|
|
 |
|
 |
 |
|
|
|
|
|
|
|
| Air |
|
|
Land |
|
|
Water |
|
|
Climate Change |
|
|
Waste |
|
|
About Us |
|
|
 Quick Links
|
Advisories
|
Online Reporting
|
| Last Review/Updated: July 8, 2002 |
|
NRBS - HomeTable of Contents |
Northern River Basins Study Final Report
3.0 Major Findings
|
||||||||||
|
Introduction NRBS Models Summary Relevant Documents |
| Related NRBS Question: | |
|---|---|
| 13. a). |
What predictive tools are required to determine the
cumulative effects of man-made discharges on the water and
aquatic environment? |
| 13. b). |
What are the cumulative effects of man-made discharges on
the water and the environment? |
| 14. |
What long-term monitoring programs and predictive models
are required to provide an ongoing assessment of the state
of the aquatic ecosystems? These programs must ensure that
all stakeholders have the opportunity for input. |
The Northern River Basins Study is one of the first integrated research endeavours to assess the cumulative impact of a broad range of industrial and municipal discharges on the water quality in large northern rivers. As such, the Study faces scientific challenges that might not be experienced in more southerly areas.
Environmental modelling in the Peace, Athabasca and Slave Rivers is a scientific challenge because these systems are very large, highly complex and experience dramatic seasonal temperature fluctuations. To further complicate matters, there is very little information on these systems upon which to base modelling efforts. Much of the background information related to water quantity and quality modelling is based on small, southern river systems possessing different physical, chemical and biological characteristics that may not be applicable to large northern rivers.
Shortly after the Study began, a modelling workshop considered the merits of constructing a comprehensive simulation model of the northern river ecosystems. The techniques of building ecosystem models are well known but problems of scale in space and time pose major challenges for collecting sufficient data for calibration. For example, sedimentation processes take place over long periods of time and great distances. In contrast, many plants and animals live for only a few years, microorganisms only a matter of days or hours, and the effects of human activities occur on very local scales.
Splicing together various sub-models to make a comprehensive model is feasible, but usually results in questionable notions of how natural ecosystems function. In brief, current state-of-the-art ecosystem modelling is not yet adequate for modelling river ecosystems. Workshop participants decided that NRBS modelling needs would be better met with sub-models that addressed individual processes, with no attempt to assemble them into an all-encompassing ecosystem model.
What follows is a brief description of the various sub-models developed within the NRBS for predicting water quality, quantity and ecosystem health within the northern river basins. The models fall into three general categories:
This Section evaluates the progress made by NRBS modelling endeavours.
A brief description of NRBS models, their usefulness and their contribution to modelling northern rivers is given below.
Dissolved OxygenThis model evaluates the influence of oxygen-demanding substances and river processes on oxygen production and consumption in the water column and builds upon the Dissolved Oxygen Stochastic (DOSTOC) model developed by Alberta Environmental Protection. This relatively simple model requires very few data compared to more complex approaches, allowing researchers to incorporate data that arose entirely within the northern river basins. Model results were then tested against measured dissolved oxygen changes in the Athabasca River.
The model was relatively successful in predicting large-scale trends in average oxygen concentrations for the Athabasca River, but was unable to capture local oxygen sags downstream of some pulp mills during the 1988-1989 period. This may have been caused by large and erratic loadings of oxygen-demanding substances or limited information regarding tributary and sewage treatment plant loadings.
In addition to DOSTOC, statistical models were developed that describe how oxygen concentrations decline in relation to distance along the Athabasca River from Hinton to Grand Rapids and from there to Lake Athabasca for the years 1988 to 1993.
Both the statistical and DOSTOC models are currently at the stage of verification and application. The Study has made considerable progress with regard to dissolved oxygen. DOSTOC may not be as complex as more sophisticated models, but it provides a simple and reliable framework for predicting dissolved oxygen changes and levels over relatively large reaches of the Athabasca River. It is also a useful tool for evaluating understanding of processes that influence dissolved oxygen concentrations in northern rivers.
Contaminant FateThe contaminant fate model builds upon the Water Quality Analysis Simulation Program (WASP) developed by the U.S. Environmental Protection Agency. Using WASP, NRBS researchers were able to model the fate and transport of a variety of organic chemicals within the Athabasca and Wapiti / Smoky River systems. The modelling effort focussed on seven contaminants associated with pulp mill effluent.
The model was designed to describe what chemical reactions occur when these contaminants enter the aquatic environment and where they end up within the ecosystem (i.e., bed sediments, water column, etc.) This model is extremely complex in comparison with the relatively simple DOSTOC described earlier. As a result, the model "consumed" all of the information available for the northern rivers and demanded more. Literature values for certain water quality variables had to be adapted for use in the northern rivers. There wasn't enough "leftover" data to evaluate the applicability of these values in northern rivers or to fully test the accuracy of model predictions.
It is difficult to summarize all the results for such a sophisticated model. WASP was much better at predicting the fate and transport of one organic contaminant (2,3,7,8 TCDF) for which there are well defined fate constants. The model was able to reliably simulate the distribution and fate of 2,3,7,8 TCDF in all compartments of the aquatic environment (i.e., water column, suspended sediments and bed sediments). It could also predict levels of the other six compounds in the water column, as long as industrial loadings are well defined. However, the model consistently overestimates levels of these six compounds in bed sediments of the Wapiti / Smoky River system.
In summary, WASP is currently at various stages of development. The model was calibrated for 2,3,7,8 TCDF, although the calibration requires a more thorough assessment. Other elements of the model are still in the formulation stage.
Further progress on this model is hampered by the lack of available information. Researchers had to contend with a weak initial database and uncertainties regarding chemical loadings into the river systems. Also, there was very little information regarding the behaviour of many of the chemical species in the environmental conditions of the northern rivers. Given these challenges, the NRBS made considerable progress in model development for the transport and fate of contaminants. However, more research and calibration is necessary for this model to have useful applications in the northern river basins.
Contaminant Distribution in the Food ChainThe food chain model was designed to simulate the bioaccumulation of organic contaminants within three fundamental components of the food chain: bottom feeding invertebrates, benthic invertebrates and fish. It also identifies the primary source of contaminant exposure for these organisms.
The model was designed to take WASP one step further to predict how environmental levels of contaminants accumulate in the food chain. At this stage of development, it is questionable whether the untested WASP results can be used in this model to produce reliable, accurate predictions.
Six of the seven chemical compounds used in WASP were simulated using the food chain model. Once again, the most reliable results were generated for 2,3,7,8 TCDF. Still, the model tends to overestimate levels of most chemicals when compared to measured levels of contaminants in these organisms.
In summary, the model proceeded to the calibration stage. However, the significant lack-of-fit between the model output and observed values suggests that considerable work is still required to evaluate the reasons that the model failed. It may be that the model fails to take into account the variability of contaminant concentrations or the variation in organisms within and among locations. In particular, more information is required regarding the validity of the food-web configuration used in the model and the spatial movements of fish.
Water Quantity and Hydrologic ProcessesSeveral models were developed or refined by the Hydrology Component of the NRBS. Collectively, these models provided a basis for evaluating the effects of flow regulation the Peace and Athabasca basins. In addition, components of these models provided an improved foundation to assess the transport and fate of contaminants.
A one-dimensional flow model was developed specifically for the Peace and Slave River systems. This model was developed to serve a number of impact-related studies initiated by the NRBS assessing the effects of flow regulation by the W.A.C. Bennett Dam on the downstream aquatic ecosystems of the Peace and Slave Rivers. This model reproduces both regulated and naturalized flows for the rivers and, unlike existing hydrologic models for the Peace River, reproduces discharges at any point along the river. At locations where detailed channel geometry was available, the model also provides accurate estimates of stage and mean channel velocity.
As this model was being developed in tandem with other NRBS studies, the total benefits of the model were not fully utilized during the NRBS. The model was applied to provide "time-of-travel" estimates in the analysis of spring break-up conditions on the lower Peace River adjacent to the Peace-Athabasca Delta. Future application of the model could include linkages with evaluating and quantifying morphologic changes along the Peace River and in the Slave River Delta. The model also has applications in meso-scale evaluations of aquatic habitat using low level multi-spectral imagery (as was done in the NRBS).
Several other models were utilized by the Hydrology and Other Uses components to address Study Board question #10. To apply the one-dimensional hydraulic model to the Peace and Slave Rivers, a geometric model had to be developed. Although this model was designed specifically for hydraulic modelling, a considerable amount of cross-sectional data was used. The actual cross-Section sites were documented, recognizing the future value of this geometric database. Pre-existing "hydraulic geometry" models were also applied to assess channel morphology on the Peace River and in the Slave River Delta. A sediment-based time scale adjustment model was also utilized to estimate how long before the regulated regime will take to come to equilibrium. Evaluation of the hydrometeorlogical conditions controlling ice-jam floods on the Peace River near the Peace-Athabasca Delta required the use of various empirically and physically based models.
The ability to ascertain the impacts of development on the aquatic ecosystem is actually a two-stage process:
Models developed within the NRBS generally fall within the stage one category. The scientific rationale behind this position is justifiable, given the lack of information that existed in the basins prior to the Study. Given this challenge, the NRBS made considerable progress in the development of predictive tools in some areas, and laid a scientific foundation in other areas for future modelling efforts. Knowledge generated within the Study regarding the impacts of human development on environmental conditions must now be used to predict the effects of these changes on living organisms.
NRBS Synthesis Reports
McCauley, E. 1996. A Review and Evaluation of Water Quality and Quantity Models Used Under the Northern River Basins Study. Northern River Basins Study Technical Report No. 82.
Supporting NRBS Technical ReportsAitken, B. 1996. Spill Response Model. Northern River Basins Study Technical Report No. 126.
CanTox Inc. 1995. A Bioenergetic Model of Food Chain Uptake and Accumulation of Organic Chemicals in the Athabasca River: Phase I. Northern River Basins Study Technical Report No. 137.
Chambers, P.A., Pietroniro, A., Scrimgeour, G.J. and I. Loughran. 1995. Assessment and Validation of Modelling Under-Ice Dissolved Oxygen Using DOStoc, Athabasca River, 1988 to 1994. Northern River Basins Study Technical Report No. 95.
Culp, J.M., Chambers, P.A. and T. Mill. 1994. Proceedings of a Workshop on Water Quality Modelling for the Northern River Basins Study. Northern River Basins Study Technical Report No. 37.
Golder Associates Ltd. 1995. Contaminant Fate Modelling for the Athabasca and Wapiti / Smoky Rivers (Volume I). Northern River Basins Study Technical Report No. 112.
Hicks, F.E., Yasmin, N. and X. Chen. 1994. A Hydraulic Flood Routing Model of the Peace River, Hudson Hope to Peace Point. Northern River Basins Study Technical Report No. 76.
Starodub, M.E. and G. Ferguson. 1996. A Kinetic Model of Food Chain Uptake and Accumulation of Organic Chemicals, Athabasca River: Phase II - Stochastic and Time Variable Version. Northern River Basins Study Technical Report No. 113.
|
...PREVIOUS |
NEXT... |
| Environment
Home | Search
| Contact
Us | Privacy
Statement |
Minister's Office Expenses Emergency Numbers The user agrees to the terms and conditions set out in the Copyright and Disclaimer statement. © 2009 Government of Alberta |
|
|