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Bay-Delta Office
Department of Water Resources

1416 9th Street,
Sacramento, Ca 95814

Mailing Address:
P. O. Box 942836,
Sacramento, Ca 94236-0001

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 REALM
  Project Contact
Eli Ateljevich
Email: eli-sava@pacbell.net
Phone: 916-653-5111

Introduction
REALM -- River, Estuary, and Land Model -- is a project started and funded by the California Department of Water Resources to develop a new model and decision support system for managing short-term operations in the Sacramento-San Joaquin Delta and its tributaries, and for planning long-term structural changes such as a Through-Delta Facility or South Delta operational gates. We are working with strategic partners such as Lawrence Berkeley National Laboratory and model-savvy GIS developers so that REALM will be able to handle a broader set of practical problems using high-performance numerical techniques tailor-fit to estuary, tide and flooding applications.

Our initial product is a 2D model. We believe that accurate, adaptive 2D computation represents the most beneficial contribution to the current range of delta simulation tools, balancing physical realism with the potential for longer simulation. We intend to add optimized 1D modeling and adaptive nested 3D computation in future releases for handling regions where the flow characteristics are particularly stratified or channelized.

Problem Background
The Sacramento-San Joaquin Delta is experiencing drastic declines in pelagic organisms, simultaneous with increased demand for water from the Delta. Policy makers are asking the Bay-Delta engineering and scientific community for answers to difficult hydrodynamic, water quality, and biological questions which current computer models are not able to provide in a timely or accurate manner. Furthermore, possible catastrophic failures in the Delta, such as levee collapses and the interruption of water supplies to the south, are difficult to analyze with existing models.

We believe the quality of modeling tools available should be commensurate with the societal, economic, and environmental importance of the water issues facing California. The scientific questions that confront us are expanding to include difficult physics such as moving flood fronts and evolving shorelines, greater scope and varied levels of required detail. No single computational engine can be handle these requirements, but a good technical design can envision the problems of the near future and allow a compatible, efficient suite of tools for simulating estuary problems.

The REALM Project
REALM is motivated by two concerns:

  • The need to improve model credibility and the range of problems that models can solve, by increasing the accuracy and speed of existing simulation models. Poor or unknown accuracy is a barrier to model credibility, and speed limits the scope of problems that can be analyzed.
  • The need to significantly increase the usefulness of models to policy-makers. Through interviews and our own experiences in practical modeling, we have identified techniques that are critical to continue solving the Department’s and California’s complex and difficult water issues in the Delta, tributaries, and bays. We also have collaborations to help develop systems tools such as a real-time data assimilation system.

In order to achieve flexibility and accuracy over a diverse range of problems, we emphasize two key techniques: adaptive computation and embedded boundaries. Adaptive mesh refinement (AMR) is a nested gridding technique that allows the model to concentrate computational detail in regions that are difficult or interesting. Nested grids (an even fraction of the coarser grid) might occur because of a flood front, abrupt change in concentration or because of a user request for detail. Embedded boundaries are a technique for representing complex or natural domains such as a bay or channel within a rectangular Cartesian grid. The advantage of embedded boundaries over other conforming methods such as unstructured grids is that the boundary can evolve accurately in response to tides or floods.

REALM will support better operational analysis and decision-making with the following features:

  • Real-time operation of the Delta using data assimilation, a mathematical mechanism for integrating measured data with an active model run. REALM’s statistical filters will allow field data to be folded into the model as it becomes available, constantly balancing model error and measurement noise and always maintaining a modeling system that is “ready to go” using the best possible depiction of current conditions.
  • Policy-based management of the Delta using model steering, where modeled values (water flow, depth, and quality) are monitored, and gates or pumps operated adaptively according to operating rules written by the decision maker. For instance, gates in the Delta could be opened or closed when computed values of water quality or depth reach pre-determined limits.
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