Watershed Setup

Tuolumne River Area
Project: Tuolumne River Watershed

Learn about model preparation, data, input files, and calibration

Setup a new HFAM application in 4 Steps

Prepare for Modeling

Prepare Time Series Data

Create HFAM Input Files

Calibrate HFAM

STEP 1 Prepare for Modeling

Project planning and data preparation are the foundation of HFAM applications. It is not unusual for these two tasks to account for more than half of the effort in a modeling analysis.

First, define the goals of the study. Hydrocomp’s clients run HFAM for multiple objectives. Which hydrologic processes and operations are essential?

The next task is to collect data and information. Historical streamflow records for calibration, historical meteorological data, reservoir operations data, and maps are required. Also, identify sources of real-time meteorological data.

To build HFAM’s model components, define the watershed land segments, reaches, and reservoirs. HFAM requires channel and land surface metrics, as well as sub-watershed drainage areas. Assign HFAM index numbers to the model components.

Step 2 Prepare Time Series Data

Historical hydro-meteorological data is essential for analysis and model calibration. Streamflow, precipitation, and evaporation are required for all watersheds; temperature, wind, and solar radiation are inputs for snow simulation.

HFAM’s meteorological database must be complete for the period of analysis. Estimation of missing meteorological data requires similar stations with overlapping records. In most applications, records for both active and inactive stations will be correlated to develop a long historical record with optimal areal coverage. One-hour time intervals are preferred, but daily data may be disaggregated to one-hour intervals.

HFAM uses current and recent “real-time” data for forecasts. The HFAM DataPrep application automates preparation of data for short periods. Hydrocomp can set up HFAM DataPrep after the historical database is complete.

Step 3 CREATE HFAM INPUT FILES

HFAM’s input files customize HFAM to each unique watershed. Although HFAM input files are in the XML format, familiarity with XML is not required to update the files. Users can display, maintain, and modify most input files through the HFAM interface.

There are five standard types of HFAM files. Time series files serve as the application’s hydro-meteorological database. The HFAM Input file contains parameters. Other files specify the watershed’s initial condition at the beginning of the simulation and track available hydro-meteorological data. The HFAM Gateway file directs HFAM to all other input and output files.

Step 4 Calibrate HFAM

Calibration is the process of adjusting model parameters to represent the watershed by fitting simulated streamflow to observed streamflow. After selecting an initial set of parameters, choose a period of 5 to 10 years for which observed streamflow and meteorological data are available.

Calibration is a stepwise process. Begin by adjusting parameters that affect soil moisture and other key hydrologic processes on the land surface. Adjust parameters to reproduce the observed mean annual volumes. Next, calibrate to match seasonal volumes and, if snow occurs in the watershed, calibrate parameters for snow accumulation and melt. Finally, adjust parameters that control hydrograph shapes.

HFAM provides extensive tools and displays to aid in the calibration process. For users who have no experience with calibration, Hydrocomp provides customized training and workshops. The HFAM Help System guides new users of the HFAM model, and documents model setup, parameters, calibration.