Fiber Optic Temperature Fiber Optic Temperature Sensing in the Walker Sensing in the Walker Basin: Basin: From Seedbeds to From Seedbeds to SeepageSeepage

Scott W. TylerUniversity of Nevada, RenoDept. of Geologic Sciences and Engineeringtylers@unr.eduhttp://wolfweb.unr.edu/homepage/tylers/index.html/

What is Fiber Optic What is Fiber Optic Temperature SensingTemperature Sensing

The measurement of temperature (and) using The measurement of temperature (and) using only the properties of a fiber optic cable.only the properties of a fiber optic cable.

The fiber optic cable serves as the The fiber optic cable serves as the thermometer, with a laser serving as the thermometer, with a laser serving as the illumination source.illumination source.

Measurements of temperature every 1-2 Measurements of temperature every 1-2 yards for as long as 20 miles can be resolved, yards for as long as 20 miles can be resolved, every 10 seconds to 60 minutes, with every 10 seconds to 60 minutes, with temperature resolution of 0.02-1.0 temperature resolution of 0.02-1.0 ooF.F.

How Does it Work?How Does it Work?

99.999% of the light energy goes down the 99.999% of the light energy goes down the fiber optic cable without lossfiber optic cable without loss

However, Rayleigh, Raman and Brillouin However, Rayleigh, Raman and Brillouin scattering all occur as light is passed scattering all occur as light is passed through a fiber optic cable. through a fiber optic cable.

The scattered returned light’s energy The scattered returned light’s energy (returned at different frequencies) is related (returned at different frequencies) is related to the temperature of the glass fiber optic.to the temperature of the glass fiber optic.

How do we know from where it How do we know from where it came?came?

The scattered light returns to the detector at The scattered light returns to the detector at the speed of light. So by counting the number the speed of light. So by counting the number of nanoseconds between our laser pulse and of nanoseconds between our laser pulse and the returned signal, the distance is simply:the returned signal, the distance is simply:

X = ½ c * time since the laser was firedX = ½ c * time since the laser was fired

For every 10 nanoseconds, the light pulse For every 10 nanoseconds, the light pulse “flies” about 1 meter.“flies” about 1 meter.

Cable lengths up to 30 kmResolution of Temperature every 1-2 meters!Temperature accuracy up to 0.01 oCInexpensive fiber costs ($0.20-$1/yard)Fiber is completely reusable and repairable in the field.

AdvantagesAdvantages

Fiber optic methods offer unparallel Fiber optic methods offer unparallel ability to continuously monitor ability to continuously monitor temperaturestemperatures

Cost of fiber optic cable is very low Cost of fiber optic cable is very low ($0.20-$1/yard)($0.20-$1/yard)

Cable is easily deployed, removable Cable is easily deployed, removable and completely repairable. and completely repairable.

WhyWhy StudyStudy Temperature on the Temperature on the Walker System?Walker System?

Many hydrologic, geologic and Many hydrologic, geologic and environmental processes are governed by environmental processes are governed by temperature.temperature.

In the Walker Basin, we can use temperature In the Walker Basin, we can use temperature to indicated areas where subsurface to indicated areas where subsurface irrigation return flows are entering the river.irrigation return flows are entering the river.

We can also use it to measure seedbed We can also use it to measure seedbed temperatures during transition to different temperatures during transition to different irrigation strategies.irrigation strategies.

Additional Project SupportAdditional Project Support

Project A: Measuring stratification and mixing Project A: Measuring stratification and mixing in Walker Lake to understand fish habitat in Walker Lake to understand fish habitat development.development.

Project A: Monitoring Walker River Project A: Monitoring Walker River temperatures to assess habitat and restoration.temperatures to assess habitat and restoration.

Project B/C: Development of improved Project B/C: Development of improved irrigation scheduling by monitoring soil irrigation scheduling by monitoring soil moisture status.moisture status.

Project E: Assessing impacts of increased flows Project E: Assessing impacts of increased flows on downstream temperatures and salinity.on downstream temperatures and salinity.

Two Example ApplicationsTwo Example Applications

Measuring mixing in the Measuring mixing in the thermocline of Lake Tahoe thermocline of Lake Tahoe (Selker, Schladow Torgersen and (Selker, Schladow Torgersen and Hausner)Hausner)

Distributed soil temperature Distributed soil temperature monitoring at UNR’s Alternative monitoring at UNR’s Alternative Agriculture Sites (Project F).Agriculture Sites (Project F).

Deep Lake Tahoe Deep Lake Tahoe MeasurementsMeasurements

June 7, 2007June 7, 2007

Lake Tahoe, CA Test SiteLake Tahoe, CA Test Site

Cable DeploymentCable Deployment

Cables were deployed Cables were deployed from the UC Davis from the UC Davis research vessel John research vessel John LeConteLeConte

Cable was lowered to Cable was lowered to the bottom of the the bottom of the lake, then pulled up lake, then pulled up 20 m20 m

Total depth was Total depth was approximately 411 m.approximately 411 m.

Weather Conditions: June 6Weather Conditions: June 6

The previous day was very cold and windyThe previous day was very cold and windy Strong westerly'sStrong westerly's

WeatherWeather Conditions: June 7Conditions: June 7

Warm, calm dayWarm, calm day Smooth waterSmooth water

Complete Vertical Profile: Complete Vertical Profile: Single EndedSingle Ended

Note the wavy pattern of the warm water interface! Causing mixing of nutrients to the bottom waters

Walker River Water Walker River Water ApplicationsApplications

Understanding groundwater/river exchanges are Understanding groundwater/river exchanges are crucial to developing hydrologic models of the crucial to developing hydrologic models of the basinbasin

Areas of localized saline groundwater inflows into Areas of localized saline groundwater inflows into the Walker River will have cool waters during the the Walker River will have cool waters during the summer months.summer months.

Fiber optic cables will be deployed for 2-4 days Fiber optic cables will be deployed for 2-4 days along selected reaches to map inflows.along selected reaches to map inflows.

Chemical sampling of inflows will be done using Chemical sampling of inflows will be done using hand drilled wellshand drilled wells

Strategies for reducing saline inflows can then be Strategies for reducing saline inflows can then be developed at the local scale.developed at the local scale.

 Linear Parallel Seepage Monitoring

Walker Lake StudiesWalker Lake Studies

The dynamics of the mixing of Walker Lake The dynamics of the mixing of Walker Lake are important for understanding habitat are important for understanding habitat and refuges.and refuges.

In coordination with project team In coordination with project team members and the USGS, periodic members and the USGS, periodic measurements of the vertical temperature measurements of the vertical temperature profile in the lake will be performed.profile in the lake will be performed.

Additional fibers will be installed in areas Additional fibers will be installed in areas of anticipated submarine groundwater of anticipated submarine groundwater inflows into the lake for input into inflows into the lake for input into groundwater models being developed.groundwater models being developed.

Seedbed TemperaturesSeedbed Temperatures

Fiber optic cables can be used to measure, at large Fiber optic cables can be used to measure, at large scales, the shallow soil temperatures.scales, the shallow soil temperatures.

Alternative agriculture studies and reduced water Alternative agriculture studies and reduced water application can allow much higher soil temperatures to application can allow much higher soil temperatures to develop, which may limit germination and plant develop, which may limit germination and plant growth.growth.

Almost 2 miles of fiber have been installed 15 cm Almost 2 miles of fiber have been installed 15 cm beneath the soil at the 5C and Wildlife Refuge Test beneath the soil at the 5C and Wildlife Refuge Test SitesSites

Temperature will be monitored to determine:Temperature will be monitored to determine: Maximum daily soil temperatures during summerMaximum daily soil temperatures during summer Infiltration rates (measured by cooling of the soil)Infiltration rates (measured by cooling of the soil) Soil Moisture by time to maximum temperatureSoil Moisture by time to maximum temperature

5C Ranch Data5C Ranch Data

Base case temperatures measured in Base case temperatures measured in mid February, prior to germination.mid February, prior to germination.

Soils are moderately coarse and Soils are moderately coarse and background soil moisture is uniformbackground soil moisture is uniform

Watch for part of the cable that is in Watch for part of the cable that is in the air (cold at night, warm in the the air (cold at night, warm in the day)day)

SummarySummary

Fiber optic temperatures are supporting many Fiber optic temperatures are supporting many of UNR’s Walker Basin Project.of UNR’s Walker Basin Project.

Low cost and detail of information in both the Low cost and detail of information in both the lake, river and soil offer unique opportunities lake, river and soil offer unique opportunities to monitor both current conditions and the to monitor both current conditions and the impacts of future decisions on the Walker impacts of future decisions on the Walker basin.basin.

The system has benefits beyond the current The system has benefits beyond the current applications, specifically to improving water applications, specifically to improving water use efficiency of irrigation.use efficiency of irrigation.

Nevada is one of the leaders in this Nevada is one of the leaders in this technology. technology.