Software Screenshots
Tuolumne River, CA
Project: Tuolumne River Watershed
Results screens from HFAM analysis runs, water resource facilities’ operations, environmental analysis, and simulation model calibration
HFAM executes hydrologic simulation applications for the operation and design of water resource facilities and both the planning and environmental analysis of watershed behavior.
HFAM Screenshots illustrate typical results and standard data requirements for operating HFAM.
Applications of continuous hydrologic simulation methods require a time series of continuous hydrometeorological data, as well as physical data, on watersheds and water resource facilities. To simplify these data, HFAM includes a comprehensive database for hydrometeorological time series.
Hydrologic models are not reliable unless they represent continuously observed watershed behavior in the region where they are applied. Calibration is essential.
Calibration of HFAM is done for all applications. HFAM matches continuously simulated and observed streamflows and snow depths and includes a variety of tools for the calibration of model parameters.
Design of Water Resource Facilities
The HFAM analysis runs investigate the designs of water resource facilities. The runs are long-term simulations of 30 to 80 years depending on the available historical meteorological data in the watershed.
Watershed behavior is modeled with and without new facilities. Analysis runs show continuous:
STREAMFLOW
SNOWPACKS
GENERATION
DIVERSIONS
RESERVOIR LEVELS
RESERVOIR VOLUME
Statistical summaries of flood frequency, watershed soil moisture, snowpacks, streamflows, hydro generation, reservoir releases, and other time series are available
A common design problem is spillway capacity analysis, for new or existing dams. When you calibrate HFAM, you may model probable maximum meteorologic conditions. HFAM long-term analysis runs made for the period of available historical hydrometeorological records provide the most severe, or runoff producing, initial watershed conditions for the probable maximum event. Probable maximum meteorologic conditions vary seasonally, as do extreme runoff producing initial conditions. The probable maximum flood for a river is the largest flood found by combining probable maximum meteorologic conditions and initial watershed conditions in any season.
HFAM results screens for continuous time series from Analysis runs
This plot shows the total snowpack water content above a reservoir during the spring snowmelt season. You can plot a snow water equivalent at a selected location and elevation for comparison to a snow course or snow pillow measurement. Data required for snow accumulation and melt simulation are hourly air temperature (derived if necessary from max-min daily), wind movement, and solar radiation (or cloud cover).
This display shows a powerhouse that is operating on a user defined weekly schedule. Between May 5th and May 11th, HFAM defaults to full powerhouse capacity to avoid spill. Generation schedules can be set as time series or as yearly patterns.
A common design problem is spillway capacity analysis, for new or existing dams. When you calibrate HFAM, you may model probable maximum meteorologic conditions. HFAM long-term analysis runs made for the period of available historical hydrometeorological records provide the most severe, or runoff producing, initial watershed conditions for the probable maximum event. Probable maximum meteorologic conditions vary seasonally, as do extreme runoff producing initial conditions. The probable maximum flood for a river is the largest flood found by combining probable maximum meteorologic conditions and initial watershed conditions in any season.
Statistical summaries of watershed behavior and facilities operations are available from HFAM long-term Analysis runs. Results produced include flood frequency, and statistical summaries for soil moistures, snowpacks, generation, reservoir releases, and other time series. Typical results screens for statistical summaries of long-term HFAM Analysis runs are;
Flood frequency for alternative flood control policies, or for the watershed before construction of the dam can be plotted.Flood frequency from long-term HFAM Analysis runs is compared to flood frequency at stream gages. HFAM will also create conditional, near-term flood frequency, e. g. flood frequency over the next six weeks.
These results are used in studies of reservoir or power plant expansions, or in studies of the long-term effects of new constraints for reservoir elevations or instream flows.
Current year snowpack water equivalent for any date can be compared to these long-term exceedance probabilities based on historical records.
Operation of Water Resource Facilities
Operational Decisions depend on what will happen over relatively short future periods of time, from a few hours to one or two years. HFAM Forecast and Probabilistic runs investigate such decisions. Watershed behavior over a relatively short future period is conditional; it is dependent on current snowpacks, soil moistures, and perched groundwater levels.
Typical results from Forecast runs are streamflows, or reservoir outflows and hydro generation;
Results are based on a meteorological forecast for the December 4th to December 18th period. These results are used for operations over the next day or several days. The model runs are repeated as real-time data is collected and as weather forecasts change. Forecast runs use only one meteorological forecast, and they typically show future conditions for only a few days. Probabilistic runs use many ‘alternate’ future meteorologic conditions based on the historical weather at that time of year and will show future conditions for weeks or months.
Typical results from Probabilistic runs are;
In this example, the current date is August 17th, 1997. A fixed weather forecast is used between August 17th and August 24th, 1997, so other weather samples do not begin until August 25th. The future release/generation schedule that is used in this model run is too large, and the reservoir has greater than 50% probability of reaching minimum pool by February 1st, 1998.
Conditional flood frequency can be significantly different than traditional or long-term flood frequency. Reservoir operations benefit by correctly anticipating the runoff and flood conditions for the current time, rather than using long-term averages.
Generation forecasts are used to plan energy purchases or sales, and to schedule hydro energy in combination with energy from other sources.
Planning and Environmental Analysis
The hydrologic effects of changing land use in watersheds, often due to urbanization, forestry or agriculture, are investigated with HFAM Analysis runs. The hydrologic effects of changes to stream channels such as building levees, or introducing spreading basins to increase infiltration to groundwater aquifers, can be investigated. The HFAM model parameters that represent watershed characteristics can be adjusted to represent altered conditions.
Land use changes often increase or decrease runoff volumes and reservoir yields, and cause runoff flow path changes. Changes to channel reaches, e.g. increased energy loss due to friction or increased cross-sections, will alter downstream peak flows and flood frequency.
Hydrometeorological Data Management
Typical data management operations are reading or writing files of time series data, in commonly used hydrometeorological data formats.
HFAM includes three independent hydrometeorological data bases for forecast, real-time and historical data. Each of these databases handles all types of data series on hourly or daily time steps. Databases are indexed using a 4-digit year to avoid the year 2000 ambiguity. HFAM utilizes historic rainfall and potential evapotranspiration data (usually estimated from Pan records) in all watersheds. Additional data series (air temperature, wind movement, and solar radiation/cloud cover) are used where snow accumulation and melt are significant. Historic streamflows are used for HFAM calibration.
Simulation Model Calibration
Simulated and observed comparisons are made using HFAM Analysis runs for streamflows, snow depths, and water equivalent, reservoir stage or volume, or other data as available. HFAM compares simulated and observed flood frequency and flow duration curves. HFAM includes tools to compare mean monthly simulated and observed flow volumes, and plots alternative measures of ‘differences’ between simulated and observed monthly flows.
Additional HFAM screens (not included) show precipitation, rainfall or liquid water reaching the land surface, runoff from the land surface, and runoff in river channels in the same units (Ac-ft or Mm3).
HFAM model calibration is based on solving the water balance equation for a watershed continuously. HFAM models all hydrologic flow paths that contribute to streamflow. The timing of runoff during the year is one measure of the model’s ability to represent constant soil moisture and perched groundwater processes in response to seasonally variable precipitation and potential evapotranspiration time series.
Flow duration curves plotted over the period of record at a streamgage are useful for calibration. HFAM also executes these plots seasonally and monthly. Duration curves are sensitive to simulation model flow path assignments; lower flows are primarily based on groundwater flows. Note: Excel created the flow duration plot above rather than HFAM 1.1. HFAM II has internal flow duration plots.
In HFAM calibration all aspects of watershed behavior; i. e., continuous hydrographs, runoff volumes, monthly and seasonal runoff distributions, flow duration curves and flood frequency, are simulated over many years. Model parameters are adjusted until the model and prototype, HFAM and the watershed being studied, behave very similarly. With comprehensive long-term continuous calibration HFAMwill model watershed behavior for meteorologic sequences that were not included in the calibration period.
