Monitoring for Sediment
Sampling Methods and Equipment
High Flow Low flow
Fluvial‐Sediment Data Needs in the U.S.Historical: Maintenance of reservoirs, channels, and hydraulic structures/bridge piers – ENGINEERING CONCERNS
n Today’s needs include but are not limited to: ‐ Legal requirements – TMDL’s‐ Contaminated sediment management‐ Best Management Practice (BMP) Evaluations‐ Fire‐burn hydrology/sedimentology‐ Stream restoration/geomorphic assessments‐ Physical‐biotic interactions‐ Global carbon budget‐ Sand budget and bar maintenance‐ Productivity of agricultural lands‐ Dam decommissioning, rehabilitation, removal
IF THIS IS YOUR PROBLEM
ENVIRONMENTAL/HOLISTIC CONCERNS
Sediment Damages (physical, chemical, biological) in N. AmericaTotal ~$50 BILLION annually (Pimental, Science, 2005,)
• Direct, sampling:– Suspended sediment: Collect representative suspended‐sediment sample, measure discharge, calculate instantaneous suspended‐sediment discharge.
– Bedload: Collect sufficient bedload samples using a sampler such as the FISP‐approved BL‐84 sampler over the stream cross‐section, calculate instantaneous bedload discharge.
METHODS OF QUANTIFYING FLUVIAL SEDIMENT DISCHARGE
SOME BENEFITS OF LONG‐TERM SEDIMENT RECORDS
Sediment flux is highly variable in short‐and long timescales.
Sediment fluxes differ with changes in land use, climate, regulation, etc
Likewise, the efficacy of stream restoration endeavors can’t be quantified without comparative (before‐and‐after) data.
SAMPLING METHODSSampling frequency
Generally dictated by the study approach and level of funding.
Less critical to collection of a discrete representative sample than site selection, and temporal and spatial variability
SAMPLING METHODS• Site selection
– Uniform flow in x‐section
– Well‐mixed flow
– Ability to sample range of flows, most importantly medium‐and‐high flows
– Availability of historical data
SAMPLING METHODS
• Sample collection methods
–Depth‐integrated sampling–Point sampling–Pumped samples –Grab or dip sampling
SAMPLING METHODS• Depth‐integration techniques
– Equal‐width increment (EWI) method
– Equal‐discharge increment (EDI) method
– Single‐vertical sample
Sampled & Unsampled Zones
Flow direction
SAMPLING METHODS• Equal‐width increment (EWI) method
– Cross section divided into (~8‐20) equal‐width increments
– Sampling transit rate for all sample verticals determined at the deepest/fastest vertical
– Collect velocity‐weighted sub‐samples from the mid‐point vertical in each width increment
– Composite all sub‐samples for analysis
Sampling Methods
Automated Pumping Samplers
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5
Single sample per bottle
Discrete Sampling
Types of automated pumped samples
Sample 1 Sample 2
Multiple bottles per sample
Types of automated pumped samplesCOMPOSITE SAMPLING
Grab or Dip sampling
TSS vs SSC Data
• Total Suspended Solids (TSS) and Suspended‐Sediment Concentration (SSC) data often used interchangeably.
• They are not the same, and may be substantially different.
• How do they differ, and which, if either, is reliable?
SUSPENDED‐SEDIMENT vs TOTAL‐SUSPENDED‐SOLIDS CONCENTRATIONS
149 paired concentrations
Including
76 samples of paired concentrations where SSED and TSS were both measured at USGS laboratories
And
73 samples—17 to 20 samples from each of 4 WEP monitoring sites—
SSED concentrations were measured at the USGS Sediment Lab and TSS concentrations were measured at the WEP laboratory.
Sampling Equipment
The Colorado River SamplerUsed until the mid-1940’s
The FISP US-D43 Isokinetic Suspended-Sediment Sampler. Isokinetic samplers used by Fed. Gov’t since mid-1940’s
Depth Integrating Samplers
US DH‐48US DH‐76
US D‐74
Sampled & Unsampled Zones
Flow direction
BL‐84 bed load sampler in operation from a bridge
BMH 60 sampler operation from same bridge setup
Sample door opened
Sample door closed
Bottom Sampling Equipment
Gravity corer
Ponar sampler
SURROGATE TECHNOLOGIES FOR SURROGATE TECHNOLOGIES FOR SUSPENDED SEDIMENTSUSPENDED SEDIMENT
Those based on:Those based on:•• Bulk Optics Bulk Optics •• Laser DiffractionLaser Diffraction•• Digital PhotoDigital Photo‐‐Optic ImagingOptic Imaging•• Pressure Difference Pressure Difference •• Acoustic BackscatterAcoustic Backscatter
Hudson River – Hydroacoustic Equipment
• Two 600 kHz RDI Sentinel ADCPs used in rotation.
Hudson River ‐‐ Calibrations
Courtesy of Sontek/YSI, Inc.
Sontek Long-Range Argonaut-SL SystemsSingle Frequency
Example: SideExample: Side‐‐Looking ADV/ABSLooking ADV/ABS
Any Questions
USGS Sediment Data and Reports On‐Line Reports:
Daily‐Value Data: water.usgs.gov/osw/techniques/sedimentpubs.html
webserver.cr.usgs.gov/sedimentwater.usgs.gov/osw/techniques/sediment/turbidity
Unit‐Value Data: General: water.usgs.gov/osw/sediment/index.html water.usgs.gov/osw/techniques/sediment
Hank ZajdUSGS30 Brown RoadIthaca, NY 14850607‐266‐0217 ext 3023