Occoquan Decision Support System


  • Climate Forecast System
  • National Weather Model
  • Supervisory Control And Data Acquisition


  • Upper Occoquan Service Authority
  • Maintenance Management System
  • Laboratory Information Management System


Optimal operation of water reclamation facilities (WRF) is critical for an indirect potable reuse system (IPR), especially when the reclaimed water constitutes a major portion of the safe yield, as in the case of the Occoquan reservoir located in northern Virginia. The area’s population growth increases the reclaimed water contribution to the reservoir. The reclaimed water contains nutrients resulting in an urgent need for timely and effective decision-making related to plant operations based on reservoir conditions. This study presents how a reservoir model is used for predicting future reservoir conditions based on the weather and stream flow forecasts obtained from the Climate Forecast System and the National Water Model. 

Courtesy: Mr. Snyder
Courtesy: UOSA​

The resulting model predictions provide valuable feedback to the operators for correctly targeting the effluent nitrates using a plant operations and optimization model called IViewOps. The system captures the time dynamic transformations in the nutrient loadings in the streams, withdrawals by the water treatment plant, WRF effluent flows, and the plant operations to manage nutrient levels based on nitrate assimilative capacity of the reservoir. The DSS can provide multiple stakeholders with a holistic view for design, planning, risk assessments, and potential improvements in various components of the water supply chain, not just in the Occoquan but in any reservoir augmentation type IPR system.

Data Flow

URUNME reads from various data sources dynamically and performs extensive data analysis and manipulation before feeding it to the model as inputs or storing it as historical trends. All the operations carried out during the entire simulation process are fully automated and use hundreds of functions in various process flow diagrams.


  • Climate Forecast System
  • National Weather Model
  • Supervisory Control And Data Acquisition


  • Upper Occoquan Service Authority
  • Hypolimnetic Oxygenation System
  • Water Treatment Plant

Operational Configuration

The reservoir model is operated once every week, running multiple future scenarios based on different combination of natural stream inflows, plant effluent flows and nitrate concentrations, and water withdrawal by the WTP.


The calibration scenario is run to evaluate the current model calibration using the last three years of observed data. It is used to validate whether the simulated water elevations, temperature, and different constituents are consistent with the values observed during the calibration period.  In case of unsatisfactory calibration performance for any water quality parameter, recalibration has to be done manually before running the remaining forecast scenarios.

A total of 24 forecast scenarios are run using various combinations of boundary conditions including (1) Forecasted  stream flows, (2) UOSA discharge, (3) UOSA effluent nitrate concentrations, and (4) WTP withdrawal. Two different forecasts are produced by the DSS: A 30-day forecast is based on NWM stream flows going out 30 days in the future. Long-range 90-day forecast, on the other hand, is used as a What-If-Analysis to simulate any worst-case scenario. For winter months, 90-day forecast is generally used to simulate an extended drought period and its effect on the reservoir. 



URUNME was used to develop a information-rich and user-friendly interactive dashboards to output the updated historical data and forecasting results for the stakeholders. URUNME employs a powerful graphic engine for data visualization. Multiple views can be used in the application to create different screens for the users. Creating a dashboard is as simple as adding a GUI element (chart, pivot table, gauge, map, grid, image, text, event manager, etc.) on the screen and dragging and dropping variables onto these panels for data binding. These GUI elements are automatically updated in case of any change to the underlying data (e.g. after a model run).

The DSS was setup using two separate projects in URUNME. The first project (model.urm) is responsible for running the integrated model and stores all the simulated and observed data in its embedded database (model.db). The database file is automatically uploaded to a dedicated FTP server after every model run. The second project (dashboard.urm) is created as an interactive dashboard, containing various menus and visual elements (charts, tables, diagrams, etc.) to show the most up-to-date futurecasting results and historical trends (shown below). The dashboard project updates its elements directly from the model.db file. URUNME, installed on the computer of different users, uses the dashboard project to download the most recent data from the server to update the outputs on a periodic basis. This structure allows multiple users to run the DSS dashboard application independent of the model implementation.

Main Screen

Other Screens


Every week, the DSS moves forward in time by predicting the reservoir water quality based on most recent initial and future boundary conditions. When the forecasted water quality going out 30 to 60 days is above the 3 mg/L Nitrate-N threshold, the DSS automatically run an optimization routine on IViewOps to determine means to reduce the nutrient discharge from the UOSA plant by simultaneously adjusting asset availability (changing maintenance schedules to bring unavailable assets such as reactors, clarifiers and pumps back online) and operational setpoints.