Hydrotowns 2: Study area choices
Laying it out
I looked into a few different ways I could define the study area. Generally I wanted to focus on the Western Cape. It's both where I live and an interesting area biogeographically as it is more or less overlaps with the Mediterranean climate and winter-rainfall areas in South Africa. Administrative boundaries, however, don't necessarily make physically meaningful ones in a hydrological context, although we do often find borders along e.g. ridge lines or rivers.
I also thought that it would be good to define things in terms of primary catchments so that if we do anything with smaller catchment levels they do not become orphaned members of some other primary catchment (and hence draining to somewhere outside the study area). It also helps to keep the area a bit smaller to reduce the computational time.
In addition to primary catchments, we could also look at the current Water Management Areas (WMA), which more-or-less amalgamate a number of primary catchments, although there are some areas which map differently. Throwing all of these together and overlaying them on a population density grid, we can start to think about how we could slice the cake:
The named primary catchment regions roughly correspond to the major river systems:
- Region E: Olifants/Doring River
- Region G: Berg River and the Overberg
- Region H: Breë River
- Region J: Gourits River
- Region K: Garden route rivers as well as the Kromme River which mouths at St. Francis in the Eastern Cape
Decision time
To me, there are two options which could be considered most reasonable looking at the map. The first would be to limit the analysis to Regions G & H, which both capture a significant fraction of the population as well as running along the bulk of the Cape Fold Mountains which define precipitation patterns. Important population centres which would be excluded are the Cederberg/Bokkeveld areas in the south of region E as well as Oudtshoorn, Beaufort West, and the Garden route.
The second option would be to consider the two WMAs which account for most of the Western Cape's catchments. These include Regions G & H as before, as well as E, J and apparently half of K (the WMA slices this region roughly at the provincial border). This option also includes a significant area of the semi-arid and sparsely populated Karoo. This could make for an interesting addition of variation to the various analyses that I would like to do but it also represents a drastically different water context.
I found it somewhat hard to make a decision in this case. I think it has something to do with not having very obvious criteria besides doing this for my own benefit. In the interest of keeping things simpler and sticking to a more biogeographically consistent area I decided I would go ahead with the two primary catchments in the South-Western Cape. Either way it should make for an interesting study area.
Exeunt
The next post will probably go on a bit of a tangent I have been thinking about after reading an article about the "human niche". In some ways it is still related and I might return to those ideas in the future.
DW