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. America Total ~$50 BILLION annually (Pimental, Science, 2005,)
METHODS OF QUANTIFYING FLUVIAL SEDIMENT DISCHARGE Direct, sampling: Suspended sediment: Collect representative suspended sediment sample, measure discharge, calculate instantaneous suspendedsediment 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.
SOME BENEFITS OF LONG TERM SEDIMENT RECORDS Sediment flux is highly variable in shortand 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 METHODS Sampling 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
Types of automated pumped samples Discrete Sampling Single sample per bottle Sample 1 Sample 2 Sample 3 Sample 4 Sample 5
Types of automated pumped samples COMPOSITE SAMPLING Multiple bottles per sample Sample 1 Sample 2
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 Sampler Used 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 48 US 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 Ponar sampler Gravity corer
SURROGATE TECHNOLOGIES FOR SUSPENDED SEDIMENT Those based on: Bulk Optics Laser Diffraction Digital Photo Optic Imaging Pressure Difference Acoustic Backscatter
Hudson River Hydroacoustic Equipment Two 600 khz RDI Sentinel ADCPs used in rotation.
Hudson River Calibrations
Example: Side Looking ADV/ABS Courtesy of Sontek/YSI, Inc. Sontek Long-Range Argonaut-SL Systems Single Frequency
USGS Sediment Data and Reports On Line Reports: Daily Value Data: water.usgs.gov/osw/techniques/sedimentpubs.html webserver.cr.usgs.gov/sediment water.usgs.gov/osw/techniques/sediment/turbidity Unit Value Data: General: water.usgs.gov/osw/sediment/index.html water.usgs.gov/osw/techniques/sediment Hank Zajd USGS 30 Brown Road Ithaca, NY 14850 607 266 0217 ext 3023 Any Questions