Data Needs

To make informed operational decisions, water managers need the following: 

  • Current and forecasted precipitation scenarios.
  • Data representing current information about the watershed and its features.
  • Information on the likely future conditions (e.g., from one hour to two weeks) of the watershed.
  • Impacts of management decisions within the watershed.

An HEC-RTS watershed consists of data, information, models, and images that represent the watershed's land areas, channels, gages, and water management features.

Data describing the current state of the system is collected through a network of environmental sensors. These sensors, owned and operated by federal, state, and local agencies, utility companies, and commercial enterprises, measure:

  • Weather conditions, including air temperature, precipitation amounts and rates, and evaporation rates.
  • Watershed conditions, such as snow accumulation.
  • Depth, velocity, and other conditions in streams, rivers, canals, and other waterways.
  • Lake or reservoir levels (from which storage volume can be inferred), water release rates through outlets, spillway gate settings, and other conditions.

By using the environmental data as inputs to models of watershed and channel processes, water managers can forecast the future state of the basin. For example, they can predict runoff hours or even days in advance based on past, current, or predicted precipitation. To do this, water managers rely on mathematical models that simulate natural processes such as infiltration, overland flow, baseflow, channel flow, etc..

An HEC-RTS forecast simulates watershed processes and the potential consequences of flooding based on input data, through the use of hydrologic, reservoir operation, hydraulic, and impact analysis models. The forecast results include flow and stage data in the channels from watershed runoff, reservoir release schedules, floodplain inundation maps, reports on floodplain impacts, and action recommendations for emergency responders. These results provide crucial information to support water management decision-making.

Using models of water management facilities, water managers can simulate and evaluate the impacts of different operational alternatives. For instance, a water manager can assess which of two operational strategies is more likely to result in higher downstream water levels during a large storm. This is made possible by forecasting future inflows and using a mathematical model to simulate the reservoir’s behavior and the downstream channel. One operational alternative might be to release water immediately from a rapidly filling reservoir to accommodate future inflows. Alternatively, the manager could delay the release, anticipating that inflows will decrease and large releases will not be necessary. With analysis software, the manager can compare these alternatives in a quantitative way. The simulation results provide valuable insights into the economic, environmental, safety, and other consequences of each option, helping the manager make more informed decisions.

Data Flow and Integration

HEC-RTS uses a data exchange mechanism to link selected analysis software for forecasting, ensuring that the software applications are executed in a coordinated manner. Data and other inputs are transferred between applications through the HEC-DSS data exchange software.

These tools include:

  • HEC-MetVue (Meteorological Visualization Utility Engine) to process observed and forecasted meteorological data (e.g., precipitation, temperature).
  • HEC-HMS (Hydrologic Modeling System) to simulate the hydrologic response to precipitation, producing outputs such as flow data throughout the watershed (e.g., inflows to reservoirs).
  • HEC-ResSim (Reservoir System Simulation) to model the behavior of reservoirs and connecting channels to help make reservoir release decisions based on inflows and environmental conditions.
  • HEC-RAS (River Analysis System) to model the behavior of channels and adjacent floodplains using either one- or two-dimensional hydraulic simulations, producing outputs such as depth grids and inundation maps.
  • HEC-FIA (Flood Impact Analysis) to estimate the consequences of water surface elevations throughout the system, such as economic damages and potential life loss.