On February 9th, UC Davis Hydrology Professor Dr. Gregory Pasternack brought 13 lucky students from his Field Methods in Hydrology class to explore one of the watersheds here at Sierra Foothill Research & Extension Center. In his 21st and likely final year teaching this course, Dr. Pasternack was kind enough to share some reflections with us below:
“I always run this class trip in February and usually the view of Deer Creek across the canyon is stunning. In the final section before it convenes with the Yuba River, Deer Creek plunges an amazing 400 feet vertical per mile. With a flow of a couple hundred cfs that we typically see in February, it's just a stunning view. I once tried to hike down into that section from Mooney Flat Road, but the bedrock is very smooth and the waterfalls too extreme, even when dry. It's a postcard-worthy view for sure.
The Schubert catchment is small yet still quite adventurous to university students. Some students come from urban regions with little outdoor experience, while others are avid outdoor adventurers yet have little practical experience with doing science in nature. The goal of experiential learning is to put students into new situations with one-on-one experiences with nature where they have to use their knowledge and experience to problem solve. Not only are students learning science, but they are learning how to work together in a team, and even how to dress effectively to do safe outdoor research. People might be surprised to hear that part of the course involves teaching about clothing, but the technology of textiles for outdoor work has improved so much and students have little exposure to thinking about safety from a clothing perspective.
Lectures are the most efficient way to inject the most amount of information into the human brain in the shortest amount of time. Unfortunately, people tend to not retain most of that information unless they perceive a critical need to know something at a given moment in time. With quick access to the internet, people are becoming less knowledgeable and more dependent on search. What a field trip like this does is provide motivation to learn and retain lecture knowledge, because it will be required to be safe and effective during the field trip as well as to complete the associated homework assignment. Down in the Schubert watershed, cell phones don't work, so you have to really know what you're doing and not rely on technology to tell you what to do.”
- Author: Helen Dahlke
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.
- Author: Alexandra Stefancich
Presentations focused on a wide variety of agricultural subjects including livestock, bees, bats, irrigation, nutrition, seed saving, wool spinning, cider pressing, soil health and much more. Participating organizations included the local FFA chapters, Nevada Irrigation District, Sierra Foothills Audubon, the 4-H Youth Development Program, UC Cooperative Extension and private agriculturalists.
The Sierra Foothill Research and Extension Center (SFREC) was involved with actively showing students how soil and sand can help filter impurities out of water through an experiment where Kool Aid (representing impure water) is poured through a variety of substrates. SFREC also taught students about watersheds, including how water flows through a watershed, and the areas in which water tends to accumulate.
Farm Day allows students the chance to see and truly connect with multiple aspects of our agricultural systems, an opportunity that many people take for granted. These hands-on activities offer students a path to discovering where their food, drink, and clothing really come from and how it is all connected to the world's ecosystems. Witnessing the interest and curiosity of the students as they traveled through the stations, was a sure sign of the event's success.
SFREC will also present to third grade students at the Yuba-Sutter Farm Day this Friday. Be on the lookout for an update next week!