H32B-01 INVITED 10:20h
Approaches and Applications of Physically-based, Spatially-distributed Integrated surface / subsurface flow modeling
Physically-based, spatially-distributed (PBSD) modeling of integrated surface water and groundwater flow is necessary for evaluating the complex processes of runoff, recharge, evapotranspiration, subsurface flow, and baseflow, to comprehensively manage water resources for diverse and competing needs such as conjunctive use, aquifer storage and recovery, flood protection, wetland restoration and minimum flow evaluation. Some current approaches to PBSD modeling of integrated surface and subsurface flow will be discussed. Challenges to PBSD integrated modeling will be presented, and application case studies will be presented.
H32B-02 10:35h
Integrated Basin-Scale Modelling and Assessment: Lessons and Challenges in Linking Biophysical and Socioeconomic Sciences for Enhancing Sustainability Outcomes
Integrated Assessment (IA) and Integrated Scenario Modelling (ISM) are being increasingly used to assess sustainability options and, in particular, the effects of policy changes, land use management, climate forcing and other uncontrollable drivers on a wide range of river basin outcomes. IA and ISM are processes that invoke the necessary range of biophysical and socioeconomic disciplines and embrace stakeholder involvement as an essential ingredient. The authors report on their IA studies in Australian and Asian river basins. They illustrate a range of modelling frameworks and tools that were used to perform the assessments, engage the relevant interest groups and promote systems understanding and social learning. The studies cover a range of issues and policies including poverty alleviation, industrial investments, infrastructure provision, erosion and sedimentation, water supply allocation, and ecological protection. The positive impacts of these studies are presented, as well as the lessons learnt and the challenges for modellers and disciplinary experts in advancing the reputation and performance of integrated assessment exercises.
http://icam.anu.edu.au
H32B-03 10:50h
HydroSphere: Fully-Integrated, Surface/Subsurface Numerical Model for Watershed Analysis of Hydrologic, Water Quality and Sedimentation Processes
A distributed, physically based and fully-coupled surface/subsurface numerical model, HydroSphere, has recently been developed for watershed analysis of hydrologic and water quality processes. It accounts for flow and transport in lateral two-dimensional surface water, one-dimensional tile drains and three-dimensional variably-saturated subsurface water. One-, two- and three-dimensional forms of the advection-dispersion equation are used to describe solute transport in the tile drains, surface water and subsurface water, respectively. Full integration of the surface, tile-drain and subsurface water regimes is achieved by assembling and solving one system of discrete algebraic equations, such that surface flow rates and water depths, tile-drain flow rates and water depths, subsurface pressure heads, saturations and velocities, as well as water fluxes between continua, are determined simultaneously. Likewise, discrete advective-dispersive transport equations for the various continua are solved simultaneously to obtain the solute concentrations in the surface, tile-drain and subsurface systems. One of the major issues calling for capabilities of surface/subsurface water interactions, water quality and erosion/sedimentation is the optimal management of water supply for fish and agricultural irrigation. For example, the USGS has demonstrated that the massive September 2002 fish-kill in the Klamath River Basin was caused by low 2002 streamflows and the resulting high water temperatures. The streams in the Klamath River Basin are fed primarily by ground water. The 2002 streamflows were lower than the flows predicted by Bureau of Reclamation based on the snowpack data alone, neglecting subsurface water data. It is also well-known that erosion/sedimentation processes impair fish habitat by impacting spawning gravel areas and upstream migration to spawning areas. The models currently being applied in the Klamath River Basin and in all Bureau of Reclamation Regions completely neglect surface/subsurface water interaction, or use sequential time lag or iterative approach. Given the limitations of these models with respect to surface/subsurface water interaction, it is imperative to enhance HydroSphere with additional capabilities to make it applicable to the major problems being faced in Western U.S. watersheds. In this paper, incorporation of capabilities to simulate temperature, dissolved oxygen, biochemical oxygen demand and erosion/sedimentation processes into HydroSphere is presented. The two-dimensional surface water representation of HydroSphere will also be extended to three dimensional, with expected benefit to process simulation in lakes/reservoirs.
H32B-04 11:05h
A Conceptual Framework for SAHRA Integrated Multi-resolution Modeling in the Rio Grande Basin
The sustainable management of water resources in a river basin requires an integrated analysis of the social, economic, environmental and institutional dimensions of the problem. Numerical models are commonly used for integration of these dimensions and for communication of the analysis results to stakeholders and policy makers. The National Science Foundation Science and Technology Center for Sustainability of semi-Arid Hydrology and Riparian Areas (SAHRA) has been developing integrated multi-resolution models to assess impacts of climate variability and land use change on water resources in the Rio Grande Basin. These models not only couple natural systems such as surface and ground waters, but will also include engineering, economic and social components that may be involved in water resources decision-making processes. This presentation will describe the conceptual framework being developed by SAHRA to guide and focus the multiple modeling efforts and to assist the modeling team in planning, data collection and interpretation, communication, evaluation, etc. One of the major components of this conceptual framework is a Conceptual Site Model (CSM), which describes the basin and its environment based on existing knowledge and identifies what additional information must be collected to develop technically sound models at various resolutions. The initial CSM is based on analyses of basin profile information that has been collected, including a physical profile (e.g., topographic and vegetative features), a man-made facility profile (e.g., dams, diversions, and pumping stations), and a land use and ecological profile (e.g., demographics, natural habitats, and endangered species). Based on the initial CSM, a Conceptual Physical Model (CPM) is developed to guide and evaluate the selection of a model code (or numerical model) for each resolution to conduct simulations and predictions. A CPM identifies, conceptually, all the physical processes and engineering and socio-economic activities occurring (or to occur) in the real system that the corresponding numerical models are required to address, such as riparian evapotranspiration responses to vegetation change and groundwater pumping impacts on soil moisture contents. Simulation results from different resolution models and observations of the real system will then be compared to evaluate the consistency among the CSM, the CPMs, and the numerical models, and feedbacks will be used to update the models. In a broad sense, the evaluation of the models (conceptual or numerical), as well as the linkages between them, can be viewed as a part of the overall conceptual framework. As new data are generated and understanding improves, the models will evolve, and the overall conceptual framework is refined. The development of the conceptual framework becomes an on-going process. We will describe the current state of this framework and the open questions that have to be addressed in the future.
H32B-05 INVITED 11:20h
Transforming Nexrad Radar Rainfall Maps to Flood Inundation Maps
The Arc Hydro geographic data model for representing water resources features of the landscape is a customization of ArcGIS for representation of water resources features of the landscape. Arc Hydro is used here to integrate the HEC-HMS and HEC-RAS flood simulation models so as to transform Nexrad radar rainfall data into flood inundation maps through the HEC models. An automated workflow sequence is established using Map2Map: an ArcGIS version 9 toolbox and Model Builder that accomplishes all the desired data transformations between the GIS and the two hydrologic models including time series data exchange for rainfall, flows and water surface elevations. An example application is presented for Salado and Rosillo Creeks in San Antonio.
http://www.crwr.utexas.edu/gis/gishydro04/index.htm
H32B-06 11:35h
Everglades restoration and the search for a supermodel
Integrated watershed management in South Florida has evolved over the past century as a necessity. The densely developed South Florida Coast and the Everglades are inextricably linked through hydrology. Agriculture and urban development were made possible by draining the Everglades. Ironically, without the vast store of water provided by the Everglades to the Biscayne Aquifer, the intense development of the South Florida Coast would not have been impossible. The impacts of early Everglades drainage were felt almost immediately and water managers in South Florida quickly learned that the management of Lake Okeechobee and the Everglades effected social, economic and natural systems throughout South Florida. South Florida Water Management District engineers were pioneers in integrated watershed management, developing a watershed management model for South Florida in the early 1970s. This model has evolved over the years and continues to be the only model available for integrating the complex dynamics of water management and hydrology from Lake Okeechobee to Florida Bay. With the authorization of an extensive 30 year project to restore the Everglades, the need for better and more sophisticated modeling approaches is apparent. Numerous efforts are underway to develop models that simulate all or part of the complex interactions between physical, biological and social systems that drive the management of the South Florida hydrology. What remains elusive is a unified vision for integrated modeling to meet the needs of the entire system. The key questions in reaching a unified vision relates to modeling strategy. Should there be a single model that addresses all of the management issues, i.e. a supermodel, or should there be an assortment of models that address individual management issues independently? Currently, efforts are underway following both approaches. Issues are explored that arise from these efforts including trade-offs between scale and detail, the dangers of over-simplification, balance between complexity and over-parameterization, the need for transparency and flexibility, ways to include uncertainty and risk, and efficient use of limited scientific and engineering resources. Recommendations are made for a modeling approach that allows for maximum flexibility using a diverse set of models in an intergrated modeling environment.
http://www.evergladesplan.org
H32B-07 11:50h
Options and Consequences: Water Banking/Leasing Issues Explored for the Rio Grande in Southern New Mexico
Since 1950, the demand for water has more than doubled in the United States. Historically, growing demands have been met by increasing reservoir capacity and through groundwater mining, often at the expense of environmental and cultural concerns. The future is expected to hold much the same. Demand for water will continue to increase particularly in response to the expanding urban sector, while growing concerns over the environment are prompting interest in allocating more water for in-stream uses. So, where will this water come from? Virtually all water supplies are allocated. Providing for new uses requires a reduction in the amount of water dedicated to existing uses. The water banking/leasing model is formulated within a system dynamics context using the object oriented commercial software package, Powersim Studio 2003. System dynamics provides a unique mathematical framework for integrating the natural and social processes important to managing natural resources and can provide an interactive interface for engaging the public in the decision process. These system level models focus on capturing the broad structure of the system, specifically the feedback and time delays between interacting subsystems. The spatially aggregated models are computationally efficient allowing simulations to be conducted on a PC in a matter of seconds to minutes. By employing interactive interfaces, these models can be taken directly to the public or decision maker. To demonstrate the water banking/leasing model, application has been made to potential markets on the Rio Grande. Specifically, the model spans the reach between Elephant Butte Reservoir (central New Mexico) and the New Mexico/Texas state line. Primary sectors in the model include climate, surface and groundwater, riparian and aquatic habitat, watershed processes, water quality, water demand (residential, commercial, industrial, institution, and agricultural), economics, policy, and legal institutions. Within the model the basin is divided into four distinct but interacting reaches and a monthly time-step is employed. River operations and water demand trends have been calibrated to historical data.
H32B-08 12:05h
Using an Integrated Hydrologic-Economic Model to Develop Minimum Cost Water Supply Portfolios and Manage Supply Risk
Water scarcity has become a reality in many areas as a result of population growth, fewer available sources, and reduced tolerance for the environmental impacts of developing the new supplies that do exist. As a result, successfully managing future water supply risk will become more dependent on coordinating the use of existing resources. Toward that end, flexible supply strategies that can rapidly respond to hydrologic variability will provide communities with increasing economic advantages, particularly if the frequency of more extreme events (e.g., drought) increases due to global climate change. Markets for established commodities (e.g., oil, gas) often provide a framework for efficiently responding to changes in supply and demand. Water markets, however, have remained relatively crude, with most transactions involving permanent transfers and long regulatory processes. Recently, interest in the use of flexible short-term transfers (e.g., leases, options) has begun to motivate consideration of more sophisticated strategies for managing supply risk, strategies similar to those used in more mature markets. In this case, communities can benefit from some of the advantages that water enjoys over other commodities, in particular, the ability to accurately characterize the stochastic nature of supply and demand through hydrologic modeling. Hydrologic-economic models are developed for two different water scarce regions supporting active water markets: Edward Aquifer and Lower Rio Grande Valley. These models are used to construct portfolios of water supply transfers (e.g., permanent transfers, options, and spot leases) that minimize the cost of meeting a probabilistic reliability constraint. Real and simulated spot price distributions allow each type of transfer to be priced in a manner consistent with financial theory (e.g., Black-Scholes). Market simulations are integrated with hydrologic models such that variability in supply and demand are linked with price behavior. Decisions on when and how much water to lease (or exercise, in the case of options) are made on the basis of anticipatory rules based on the ratio of expected supply to expected demand, and are used to evaluate the economic consequences of a utility attitude toward risk. The marginal cost of supply reliability is also explored by varying the water supply reliability constraint, an important consideration as the rising expense of new source development may encourage some communities to accept a nominal number of supply shortfalls. Results demonstrate how changes in the distribution of various transfer types within a portfolio can affect its cost and reliability. Results also suggest that substantial savings can be obtained through the use of market-based risk management strategies, with optimal portfolio costs averaging as much as 35 percent less than the costs of meeting reliability targets through the maintenance of firm capacity. Both the conceptual and modeling approach described in this work are likely to have increasing application as water scarcity continues to drive the search for more efficient approaches to water resource management.