Data Needs

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

  • Current and forecasted precipitation scenarios.
  • Data describing the present state of watershed, including channels and water management facilities (reservoirs, diversions, and other controllable system features).
  • Information on the likely future conditions (e.g., from one hour to two weeks) of the watershed.
  • Insights into the consequences of management actions that affect the future states of both natural and managed systems.

An HEC-RTS watershed consists of data, information, models, and images that represent the watershed's land areas, channels, gages, and water control 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 future water availability. For example, they can predict runoff from a watershed hours or even days in advance based on past, current, or predicted rainfall. To do this, water managers rely on mathematical models that simulate processes like infiltration, overland flow, baseflow, channel flow, and other relevant watershed and channel dynamics.

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 control 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 watershed response to precipitation, producing outputs such as flow data throughout the watershed including inflows to reservoirs and runoff downstream of 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 simulations. It provides outputs such as water surface elevations, depth grids, and inundation maps based on flow data.
  • HEC-FIA (Flood Impact Analysis) to estimate the consequences of water surface elevations throughout the system, such as economic damages and potential life loss.

HEC-RTS enables water managers to easily access up-to-date information on the current and predicted states of a watershed. This is achieved through effective information-sharing technology, including specialized websites for data dissemination.