ESM108 Class Field Trip to the
Kings River Experimental Watershed (KREW) part of the
Southern Sierra Critical Zone Observatory (SSCZO)
Upper Site (Soil moisture and Vegetation monitoring)
We will walk as a group about ½ mile up the access road to the P301 Flux tower and CZT-1
instrumented tree. We will talk about these installations and their role in KREW environmental
monitoring and biometeorology. At this point we will split up into groups with one group doing
vegetation monitoring one doing soil moisture monitoring and finally one installing a weather station
and instrumenting soil pits across a meadow/forest transition. After about two hours, we will switch
groups. While at the sites, please be careful not to disturb or impact existing monitoring equipment. BE
SURE TO TAKE NOTES! as it can be hard to reconstruct what you did when you are writing things up
back in Davis.
Activity 1 Vegetation Survey
There are many reasons to study vegetation in the landscape. Plants are the primary producers
which drive ecosystems, protect against erosion, provide habitat and are instrumental is cycling water,
carbon and nutrients in ecosystems. At this site we will be surveying the dominant vegetation,
coniferous trees.
When monitoring forests, researchers commonly take inventory type measurements. This
involves recording species, diameter and height measurements of trees. At the SSCZO each group will
take a complete inventory of all trees over 20 cm DBH (diameter at breast height, aka 1.4m or 4.5 ft
above the ground surface) of one hectare adjacent to the Flux tower. A hectare is 10,000m2 or a 100m
by 100m quadrant
After laying out the quadrant boundaries, you will note slope and aspect of the site and the
species, circumference and height of the vegetation. You will take GPS points of all the pine trees
<50cm DBH and tag them with tape. In addition you will tally all the trees less than 20 cm DBH by
species. You will use the vegetation survey data to plot species composition and estimate carbon and
water storage in the trees.
Species:
The South Sierra Critical Zone Observatory (SSCZO) is comprised of a mixed conifer-forest. This forest
is made up of ponderosa pine (Pinus ponderosa), sugar pine (Pinus lambertiana), white fir (Abies
concolor), Incense-cedar (Calocedrus decurrens) and Black Oak (Quercus kellogii). We also find
lodgepole pine (Pinus contorta) in meadows, wet areas and at higher elevations. Deerbrush, manzanita,
chinquapin, tan oak, bitter cherry, squaw carpet, mountain whitethorn, gooseberry, rose, and mountain
misery are common shrub species in the understory although this will largely be covered by snow during
our visit and you do not need to catalog them. As a short hand on your data sheets you will record
species as the first two letters of Genus name and the first to letters of the species name, so white fir
would be Abco. We will talk about identifying these species in the field.
Circumference:
Using a soft tape you will measure the circumference of the trees at a height of 1.4m. This height
is the standard used in forest inventory to measure diameter at breast height, because it is convenient and
avoids the ground swell that you may see at the base of trees. Using basic geometry we can calculate the
diameter of the trees based on the circumference.
Height:
Tree heights will be measured using a clinometer, which is a device that measures angles to
determine tree height. By walking a known distance from the tree and measuring the angle to its top, we
can use basic trigonometry to calculate the tree height. (Remember SOH CAH TOA).
Activity 2 Soil Moisture survey
Snow is the dominant form of precipitation at this elevation in the sierra and one of the primary
objectives of the SSCZO is looking at snowmelt processes and what will happen to ecosystems across
the rain/snow transition zone as climate changes. Since the snow has all melted, we will look instead
this year at soil moisture. We will think about soil moisture as a proxy for snow as the areas with higher
soil moisture have more recently had snow persistent on the landscape.
Soil moisture survey:
We have a variety of ways we are measuring soil moisture at the site. One of these is the
COSMOS sensor which is mounted on the P301 flux tower and measures soil moisture across a large
grid (200m2). We will take point measurements along spokes starting at the flux tower and extending
out to the boundaries of the grid. We will do this with a hand held instrument called a Hydrosense TDR
that you calibrated in lab. We will locate these spokes and follow them using a combination of
compasses, GPS units and distance tapes. We will record both the factory calibration and the travel time
so we can apply our own calibration later. We may also take measurements from multiple depths. If
time allows, we will collect samples for lab calibration of the instruments. These measurements will
help us to interpret the spatially averaged measurements from the COSMOS sensor.
You will also get an opportunity to observe a neutron probe soil moisture measurement which uses a
similar technique as the COSMOS but uses a self contained source of neutrons an represent more of a
point measurement.
Activity 3 Meadow Weather Station and soil pits
In this activity you will install a Visala weather station in a meadow location adjacent to the flux
tower and CZT-1. This weather station will collect data throughout the summer and help to understand
the Evapotranspiration (ET), energy balance, and hydrology of the meadow. You will also participate in
the installation of an instrumented soil pit in the meadow and adjacent to the meadow. The soil moisture
sensors (5TM and GS3) will complement soil matric potential sensors and help to understand changing
soil hydrology at the site as well as help to close the surface energy budget by measuring energy lost to
the subsurface. You will also look at soils from the two different pits and talk about differences in soil
development at the two sites.
Weather Station Installation:
The weather station we will install is a Vaisala MXT 520 all-in-one met station (Temp, RH,
Baro, Wind, and Precip) plus an NR-Lite. We will see how to wire in sensors to the logger, provide for
a self contained power supply and discuss challenges in taking automated measurements in the field.
Soil Pit installation:
A standard means of viewing, analyzing and identifying soils is with a soil auger. By looking at a
disturbed soil sample we can determine soil texture and identify key components of a particular soil
matrix. More involved methods for determining soil texture include sieve analysis, hydrometer method,
and laser particle size analysis which need to be done in the lab.
To gain more insight into the physical properties of a soil it is requisite to take intact or
undisturbed soil cores for analysis in a laboratory using a soil sampler designed to take specific sized
cores. The cores will be of known volume, so that the bulk density of the sample can be ascertained by
weighing the sample and dividing the mass by the volume of the core:
𝜌𝑡 =
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑡ℎ𝑒 𝑠𝑜𝑖𝑙 𝑎𝑛𝑑 𝑤𝑎𝑡𝑒𝑟 𝑀𝑠 + 𝑀𝑤
=
𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑡ℎ𝑒 𝑐𝑜𝑟𝑒
𝑉𝑡
These cores are taken to a laboratory to determine other soil properties including saturated hydraulic
conductivity and determination of soil moisture release curves. These aforementioned properties give us
information on how water moves through a particular soil and the energy with which water is held in the
soil (matric potential).
Soil Pit and instrumentation:
Installing soil moisture sensors allows us to determine how the water content of a soil changes
over time and during different seasons of the year. In addition, we can see wetting fronts from water
that infiltrates the soil as snowmelt begins and assess the extent to which the soil becomes saturated, as
well as, determine how much water is removed from the soil during the summer months by
evapotranspiration. We will auger a soil pit, install 5TM or GS3 sensors and hook them up to a
datalogger to monitor soil temperature and moisture over various temporal scales. We may also talk
about water table delineation if we encounter the water table.
What we will be doing:
Soil Depth:
 Using a rod of known length with gradations, we can assess the depth of a soil by driving the rod
down into the soil (if the soil is deeper than the length of the rod, we say that soil depth is
greater than that length)
Taking Undisturbed Soil Cores:
 We will be using the Uhland Sampler to take undisturbed soil cores at depths where the soil
moisture are going to be installed
Installation of soil moisture monitoring equipment:
 After augering the holes for textural analysis, we will install two 5-TE sensors at two different
depths to determine how soil moisture changes with depth, and take undisturbed soil cores to
perform a field calibration of the sensors.
Lower Site (Stream and monitoring)
The groups going to the lower sites will drive approximately 20 minutes to the lower portions of
the watershed. Providence Creek (P301) will be the first visit for the Saturday group. We will discuss
the differences between a weir and a flume, and discuss the sediment basin. Both groups will head up to
the P300 weir where students will be shown the gauging shed. Measurement activities will be explained
specifically for P300 and generally for KREW. After viewing the shed and discussing measurement
activities, we will shift focus to the weir. We will discuss the design and purpose of the weir and how
it relates to the staff gauge. Students will be instructed how to read the staff gauge and how to calculate
flow. We will get in the stream and measure the dimensions of the weir and place a pressure transducer
at the staff gauge.
The groups will then move to the Lower Providence Creek or Big Creek and do the activities
outlined below. On Sunday, the groups will visit both sites, retrieve data from dataloggers deployed by
the Saturday groups. Retrieved data will be used to examine diurnal cycles of temperature and water
depth during our visit. BE SURE TO TAKE NOTES! as it can be hard to reconstruct what you did
when you are writing things up back in Davis.
Activity 4 Stream Measurement
Flow and Transport:
In addition to the permanent sites higher up in the watershed, we will also conduct some flow
assessment activities at this location. We will use several methods to estimate stream velocity and relate
these to discharge by surveying a stream cross section. We will do Salt Slug Flow Measurement where
we us salt as a tracer and measure the travel time down the stream. We will learn how to use a Flow
Tracker Sonic Flow meter and a pigmy type flow meter to estimate velocity and look at velocity changes
across the creek.
Diurnal Measurements:
We will drop a pressure transducer in the stream to measure the variation in stream stage over a
day as well as variations in temperature.
Water Quality Parameters:
We will also collect various water quality parameters (EC, pH, Temp, DO) and well as learn how
to collect samples for water quality analysis.
Station 5 Stream Surveying
In this section you will use a laser level to survey in the cross section and longitudinal section of the
stream. You will work together in teams to survey in the bank and channel geometry in order to
calculate cross sectional area measurements for flow estimation. You will also do a longitudinal (long
axis) of the stream that you can use to calculate the flow using the Manning Equation approach. The
geometry of the stream channel will be used with the velocity measurements to calculate discharge. We
will compare discharge measurements we come up with to the measurements at the permanent
installations.