Hydrological And Hydraulic Modeling

Water shortage, water pollution and flood impacts are among the most urgent problems in river management. The number of flood disasters worldwide has increased significantly in recent years. While this may partly be due to a changing climate, the additional utilization of flood plains for transportation corridors, housing, and agriculture also result in a reduction of the natural capacity of catchments to attenuate runoff.

Dams and reservoirs store water for power, potable water supply, and irrigation, and are also used to mitigate the potentially devastating effects of floods and droughts. At the same time they may have negative environmental and social impacts. There is therefore an increasing demand for detailed and accurate assessments of the environmental impacts of these facilities, and for optimizing operation of existing dams to minimize the adverse effects while maximizing the benefits. Effective management of water resources for agricultural uses can also benefit through efficient water use, predicting droughts or watering cycles through a combination of precipitation and soil moisture monitoring supported by hydrology modeling.

It is challenging to maintain quality water supplies to existing communities, let alone planning for the future growth. Much of the infrastructure utilized in the collection, treatment, and distribution of water is aging and requires assessment to determine the best replacement and rehabilitation strategies. Clean, efficient, and reliable water supplies ensure the sustainability of a community, with improved human health and economic viability. Wastewater planning is equally important for a community’s long term success. Efficient collection, treatment, discharge, and reclamation require water managers to leverage the best available technologies.

What is modeling and how can it improve the management of water resources?

Models can be used to characterize and predict the movement and quality of water. By simulating natural water processes, engineers, hydrologists and managers are able to isolate parts of the hydrologic cycle or their infrastructure system into manageable pieces to better understand the movement of water across the landscape and within engineered systems. Modeling can be conducted using physical scale models, empirical models, and numerical models. Physical scale models utilize constructed representations of the system of interest. Empirical models synthesize collected field data and utilize statistical relationships to study a system. Numerical models typically make use of computer programs to solve mathematical approximations of governing physical equations for water movement. Additionally, numerical models provide a means of moving beyond point-based measurements to develop a continuous and comprehensive picture of hydrologic conditions. Numerical models can be thought of as a way to enhance our understanding of data collected in the field.

Data collection is an integral aspect to model development. Quality data leads to quality model output, which leads to informed decision making. Without high quality data to calibrate and verify model output the results of a model are not useful. Reliable data is the foundation for the model development. Once the data has been input into the model and the appropriate parameters set, the next step is to calibrate the model to real world conditions using additional measured data. For example, rainfall measured by a tipping-bucket rain gauge or a stream flow measured by a flow monitor. Once you have verified that the model simulates real world conditions, and you have confidence the model is accurately reflecting natural processes, you can then modify the parameters or inputs and analyze these various scenarios and alternatives to better understand how to manage water resources.

Modeling the Earth’s natural processes has become an integral part of planning for future needs, preserving natural resources, designing and maintaining infrastructure, reducing costs and planning for natural disasters. Models facilitate the comparison of essentially unlimited scenarios. They allow us to cost-effectively allocate finite resources (water, financial or manpower). Models help us mitigate the financial and human impacts of flooding and to plan evacuation routes and priorities.

Organizations that are concerned with all aspects of the water environment, including water resources, agricultural utilization, urban infrastructure, and coastal and marine environments, all have an interest in computer generated hydraulic and hydrological models. This includes public agencies, private sector businesses, as well as academic research institutes, individuals and community groups. Examples of interested parties include: The US Federal Emergency Management Agency, The United States Geological Survey, Bureau of Reclamation, US Department of Agriculture, Natural Resources Conservation Service, local counties and cities, municipalities, flood control agencies, irrigation districts, water providers, and power utilities.

Use of sophisticated databases, numerical models, geographic information systems (GIS), and web technologies, embedded in highly intuitive graphical user interfaces with comprehensive visualization techniques and configurable decision logics, can greatly enhance water resources analyses and management. The collective use of these technologies is called decision support systems (DSS). DSSs enable users and decision makers to focus on the transparency and accessibility of results. Modeling and technology tools can then facilitate presentation of results to governmental institutions, private and public stakeholders as well as communities involved/interested in environmental and water resource issues.

DSSs, which integrates the components above, is a custom-made, flexible and dedicated management system, which will empower you to:

• Provide timely, transparent, well informed and reproducible answers to important questions
• Streamline business processes and workflows to reduce time and cost requirements
• Provide overview and structure of data and information
• Transform data and information into knowledge and produce understandable results and decisions
• Assist in developing new processes for the more efficient use of water, whether that is for conserving water for irrigation, optimizing hydropower generation, forecasting flood events or many others.

A DSS can include a number of interactive and integrated components:

Data and information management
The data and information component is integral in developing a DSS. This component focuses on integrating databases and connecting various data sets (islands) into a dynamic framework with advanced display, mapping, query and presentation capabilities.

Analysis and modeling
The data framework provides the basis for further analysis and interpretation of data and information. Depending on the stage and scope of the DSS the analysis can range from simple to complex using a wide range of models and tools.

Scenario management and alternative formulation
The DSS framework is capable of supporting and providing information for project feasibility and planning projects, including facilitating cost estimating and project prioritization. The DSS framework can also support design and implementation tasks, such as alternatives analysis and verification of project goals. Upon implementation the project may have an operations component requiring real time and online decision making.

Decision making
Configurable GIS and web-based interfaces are tailored to meet specific needs and requirements. Advanced graphics, online access, custom rules and interpretations can be embedded into the DSS to support and provide the basis for decision makers to make timely, reproducible and well informed decisions.

City of Vancouver, Washington

The population of the City of Vancouver, WA, has increased by approximately 9% since 2000. This rapid growth has been accompanied by an expansion of the City's service area. DHI, working for the City’s Engineering Services division, updated the sanitary sewer system hydraulic model, and calibrated it to dry weather flow.

The extent of the model was expanded to include areas that have undergone significant development. Additionally, the pressure sewer system, including fifteen pumping stations and approximately 20 miles of forcemain piping, were added to the model. The updated hydraulic model contains over 2,300 pipes total. The model was calibrated to dry weather flow, using gauging data from flow monitors located throughout the collection system.

San Francisco Bay, California

FEMA has contracted DHI, to undertake a Coastal Hazards Analysis FIS restudy for the Central region of the San Francisco Bay covering an area from the Golden Gate Bridge to the west, San Mateo Bridge to the south, and the Richmond Bridge to the north.

Phase 1 of this project was completed in August of 2005, and included data collection (LIDAR, bathymetry, water levels, etc), participating in community planning and coordination meetings, and finally developing a detailed modeling approach based on the field survey and historical data that was gathered. Phase 2 encompasses the execution of the detailed modeling approach developed under Phase 1, to perform the detailed coastal and riverine analysis and hazard zone determination, and finally to produce the detailed FEMA flood maps and DFIRMS. Hydrodynamic modeling (water levels, currents and waves) is performed using DHI’s MIKE 21 modeling.

Broward County, Florida

DHI was responsible for coordinating the development of an integrated water resources management master plan that evaluates a variety of alternative water supply sources and develop a plan capable of satisfying Broward County's 2025 water supply needs. In addition to meeting projected 2025 municipal and industrial water demands, the plan needed to:

1. maintain or improve the level of flood protection
2. prevent further saltwater intrusion in the Biscayne Aquifer
3. maintain seepage from adjacent water conservation areas at current levels
4. prevent adverse effects to protected or improved wetlands.

The DHI team was responsible for reconfiguring existing integrated surface and ground water models (MIKE SHE/MIKE 11) of the surface water and water table aquifer and a density-dependent regional ground water model (SEAWAT) to evaluate up to 45 alternative water supply projects. The models were modified to reflect 2025 land use and permitted withdrawals under typical and 1-in-10 year drought conditions. Results from the alternative analyses were used to eliminate under– and over-supply, reduce costs, meet 2025 water demands, and water resource goals for flood protection, saltwater intrusion, ground water seepage, and wetlands.

Hydrological and hydraulic modeling software is commercially available throughout the world. The most comprehensive suite of modeling software is the MIKE series of software developed by DHI. DHI is a pioneer in the field of numerical water modeling and has decades of experience modeling the world of water. For water modeling applications, Stevens Water Monitoring Systems recommends MIKE software by DHI.

DHI Water & Environment (DHI) is an independent, self-governing, research and consulting organization with corporate headquarters located just outside of Copenhagen, Denmark. International offices operate in North America, Europe, Australia, New Zealand, Asia and South America. Worldwide, DHI has a staff of approximately 900 people, the majority of whom are professional engineers and scientists with post-graduate qualifications and several years of consulting, research and development experience.

DHI offers a broad spectrum of services, software tools and model test facilities related to offshore, coastal, and port hydraulics; integrated water resources; river, lake, reservoir, water quality, and ecology; urban hydraulics; and environmental engineering. DHI is a full service research and consulting organization that is actively involved in many projects dealing with all aspects of the water environment.

DHI water modeling solutions include:

Urban Modeling

• Water Distribution Systems
• Stormwater Collection Systems
• Sanitary Collection Systems
• Wastewater Treatment Systems
• Real Time Control, Operation & Management
• Water Savings & Reuse
• Risk Assessment & Management

Water Resources Modeling

• Integrated Surface Water & Groundwater Systems
• Watershed Hydrology
• River, Lake & Reservoir Hydraulics
• River Channel Hydraulics and Sedimentation
• Water Use Planning, Management &Optimization
• Irrigation and Drainage
• Flood Forecasting & Management
• Total Maximum Daily Load (TMDL)

Marine Modeling

• Port & Harbor Hydrodynamics & Waves
• Coastal & Shoreline Morphology
• Marine Environments and Ecology
• Wave and/or current loads on structures
• Numerical Metocean hindcast & Forecast analysis
• Offshore Energy Resources
• Environmental Impact Assessments
• Physical Model Studies
• Coastal Zone & Shoreline Management
• Coastal Flooding