The CLUES Project: Predicting the Effects of Land-use on Water Quality – Stage II
Objective 1: CLUES Catchment Modelling Framework (NIWA)
A range of new features and functionality has been added to CLUES GIS framework. A user can now change land use interactively on the screen with the aid of a mouse and subsequently overlay the new scenario on a catchment boundary to predict the yield of nitrogen, the extent of nitrogen leaching and the economic cost of the land use change. These features are the result of integrating SPARROW, OVERSEER® and the HARRIS Consulting (HC) economic models. Some work has also begun on incorporating SPASMO into the framework. At the time of writing, a small amount of cosmetic work remains to be done to improve the interface, in response to comments from end-users.
The main development has been the GIS menu shown below in Figure 6-1, and it builds on the toolbox developed in Stage 1 (Section 5 of Woods et al. 2004). The toolbox is designed to work within ARCGIS 8.3 or ARCGIS 9.
Figure 6-1: CLUES toolbox with new functionality developed in Stage II. This includes tools to sketch, overlay and query new scenarios.
Some of the CLUES user interface capabilities were explained in the Stage 1 report (Section 5 of Woods et al. 2004), and others are demonstrated in the following sub-sections.
Land use change scenario tool
New land use scenarios can be created “interactively” and up to 5 different scenarios stored and queried. An area on the screen is sketched over an underlying map of catchments and current land use. This is done simply by selecting a drawing tool and sketching over an area of an existing land use map on the screen. The sketch can be edited and changed easily. New land use classes are assigned by using a drop-down tool and selecting a class. Currently the following land use classes can be selected: dairy, sheep and beef, deer, grazing stock, fruit, viticulture, vegetable growing, arable crops, forest and non-pasture.
Figure 6-2 shows a screen shot of a new land use sketch and the drop-down list for selecting land use classes.
Figure 6-2: A screenshot showing a new area sketched out (in bright green) to represent dairying (where existing land use was “forest”). Land use classes can be selected from a drop-down menu and assigned to new areas sketched.
Overlay new land use scenarios on catchment boundary
A newly sketched scenario can be overlaid on an existing catchment map and land use areas calculated for each river/stream catchment by using the “update land-use scenario” tool shown in Figure 6-3 below. This function only requires the entry of a scenario number and the relevant catchment map details. The overlay procedure is relatively quick (4 to 5 minutes) and once complete the new scenario is available for a model “run”. The overlay procedure will replace existing land use data with the new information entered. Current land use data is retained where no changes were made.
Figure 6-3: Overlaying new land use with existing catchment boundaries consists of simply filling out a form that selects the relevant catchment layer and nominating a scenario number.
Integration of SPARROW, OVERSEER® and HC (Harris Consulting) models
At the time of writing the SPARROW, OVERSEER® and HC models have been integrated into the GIS environment. When CLUES is executed all three models are invoked to produce outputs of “in-stream” nitrogen, nitrogen leaching amounts and the relevant economic analysis. The SPARROW, OVERSEER® and HC models are described in Section 7.1 (SPARROW), Section 9 (OVERSEER®), and Section 8 (HC).
Figure 6-4 and Figure 6-5 below illustrate model runs before and after a new scenario is sketched and overlaid. The resulting “in-stream” nitrogen loads are shown by the colours of the surrounding catchments for the two scenarios.
Figure 6-4: A CLUES run with current land use.
Figure 6-5: A CLUES run with new land use (where a “forested” area of the catchment has been replaced by “dairying”).
The results of a model run and its associated calculations can be viewed by using a query tool in the toolbox. Any part of the catchment network can be queried to list values for both current and new scenarios. Examples of values listed are: nitrogen loads, nitrogen leaching (OVERSEER®) and nitrogen loss (HC model), and economic data such as GDP, FTE and CFS (HC). Figure 6-6 shows an example of a screen query of a river reach.
Figure 6-6: A screenshot showing the results of a query at a reach of the catchment where land use has been changed from “forest” to “dairy”.
Integration of SPARROW phosphorus model
Now that the national SPARROW model for New Zealand has been completed, a first draft model is available for the effect of land-use change on phosphorus loads in rivers. The method for generating the phosphorus loads is described in Section 7.1.3.
To implement this in the CLUES user interface, we have added to the CLUES Toolbar an extra button to allow the CLUES user to toggle between viewing the maps for estimated nitrogen and phosphorus.
Figure 6-7: Enhanced user interface, allowing user to toggle between N and P maps.
Figure 6-8: Map for phosphorus load, obtained from the screen shown in Figure 6-7 by clicking on the new toggle button. Legend for phosphorus is shown at left.
Proposed next steps
• Add new features to CLUES framework so that users can work with land-use change scenarios.
• Link more models to the CLUES framework: SPASMO, revised OVERSEER®, more Harris Consulting models.
• Finalise user interface for CLUES framework so it is easier to use and understand.
Contact for Enquiries
MAF Information Services
Pastoral House
25 The Terrace
PO Box 2526
Wellington, NEW ZEALAND
Fax: +64 4 894 0721
Contact this person
