Eutrophication Explorer

Version 0.29

The NIWA Eutrophication Explorer app is a tool for visualising model predictions and historical measurements of attributes important to eutrophication. These include nutrient concentrations in stream and estuary water, indicators of eutrophication such as water visibility and chlorophyll concentration, and abundance of periphyton and macrophytes. The purpose of the app is to help identify sites at risk of eutrophication in a map-based setting, and to inform decision-making about risks and mitigation.

Background information on Eutrophication is available on the wiki for NIWA's Eutrophication Risk Assessment programme: https://teamwork.niwa.co.nz/display/ERA

Map

The central feature of the app is the map, which shows the Catchment Boundary and Hydrological Features (streams, lakes, estuaries) plotted on top of a physical map. Markers can also be added to indicate Monitoring Sites.

The map includes:

• Toolbar - in the top left corner. This includes tools for zooming the map and editing the Feature Groups in the Scenarios tab.
• Layers Control - in the top right corner. This allows the user to show or hide the different map layers.
• Add Low Order Streams - streams of Strahler order 3 or greater are shown by default. Lower order streams can be displayed, but will slow down the app.
• Legends - in the bottom left corner. There are two legends, one describing the colouring of the Hydrological Features (streams, lakes, estuaries) and one describing the colouring of the Monitoring Sites.
• Click on a feature for a pop-up summary of that feature.

Save Work/Load Work

These buttons are cloated at the top right, and allow the user to save their work as a file on their local computer, or reload a file.

Models

The Models tab controls the display and colouring of stream lines and other hydrological features on the map. The stream segment lines come from the River Environments Classification (REC) network version 2.4 ( reference below ).

Clicking on a stream segment will display a pop up box with the predicted values (usually representing the median). Each segment is labelled by its unique REC nzsegment number.

Select models to work with:

This table allows the user to add and use model predictions from the database.

• Clicking opens the database for the user to select modelled variables (see Notes below).
• The user can change the bands in the table, or click to view or upload spatial bands from a file.
• Model predictions can be combined by adding them to a “Set” (e.g. Set 1).

Select predicted variables to work with:

This pop up window allows the user to add model predictions from the database.

• DIN is dissolved inorganic nitrogen.
• Substrate class is an area-weighted average based on the classification of Leathwick et al. (2010) (1 – mud, 2 – sand; 3 – fine gravel; 4 – coarse gravel; 5 – cobble; 6 – boulder; 7 – bedrock).
• Productive Reach indicates whether the segment is in a Cool Dry microclime with Soft Sedimentary materials. Such conditions naturally favour growth of algae.
• Chlorophyll-a is the 92nd percentile of chlorophyll-a concentration (mg/m2) in organisms attached to the stream bed, i.e., the level which is exceeded 1 month in 12, on average.

Select scenario to display:

This pull-down menu allows the user to change which modifications are applied to the models (see Scenarios tab).

Select set of variables to view:

This table allows the user to group the models and observations into “Views” and define how these are displayed, combined and traced. The display modes and combination methods available depend on whether the variables are numerical, and whether bands or preset bands are available for those variables.

Modes of display are:

• Value - shows the modelled concentrations (usually the predicted median value).
• Bands - assigns the value to A/B/C/D bands according to the thresholds entered above.
• Ratio - assigns the value to A/B/C/D bands according to its multiple of the threshold selected in the models table. A/B/C/D bands are defined as 0-0.5, 0.5-1.0, 1.0-2.0, and >2.0 of this threshold value.
• Preset Bands - assigns the value to A/B/C/D bands according to the table.
• Preset Ratio - assigns the value to A/B/C/D bands according to the table. A/B/C/D bands are defined as 0-0.5, 0.5-1.0, 1.0-2.0, and >2.0 of this threshold value.
• Preset Show - shows the spatially varying threshold values from the table corresponding to the threshold selected in the models table above.

Choose methods are:

• First - in any mode, chooses the value of the first variable in the set.
• Worst - for band and ratios, chooses the worst band achieved in each segment.
• Best - for band and ratios, chooses the best band achieved in each segment.
• Add - for values, adds the values at each segment. Used for accumulating loads.

Trace methods are:

• No Trace - values and bands are not traced.
• Upstream - values and bands are traced upstream.
• Downstream - values and bands are traced downstream.

Sources:

The following publications give further information on the modelled variables:

• Amy Whitehead (2018) Spatial modelling of river water quality state: Incorporating monitoring data from 2013 to 2017. Ministry for the Environment, Publication reference number CR 333.

• Cathy Kilroy, Amy Whitehead, Simon Howard, Michelle Greenwood (2019) Modelling periphyton in New Zealand rivers: Part 1 An analysis of current data and development of national predictions. Ministry for the Environment, Publication reference number CR 344.

• Leathwick, J.R., Snelder, T., Chadderton, W.L., Elith, J., Julian, K., Ferrier, S. (2010) Use of generalised dissimilarity modelling to improve the biological discrimination of river and stream classifications. Freshwater Biology 56: 21-38.

• River Environment Classification (REC) Database v2.4.

• Freshwater Ecosystems of New Zealand (FENZ) Database.

• Fleur Matheson, John Quinn, Chris Hickey (2012) Review of the New Zealand instream plant and nutrient guidelines and development of a new decision making framework: Phases 1 and 2 final report. NIWA Envirolink Report.

• Maxime Morel, Doug Booker, Frederic Gob, Nicolas Lamouroux (2020) Intercontinental predictions of river hydraulic geometry from catchment physical characteristics. Journal of Hydrology 582: 123292.

Scenarios

The Scenarios tab allows the user to define modifications to the model predictions on the Models tab. A scenario is defined as one or more modifications, and each modification applies to one model prediction within one feature group ( e.g. a group of streams in a headwater catchment).

Define feature groups to modify:

This table allows the user to define groups of hydrological features (i.e., streams, lakes and estuaries). When a new feature group is created, it includes all hydrological features inside the bounding box of the catchment by default. The bounding polygon can then be edited using the polygon, edit and delete buttons on the map toolbar on the left hand side of the map.

Define modifications:

This table allows the user to define modifications to the model predictions on the Models tab. Each modification modifies one predicted variable within one feature group. Available types of modifications are:

• Multiply - this multiplies the numerical model prediction by the given multiplier.

Define scenarios:

This table allows the user to define and display scenarios. A scenario consists of one or more modifications.

Observations

The Observations tab allows the user to display stream, lake and estuary monitoring sites.

Select observations to work with:

This table allows the user to add and use observations from the database.

• Clicking opens the database for the user to select variables (see Notes below).
• The user can change the bands in the table. These values are synchronised with the bands in the Models table on the Models tab, so that matching model predictions and observations always use the same bands.
• One observation variable can be added to a “Set” at a time (e.g. Set 1, see Models tab above).

Markers

Observation Monitoring Sites are shown as markers on the map. The colouring of the markers depends on the current display model of the set, and is shown in the marker legend.

Clicking on a site marker on the map will open a pop-up window showing the median value for the variables monitored at the site. Additionally, a time-series chart showing the currently selected variable will automatically be displayed for the site.

Time series plot:

When you click on a site, the time series monitoring data for the selected variable at the selected site are displayed. The y-axis scale can be set to be the same across all sites. The data points are coloured according to which band they fall in, if available.

The time series plot can be explored using the mouse to zoom and pan. Hovering over the data points shows their value. Double click the plot to restore the original axes.

Sources:

The following publications give further information on the monitored data:

• Larned, S.T., Whitehead, A.L., Snelder, T.H., Fraser, C., Yang, J. (2018) Water quality state and trends in New Zealand rivers: analyses of national data ending in 2017. NIWA Client Report 2018347CH prepared for the Ministry for the Environment. NIWA, Christchurch.

• David R. Plew, John R. Zeldis, Bruce D. Dudley, Amy L. Whitehead, Leigh M. Stevens, Barry M. Robertson, Ben P. Robertson (2020) Assessing the Eutrophic Susceptibility of New Zealand Estuaries. Estuaries and Coasts.