Interagency Water Quality Monitoring Workshop January 15, 2002 Santa Rosa, CA
Interagency Workshop • Reason: Agency disagreement over how to implement project specific water quality monitoring related to THPs. • Objective: “Can/how can suspended sediment and turbidity monitoring be used to isolate and quantify discharges of sediment coming from specific THPs?”
Interagency Workshop Agencies • CDFG • CDF • CGS • CA State Parks • NCRWQCB • Central Coast, Central Valley, Lahontan, and San Francisco Bay RWCBs
Interagency Workshop Speakers • Dr. Robert Beschta, OSU • Jack Lewis, USFS-PSW • Randy Klein, RNP and consultant • Graham Matthews, consultant
Dr. Robert Beschta’s Topic • Overview of principles and processes related to turbidity and suspended sediment monitoring. • Basic information on suspended sediment concentrations (SSCs), sediment transport, and sediment rating curves.
Oak Creek, near Corvallis Clay loam soils Rotational mass failures 1850 ac 60 in. precip. Flynn Creek, near Newport Sandy/silty load Shallow debris slides 550 ac 90 in. precip. Comparison of Two OR Streams
Suspended Sediment Concentration Data • Suspended sediment rating curves: • High variability within storms • High variability between storms • High variability from year to year • Additional SSC data—likely to only confirm variability
Suspended Sediment Concentration Data • SSC’s higher on rising limb of hydrograph due to greater supply. • SSC’s higher in fall, early winter due to seasonal flushing. • SSC’s different between years due to rainfall intensity and amount.
Beschta’s SSC Conclusions • Very difficult to determine background SSC, even given good streamflow data • Reliable sediment load estimates will require the use of automated equipment in most cases.
Turbidity Measurement • Measurement methods have changed over time. • Primary factor affecting turbidity are: • Concentration of particles in suspension • Size of particles in suspension • There is a good relationship between turbidity and SSC for a given watershed.
Turbidity Monitoring Advantages • Immediate measurement in field possible. • Continuous measurement possible. • Instream sampling location not a problem. • Single grab samples often represent conditions over an entire cross-section.
Turbidity Monitoring Disadvantages • Separate relationship between SSC and turbidity needed for each basin. • Different types of turbidimeters provide different readings. • Grab samples require staff to be in the field at night, weekends, hazardous conditions.
Patterns of Sediment Transport • Most sediment transported under very high flows. • Sediment transport usually peaks just before the hydrograph peak. • Runoff events following the annual peak flow will likely have lower SSCs at a given discharge.
Possible Monitoring Approaches • Comparison against a water quality standard. • Before and after treatment. • Above and below treatment. • Untreated control and treated watershed ***Pre-treatment data is needed for 2, 3, and 4.
Jack Lewis’ Topic Sample design for water quality monitoring projects. Types of designs include: Controlled experiments Uncontrolled experiments Before-after control-impact (BACI) studies
Sample Design • Uncontrolled experiments are common. • Problem with treated/untreated and before/after with no control • Difference may be due to factors unrelated to the treatment. • BACI studies can be analyzed statistically.
Illustration of BACI analysisfor a Paired Watershed Study • Caspar Creek sediment concentrations • Quasi-simultaneous pumped samples • Control Trib = Iverson (IVE) • Treated Trib = Gibson (GIB) • Sampling was focused on high flows • Drought necessitated looking 2 years before and after treatment • Analysis uses 42 data pairs before & after
Caspar Creek SSC Data • Use variability exhibited by GIB and IVE. • A statistical power analysis can be used to determine the sample size needed both before and after treatment to detect a true difference of x percent in SSC. • Assume a significance of 5% and a power of 80%.
Upstream/Downstream Pairing • Smaller variation for Caspar Stations JOH and LAN. • Upstream station not an ideal control for downstream station due to historical logging impacts and channel gradient differences. • Similar conclusion reached for Miller Creek in Humboldt Co. by Markman (1989).
Continuous Automated Turbidity Measurement (TTS Sampling) • Continuous turbidity measurement. • Random sample of SSC weighted to high streamflow events. • Periodic SSC samples allows validation of continuous turbidity data. • Use of turbidimeter with a wiper over the sensor far superior to units without wipers.
Hardware Turbidity Sensor Stage Sensor Data Logger Laptop Pumping Sampler
Manual Sediment Data Collection • Expensive in long run. • Likely to miss storm peaks. • Hazardous during storm conditions. • Difficult to execute during high flows.
Automated Sediment Data Collection • Initially more expensive than manual sampling. • Requires less field time. • More time for data processing. • More technically demanding. • Not always reliable. • More likely to collect good data at high flows.
Ideal Monitoring Design • Study objective well formulated. • Before and after treatment measurements (i.e., pre-treatment data). • Treated and control areas established. • Simultaneous measurements of same quantity are necessary.
Randy Klein’s Topic • Physiological impacts of sediment discharge. • Chronic erosion processes important because they create chronic turbidity • Chronic turbidity has biological implications. • Sediment budget work completed with air photos described as not relating well to true biological impacts to fish.
SSC Data Collected in RNP and Other North Coast Basins • Heavily Disturbed watersheds: • Panther Creek • Lacks Creek • Reference watersheds: • Little Lost Man Creek • Upper Prairie Creek • Elder Creek
Klein’s Conclusions • Pre-project data collection is essential. • Control streams do not have to be pristine-just in quasi-equilibrium. • Intensive monitoring of all THPs is not necessary. • In some cases intensive THP monitoring is feasible and justifiable—particularly if designed so data can be applied elsewhere. • Science gives us the ability to predict erosional responses and take preventative actions.
Graham Matthew’s Topic • Case studies in field applications of turbidity and suspended sediment monitoring. • Compared and contrasted equipment needed for sediment sampling on small streams and large rivers.
First Case Study:Trinity River Basin • Study completed for TMDL work. • Sediment samples taken at 75 sampling sites throughout watershed. • Only a few storms sampled—so sediment load could not be calculated. • Does provide relative sediment loading by sub-basin. • Shows where to focus restoration funds and highlights where land use practices may need to be altered.
Second Case Study:South Fork Noyo River Basin • Nine sample sites installed in 2001. • Suspended sediment load vs. drainage area relationship developed. • Showed 2 distinct linear portions. • Sediment yield increased dramatically in lower reach—due to remobilization of stored sediment by moderately-sized storms.
Hypothetical THP:Example of Possible THP Approach • Each speaker explored monitoring alternative for the hypothetical THP. • 3 logging units in Harry Weir Creek, tributary of Redwood Cr. • Unit 1: 48 ac, thin, tractor. • Unit 2: 30 ac, clearcut, cable. • Unit 3: 58 ac, shelterwood removal, tractor, 2500 ft new road.
Hypothetical THP:Agreement Among Speakers • Pre-project data necessary. • Project settling not ideal. • Difficult to find treatment and control sites with similar size, slope, geology, etc. • Several different possible scenarios suggested by speakers.
Figure 1. Lewis’ Sampling Stations Control Treatment Above and Below Road Crossings in 2 Locations
Figure 2. Klein’s Sampling Stations Above Below Basin Level Station
Figure 3a. Matthews’ Sampling Stations Before and After
Figure 3b. Matthews’ Sampling Stations Above Below
Figure 3c. Matthews’ Sampling Stations Control Treatment