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System Title |
5.1 NIWA River Environment Classification |
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| Keywords | New Zealand rivers; riverine environment, classification |
| Description | River systems are divided into units based on similarities and differences in a range of physical variables. The underlying assumption is that the physical variables chosen (" controlling variables") determine the physical habitat and therefore the biota most likely to be found there. Available physical databases are used to classify river reaches using "rules" developed by an expert panel. This classification system is still being refined. The physical variables used are as follows:
Variables have not been identified at the reach scale. Further information is in the detailed description. |
| Original Purpose | This was to develop a robust river environment classification system that could be used for comprehensive river management and scientific purposes. It was intended that the system would be compatible with currently available data; able to be operated at a range of spatial scales; and that it would be able to be used by regional councils. It was also intended that the system could be used for State of the Environment reporting and that it could assist with the development of targeted management objectives and with assessing significance of particular river environments. |
| Status | 1997-9: development ongoing |
| Organisation | NIWA Research Ltd. |
| Jurisdiction | It was intended that a fully national system would be available by 2002. |
| Contact person | Ton Snelder/Barry Biggs |
| Address | P.O.Box 8602 Riccarton Phone 03 348 8897 Fax 03 348 5548 Email t.snelder@niwa.cri.nz b.biggs@niwa.cri.nz |
| Available format | GIS (ArcView shape files) |
| Access | - |
| Geographical coverage | National |
Operational Specifications |
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| Scale of Operation | It is intended that the classification system will be able to be used at broad (low resolution) and fine(high-resolution) scales depending on management requirements. |
| GIS Compatibility | This classification system is designed to operate using GIS down to the valley topography level. The actual classification output is provided in GIS format. Smaller scale (lower classification levels) classifications will require field analysis. |
| Relationship between levels in the classification system | The system is designed as a series of linked hierarchical levels with each environment level being broadly constrained by the level above. |
| Contributing databases/classification systems | The first three levels of the system use the following databases:
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| Contributing database GIS compatibility | Yes |
| Relationship with other classification systems and spatial frameworks. | Rivers are included in the UNEP GRID New Zealand wetland classification system, although the focus of UNEP-GRID appears to be on palustrine wetlands. The NIWA system classifies environments rather classifying biota. The exact nature of linkages between the two systems has yet to be determined. |
| Relationship with other databases |
Current and emerging use for: |
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| Assisting with determining historic state/ baseline | It could assist with the determination of the historic state of some aspects of freshwater systems including biodiversity by identifying reference sites. |
| Assisting with determining current state/ baseline | The classification system is not intended to describe biological communities (compared with the UNEP GRID New Zealand classification system) but it may assist with this. The classification characterises environment and therefore provides the context. |
| Asssisting with scenario building and modelling of possible futures | Possible- needs investigation |
| Risk Assesment | It may be possible to identify river catchment /valley segments that would be at risk from particular activities. |
| Monitoring site selection and sample design | It is possible to use the system for site selection purposes. This would require a minimum level of information. The system can be used to select reference sites for monitoring. |
| Aggregating and reporting data locally, regionally and/or nationally | The system allows the aggregation of data upwards. Reporting will be possible at the local, regional and national scales. |
Current use (who,level,why)
The system has been trialed and tested with biological communities in Canterbury and Waikato Regions.
User friendliness/public and decision maker understanding
The current nomenclature is difficult to use and conveys little information without extensive reference to tables and charts. More easily recognizable names could be developed.
Classification system strengths
- Hierarchical system
- A top-down classification system may provide a better basis for assessing the effects of changes in environmental conditions than a bottom up classification system.
- The classification outputs are in GIS format. This provides a useful tool to aggregate and differentiate river systems into classes that are at an appropriate scale for addressing particular issues.
- It can facilitate the development of specific management objectives and planning.
- There is support in some management agencies for the system because it is seen to offer a way to organise information and transfer knowledge by identifying areas of similarity
Current limitations of framework
- There is a need to determine the most relevant classification level to answer questions being asked. This may lead to inconsistencies and difficulties with data aggregation.
- The system has only been tested in small areas. More work is required to test its application to a wider range of areas and to test how ecologically relevant the classes are. More work would increase confidences in the break points between categories within each variable are appropriately located and biologically valid.
- This system has used expert judgement to define the key variables rather than modelling to determine key variables. Some experts consider that this has resulted in redundancy because there are many non independent variables. This increases the complexity of the system if the entire system is used.
- This is a complex system as there are 6x5x6x8 potential classes at the land cover level. However the system is used at only the levels needed to answer the questions asked. This reduces the number of potential classes in a particular application. Such an approach could, however, lead to inconsistencies between applications and areas.
- Some management agencies question whether the system will be widely accepted. There is some concern that this could be a gold plated system rather than a pragmatic system suited to management. On the other hand the system seeks to provide a blend of pragmatism and good science.
- The current nomenclature is clumsy and difficult to use and provides no direct information about the environment being described. It has been observed that this would also apply to some other classification systems (e.g. NZ Soil Classification). The developers state that the class should be chosen to adequately portion the particular properties (eg water quality, biota, flow statistics etc) being considered in an application. They suggest that in most cases only a limited number of classification levels would be used. For example the source of the flow level should be enough to portion broad scale patterns of invertebrate distribution in most of New Zealand.
References
Biggs,B.J.F.1996. Patterns in benthic algae of streams. Pp. 31-55 In Algal Ecology. Academic Press.
Snelder,T; Biggs,B.;Shankar,U.; McDowall,B.; Stephens,T.; Boothroyd, I. 1998. Development of a system of physically based habitat classification for water resources management for New Zealand rivers. Prepared for: Canterbury Regional Council, Tasman District Council, Southland Regional Council, Environment Waikato, Taranaki Regional Council. NIWA Client Report CHC98/68. 136p
Snelder,T.; Clarke,C. 1998. Management framework for ecological values of rivers. Prepared for the Ministry for the Environment. NIWA client report CHC98/70. 45p.
Detailed description
The first 3 levels of the NIWA river habitat classification
Regional Scale |
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| Variable with classes used | Code | No. of classes | Notes |
| 1. precipitation:median flow in m3/s/km2 breakpoints: <0.01 >0.01 |
PA PB |
2 | From water resources archive |
| 2. temperature (mean max monthly air temperature) breakpoints: <13C 13-19C >19C |
TA TB TC |
3 | From 600 climate sites interpreted to a surface of New Zealand. |
Catchment/Subcatchment Scale |
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|---|---|---|---|
| Variable with classes used | Code | No. of classes | Notes |
| 1. Source of flow Spring Lake Wetland Lowland Hill country Non glacial mountain Glacial mountain Coastal Regulated rivers |
S Lk W L H M G C I |
9 | Breakpoints defined The significance of some of these divisions can be questioned eg spring and lake. |
| 2. Geological categories Greywacke Marble/limestone Schist Granite Argillite Andesite/rhyolite Tertiary mudstone/siltstone |
Gr M S G A V T |
7 | Breakpoints defined Geological categories derived from grouping LRI categories for the study areas. Further development required. |
| 3. vegetation/land use tussock pasture beech scrub lowland podocarp exotic forestry |
T P B S N3a EF |
6 | Based on NZLRI. Breakpoints by expert panel. Only includes categories in trial catchments. The accuracy of some data is questionable. |
| 4. Flow variability = no. of floods >three times the medium flow/yr. 0-5 5-10 10-15 15-20 >20 |
A B C D E |
6 | Shown to be correslated with several benthic community parameters. |
Valley Segment |
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|---|---|---|---|
| Variable with classes used | Code | No. of classes | Notes |
| 1. Channel type: Step/pool Incised Flood plain single thread Flood plain braided Entrenched |
SP I FS FB E |
5 | May only be relevant for recreation/landscape purposes. Further refinement of categories needed. |
| 2. Elevation (metres) 0-10 10-200 200-500 500-1000 1000-1500 >1500 |
A B C D E F |
6 | affects temperature and native fish migration |
| 3. River size (discharge at median flow). (m3/s) <1 1-5 5-10 10-20 >20 |
A B C D E |
5 | Potential distribution of many species may be defined by a mix of elevation and size alone (McDowall in press). |
Reach Scale
Reach scale variables locate the habitats of different components of the ecosystem. Variables are still to be developed.