This article describes a NIWA QGIS prototype plugin ("REC2") to enable simple upstream and downstream search on the New Zealand River Network (also called "River Environment Classification, version 2").
Follow the instructions below to add the REC2 plugin with upstream/downstream search capability.
- Have QGIS and the "REC2" plugin installed.
- Click REC2 -> Setup -> OK; REC network will be displayed
- Zoom to area of interest
- Click REC2->Upstream/Downstream Search; and click on select reach button
- Click on Reach on Network
- Click "Search Upstream" or "Search downstream" - the traced reaches will be added as new layers
If you are going to use this, then for a more complete map you will want to do two things AFTER you start the REC2 plugin as described above.
1. Add a background (context) layer, such as aerial photography or topo maps. Suitable map layers are available as WMS services from LINZ Data Service and from Landcare Research
eg: for aerial photos see - https://data.linz.govt.nz/set/2-nz-aerial-imagery/webservices
for topo maps see - https://data.linz.govt.nz/layer/767-nz-topo50-maps/webservices/
Set up the WMS service, connect and add the layer, plotted beneath the other layers.
2. Add a lakes layer. The REC is a network of river and stream reaches. This network is carried through lakes as lines, so if you so desire, you can open a layer of lakes polygons to plot on top of the REC layer so the map looks more attractive.
NIWA provides a WMS layer showing lakes polygons at: http://gs.niwa.co.nz/niwa/wms? Connect to this WMS service and open the niwa:lakes layer. Plot this on top of the other layers.
You will finish up with a QGIS map canvas looking something like this (which shows the upstream network from the Hutt River mouth and a lakes layer at Lake Wairarapa):