Llobregat Field Work & Identification of Eligible Restoration Areas

This weekend I explored a segment of the Llobregat that I had skipped in my original trek down the river in 2008. In my original field survey I decided to visit Manresa, which lies on the Cardener river, not the Llobregat, but a main tributary. This detour took me West of the Llobregat for a morning, and then South, downstream the Cardener until the two waterbodies meet in Castellgalí. This weekend I returned to see the segment I missed, between the confluence of the Llobregat and Cardener rivers, until the monastery of Sant Benet del Bages further upstream.

In the last few months, I have been learning the Stream Network Temperature Model (SNTEMP) developed by the United States Geological Service (Bartholow 2000). The model support is strong and there is helpful guidance for collecting field data to feed the model (Bartholow 1989). Therefore during the field exploration I had a few questions on my mind:

 What does the riparian vegetation look like? What is the species composition? How much shading does it provide?
 How difficult will it be to gather the field data on topography and vegetation for the temperature model as outlined by Bartholow (2000)?
 Are there any segments that might be deemed appropriate as a reference segments?

Returning to the river made me re-think how I should be collecting data for the model. The SNTEMP model allows users to divide the stream segment into various regions based on topographic and vegetative features. I had initially done this based on general stream characteristics between the Baells to Abrera:

Zone 1. Pre-Pyrenees segment. Baells to Can Rosal.
Zone 2. Industrial Colonies. Can Rosal to Sallent.
Zone 3. Central Bages. Sallent to Castellbell i el Vilar.
Zone 4. Montserrat. Castellbell i el Vilar to Olesa.
Zone 5. Final reach. Olesa to Abrera Water Treatment Plant.

To get a sense of how these geographic features fit in with the tributaries, point sources and other critical points you can look at the Skeleton Network that I have developed for the model.

My current endpoint is the Abrera treatment facility, but eventually, I would like to extend the model to Sant Joan Despí. Until this weekend, I was confident that this organization would be appropriate.

However my field work suggested that I may need to break up the stream features to smaller sub-segments and focus on a smaller segment first. Not only will this help me gradually build up to a larger model, but focusing on a smaller segment would also allow me to more clearly answer my research question that concerns vegetation. Recall that my question is: Can ecosystem services related to temperature maintain stream temperatures remain below critical threshold values?

Since stream shade plays such a key role in regulating stream temperature, I need to compare conditions with and without stream shading functions. Therefore I would like to identify eligible restoration areas, ie. segments where the shading function does not exist now, but could in the future. As my field work showed, not all areas are equally in need of river bank restoration. Some areas are in good shape, some areas have no vegetation at all, and some places are somewhere in between. My ideas is to first look at those stream segments in the worst shape, and then model what it would look like if those areas were improved. The most degraded areas would be my eligible restoration areas, defined as a stream segment with less than 20% of its riparian vegetation. Since my broad topographic areas have already been defined, these areas will only differ with respect to their vegetative conditions. I will then be able to model the impact of moving these areas from 20% vegetation cover to 70% vegetation cover.

This approach would imply that I identify the eligible restoration areas on a relatively fine scale. Conveniently, there are several eligible restoration areas in the last part of the river between Abrera and Olesa de Montserrat. Therefore my sense is that I should begin by focusing on that segment first.


References
Bartholow, J.M. 2000. The Stream Segment and Stream Network Temperature Models: A Self-Study Guide. US. Geological Survey. US Department of the Interior. Version 2.0 March 2000. Open File Report 99-112.

Bartholow, J.M. 1989. Stream Temperature Investigations: field and analytic methods. U.S. Fish and Wildlife Service. Washington D.C. Instream Paper No. 13. Biological Report (89) 17.