Design of the visualisation – ElleVis

Based on feedback from participants and bearing in mind the visualisation requirements of the Resource Consent, several prototypes of ElleVis were developed. The final design of ElleVis, as shown in Figure 5.2, has three main components: a “traffic light” summary table described in Section (5.2.1); a map showing lake extent described in Section (5.2.2); and a lake level time series graph described in detail in Section (5.2.3). The tool allows users to configure lake opening scenarios and select the conditions under which they are viewed. Configuration of lake opening scenarios is through an opening rules interface described in detail in section (5.2.4). The visualisation components are discussed in

5.2.1

“Traffic light” summary table

The “traffic light” summary table shown in Figure 5.3 represents an overview of information about the impact of the opening regimes on lake values. The cells are colour coded to help stakeholders distinguish which lake values are good (green), tolerable (amber) and unacceptable (red) based on the opening regime in place. The summary table view provides stakeholders with overview information on lake values at a glance for the opening regime entered. Each row in the table represents one lake value (for example “sheep”, “banded dotterels”) with each colour in a cell representing the lake level conditions for that month. Each cell in the summary table contains a computed average of lake levels for a month based on the opening regime entered by the user. The average lake levels were computed as an extension to Plover. The use of averages in showing lake levels has been used previously by Lorie

Geo-spatial map Time series graph

“Traffic light” summary table

(2006) in his design of decision support tables to solve water resources management issues (see Chapter 2, Section 2.8.6).

The following list consists of lake values in the summary table, which were chosen on basis of data availability and stakeholder interests.

• Agricultural livestock o Cows o Sheep • Bird life o Little Shag o Pied Stilt o Banded Dotterel o Black Swan o Black Billed Gull o Kingfisher • Native fishery o Short-Finned Eel o Black Flounder o Bullies o Smelt

The concept of the “traffic light” was applied to the choice of colours used in the summary table. “Traffic light” indicators

Monthly time steps

Lake values

colour red in most western cultures has always represented danger: “stop or suffer the consequences”. Red was chosen to show unacceptable conditions exist for that lake value. Green was chosen to show when good conditions exist for that lake value. The range between “good” and “unacceptable”, which are “tolerable” conditions, was denoted by the colour amber. The use of shaded cells to indicate the best and worst results has been used previously by Lorie (2006). A similar coding was used in this study. Information was sourced from different sources and expert judgement was used to identify acceptable lake levels. The following rules govern how the “traffic lights” were computed for lake values based on lake water levels at varying times.

Livestock (Cows and Sheep)

Livestock can be found in all areas round the lake, and farmlands are inundated if the lake is very high. For this reason, farmers prefer low lake levels as that allows them to fully utilise their paddocks/fields to fatten their stock. Another reason is that livestock are likely to develop footrot when they stand in water if high lake levels flood the paddocks.

Graeme Horrell3_{, a hydrologist from National Institute of Water and Atmospheric Research (NIWA),}

stated that farmers are more comfortable for the livestock to graze when the lake level is close to 700mm AMSL. When lake levels are 1020mm AMSL, farmers find this unacceptableas North-Westerly gales at this lake level leave much of the land inundated (G. Horrell, personal communication, May 10, 2011).

Hearnshaw and Hughey (2010) noted that cows have a higher tolerance range than sheep in terms of water depth. (The tolerance range is defined by Hearnshaw and Hughey (2010) as the range where lake values can survive in the long-term.)

Using the maximum and minimum absolute values from Horrell regarding lake levels, and Hearnshaw and Hughey’s (2010) views on tolerance ranges, the rules (Table 5.1) for colour coding the summary table for livestock (cows) are:

Table 5.1 Summary table rules for cows

0 AMSL – 700 AMSL = Green 701 AMSL – 1020 AMSL = Amber

>1020 AMSL = Red

Since the tolerance range for livestock (sheep) is much narrower in terms of lake level, the colour coding (Table 5.2) for the summary table representations based on Horrell’s estimation, which involves sheep, are:

Table 5.2 Summary table rules for sheep

0 AMSL – 650 AMSL = Green AMSL– 800 AMSL = Amber

>801 AMSL = Red

Birds (Little Shags, Black Swans, Black-Billed Gulls, Australasian Bitterns and Kingfishers)

There are two main groups of birds used in this study. One group ─ Little Shags, Black Swans, Black- Billed Gulls, Australasian Bitterns and Kingfishers ─ benefit most from lake levels that are permanently high (K. Hughey4_{, personal communication, November 10, 2010). Low lake levels are most harmful to}

them. Based on this, the rules (Table 5.3) for colour coding the summary table for the birds are:

Table 5.3 Summary table rules for birds -Little Shags, Black Swans, Black-Billed Gulls,

Australasian Bitterns and Kingfishers

1000 + AMSL = Green 600 – 999 AMSL = Amber

< 599 AMSL = Red

The other group ─ Banded Dotterels − are part of the guild of shallow wading birds and are found predominantly on the banks and swampy areas of the lake (K. Hughey, personal communication, November 10, 2010). These birds benefit most from low lake levels. High lake levels threaten their existence. The rules (Table 5.4) for colour coding Banded Dotterels are:

Table 5.4 Summary table rules for birds – Banded Dotterels

0 – 600 AMSL = Green 601 – 999 AMSL = Amber

1000+ AMSL = Red

Native fishery

Short-Finned Eels and Black Flounder are bottom dwelling fish that require deep water to breed, swim and migrate (Jellyman & Smith, 2009). Therefore, lake levels above 1000mm AMSL are good for them. The rules (Table 5.5) for colour coding the summary table for Short-Finned Eels and Black Flounder are thus:

Table 5.5 Summary table rules for native fishery

0 – 443 AMSL = Red 444 – 999 AMSL = Amber

1000+ AMSL = Green

Smelt and Bullies are mid-water dwelling fishes and are non-migratory (Jellyman & Smith, 2009). They are found to tolerate the entire range of varying lake levels found in Te Waihora/Lake Ellesmere. Therefore, they are in an acceptable/good state all year round and have the colour green denoted for them in the summary table.

5.2.2

Interactive spatial map

The interactive map shown in Figure 5.4 allows stakeholders to see the consequences of different opening regimes on the extent of the lake. The image is a topographic map with the lake superimposed. A slider beneath the image allows the extent of the lake during the year to be explored on a day by day basis.

The data for computing the spatial extents of the lake were sourced from the Environment Canterbury (ECAN) LIDAR5 _{data in the form of a 2m by 2m digital elevation model (DEM)(Hill, 2009).}

5.2.3

Time series graph

The time series graph shown in Figure 5.5 shows the level above mean sea level (AMSL) of the lake over the year. The graph is augmented with blue shaded areas that show when the lake has been opened to the sea.

Surrounding lands Te Waihora/Lake Ellesmere

Monthly time steps Slider

5.2.4

Opening rules interface

The opening rules interface shown in Figure 5.6 allows rules that specify the lake opening regime to be used in the simulation. Rules are entered in the form of a start date from which the rule is valid and an opening level (or trigger level) at which the lake should be opened to the sea. Up to three rules can be specified. This is consistent with the Plover model and the Resource Consent that has three opening scenarios of dates and trigger depths to open the lake. It has been applied to the design of the rules interface to allow for multiple rules, as shown in Figure 5.6. Stakeholders have the flexibility to delete, edit and view selected rules when using the visualisation tool. This was included in the form of edit and delete buttons on the rules interface and a grid layout to display selected rules. For any opening regime, three different annual rainfall models can be shown by selecting Dry, Normal or Wet year from the right hand panel. Data on typical Wet, Dry and Normal years in the catchment region of Te Waihora/Lake Ellesmere was used for the simulation. Any change in selection updates all the visualisation elements.

Further, a checkbox that serves as an option for stakeholders to set an initial lake level from the start of the year (1st of January) could also be specified. This is because the level of the lake at the start of the year affects the lake openings and has a resulting effect on lake values. Documents sourced from the Resource Consent suggest that visualising the lake from a particular level at the start of the year is very beneficial to stakeholders, and hence, needs to be included on the opening rules interface. Finally, once an opening regime has been specified, the calculate button causes the simulation to run and the visualisation to be updated. The next section reports on a study of ElleVis, to assess its usability and identify any weaknesses with the design.

Figure 5.6 ElleVis opening rules interface