curriculum, by physically doing some of the activities as well as creating mock units for their classrooms that integrate Project WET activities and other resources. In addition to getting acquainted with the curriculum guide, the teachers were treated to two educational lessons, and a trip down to the Lower Yuba River. The first lecture was by Doug McCreary, who gave an overview of oaks in California and the role they play in our foothill ecology. SFREC Director, Jeremy James followed with a lecture about invasive species, how they invade and the impact they can have in our ecosystems. While down at the Yuba River, teachers practiced interpreting river health through analyzing the benthic macroinvertebrates that were collected with the help of Kelly Santos of Sierra Streams Institute.

Look out for the return of FIT+ to SFREC in the upcoming year!