Scope 5 - Environmental Impact Assessment

We have chosen the following example (summarized from Walters, 1974) to show one way in which modelling techniques and procedures can be used for a rapid preliminary EIA of a specific large-scale regional project. The example selected for study was a large hydroelectric development in the James Bay Territory of Quebec, Canada, covering the La Grande basin, an area twice the size of England. To be built over a 12-year period, the project envisaged the construction of four power houses, four main dams, 12 spillways, six control structures, 130 km of dikes, and three ancillary reservoirs. Four major river systems would be affected. Upon completion, the project would provide more than eight million kilowatts of power. 

The preliminary EIA was undertaken in the following way. A support staff of five professionals with experience in related resource systems, simulation modelling, and programming collated information during an initial three-week period. This was followed by an intensive workshop involving about 20 participants. The problem was defined, the model was developed, and its behaviour explored during this five-day period. The modelling and evaluation techniques incorporated many of the features described in Chapter 5, and a full description of both the techniques and the workshop procedures can be found in Walters (1974) and Holling and Chambers (1973). 

At the outset, the spatial dimensions of the study had to be selected. Was an examination to be made of potential impacts throughout all of Canada, in only the Province of Quebec, in only the James Bay Territory , or in only the watersheds directly affected? To make this first assessment feasible, the group decided to concentrate on the scale of the watersheds, leaving the analysis of impacts at larger scales for the future. 

The participants then identified a basic set of specific predictions which the model had to handle. First, it was decided that the model must represent the broad impact on land area, water coverage, and shorelines of the hydroelectric dams and diversions. This was essentially a data summary and bookkeeping problem. Second, it was necessary to show the overall biotic response over time to these gross changes; it was expected that the development would destroy habitat for some organisms, but improve conditions for others. Third, it was believed that hydro-electric development would alter the temporal stability of aquatic and shoreline environments, by reducing variations in water flows. The model must predict the impact on vegetation, fish, and wildlife. Fourth, construction and maintenance activities would generate various water pollutants, especially silt. The model was expected to provide spatial and temporal distributions and dispersal of these materials, and to predict biotic impacts for at least some extreme conditions. Finally, the development would dramatically alter accessibility of the area, which might result in greatly increased human activity. The model was to represent the general impact of increased exploitation on animal populations of the area. 

The identification of these requirements led to the selection of the five sub-systems shown along the top and again to the far left of Table A5.1. Sub-systems missing from the table include the marine environment and the atmosphere. Hydro-electric development will alter marine conditions, especially winter ice patterns, and there is also the possibility of climatic changes. However, meaningful predictions concerning these questions would require the development of very specialized and complex spatial models, which were beyond the scope of the short workshop.

It was also necessary to decide on a system for representing spatial patterns. The participants agreed to divide the area into a series of irregular land units, each containing no more than one component of the hydroelectric development (e.g., one dam) and small enough to be considered homogeneous with respect to transportation access and general productivity for wildlife and fish. 

Each of the five sub-systems has inputs (demands) from other sub-systems as well as outputs (supplies) to other sub-systems, as shown schematically in Table A5 .1. Sub-models based on these concepts were developed, following the procedures outlined in Chapter 5, by sub-groups, each containing policy-makers, resource specialists, and one staff person. The emphasis was on understanding the behaviour of the sub-models, attempting to formulate relations between variables, and choosing appropriate levels of precision. The programming and mathematics were kept in the background as a technical translation problem, so that the group could concentrate on the key issues of conceptualization. 

As the sub-models (details in Walters, 1974) were being programmed, the participants were reformed from their sub-model groups into three policy analysis groups, reflecting three broad categories of impact: resource development, environment, and Indian welfare. Each group was asked to do three things: (1) to develop a list of impact indicators that best indicated those aspects of concern to the interest group; (2) to develop a set of a priori intuitive predictions about the effect of each intervention on each output indicator variable; (3) to formulate several overall management scenarios, each expressed as a combination of policy actions, which the group felt would represent different management goals. 

The intuitive impact predictions were made with essentially the same techniques as those discussed in Chapter 4, with the predicted impact of each action on each impact variable simply shown as 0, + , or -, first during the construction phase, and then after the construction. A section of this table is shown in Table A5.2 for the post-construction phase with the predictions of the model included for comparison.

Table A5.1 Information Transfers between the Five Sub-Systems in the James Bay (La Grande Basin) Model

The key result was that the impacts (positive or negative) predicted by the model were often exactly opposite from what had been expected (26 instances in Table A5.2). In every case, a simple explanation for the difference was clear after brief examination of the model structure, and the participants generally agreed that there had been obvious f1aws in their intuitive reasoning. 

Table A.5.2 Qualitative Summary of Management Interventions, and their Simulated Impacts according to the James Bay Model as opposed to Intuitive Predictions of Workshop Participants. Sign before each Slash is Intuitive Expectation of Impact ( + for Beneficial) Sign after Slash is the Model Prediction

An example of some detailed predictions of two management scenarios is shown in Figure A5.1. The model made three major predictions which were counter to any expectations expressed either by the workshop group or in published statements related to James Bay area. First, by providing an overall bookkeeping assessment of the land and water areas involved in hydroelectric development, the model pointed out that the direct impacts of dam construction were not likely to be too significant; only a small percentage of the land would actually be inundated. Second, by far the largest impact on fish and wildlife resources was likely to come from the increase in recreational demand; in retrospect, it is obvious that even small recreational fisheries can seriously deplete northern lakes and streams that can support only a few per hectare, turning over only once every several years. Finally, it was found that even without the dams, serious future environmental consequences were predicted. After the model had been tested with the standard La Grande Complex construction plan, a comparison was made with an even more elaborate dam and diversion plan which had been contemplated (the Complex du Nord). The hydrology sub-model predicted that the La Grande Complex would not result in much regulation of water flows and levels, so reservoirs would be surrounded much of the lime by large mudflat areas which would not be attractive for recreation (geese might prosper, however). On the other hand, the diversion scheme in the Complex du Nord should result in much more stabilized flows and levels, making river banks and reservoirs more attractive for recreation (but some waterfowl habitats would be lost). 

Considering these predictions, it is not surprising that the workshop suggested several kinds of impact assessment studies. In particular , it appears that emphasis should be placed on monitoring of lands and waters which are not directly involved in the development, but which would be made accessible for recreational use. Also, the impacts of the construction workers should be carefully monitored. The model predictions were critically sensitive to the hypotheses concerning Indian values and resource utilization. While this had always been recognized, there had been no clear focus for data collection until the model had been developed. 

Obviously, many of the parameter estimates used in the model were pure guesses; in many cases better estimates simply did not exist, especially those related to recreational demand. Simulation models in resource management are often open to this criticism, and typically, the conclusion is drawn that modelling is premature. The James Bay workshop demonstrates the fallacy of this conclusion; the model itself provided the strongest justification for a research and monitoring programme. We tend to forget that all data collection is guided by some model of nature; workshops and other exercises only try to bring this model out into the open so that its basic assumptions can be examined objectively. 

Assessment of the impact of the La Grande development is continuing, and the James Bay Energy Corporation has been responsible for monitoring environmental changes since 1974. A recent workshop (Marsan, 1977) has recommended the network design shown in Figure A5.2 for the post-construction period in the 1980s. An intensive programme (for that hatched and solid black areas in the figure) would include monitoring of both physical-chemical and biotic indicators (e.g., temperature, pH, dissolved oxygen, total dissolved solids, primary productivity, plankton standing crop, fish populations, etc.) in disturbed (reservoirs) and control water bodies. Extensive monitoring (at the locations marked by dots in the figure) would be for the physical-chemical indicators only. Ecological models developed and validated with data obtained from the intensive monitoring programme would be used to understand the cause-effect relationships in reservoir eco-systems, to integrate the subject-matter by means of interdisciplinary workshops designed to develop conceptual models, and to predict the state of the biotic indicators in the reservoirs.

References 

Holling, C. S. and Chambers, A. D. (1973) Resource science: the nurture of an infant. Bioscience 23, 13-20. 

Marsan, A. (1977) Monitoring environmental changes in the La Grande system. Proc. Study Group Session. Société d'énergie de la Baie James: Montreal. 36 pp. 

Walters, C. (1974) An interdisciplinary approach to development of watershed simulation models. Tech. Forecasting and Soc. Change 6, 299-323.