Developing Sediment Criteria for Water Quality Discussion

During the discussion, I wasn't sure everyone was quite up to speed with the whole SABS framework...so I'm putting up these figures and tables from the paper to try and walk you through the most important points.

We definitely talked about the first figure above. It is the basic framework and main points to follow in the process of developing water quality criteria for suspended and bedded sediments.  The framework is not necessarily limited to sediment criteria...it could be used for any non traditional pollutant that researchers have not been able to test in a laboratory toxicity test setting.

In tables 1 and 2, Cormier et al. go through a hypothetical example to show you how the process might work.  You can see in Table 1 which statistical tests they used and what they intended to learn from the tests. The response indicator they chose was EPT richness.

In table 2, you can see the results of the statistical analysis.  The bottom line (which I circled) is the criteria they chose as their benchmarks for management.  They decided on these numbers for a hypothetical manager trying to protect EPT richness in a mid-Atlantic stream.

Here are some of the questions we went over and how everyone answered:

               What are some ways the authors suggest sediment can affect the biological integrity of waterways?

Low water clarity impairs visibility affecting many animal behaviors such as prey capture, predator avoidance, recognition of reproductive cues, and other behaviors that alter survival.

At very high levels, suspended sediments can cause physical abrasion and clogging of filtration and respiratory organs.

Suspended particles decrease light penetration required for photosynthesis

What are the sources of deposited and bedded sediments? How do human activities increase the rate at which the sediment gets into streams?

Topsoil erosion from land in the watershed

-          Deforestation

-          Agricultural runoff

-          Construction without proper silt fences

Suspended sediment removed from stream banks and from the bed of an upstream channel

-          Channelization

-          Removal of riparian zones

Direct discharge from municipal, industrial and agricultural sources

  

What is the U.S. EPA’s SABS Framework? How does it assist in the development of water quality criteria and restoration targets?

The SABS framework uses a risk assessment approach to estimate effect thresholds for unacceptable levels of SABS in water bodies.

It uses several statistical procedures to compare the estimated effects levels derived from field and laboratory data.

Protective water quality criteria levels are created with scientific evidence to back them up.

  

What were the two levels of protection the team developed for criterion values? Why did they need both? What values did they choose? Were they justified?

ALU: Aquatic Life Uses and MALU: Minimally acceptable aquatic life uses

ALU beneficial in intact ecosystems

MALU beneficial in developed areas which need to set achievable restoration targets.

No more than 7% fines for ALU and no more than 14% fines for MALU

Yes, 7% is justified in that it was deemed protective of the resource and held under the Species Sensitivity Distribution method (most protective precedent). 14% is justified in that it was the mean effect threshold of all methods for MALU.