Monitoring for Sediment - cdn.cloud1.cemah.net · • Direct, sampling: – Suspended ... where...

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