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International Aquatic Modelling Group

Strategic Plan


The International Aquatic Modelling Group (IAMG) is designed to facilitate an integrated, applied, research programme which will develop methods of assessing the interactions between instream flora and fauna and aquatic habitats. The group aims to meet the increasing demands for improved operational tools specifically designed to provide better quantitative assessment of the effect of artificial influences on aquatic ecosystems. This will be achieved through the development and application of innovative scientific and analytical procedures to the issues in question, using a broad multi-disciplinary approach.

At present there are a large number of individual organisations and researchers examining topics directly related to the issues addressed here. There is not, however, a framework for the focused, integrated and timely exchange of current research progress and output, or for the development of strategic, multi-national, co-operative research programmes. The IAMG is intended to provide the above, capitalising on existing individual and networked research programmes, through the focusing of the particular expertise and strengths of these programmes within a clear set of research areas. This will assist the production of the best achievable assessment methodologies for applied use in aquatic ecosystem management.


The requirement for quantitative tools which can assess the impact of artificial influences on aquatic ecology in a consistent and reproducable manner has increased over the past two decades. Several methods have been developed in response to this demand. These include the Habitat Evolution Procedures (HEP) and the Instream Flow Incremental Methodology  (IFIM). At present these existing tools have come under criticism, especially in their applicability to the holistic ecosystem management. There is a growing recognition that such an approach to the management of aquatic systems will require the development of tools which utilise integrated physical, chemical and biological process driven methods. It is to this end the IAMG has been formed to develop an array of tools that may be applied to the management of aquatic systems, using a fully integrated approach coupled with the application of the best available data collection and modelling techniques.

Areas of Integrated Research Focus

Present areas of integrated research focus will be represented by following sub-groups of IAMG


1. Physical measurements

This element of research is intended to address several aspects of spatial characterization of aquatic ecosystems at spatial scales representing target species micro-habitat, macro-habitats, river reaches, river systems, and watersheds. There are three main focus areas to be followed in this group. 

1a. Collection Strategy:

This effort is also intended to focus research at the applied level which can improve more efficient field measurement strategies suitable for better aquatic habitat characteristics and for direct use in advanced 2-d and 3-d hydraulic modeling. The evaluation of different existing sampling strategies, their modification and development of strategic framework are the present  task. Those broad framework should be specified for various river types, assessment objectives, considering the requirements of biological and physical modelling and provide the comparability of the results. The summary description of existing sampling techniques including short “pro- and contra” analysis will be provided in the first step.

The existing database will be continuously overviewed, classified and provided to other subgroups for  models evaluation purposes.

1b. Instrumentation:

Research will include the evaluation of new technologies for highly accurate cost effective spatial mapping, involving instrumentation such as differentially corrected global positioning systems, depth pressure transducers, hydro-acoustic arrays for bottom profiling, and integration of other advanced survey techniques using total stations with automatic target search, and remote sensing.

1c. Scale Transfer:

This research is intended to evaluate appropriate techniques which permit to characterise aquatic ecosystem over a variety of spatial scales, while maintaining meaningful representations of the spatial requirements of target organisms. Research will initially focus on addressing accuracy of spatial measurement scales (i.e. micro-habitat, macro-habitat, and reach level characterizations). The evaluation of mapping methods, transferability of the results of micro-habiat measurement for the meso- and macro-scale, should be the present objectives. GIS analysis of spatial interactions, sensitivity studies and generalization procedures has to be developed in present projects. The result of this activities should be implemented in the development of sampling strategies.


2. Temporal Analysis

2a. Flow 

The focus group will examine the functional relationships between temporal physical habitat fluctuations and biological response with the aim of determining the limiting conditions for aquatic population dynamics in rivers. The main biological reference species to be examined are fish and macro-invertebrates although macrophyte species will also be examined since their growth is affected by physical habitat and may also lead to changes in aquatic habitat for other species. An important aspect of this work will be the field validation of model results. This will require the selection of river study sites where long-term records of biological and physical data have been collected. The group will also develop methods of expressing changes in aquatic habitat with time (eg: Habitat time series, habitat duration curves, Continuous Under Threshold habitat curves) to aid the interpretation of model results.

2b. Morphology

The scale of the impact of artificial influences on river systems may vary from a few kilometers to several hundred kilometers length of river. As a result, there is a need for a consistant, repeatable, method of defining river habitats, on the meso- or macro-habitat scale, to allow the extrapolation of aquatic habitat model output from local studies (eg: using PHABSIM) to larger areas of river. This area of work will be partially addressed by the Physical Spatial Measurements focus group. However, there are important temporal aspects to this work, for example in the study of temporal changes in the distribution of habitats within rivers, which will require close collaboration between focus groups.

2c. Biology

The temporal analysis focus group will also examine the relationship between flow variability over time and its impact on aquatic population dynamics. In particular the focus group will examine the response time of aquatic species to changes in flow. This work may require the development of  new “Eco-hydrological” data to describe both frequent and unfrequent flow conditionstaking biological behaviour into account.


3. Hydraulic modelling 

3a. Introduction

Over the last twenty years there has arisen a need to incorporate a representation of the hydraulic environment of streams in models of aquatic habitat, particularly in relation to the determination of the environmental flow requirements of streams. A common approach to hydraulic modelling for habitat studies is the use of models contained within the PHABSIM (Milhous et al 1984). This approach is based on a detailed one-dimensional hydraulic characterisation of a limited river reach under steady flow conditions. The IAMG believes there is a strong need to focus on the gap between the existing model technology and the requirements of modelling the whole aquatic ecosystem at a range of spatial and temporal scale.

A large number of hydraulic models are available for use in modelling aquatic habitat, but very few of them are currently being used. The potential of alternative modelling approaches such as two and three dimensional solutions to the Navier-Stokes equations (Ghanem et al., 1994; Olsen and Alfredsen, 1994), characterising the near-bed flow environment (Davis and Barmuta, 1989) and statistical hydraulic models (Lamaroux et al., 1992) have been discussed but as yet not achieved wide application in studies of aquatic habitat. The evaluation and development of these innovative approaches for use as operational tools is of special interest to the Hydraulic Modelling Sub-Group.

3b. Objectives

The IAMG Hydraulic Modelling Sub-Group aims is to improve the evaluation of aquatic habitat by developing, validating and making widely available suitable, reliable and efficient hydraulic modelling techniques.

The key emphasis of the hydraulic modelling sub-group  is to identify useful tools for aquatic modellers compatible with current biologic modelling approaches. To do this it will be necessary to draw on the resources of the biologic sub-groups in the IAMG. Any hydraulic model development within the group must have a sound biologic basis.

3c. Focus Group A: Defining Steady State Hydraulic Modelling Techniques

The first main objective of the Hydraulic Modelling Sub-Group is from a biologic point of view to state the description of physical variables required to evaluate the habitat of aquatic biota. (this requires a link to Sub-Group D, Biologic Life Cycle Requirements). Such a description should include the physical properties of relevance such as velocity and depth, the scale and location at which these properties are important and the required characterisation of any spatial and temporal variations of these properties. In principle, a model of the interaction between species habitat selection and the physical stream environment should be identified prior to selecting appropriate hydraulic models. 

A representative list of suitable hydraulic models using different modelling approaches that could be used in an aquatic modelling study will be provided by the group. Both well established and more innovative techniques will be selected for this list. A summary description of the models will be prepared including field data requirements, calibration facilities, required computer performance, type of results, validation possibilities and a reference list. 

3d. Focus Group B: Field Validation of Steady State Hydraulic Models

The next important objective of the Hydraulic Modelling Sub-Group is the field validation of these modelling approaches for aquatic habitat studies. Scientifically approved methods for validation of the hydraulic model performance must be ensured or established. The uncertainty in the predictions of the physical habitat characteristics and the minimum data collection and modelling effort required to apply them under the range of circumstance encountered in the streams will be determined and evaluated. Sub-group A, Physical measurements, will provide data from a number of test sites for model validations.

3e. Focus Group C: Dynamic Modelling of Stream Hydraulics

Another important objective for the hydraulic modelling group is to focus on the need for modelling on a larger spatial and temporal scale. This must also consider modelling of dynamic changes like sediment transport and deposition, ice formation and other dynamic physical processes in streams. In order to understand and manage the whole aquatic ecosystem dynamic hydraulic models must be used over a long time-scale giving the opportunity of studying both short-term and long-term variations in the physical habitat and effects on the ecosystem. This objective is linked to Sub-Group C, Temporal Analysis.

3f. Focus Group D: Technology Transfer

The final objective is to develop a set of guidelines to be used by aquatic modellers for selection of the most appropriate hydraulic model for their particular application. Where hydraulic models are not available to predict certain habitat characteristics in an operational mode, the group will initiate research into the development of an appropriate hydraulic modelling approach. This objective has an important link to Sub-Group E, Assessment and Evaluation.


4. Biological life-history

 4a. Evaluation of sampling methods

There is some confusion concerning habitat preference curves. Habitat conditions preferred by a fish population can appear to be different depending on the method used to observe the used habitat (direct observation from the bank, underwater observation, electrofishing, underwater traps). Other factors determining the habitat use of a fish are life stage (length), season, time of day, activity (feeding, resting), migration. Especially differences in habitat use between different seasons have to be considered. Other variables in addition do depth, velocity and substrate will be evaluated . 

4b. Ecological analysis and interpretation of habitat sampling data

The ecological interpretation of habitat sampling data is often omitted.  In many cases used data are inappropriate because they were developed for streams with other characteristics. Therefore, ecological interpretation has to be included at different levels. Fish density dependance and related space limitation/carrying capacity have to be included.

4c. Eco-metrics

This approval is going away from using preferrence/suitability curves. Eco-metrics methods will be evaluated (optimal foraging behavior). 


Technology Transfer

The Institute for Natural Systems Engineering (INSE) at Utah State University has agreed to establish several support services for the IAMG.  First a world wide web (WWW) home page is being established which will list the on-going research elements underway within the IAMG, participating agencies and investigators and help for contacting individual collaborating investigators/agencies.  The WWW page would be updated on a frequent basis to keep exchange of the exchange of on-going research focus and results current.  In addition, the INSE will host an anonymous FTP site as a depository of reports, software, etc. to facilitate scientific exchange of data, information, and modeling tools for use by interested parties.  Finally, the INSE will also host a Bulletin Board Service (BBS) forum on instream flow assessment methods where questions, answers and debates on methods and study results can be carried out via the Internet. The BBS will serve as a convenient forum for more focused interchange of ideas  and comments within the active research community on instream flow assessment methods.