A question of place?
We would like invite research teams that have described “spatial variability” in nutrient fluxes at any scale from the field to the basin to share their experiences. We will attempt to synthesize what we get and report back to the group. We need to further clarify what we mean by spatial variability and distinguish it from the extensive literature describing the diversity of diffuse pollution sources. What we are seeking to establish is whether the landscape sources of diffuse pollution are more additive or more dependent on spatial relationships (in which case you can not simply total emission sources in the landscape to calculate the basin load). In fact the question is probably not this simple. A better question might be: under what conditions are pollution sources not additive so that understanding landscape position and connectivity become important to understanding watershed and basin loading of pollutants? A related question that came up in the discussion was: why do we assume that best management practices are additive in the landscape? In this case, knowing spatial dependencies might become important in optimizing the placement of BMPs.
We have listed some questions below. If you could copy and paste these questions into a word processing program, answer the questions that seem appropriate to your work, and then copy and paste back into a comment/reply to this post (or email if you prefer), we will then read, collate, and attempt a summary and synthesis. In the first comment, Dr. Dorioz has provided answers to the questions from his research experience, as an example.
Questions about your study:
Project name and contact:
Detailed description (if you want to specify):
Water quality parameters:
Water quality issue:
Scale (field, farm/group of fields, watershed, basin):
Comments on scale and approach (optional):
Land use diversity in treatment/study area:
Important agricultural practices in treatment/study area:
Mass balance considerations (rough):
ROLE OF LANDSCAPE PATTERNS AND SPATIAL RELATIONSHIPS (FROM YOUR WORK)
Does your work suggest that emissions of diffuse pollutants are additive or not:
If areas that you expect would have high diffuse exports don’t meet that expectation, what do you suspect are the major causes of the reductions:
Are there any areas where the pollutant load to receiving surface waters exceeds your expectation (pollutant flux in excess of loading values):
What seem to be the most important landscape features modifying the site-level source emission (under any conditions, e.g. extreme storm flows, snow melt runoff, base flow):