Monitoring the hydrologic cycle in the Sierra Nevada mountains Photo © Roger J. Wyan Photography
Monitoring the hydrologic cycle in the Sierra Nevada mountains
Photo © Roger J. Wyan Photography
What is the hydrological cycle?
Why do scientists measure the hydrological cycle?
Who we are and where are we located?
How do we calculate the water balance for a tree?We measure
Collecting and retrieving data.
Effect of increased density of the forest and forest treatments on water cycle.
What is the hydrologic cycle?The hydrologic or water cycle is the movement of water on, above, below, and through the earth’s surface.
Biological Property
TranspirationPhotosynthes
is
Chemical PropertyPrecipitationDissolution
EnergyEnergy transfers through the water cycle
Processor Properties of Water (Adapted from Ripl and Hilmann, 2000)
“Water: the Bloodstream of the Biosphere”
Why do scientists measure the hydrologic cycle?
Weather forecasting Water use forecasting Understand climate trends Flood preparation Hydrologic modeling
Why is it important for scientists to measure the hydrologic cycle?
Who We Are: The Southern Sierra Critical Zone Observatory
Professors, students and staff from over 9 different universities and institutions
Main site is located 10 mi E of Shaver Lake
Second site in Sequoia National Park
3 additional flux tower sites at different elevations
Image courtesy SSCZO
The Southern Sierra Critical Zone Observatory
The Critical Zone lies between rock and sky... where water, atmosphere, ecosystems, and soils interact. It is essential to life on Earth, including food production and water quality. (NSF 2005)
The SSCZO is one of 10 observatories throughout the US
We focus on how the CZ interacts with water Key goal: to predict how water budgets and
vegetation will respond to climate change, land management and disturbance.
4 measurement stations located west to east transect at approx. 800 m elevation intervals beginning at 405 m.
All the sites were on soil developed from granitic parent material, and had vegetation that had not been disturbed recently.
Four Critical Zone measurement stations in and around the Upper Kings River basin
.
.. .Illustrated map courtesy Lynn Sullivan
From Goulden et al., 2012
Water BudgetPrecipitation (P) = Evapotranspiration (ET) +Runoff (Q) +Recharge (R) +Change in Storage (ΔS) (can be soil moisture or groundwater)
P = ET + Q + R + SP ET + Q + S
Note: in granitic mountains, such as the Sierra Nevada, R & ΔSgroundwater are often very small
Precipitation (P)Tree transpiration (T)
Evaporation from soil (E)
Runoff (Q)
Deep percolation (R)
Which are the stores & which are the fluxes?
Rainfall Partitioning
Tree image courtesy SSCZO
Groundwater
Atmosphere
Soil Moisture
Infiltration/Recharge (R)
Precipitation
Domestic
Evapotranspiration
Sublimation
Irrigation
Infiltration
ReservoirsRunoff
Environmental Flows
Can one scale up from a single tree to estimate the water balance of a forest?
Measuring Streamflow
Flumes make the stream fit into a known shape.
Runoff is the movement of water over the land surface.
Stream flow is the flow of surface water runoff contained in a stream channel.
Water depth sensors measure the height of water.
Photos courtesy SSCZO and USFS
Tipping Bucket rain gauge measures liquid and solid precipitation
Precipitation measurementsPrecipitation is the general name given for any form of condensed water that falls to Earth’s surface.
Snow depth sensors use sound to record snow depth
Snow pillow records weight of snow
Photos courtesy SSCZO and USFS
Measuring evapotranspiration
The movement of water from the liquid phase to the gas phase occurs by evaporation and/or transpiration.
Evaporation is the change of water from a liquid to a gas by heating.
Transpiration is water released from plants.
Combined, this process is called evapotranspiration.
Sap flow
Flux tower instruments
Photo © Roger J. Wyan Photography
Photo courtesy SSCZO
Measuring evapotranspiration
The eddy-covariance flux tower measures water vapor from the surrounding forest. The tower measures: - wind speed and direction- CO2 and H2O gas concentrations- air temperature - relative humidity- solar radiation
The flux tower extends high above the surrounding forest.
Photo © Roger J. Wyan Photography
Visualizing tree's heartbeat: A sap-flux meter monitors a Critical Zone Tree.
Photo courtesy SSCZO
Measuring soil moisture
Water that does not flow to the stream channel moves through the soil and/or rock through a process called infiltration. This water is known as groundwater.
Soil moisture sensors buried at different depths underground.
A series of soil moisture sensors buried underground to understand water uptake by tree roots.
c
Photo courtesy SSCZO
Image courtesy SSCZO
Weather stations
This weather station is used to
measure:
- air temperature- wind speed- relative humidity- solar radiation - precipitation- snow depth
Peak snow depth many years ago
Photo courtesy SSCZO
Collecting and retrieving data An immense amount of data are collected
each year. Instruments are located in remote areas,
making it hard to collect data on foot during the winter
Data stored on a datalogger and can be
downloaded with a laptop
From Kerkez et al., 2012 Photo © Roger J. Wyan Photography
Collecting and retrieving data
The wireless embedded sensor network (WSN) was developed to make it easier to collect data remotely.
Cell phone on the flux tower can be called to retrieve data.
Small radios send data from one node to the next, and end at the base station at the flux tower.
Photo © Roger J. Wyan Photography
From Kerkez et al., 2012
Powering instruments
A series of solar panels and
batteries power all the
instruments within the basin.
Photo courtesy SSCZO
Photo courtesy SSCZO
Photo © Roger J. Wyan Photography
Explore a tree root model by P. Hartsough: https://youtu.be/L9F-QgQb2YY
Fun with Trees:One large healthy tree can lift up
to 4,000 liters of water from the ground and release it into the air.
A tree can absorb up to 48 pounds of carbon dioxide per year and sequester 1 ton of carbon dioxide by the time it is 40 years old.
One large tree can provide a day's supply of oxygen for up to four people.
By late summer, trees transpire more water than we can measure in the soil. Perhaps there is a deeper rooting depth.Excavate the tree to discover the root system.
Image courtesy SSCZO
TRANSPIRATION
Image courtesy OpenStax
TRANSPIRATION
Stoma open, transpiration draws water outside the leaf
RoothairsWater uptake in roots
Cohesion (H-bonds) and adhesion (to cell walls) in the xylem draw the water to the leaves
Wat
er P
oten
tial G
radi
ent
Outside air Ψ= -10 to -100 MPa
Root xylem ψ=-0.6MPa
Soil ψ = -0.3MPa
Trunk xylem ψ=-0.8MPa
Leaf (cell wall) Ψ= -1Mpa
Leaf (air spaces) Ψ= -7MPa
Negative ψ (high)
More negative ψ (low)
Ψ = water potential (units = Pressure)Image courtesy SSCZO
Sierra National forests have had a tradition of fire suppression for the last 100 years.What might be some of the consequences of fire suppression?
FOREST HISTORY
Photo by Eric Knapp, USFS
THINNED UNIT WITH CONTROL IN BACKGROUNDSTANISLAUS-TUOLUMNE EXPERIMENTAL FOREST
How much water is being lost due to excess tree canopies?
How much moisture is getting caught in the canopy and evaporating into the air?
Photos by Matthew Meadows
Summary Water balance is accounting for the
partitioning of precipitation into various fluxes and stores.
Water accounting can be done on any time step; we often do it on an annual time step.
Soil moisture is a store important for tree growth.
We can do a water balance on a tree (sapflux) or a forest (flux tower).
Scaling up from a point measurement involves making assumptions about spatial patterns.
Sierra Nevada forests are overgrown.
Complex-forested terrain surrounding P301, with patchy snow.
Photo by Matthew Meadows