Research and Development Office

Climate Change: Application of HydroGeoSphere (HGS) Thermal (Temperature) Modules for Evaluation of The Impacts of Climate Change on Water Resources and Fish Ecosystems

Project ID: 3821
Principal Investigator: George Matanga
Research Topic: Water Supply Forecasting
Priority Area Assignments: 2010 (Climate Change and Variability Research)
Funded Fiscal Years: 2010
Keywords: None

Research Question

HGS is a comprehensive, robust hydrologic modeling tool with the capability for simulation of fully-integrated surface/subsurface water flow and solute/thermal transport model. By providing a holistic and physically-based representation of the hydrologic system, HGS is well suited for assessing climate-change impact analysis of water resources, as well as ground water resources. The impact of climate change on ground water is not direct in some cases. Hence the impact-analysis on ground water may need evaluations of the interactions between surface water and ground water. Hence HGS is valuable for such problems due to its capability to handle fully-coupled surface/subsurface flow systems.

HGS's capability to handle thermal (temperature) transport in an integrated manner renders the model valuable for evaluating fish-health in ecosystems. Furthemore, HGS is the only numerical model that can be used, for example, to evaluate impacts of ground water. It is also valuable for identifying recharge areas in which cold water is most likely to be found.

Using downscaled general circulation model (GCM) data, apply HGS to generate plausible climate change scenarios for the select hydrologic basin and investigate the following questions:

* What is the range of predicted stream temperatures under expected climate change scenarios?

* Under which scenarios, if any, does the predicted stream temperatures pose a risk to fish health? What insight does the model provide to mitigate such scenarios?

* What impact do the climate change scenarios have on reservoir volumes, streamflow, and correspondingly, power generation?

* Can the same predictive temperature and flow results provided by HGS be achieved using MODFLOW/GSFL?

Need and Benefit

Climate change and its impact on stream temperature and flows are key issues impacting water resources in California, and pose challenges for sustainable water resource management. To address water resource management issues in California, various Federal and State agencies, including Reclamation and the California Department of Water Resources, have utilized modeling to gain further insight into hydrological and operational dynamics. Computer models are indispensable tools for effective water resource management and climate-change impact analysis. As part of this effort, Reclamation and partners (HydroGeoLogic, University of Waterloo and Laval University) have developed HGS, an integrated surface-subsurface water model.

Ecologists have long been aware of the importance of interactions between the surface, subsurface and atmosphere on the overall health of a water body. Dickinson et al. (1998) note that "Interactions between land and the atmosphere affect not only standard climatic parameters, such as moisture and temperature, but also determine the presence and productivity of natural and managed ecosystems." Recent research has demonstrated that the interaction between the surface and subsurface may be an important contributor to the thermal conditions in surface water bodies through the discharge of ground water (Woessner 2000, Brunke and Gonser 1997). The evaluation of climate change on basin scale hydrology requires a capable, robust hydrological model. Physically-based fully integrated surface-subsurface models can assess these impacts in a holistic manner without the need for iterative-coupling between systems, an approach prone to mass balance errors and other inefficiencies. In combining integrated surface-subsurface simulation capability with thermal transport, HGS is a unique and extremely powerful climate change simulation tool.

There are a number of Reclamation programs and activities that require assessment of water temperature as an indicator of ecosystem health and sustainability. The San Joaquin River Restoration settlement in California, for example, focuses on the restoration of historic Chinook salmon populations in the river. Climate change induced increases in stream temperature impacts fish health, requiring consideration of water temperature in the design and evaluation of specific restoration plans. Reclamation faces similar issues elsewhere, for example in the restoration of the Klamath River, Oregon. Use of HGS takes steps towards a more integrated approach to assessing stream temperature concerns. This need is required in Reclamation regions affected by ecological restoration and studies involving fish-health.

Funding of the proposed work will enhance Reclamation's need to address climate change aspects including impacts on stream temperatures, fish health, streamflows, reservoir volumes and power generation.

Contributing Partners

Contact the Principal Investigator for information about partners.

Research Products

Bureau of Reclamation Review

The following documents were reviewed by experts in fields relating to this project's study and findings. The results were determined to be achieved using valid means.

HydroGeoSphere: A Robust Hydrologic Modeling Tool (final, PDF, 60KB)
By George Matanga
Publication completed on September 30, 2010

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