Principal Investigator: Dennis Busch
Co-Investigator(s): U.S. Geological Survey
Organization(s): University of Wisconsin-Platteville, Pioneer Farm
Sponsor: Clean Water Legacy Act
Award Amount: $32,300
Start Date: 5/18/09 | End Date: 6/1/2011
Project Manager(s): Adam Birr
Evaluation of Alternative Surface-Water Monitoring Protocols Final Report (PDF: 899 KB / 17 pages)
Edge-of-field runoff driven by rainfall, snowmelt, or a combination of rain and snowmelt, produce discharge events that vary greatly in total volume. It is difficult, if not impossible, to accurately pre-program automated samplers so that both small and large events are sampled adequately. What often occurs is insufficient samples are collected during small runoff events and sampler capacity is exceeded during large runoff events. To overcome this challenge, Pioneer Farm, in cooperation with the United States Geological Survey (USGS), has monitored runoff events in real-time via remote connections and adjusted the time between samples so that a much larger range of events can be monitored. Unfortunately, this method increases costs due to increased labor and increased sample handling and preparation.
This project is evaluating low-cost alternatives to the current monitoring procedure used at the Pioneer Farm. This work would be very informative for establishing sampling methodology for both Total Maximum Daily Load (TMDL) source assessment and implementation activities.
This research project compared the current monitoring protocol used by UW-Platteville Pioneer Farm and UW-Extension Discovery Farms that meet EPA guidelines (EPA) with two alternate, low-cost methods: 2-part flow-weighted automated sampling (2-Part FWC) and single-stage passive samplers (SS Siphon).
Current Monitoring (EPA)
Pioneer Farm monitoring methods (referred to as the EPA Method for this project) utilize a pre-calibrated H-flume with a pressure transducer stage recorder to determine flow. Samples are triggered based on time interval that is adjustable real-time remotely via radio telemetry and internet communication. After collection, samples are cooled in the refrigerated sampler until retrieved by a technician.
Alternative Method: 2- Part flow weighted automated sampling (2- Part FWC)
This method used an automated sampler capable of collecting samples based on two flow intervals simultaneously.
For this method, one sampler with a 24 bottle carrousel was set to two flow-weight compositing intervals: bottles 1-12 were set to 0.01 mm interval for small events, and sample bottles 13-24 were set to a 0.4 mm interval for large events.Two replicates (referred to as A and B) were installed at the Pioneer Farm.
Alternative Method: Single-stage passive sampler (SS Siphon)
The method uses a passive sampler, which means it collects a sample without any external control or activation. The sample begins to collect when surface-water height in the flume exceeds the maximum height of the intake tube. This initiates a siphon and the sample bottle fills rapidly. Three siphon samplers are located along side each flume with their intake tube sample heights fixed inside the so that samples are collected at 0.2’, 0.5’, and 1.0’ stages. Two passive sampler replicates were installed at the Pioneer Farm.
All monitoring stations were managed and operated in conjunction with the United States Geological Survey for the duration of this study as described in the USGS Open File report 2008-1015 Methods for data collection, sample processing, and data analysis for edge-of-field, streamgaging, subsurface-tile, and meteorological stations at Discovery Farms and Pioneer Farm in Wisconsin, 2001-7.
It is important to note that not all runoff events that occurred during the experiment are included in this analysis. There were occasions when events were missed due to equipment failure or operator error. Failures occurred on all systems - including the USGS-PF operated sites. For example, large runoff events washed out the flume on one site, sampler lines froze on another, batteries failed on another, and aquarod data was overwritten during runoff events of long duration. While failures were more frequent with the FWC and SS-Siphon samplers when compared to the USGS-PF samplers, PF technicians have been operating these systems for 8 years and are much more familiar with these systems. For this reason, the comparisons were based on events for which data was available from both sampling systems. If all events were included, the observed differences may be more a result of operator experience than inherent capabilities of sampling equipment.
Three metrics were used to compare the two alternative methods to the EPA method:
Relative error of event loads (nitrogen, phosphorus, and sediment) calculated by 2-part flow-weight composite and single-stage sampling strategies. The relative error will indicate how closely the alternative method compares to the EPA method. For example, a relative error of 90% would indicate that the alternative method calculated a load that was 10% less than the actual load.
Precision of 2-part flow-weight composite and SS Siphon methods. The precision, or coefficient of variation (CV), will indicate how well the alternative methods are able reproduce load estimates. If sampling methods are imprecise (have a large CV) they may not be useful in evaluating BMPs. The CV is a ratio of the standard deviation to the sample mean; therefore events with large differences in sample means can be directly compared.
Costs of alternative methods including: equipment, operation, and maintenance.
2-part FWC sampler method
SS Siphon passive sampler
For more information please refer to the Final Report.
Supervisor, Clean Water Technical Unit