Progress 05/01/99 to 04/30/05
Outputs
A comprehensive annotated literature review was compiled on ice thickness and ice-bridges. A layered freeze-thaw model was developed to account for ice thickness changes associated with either the build-up of ice bridge surfaces or with the removal or compaction of snow. Model analysis and the literature review have helped make a general recommendation that water depth be greater than 2 m. for ice-bridge sites and that upwelling areas be avoided. Literature review, modeling work, and stream water temperature data indicate a strong association between air temperature and water temperature for mid-sized to large streams and a systematic increase in temperature longitudinally from headwaters to mouth for small streams exposed to direct solar radiation. The SNTEMP and SSTEMP models were found to be potentially useful for energy balance and stream network simulations. Simpler models were also useful but needed modifications to accommodate high latitude effects on maximum
sun angles and day length. Stream buffer widths greater than one tree height from the stream, and buffers displaced greater than one tree height from the streams south bank were judged ineffective for temperature control. Little increase in stream temperature is expected directly due to the effect of timber harvest on watershed substrate heating because of the high latent heat of fusion and latent heat of vaporization relative to the specific heat of soil and regolith. However, the permafrost table is likely to be lowered, the rate of seasonal-frost thawing increased, and the maximum depth of seasonal frost decreased in response to forest removal. The latter result is due to reduced transpiration losses after tree removal and the subsequent higher soil moisture contents entering into the winter freezing season. This effect may be most pronounced during the second, and subsequent winters after harvest.
Impacts
Information gained to date has contributed to the development and passage of revised riparian management standards for interior Alaska and influenced on-going discussions of standards for south-central Alaska. Information was provided to the Science & Technology Committee of the AKDNR-DOF for their review of Regions II and III riparian standards. Written commentary was provided to the review committee for Region II, stressing that buffer design must consider that water in streams is moving and therefore is not subjected to constant conditions throughout the day or length of stream. The importance of the pre-harvest temperature signature of a stream as a reference for impact assessment was stressed. In addition, the lack of significant contribution of buffers starting far from the bank or vegetation providing shade only at low sun angles was noted. In addition to a workshop for forest, fish, and water managers, and contributing to two additional presentations, the PI
has provided a critical review of a stream temperature-timber harvest analysis done in Washington State. Response to the latter review resulted in significant improvements in that groups results and the general utility of their research. Finally, the techniques and models developed in this project related to soil freezing and thawing, may contribute to the assessment of climate change effects, fire effects, and vehicle impact on tundra stability, by providing a tool that integrates changes in vegetation, snow depth, and air temperature.
Publications
- Fox, J.D. and Robert Ott. 2000. Ice thickness and ice bridges: An Annotated Bibliography. In: Welborn, M. (ed.) Region III Forest Resources & Practices Riparian Management Annotated Bibliography. Compiled by Region III Science/Technical Committee. Report to the Alaska Board of Forestry. AKDNR Division of Forestry, and AK Dept. of Fish & Game. August 2000., pp.103-126.
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Progress 01/01/04 to 12/31/04
Outputs
A comprehensive annotated literature review has been compiled on ice thickness and ice-bridges. Freeze-thaw models have helped make a general recommendation that water depth be greater than 2 m. for ice-bridge sites and that upwelling areas be avoided. Literature review, modeling work, and stream water temperature data indicate a strong association between air temperature and water temperature for mid-sized to large streams and a systematic increase in temperature longitudinally from headwaters to mouth for small streams exposed to direct solar radiation. Work with the SNTEMP and SSTEMP models is continuing. Little increase in stream temperature is expected directly due to the effect of timber harvest on watershed substrate heating because of the high latent heat of fusion and latent heat of vaporization relative to the specific heat of soil and regolith. However, the permafrost table is likely to be lowered, the rate of seasonal-frost thawing increased, and the
maximum depth of seasonal frost decreased. The latter result is due to reduced transpiration losses after tree removal and the subsequent higher soil moisture contents entering into the winter freezing season. This effect may be most pronounced during the second, and subsequent winters after harvest.
Impacts
Information gained to date has contributed to the development and passage of revised riparian management standards for interior Alaska and influenced on-going discussions of standards for south-central Alaska. Information was provided to the Science & Technology Committee of the AKDNR-DOF for their review of Region II, south-central Alaska, riparian standards. Written commentary was provided to the review committee stressing that buffer design must consider that water moves and therefore is not subjected to constant conditions throughout the day or length of stream. The importance of the pre-harvest temperature signature of a stream as a reference for impact assessment was stressed. In addition, the lack of significant contribution of buffers starting far from the bank or vegetation providing shade only at low sun angles was noted. In addition to previous workshops and presentations the PI has provided a critical review of a stream temperature-timber harvest analysis
done in Washington State. Finally, the techniques and models developed in this project related to soil freezing and thawing, may contribute to the assessment of climate change effects on the allowable number of oil-industry workdays on the tundra of Alaskas north slope. The allowable workdays are limited by thresholds of snow cover and depth, and soil frost in the fall and spring. The latter can now be simulated given various scenarios of temperature and precipitation.
Publications
- Fox, Jr., John D. 2004. Discussion of: Prediction of Stream Temperature in Forested Watersheds, by V. Sridhar, Amy L. Sansone, Jonathan LaMarche, Tony Dubin, and Dennis P. Lettenmaier. JAWRA 40(6):1659-1660.
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Progress 01/01/03 to 12/31/03
Outputs
During this reporting period work continued with the SNTEMP and SSTEMP models to explore their potential for research and operational use in interior Alaskas extreme environment. These models should allow an opportunity to evaluate the robustness of the results achieved to date with simpler procedures, as well as, extent the insights from channel cross-section to channel networks. These more complex models, however, have presented some challenges. I have been in contact with colleagues familiar with their operation in the lower 48, and currently am being guided in the intricacies of their application through a self-study course and personal communication with these people.
Impacts
The Alaska State Legislature passed a bill in 2003 adopting revised riparian management standards for region III (interior Alaska). Work sponsored by this project contributed to the formulation of these revised standards. A similar effort has been started for region II (south-central Alaska) for which this research will also be relevant.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
In this reporting period the emphasis has was on developing computer models to move toward a capability of simulating the likely effects of timber harvest on stream temperatures. A range of models are being tried, including the fundamental physics relationship between temperature change, specific heat, mass, and energy flux, and models which elaborate on these principles in order to apply them to specific topographic, vegetative, and stream regimens. I have found, for instance, that the change in stream temperature observed longitudinally in the channel from headwaters to mouth, can be largely explained by the simple model of solar energy input along the water surface under a specified flow rate. This crude calculation is then being elaborated using the models SSTEMP for stream segment temperature and SNTEMP for trying to capture the effect of the stream spatial network on the result. Vegetation changes in the riparian zone are then simulated, altering the stream
energy balance. The specifics of ice growth at channel cross-sections and the influence of ice-bridge construction are also being simulated with a degree-day model for layered media in order to include the effect of snow depth and density on ice-growth. Efforts are still in progress in terms of model application, evaluation, and validation.
Impacts
Information gained to date has been given to local managers and through the principal investigator's membership on an interagency technical committee, has contributed to the development of revised riparian management standards for interior Alaska (Region III). The legislative bill containing the proposed changes, while widely endorsed by stakeholders and unopposed politically, failed to be acted on in the 2002 session. This bill is being reintroduced for the 2003 Alaska legislative session. In addition, a well-attended riparian management workshop was conducted in 2002 to extend the knowledge gained in this project and others to forest, fish, and water managers. Two additional presentations of a powerpoint slide show developed by the PI and a colleague have been delivered.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
This project concentrates on investigating three questions pertinent to interior Alaska streams: Can ice-bridges increase ice thickness such that fish or fish habitat might be negatively affected? How does summer water temperature vary with downstream distance regardless of local buffering by riparian vegetation? Can stream temperature be affected by broad-scale changes in watershed vegetative cover, independent of riparian buffers? We approach these question by a combination of literature reviews, simulation experiments, and field measurements. We have completed a review of historic ice-thickness measurements for Alaskan streams and rivers, as well as the literature related to ice-bridge construction and experiences and the possible effects of river ice or ice bridges on fish habitat. This information will be supplemented with photos and measurements made on actual ice-bridges constructed in the interior as opportunity allows. A layered model to account for ice
thickness changes associated with either build-up of ice bridge surfaces or with the removal or compaction of snow has been developed. To understand the changes in summer stream temperatures with distance downstream we will be making stream temperature measurements on selected streams and also using a range of simple to complex computer models to explore the dynamics of water temperature and sensitivity to riparian shade. An annotated bibliography on ice thickness data and ice-bridge construction has been completed. Models of water temperature-dynamics are being modified or programmed for use in this project. The SNTEMP and SNTEMP models are of particular interest. A multi-layered model of ice-growth with snow cover is being used to investigate ice growth under different ice-bridge management regimes and weather conditions.
Impacts
While this project is not complete, insights gained to date have been shared with local managers through the Science and Technology review committee for the Alaska Forests Practices Act. Information will also be presented at an upcoming Society of American Foresters Continuing Education Workshop on Riparian Zone Management. It has become obvious that areas of upwelling along salmon spawning streams are not good sites for ice bridge construction from an engineering and safety perspective. Project results also indicate that channel blockage due to ice-bridge ice growth would not be a problem where water depths were expected to be greater than 2 meters deep. However, the hydraulic impact of ice bridges on upstream and downstream channels under normal operating conditions and upon collapse in the spring are unknown. Observations and energy balance considerations indicate that temperature increases from upstream to downstream are somewhat dependent on stream channel
orientation, width and riparian buffer height and presents throughout its course. We anticipate additional useful results as the project advances.
Publications
- No publications reported this period
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Progress 01/01/00 to 12/31/00
Outputs
This project is dealing with several questions associated with the direct and indirect effects of timber harvest activities on stream temperature regime. The focus is on answering, or at least exploring, questions pertinent to interior Alaska streams: Can ice-bridges increase ice thickness such that fish or fish habitat might be negatively affected? Can we predict how ice thickness will respond to alteration in construction techniques and weather? How does summer water temperature change as a function of downstream distance, regardless of local buffering by riparian vegetation? Finally, can stream temperature be affected by broad-scale changes in watershed vegetative cover independent of riparian buffers? We will be exploring these questions by a combination of literature reviews, simulation experiments, and field measurements. We have just completed a review of historic ice-thickness measurements for Alaskan streams and rivers, as well as the literature related to
ice-bridge construction and experiences and the possible effects of river ice or ice bridges on fish habitat. This preliminary information will be supplemented with photos and measurements made on actual ice-bridges constructed in the interior as opportunity allow. Knowing undisturbed river ice thickness in a channel segment from historical records or from ongoing measurements, various models of ice growth as a function of freezing-degree-days will be tested. We anticipate using a layered model to account for ice thickness changes associated with either build-up of ice bridge surfaces or with the removal or compaction of snow. To understand the changes in summer stream temperatures with distance downstream we will be making stream temperature measurements on selected streams and also using a range of simple to complex computer models to explore the dynamics of water temperature and sensitivity to riparian shade. This project is in its early stages. However, an annotated bibliography
on ice thickness data and ice-bridge construction has been completed. Several candidate models of ice growth and water temperature dynamics have been identified and will next be obtained and/ or programmed for this project's use. In addition, a multi-layered model of river freezing with snow cover is being modified for use in this project.
Impacts
The annotated bibliography and literature review of ice thickness and ice-bridges has already been incorporated into discussions and a report released by the Science and Technology Committee appointed to help review riparian standards under the Alaska Forest Practices Act for interior Alaska. We anticipate additional useful results as the project advances. Preliminary results indicate that channel blockage due to ice-bridge ice growth would not be a problem where water depths were expected to be greater than 2 meters deep. Preliminary analysis of summer water temperature data taken for a stream on the Kenai Peninsula, indicates that observed increases in temperature from upstream to downstream are of the order of increase expected from energy exchange independent of riparian buffer modification.
Publications
- Fox, J.D. and Robert Ott. Ice thickness and ice bridges: An Annotated Bibliography. In: Welborn, M. (ed.) Region III Forest Resources & Practices Riparian Management Annotated Bibliography. Compiled by Region III Science/Technical Committee. Report to the Alaska Board of Forestry. AK DNR Division of Forestry, and AK Dept. of Fish & Game. August 2000. , pp. 103-126.
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Progress 01/01/99 to 12/31/99
Outputs
This is the first reporting period for this project that has the following objectives: 1.) to review the literature on ice-bridge design and consult with local foresters, loggers, and road engineers to document current local practices. 2.) to establish the utility of ice-thickness prediction schemes in forecasting the effect of ice-bridges on river-ice thickness for interior Alaska conditions. 3.) investigate the natural regimen of stream water temperature with distance downstream, and review models that might be used to extend site specific and year specific results to be useful for planning and regulatory purposes, and 4.) perform a review and analysis of the potential effects of watershed surface changes on groundwater and steam baseflow temperatures. Progress to date has been to complete a draft of the ice-bridge annotated bibliography, isolation of candidate models for ice-thickness calculations, and models for stream energy balance and water temperature
estimation. The completed bibliography will be submitted to the State of Alaska Dept. of Natural Resources and the interagency Stream Classification Committee for Region III which is reviewing the riparian standards of the State Forest Practices Act. Work on other objectives is continuing.
Impacts
This project aims to help resolve current controversies over the impact of ice-bridges on fish habitat. The results should help develop strategies for the protection and restoration of important fish habitats without sacrificing completely the benefits of land resource utilization.
Publications
- No publications reported this period
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