Hamlet, Alan F., and Dennis P. Lettenmaier, “Effects of climate change on the hydrology and water resources in the Columbia River basin.” Journal of the American Water Resources Association 35 (1999): 1597-1623. (reviewed by Martin Anderson)
Summary:
This study used past hydrological data from the Columbia River basin and global, local, natural, and man-made condition and trends to predict via a computer model what effect these current conditions would have on the flow of the Columbia River 20, 40, and 90 years in the future. The main scientific concern and focus of this study was on the effect of a long term global warming and how that would affect the hydrology of the Columbia River basins suitability for continued human use. Particular focus was placed on the reserve and refill capacity of the system of dams currently in place and how hydrological changes would affect power-generation and commercial use of the river. The authors focus on the portion of the Columbia River basin east of The Dalles, Oregon and the snow-melt regions of British Columbia.
Using a ColSim (Columbia Simulation) computer model of the Columbia River Basin running four separate climate prediction protocols and a number of condition-specific protocols the authors ran a high resolution (looking at the river in section of 1/8 degree latitude/longitude square) model of the basin. The time scale on the model was an average monthly flow prediction over a maximum of 90 years. The overall modeling took into account the effects of the El Nino/La Nina cycle, the Pacific Decadal Oscillation, hydrology of aquifers and ground water absorption, of dam refill/release related to commercial and power-generation, flood control measures, flow targets set for habitat and fish preservation, agricultural withdrawal, recreational concerns, and a global and local mean average temperature rise over the course of the model via an atmospheric CO2 injection model. This model minus the global warming was tested against known water levels and flows taken from 1967-1988 and found to be valid for the purposes of climactic and hydrological modeling in the Columbia River basin.
The authors came to a number of conclusions regarding the results of the ColSim. The model showed a sustained decrease in the amount of snow fall by about 1/3 per model year (2045 and 2095) relative to current levels. This was accompanied by a more dramatic decreased year to year hold over in snow cover. These were both linked to the predicted increase of between 1-3 degrees Celsius for the basin in 2045 and between 2-6 degrees Celsius by 2095 with the highest variation coming in the summer months.
What this comes down to is that for the models years and from model year to model year the trend in the Columbia River basin is for an earlier and reduced peak flow which would spread out and change the peak flow from spring/ summer to winter/spring. This would change the Columbia from a snow-melt river to a transient snow system due to decrease snow pack and increased winter precipitation and run-off coupled with increased temperatures. According to the model this would not significantly affect the human use of the river in 2025, but by 2045 there would be a strain on the river which would require some loss of usage and by 2095 reduced flows would no longer support the current levels of water usage.
Critique:
As to the conclusion of this paper, the authors were using a computer model that is still in the process of development and like any model it can be further refined, change and augmented depending on the variables and factors which it is designed to use. With that in mind the authors did a great deal of work to put as many variables into and used as many protocols as possible when designing their model.
This paper is full of graphs, descriptions, and diagrams that illustrate the modeling done with the authors system before it was set to look at the future and most of them match very closely what has been seen in the past. The validity of the model appears to be good and well thought out. The conclusions that the authors draw from their model seem to be well founded. It certainly makes sense that increased temperatures and milder weather would both increase precipitation and decreased snow pack which would decrease the overall flow and change the periods in which the Columbia River flows.
As the authors note their models does not predict the future with any claim to accuracy, but if even half of what the models shows is true the Columbia River and the people that rely on it will be in trouble in less than 30 years. It is startling to see how the effect of man has become a global condition which not only affects us significantly but destroys other biological and natural systems as well.
Robert D. Clark Honors College, University of Oregon
HC 441: Science Colloquium, Columbia River Ecology
Fall term, 2005
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