A dynamically-coupled groundwater, land surface and regional climate model to predict seasonal watershed flow and groundwater response, FINAL LDRD REPORT.
This final report is organized in four sections. Section 1 is the project summary (below), Section 2 is a submitted manuscript that describes the offline, or spinup simulations in detail, Section 3 is also a submitted manuscript that describes the online, or fully-coupled simulations in detail and Section 3, which is report that describes work done via a subcontract with UC Berkeley. The goal of this project was to develop and apply a coupled regional climate, land-surface, groundwater flow model as a means to further understand important mass and energy couplings between regional climate, the land surface, and groundwater. The project involved coupling three distinct submodels that are traditionally used independently with abstracted and potentially oversimplified (inter-model) boundary conditions. This coupled model lead to (1) an improved understanding of the sensitivity and importance of coupled physical processes from the subsurface to the atmosphere; (2) a new tool for predicting hydrologic conditions (rainfall, temperature, snowfall, snowmelt, runoff, infiltration and groundwater flow) at the watershed scale over a range of timeframes; (3) a simulation of hydrologic response of a characteristic watershed that will provide insight into the certainty of hydrologic forecasting, dominance and sensitivity of groundwater dynamics on land-surface fluxes; and (4) a more realistic model representation of weather predictions, precipitation and temperature, at the regional scale. Regional climate models are typically used for the simulation of weather, precipitation and temperature behavior over 10-1000 km domains for weather or climate prediction purposes, and are typically driven by boundary conditions derived from global climate models (GCMs), observations or both. The land or ocean surface typically represents a bottom boundary condition of these models, where important mass (water) and energy fluxes are approximated. The viability and influence of these approximations on the predictions is not well understood because of the detail and complexity in land and subsurface processes and the need for computational efficiency. However, theoretical and experimental data suggest that these interactions may have a profound impact upon hydrologic and climatic budgets and weather predictions. Conversely, land-surface and groundwater models are typically applied on smaller domains (< 10 km in scale) to analyze runoff, streamflow, infiltration, evapotranspiration behavior, but are still influenced in many ways by couplings with the atmosphere (as in precipitation and temperature). Atmospheric inputs to these classes of models are typically represented as simplified ''upper'' boundary conditions, derived, in part, from coarse observations, uncoupled simulations, or other idealized simplifications. In this project, we developed a framework to couple these models by developing a new land-surface/subsurface model and coupling it to a regional climate model at the same temporal and spatial scales. We focused the coupling to examine the role of important mass and energy couplings between these models as a means to understand the difference between traditional and detailed approaches to this interconnection. From this understanding of these interconnections, we were able to determine to what extent these connections need to be abstracted or preserved in modeling atmospheric, land-surface and groundwater interactions. We have found a strong connection between groundwater dynamics (i.e. aquifer storage) and energy fluxes at the land surface and in the Atmospheric Boundary Layer (ABL). The following papers outline this connection theoretically, demonstrate it with coupled modeling and propose strategies for better observing it in real settings.
- Research Organization:
- Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 902346
- Report Number(s):
- UCRL-TR-228343; TRN: US200717%%549
- Country of Publication:
- United States
- Language:
- English
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