Consulting & Facilities

Hydraulics Sedimentation Laboratory

The University of Tennessee, Knoxville
851 Neyland Drive, Knoxville, TN 37996-2313
Laboratory Director: Dr. Thanos Papanicolaou, (865)974-7836, tpapanic@utk.edu
Laboratory Manager: Dr. Achilleas Tsakiris, atsakiri@utk.edu

 
Welcome to the Hydraulics and Sedimentation Laboratory at the University of Tennessee, Knoxville, where we specialize in gamma spectroscopy analysis of environmental samples.

Gamma Detector

Gamma Detector

Fallout radionuclides (namely 7Be, 137Cs, 210Pb, 214Bi and 226Ra) are excellent tracers in sediment studies because they are delivered naturally in the precipitation and they bond rapidly and strongly to sediment making them fairly conservative. Additionally, the use of fallout radionuclides in environmental studies has been well documented in numerous environments.

Gamma spectroscopy is an established method used to measure the photon emissions at certain energy levels thereby calculating the decay of radioactive material. Gamma spectroscopy can be used to determine the radionuclide activities in upland soils, channel bed and banks, suspended sediments, lake sediments, and precipitation. Gamma spectroscopy provides a simple and non-destructive means of analyzing the radioactivity of environmental samples. Moreover, preparation of samples for gamma spectroscopy analysis is minimal.

We have established a Gamma Spectroscopy lab at the University of Tennessee, Knoxville to facilitate the analysis of fallout radionuclides (particularly 7Be, 137Cs, 210Pb) in environmental samples. Our lab contains a High-Purity Germanium Detectors (HPGe) with a low background cryostat and shield. The high purity germanium crystal with a carbon fiber window has a 69.7-mm diameter and a 27.6-mm length. The performance statistics of the detector either meet or exceeded factory certification.

Gamma DetectorThe system has been calibrated using constructed standards. Two different Standard Reference Materials (SRMs), which contained a suite of radionuclides including 137Cs and 210Pb, were used during calibration. The methods for standard preparation and detector calibration have been documented in multiple locations including Bonniwell (2001), Wilson (2003), Wilson and Kuhnle (2008), and Denn (2010). Sediment samples have been analyzed in polystyrene Petri dishes (48 mm D x 8 mm H) and ranged in weights from 1 g to 20 g.

Quality assurance was established using the NIST Ocean Sediment Environmental Radioactive Standard (SRM 4357). The SRM has a certified activity of 137Cs of 0.013 ± 0.001 Bq/g and a range of 0.011 to 0.016 Bq/g. The SRM has uncertified activities of 210Pb and 214Bi. The range of activities for 210Pb is 0.014 to 0.035 Bq/g; the range of activities for 214Bi is 0.009 to 0.020 Bq/g. Measured activities averaged 0.010 ± 0.001, 0.024 ± 0.004, 0.012 ± 0.001 Bq/g (n = 3) for 137Cs, 210Pb, and 214Bi, respectively.

References

Bonniwell, E.C. 2001. Evaluating soil erosion and sediment transport with radionuclides. Ph.D. Dissertation, Case Western Reserve University, Cleveland, OH. 265 pp.

Wilson, C.G., 2003. The transport of fines sediment through three NERR estuaries using radionuclide tracers. PhD. Dissertation, Case Western Reserve University, Cleveland, OH.

Wilson, C.G., Kuhnle, R.A., 2006. Determining relative contributions of eroded landscape sediment to the suspended load of Goodwin Creek using 7Be and 210Pbxs. USDA-ARS National Sedimentation Laboratory Research Report 053, Oxford, MS.

Denn, K.D. 2010. Sediment budget closure during runoff-generated high flow events in the South Amana sub-watershed, IA. M.S. Thesis, The University of Iowa, Iowa City, IA.

 

Flumes

Water-Sediment Recirculating Flumes

HSL Turbulence Flume

Dye experiment in the turbulence flume of HSL

Two flumes are housed in the Hydraulics and Sedimentation Laboratory (HSL) of the University of Tennessee at Knoxville for basic educational and advanced technical research.

The first flume is a state-of-the-art, self-contained, recirculating, tilting flume with a working section length 10.0 m (32.8 ft), width 0.60 m (2. 0 ft), and depth 0.50 m (1.65 ft). The flume slope can be adjusted electronically up to 5% allowing replicating slopes typical in steep streams. The flume length guarantees that fully developed flow conditions are present during experimental runs. A pump powered by a 30 HP motor is used to recirculate flow with maximum discharge of 170 lit/sec (2700 gallons per minute) from a water tank with capacity of 6,800 lit (1,800 gallon). The floor of this flume has a 0.91 m (3.0 ft) long, 0.30 m (1.0 ft) wide aperture, which is located 2.00 m (6.5 ft) upstream of the flume exit section. This aperture allows the mounting of a false floor, which can house acoustic, or pressure transducers for monitoring bedload transport and turbulent pressure fluctuations. Alternately, a spawning box with vertical pressure piezometers can be attached underneath the aperture for simulating flushing flows in gravel mountain stream and subsurface hydrology studies, as well as for modeling of the movement of peripheral flow in porous material.

HSL Sediment Flume

Side view of the sediment flume with the sediment diffuser atop the flume headbox

The second flume is also a self-contained, tilting flume that recirculates water but also sediment. The sediment flume is 10.0 m long, 0.60 m wide and 0.50 m deep. The flume slope can be adjusted electronically in 0.1% increments up to 5% allowing replicating high gradient streams. Flow in the flume is provided by a pump powered by a 15 HP motor capable of a maximum discharge of 100 lit/sec (1,600 gallons per minute). This flume has an integrated sediment recirculation system operated by compressed air. A sediment trap spanning the flume width at the flume exit section collects outgoing sediment, which are then routed to a diffuser at the flume headbox via a diaphragm pump. The sediment recirculation system can recirculate sediment with diameter up to 50 mm (2 inches) at a rate 4x10-4 m3/sec.

Each flume is equipped with a digital magnetic flow meter for monitoring the flow volumetric discharge with accuracy of 0.001 gpm. The bed slope of each flume can be adjusted in 0.1% increments via a digital inclinometer mounted underneath the flume. The flume sidewalls and floor of both flumes are made of scratch-resistant, transparent acrylic, which allows optical access for laser-based velocity measuring instruments (e.g., PIV, LDV) and camera imaging. A combination of carriages can be mounted onto rails spanning the flume length for mounting instruments including lasers, Acoustic Doppler Velocimeters (ADV), video-cameras, thermal cameras, ultrasonic transducers and point gauges. Also available is a carriage with an adjustable arm, specifically designed for accurately positioning a Laser Doppler Velocimeter (LDV) probe and making measurements through the flume sidewall.

The two flumes can simulate a variety of processes in water resources. These include simple hydraulic models such as, uniform and gradually varied flow, hydraulic jumps, and broad crested weirs, as well as more complicated models such as turbulent flow structure around obstacles and hydraulic structures, sediment transport of sand and gravel bed-streams, scour around hydraulic structures, hyporheic flow and transport processes, knick points, head cut formations, and rill erosion.

Conduit Erosion Flume

HSL Conduit Erosion Flume

HSL Conduit Erosion Flume

The conduit erosion flume is designed by Prof. Thanos Papanicoalou and Dr. Mohamed Elhakeem. The flume has been used to estimate the critical erosional strength of both cohesive and non-cohesive soils. This type of flume is preferred over other available devices since it can replicate the conditions that are typically encountered in nature when fluvial erosion occurs. Flow in the conduit flume is pressurized allowing it to generate shear stresses ranging from 1 to 25 Pa and, thus, permitting the testing of well-consolidated and aged cohesive soils. The conduit flume, being a closed system and with an optimum length of less than 4.5 m, is equipped with a power generator and designed to operate in the laboratory or in the field. Being a straight flume, it generates weaker secondary cells comparatively to annular flumes thus isolating the contributions of secondary currents in picking up sediment grains or breaking aggregates. The flume has an operational flow rate ranging from 0.0025 to 0.0117 m3/s, based on the upper and lower limits for maintaining a fully developed turbulent flow. These flow rates corresponded to bulk velocities of 0.5 to 2.3 m/s and applied shear stresses of 1 to 21 Pa.

Open-Channel Erosion Flume

open_channel_erosion

The water-and-sediment recirculating flume to estimate the critical shear stress of collected bank soils.

A state-of-the-art, water-and-sediment recirculating flume (Figure 3) was designed by the Papanicolaou team. The flume will be used to estimate τc and is preferred over other available devices including jet tests and annular flumes to estimate τc.

A section of the flume has been modified to incorporate a sample box (length = 30 cm; width = 10 cm; height = 5 cm). The collected samples will be trimmed with a razor and wire saw to fit the dimensions of the sample box so that the surface of the sample is aligned with the flume bed. Every effort will be made to preserve the original roughness and microstructure of the sample surface.

The flow rate will be incrementally increased to alter the corresponding applied shear stress to the sample. Suspended sediment will be collected after the flow rate has stabilized during each increment in two, 1-L bottles from sampling ports just downstream of the sample box.

 

Field Infrastructure

Clear Creek Infrastructure

Studies in the Clear Creek watershed are focused within a 26-km2, predominantly rural, sub-watershed in the headwaters. The sub-watershed has an infrastructure maintained by the Hydraulics and Sedimentation Laboratory (HSL) at the University of Tennessee, Knoxville, to monitor rainfall, streamflow, suspended sediment concentration, and other water quality parameters. Extensive geospatial and biogeochemical databases exist for the sub-watershed, as well as a detailed history of land use and management practices.    The current and historical databases of management practices for Clear Creek were obtained from local USDA-NRCS representatives and the data include the timing, location, amount and type of tillage practices performed, as well as the seeds planted and crops harvested.

Clear Creek Watershed

Clear Creek Watershed

Experimental Plot

(a) An experimental plot in Clear Creek subdivided in rows of corn (b) and soybean (c) for measurements of SOC and CO2 fluxes. (d) A PVC tube inserted in the ground to which a CO2 sensor is placed for soil respiration fluxes.

Table 1: Types of data available at Clear Creek
wind speed
wind direction
air temperature
humidity
atmospheric pressure
total solar radiation
NEXRAD precipitation
precipitation depth & chemistry
leaf wetness
vegetation inventory
vegetation remote sensing
soil temperature
soil water content
soil heat flux
soil chemistry
soil nutrients
soil organic content
soil yields
soil fauna
soil survey data
surficial geology
soil mineralogy
digital elevation model
LIDAR elevation data
land use/land cover
demographic data
economic indicator data
stream stage & flow
suspended sediment measurements
channel stability
channel profiles
stream turbulence
stream temperature
stream conductivity
dissolved oxygen
stream nutrients

 

Dual tipping bucket rain gage in Clear Creek

Dual tipping bucket rain gage in Clear Creek.

Experimental Test Plots

HSL has established small scale tests plots in the sub-watershed (~100 m2), which are equipped with multiple sensors and Parshall flumes. The plots provide opportunities for evaluating local processes. Larger scale experimental fields are also used for exploring interactions between management practices and environmental parameters.

Dual Tipping Bucket Rain Gauge Platform

Tipping bucket rain gauges are used for monitoring precipitation data throughout Clear Creek. For the studies in Clear Creek, the concept of a dual tipping bucket rain gauge platform provides added benefits of continuous data collection and quality assurance that far outweigh the added cost of an additional rain gauge. The platforms contain a data acquisition system, as well as mounting space for cellular data transmission antennas and solar panels.

Automated Double Ring Infiltrometers at a Clear Creek test plot

Automated Double Ring Infiltrometers at a Clear Creek test plot

Double Ring Infiltrometers

In order to perform infiltration measurements for different spatial and temporal scales in Clear Creek, ten automated double ring infiltrometers have been developed by HSL.  The double ring infiltrometers measure capacity rate infiltration or infiltration during ponded surface conditions.  A secondary measurement with the double ring infiltrometer is vertical saturated hydraulic conductivity (Ksat) in the upper 2-3 cm of soil.

The HSL-team has automated the process so single investigators can run multiple infiltrometers simultaneously.  Water is added automatically to both the inner and outer rings until the ponding depth reaches a specified mark (~8 cm).  The water level in the inner ring is then allowed to drop 2-3 cm before refilling to its initial water level while a constant head is maintained in the outer ring.  The increment of time between refilling and the volume of water needed to maintain constant head in the inner ring is automatically recorded.

Measuring the saturated hydraulic conductivity of unsaturated soils by in-situ methods is more difficult than measuring Ksat for saturated soils.  The original unsaturated soil must be artificially saturated to perform the measurements.  Large quantities of additional water may be needed to saturate the medium, which results in a more elaborate and time-consuming measurement.  The results of these in-situ measurements of Ksatare commonly called the field-saturated hydraulic conductivity.

Soil Moisture Probes
Soil moisture influences the rate of decomposition for Soil Organic Carbon (SOC) and resulting CO2 fluxes from the soil; however, it exhibits large spatial variability.  To monitor this variability in soil moisture, several low power motes with Decagon dielectric constant soil moisture probes are installed in Clear Creek.  The motes are programmed to form a sensor network to and from a distributed soil moisture sensor.  Clusters of sensors are deployed with each sensor at a different depth to develop a profile of soil moisture.

Soil moisture and temperature probes

Soil moisture and temperature probes

Sample output from probes - daily variation in soil moisture and temperature

Sample output from probes – daily variation in soil moisture and temperature

Rainfall Simulators
Three medium-sized Norton Ladder Multiple Intensity Rainfall Simulators are available for proposed field experiments to create artificial rain events of different magnitudes that eliminates the need to wait for natural rainfall events to occur.  The HSL simulators were manufactured at the USDA-ARS National Soil Erosion Research Laboratory and calibrated against natural rainfall considering drop size distribution, drop velocities, momentum, and kinetic energy in addition to rainfall intensity and spatial uniformity.

Rainfall simulator

Rainfall simulator

Top view of rainfall simulator

Top view of rainfall simulator

Rainfall intensity controller

Rainfall intensity controller

The basic unit of each simulator has an aluminum frame with the following dimensions: 4.5 m (L) x 1.5 m (W) x 2.7 m (H).  The frame has 4-telescopic legs to keep the simulator level and the nozzles.  The frame is a self-contained unit that includes 4 nozzles, piping, an oscillating mechanism, and a drive motor.  The Spraying Systems Veejet 80100 nozzles are spaced 1.1 m apart and produce spherical raindrop with a median drop size of 2.25 mm and an exit velocity of 6.8 m/s.  With the nozzle at least 2.4 m above the ground, the impact velocities of almost all drops are nearly equal to the impact velocities of those from natural rainstorms.  The maximum rainfall intensity produced by the simulator is 135 mm/hr and the intensity can be changed instantaneously during operation.

Water supply tank, generator, and windshield for the rainfall simulator

Water supply tank, generator, and windshield for the rainfall simulator

Each simulator has a 5-HP gasoline engine pump and a system of valves that allows internal water pressure to be adjusted from 13 to 41 kPa (2 to 6psi).  Gauges atop each simulator allow for accurate manual adjustment.  A small generator (Figure 6) is used to supply power to the pumps and the rainfall intensity controller. For remote field sites, water is supplied to the simulators using large storage tanks of 1500 L (400 gallons) capacity. The runoff water may be re-circulated to the tank with a pump has a textile filter material with very low porosity at its suction side.  Wind shields are essential for field use of the rainfall simulators.  The slightly porous, fabric sheets are used to retard air flows.  They have the advantage of being partially absorbent, so that any stray spray reaching the windshield is absorbed and drained through the fabric, rather than being splashed back.

Instantaneous-profile Laser Scanner
The Instantaneous-profile Laser Scanner collects longitudinal profiles of soil surface micro-topography, which controls the flow of runoff over the soil surface and ultimately the amount of soil and SOM loss. The laser scanner provides a 3-D map of the soil surface (or micro-roughness) at the particle-size scale. The horizontal and vertical resolutions of the scanner, which are both 0.5 mm, capture the micro-scale changes in soil roughness. The laser tracks along a 4-m rail, which can be wheeled to all locations within a field.

Instantaneous profile laser scanner for measuring surface micro-topography

Instantaneous profile laser scanner for measuring surface micro-topography

Scanned surface showing microroughness

Scanned surface showing microroughness

A student using the PP systems CO2 sensor in a test field of the Clear Creek watershed

A student using the PP systems CO2 sensor in a test field of the Clear Creek watershed

CO2 Flux Chambers

Direct measurements of CO2 fluxes from the soil are measured through in situ gas chambers from PP Systems (EGM-4 with SRC-1 chamber). PVC tubes with a 10-cm diameter and a 20-cm length are inserted into the soil surface. The PP systems CO2 sensor is placed on top of the tube forming a seal and a small laser illuminates the CO2 emitted from the soil. The closed chamber measurements to measure surface soil CO2 efflux are performed at sampling frequencies designed to estimate the seasonal cumulative flux for the different land use systems being evaluated. Direct CO2 measurements from the soil provide validation data for the biogeochemical models.

Visible Near InfraRed (VNIR) Spectrometers

Visible near infrared spectrometers, VNIR are used to measure and interpolate surface organic matter.  These sensors are helpful in field scale mapping of the surface soil organic matter content.  This technique can provide accurate estimations of SOC concentrations in surface soils and identify within-field variability of SOC at a pixel level.  These instruments work on the premise that compositions of the organic constituents in surface soils have a strong influence on the spectral reflectance of soils especially in the visible and near infrared wavelengths.  For example, mollisols and alfisols, two dominant soil orders in Clear Creek, have different reflectance curves based on their organic matter content.  The sensors provide the necessary data to construct a relationship between image intensity and surface organic matter content

Water Level Sensors
Standard pressure transducers consist of the pressure transducer connected to a self-contained datalogger through a cable.  The cable is vented to compensate for changes in barometric pressure.  The datalogger is powered by two 9-V batteries and can store data for extended periods.  The sensor measures the pressure of the overlying water, which is related to the depth of the water.  A laptop or PDA can easily download the stored data.  Currently, these pressure transducers are deployed in multiple sites providing flow data for Clear Creek.

Pressure transducer installed in a stilling well among T-posts

Pressure transducer installed in stilling well among T-posts

Close up of the stilling well

Close up of the stilling well

Enclosed datalogger that is attached to the pressure transducer

Enclosed datalogger attached to the pressure transducer

Laser Sampler

Laser Sampler

Laser Sensor

Laser sensors have similar advantages to other remote acoustic/radar sensors; however, are often more expensive. The laser sensors do work better in turbulent environments, where acoustic pulses can be disrupted by bubbles. This sensor has been instrumental to one project, which is in an extremely turbulent system.

Automatic Water and Sediment Samplers

SIGMA automatic water and sediment samplers are installed in conjunction with the pressure transducers.  The SIGMA samplers are currently programmed to automatically collect twenty-four 1-L samples at regular time intervals over the courses of runoff hydrographs.  SIGMA samplers are also installed below the test plots to collect runoff.

Water Quality Sondes

Three Hydrolab DS5X data sondes are is equipped with temperature, conductivity, dissolved oxygen, pH, chlorophyll, and turbidity probes utilizing extended deployment design principles.   These data sondes and other real-time water quality sensors have been installed in Clear Creek.

Nutrient Systems Pak Analyzer

Nutrient measurements are conducted using the SubChem Systems Pak Analyzer, which utilizes continuous flow analytical methodologies that are optimized for rapid in situ measurements of dissolved nitrite, nitrate, ammonia, phosphate, silicate, iron(II), and iron(III).  Clear Creek, as part of the Upper Mississippi River Basin, is an important location to study nitrogen and phosphorus transport phenomena associated with heavy row cropping that contribute to eutrophication and, eventually, gulf hypoxia.

Sediment Sensors

The sediment sensors listed below are designed to measure either erosion or deposition in the channels, as well as along the banks.  They are also useful for quantifying transport rates.

Photo-Electric Erosion Pins
PEEPs, allow for automatic monitoring of erosion and deposition events, particularly related to river banks and channels. The PEEP has a series of diodes, which covert the available solar radiation to a voltage measurement.  The magnitude of the voltage reading corresponds to the number of diodes exposed and the distance that the bank has eroded.  Currently, two projects are underway, which require PEEP measurements for bank erosion.

PEEP installation on a channel bank

PEEP installation on a channel bank

Measuring bank erosion using a PEEP

Measuring bank erosion using a PEEP

Sedimeter
The Sedimeter measures erosion and accumulation of sediments with a resolution of 0.1 mm or better.  It can also measure near-bed turbidity, which is intimately related to the sediment concentration.  The sensor consists of an array of 36 infrared optical backscatter detectors used to measure turbidity. 

Sedimeter Installation

Installing Sedimeter in a Stream

Sedimeter

Sedimeter installed on a lake bed

RFID

RFID technology uses transponders, which transmit a single coded sequence for identification purposes.  This state-of-the-art technology has recently been applied to sediment tracking studies, in which artificially designed particles containing RFID transponders are released into the flow.  Their pathways are recorded using a receiving antenna that detects the coded signal as the transponder passes below it.  In addition, the transponders are full recoverable.  The RFID systems consist of three parts: a transponder (either active or passive), a reader, and an antenna.

A student testing the RFID reader

A student testing the RFID reader

Sand Monitors

Sand monitors are originally designed to measure the sand flow rate in oil pipes; however, this technology is being applied to measure bedload rates in mass /unit length.  Sand monitors are useful for measuring the coarser material that moves atop the stream or lake bed.  The sand monitors are automated and converts the collision of particles on the sensors into a bed load rate.  It is state-of-the-art equipment and can be used to perform a mass balance of the bed load material that is exiting and entering a body of water