HEC-DSS (Hydrologic Engineering Center – Data Storage System) is a standardized data format used to store, manage, and exchange hydrologic time-series data. DSS files are widely used in hydrologic modeling workflows to maintain consistent, accessible datasets. Data in a DSS file is organized using a structured pathname system, where each part of the pathname conveys specific information about the dataset. Understanding these pathnames is essential for accessing, analyzing, and interpreting time-series data in hydrologic models.
In CivilGEO’s software, the DSS Data File & Path dialog box allows the user to select the DSS file and the time series data records stored within it. To learn more about the DSS Data File & Path dialog box, refer to this article in our knowledge base.
HEC-DSS Pathnames
A DSS file organizes its datasets into pathnames, which may contain up to 391 characters. Each pathname is conventionally divided into six parts, with each part allowing up to 64 characters. The standard naming convention for pathname parts is listed below:
| Part | Description |
|---|---|
| A | Project, river, or basin name |
| B | Location |
| C | Data parameters (e.g., FLOW, PRECIP) |
| D | Starting date of block, in a 9-character military format (dd/mm/yyyy) |
| E | Time interval |
| F | Additional user-defined descriptive information |
Each part of the pathname has a specific purpose, such as identifying the project, location, data type, time interval, or scenario. Among these, Part C is important because it defines the type of data stored in the DSS file, such as streamflow, precipitation, losses, canopy storage, soil moisture, routing flows, and more.
What is Part C?
- Part C is also known as the Descriptor.
- Part C identifies the variable, parameter, or data type for both regular and irregular interval time series data. This allows the software to recognize, retrieve, process, and plot the correct data from a DSS file.
- Standard Part C descriptors are predefined to maintain consistency across projects.
Note: The availability of descriptors is project-specific and depends on which hydrologic methods (such as loss, transform, routing, or reservoir) are being used.
List of HEC-DSS Part C Descriptors
HEC-DSS provides a wide range of standard Part C descriptors for different hydrologic modeling purposes. These descriptors can represent either computed data or manually entered values. The following table lists the commonly used standard HEC-DSS Part C descriptors:
| Descriptor | Description |
|---|---|
| AREA | Computed area for a reservoir element. |
| ATI-COLD | Computed antecedent temperature index for cold content in the snowmelt method. |
| ATI-COLDRATE | Manually entered antecedent temperature index versus cold-rate function (paired data). |
| ATI-MELT | Computed antecedent temperature index for melt-rate in snowmelt. |
| ATI-MELTRATE | Manually entered antecedent temperature index versus melt-rate function (paired data). |
| COLD CONTENT | Computed cold content in snowmelt. |
| CROP COEFFICIENT | Manually entered cross section in the paired data manager. |
| ELEVATION | Computed pool elevation for a reservoir element. |
| ELEVATION-AREA | Manually entered elevation-area function defined in the paired data manager. |
| ELEVATION-OBSERVED | Observed pool elevation for a reservoir element using an optional observed elevation time-series gage. |
| ELEVATION-RESIDUAL | Residual elevation for a reservoir element with observed elevation. The residual is calculated as computed flow minus the observed elevation. |
| ELEVATION-STORAGE | Manually entered elevation-storage function defined in the paired data manager. |
| ET-CANOPY | Computed actual evapotranspiration from the canopy layer in the soil moisture accounting loss method. |
| ET-SOIL | Computed actual evapotranspiration from the soil layer in the soil moisture accounting loss method. |
| ET-SURFACE | Computed actual evapotranspiration from the surface depression layer in the soil moisture accounting loss method. |
| EXCESS-CANOPY | Computed incremental precipitation minus canopy interception in the soil moisture accounting loss method. |
| FLOW | Final computed flow for an element. |
| FLOW-AUX | Outflow from a reservoir through the auxiliary discharge. |
| FLOW-BASE | Computed baseflow for a subbasin element. |
| FLOW-COMBINE | Computed total inflow to an element. |
| FLOW-DIRECT | Surface flow computed by transforming excess precipitation for a subbasin element. |
| FLOW-DIVERSION | Computed diversion flow for a diversion element. |
| FLOW-IN | Total inflow to a reach element. |
| FLOW-LOCAL | Local flow at a junction when the basin model is set to compute local flow at junctions. |
| FLOW-LOCAL-SIM | Computed local flow without blending for a junction when observed flow is present, blending is used, and the basin model is set to compute local flow at junctions. |
| FLOW-LOSS | At a reach, the computed channel losses. |
| FLOW-OBSERVED | Observed flow for an element using the optional observed flow time-series gage. |
| FLOW-RESIDUAL | Residual flow for an element with observed flow. The residual is calculated as computed flow minus the observed flow. |
| FLOW-SIM | Computed flow without blending at an element when observed flow is present, and blending is used. |
| FLOW-UNIT GRAPH | Manually entered unit hydrograph in the paired data manager. |
| GROUNDMELT | Manually entered annual ground-melt pattern in the paired data manager. |
| INFILTRATION | Computed infiltration from the surface layer to the soil in the soil moisture accounting loss method. Also, the amount of loss attributed to infiltration in the deficit constant loss method. |
| LIQUID WATER | Computed liquid water in the snowpack in snowmelt. |
| MELTRATE | Manually entered annual melt-rate pattern in the paired data manager. |
| MOISTURE DEFICIT | Computed moisture deficit in the deficit constant and gridded deficit constant loss methods. |
| OUTFLOW-GW | Computed outflow from a groundwater layer to channel baseflow in the soil moisture accounting loss method. |
| PERC-SOIL | Computed percolation from the soil layer to the upper groundwater layer in the soil moisture accounting loss method. |
| PERC-GW | Computed percolation from the upper groundwater layer to the lower groundwater layer or from the lower groundwater layer out of the system in the soil moisture accounting loss method. |
| PERCENT-GRAPH | Manually entered percentage curve in the paired data manager. |
| PRECIP-EXCESS | At a subbasin, incremental precipitation minus losses. |
| PRECIP-EXCESS-CUM | At a subbasin, cumulative precipitation minus cumulative losses. |
| PRECIP-CUM | Cumulative precipitation for a time-series gage. |
| PRECIP-INC | Incremental precipitation for a time-series gage or subbasin element. |
| PRECIP-LOSS | At a subbasin, the incremental precipitation that was converted to loss during loss calculations. |
| PRECIP-LOSS-CUM | At a subbasin, the cumulative precipitation that was converted to loss during loss calculations. |
| PRECIP-LWASS | The liquid water available at the soil surface calculated for a subbasin by a snowmelt method. |
| PRECIP-LWASS-CUM | The cumulative liquid water available at the soil surface calculated for a subbasin by a snowmelt method. |
| PRECIP-STAND DEV | At a subbasin, the standard deviation of incremental precipitation for each time interval computed using gridded precipitation. |
| RECOVERED DEFICIT | Computed recovery of the deficit by evapotranspiration in the deficit constant and gridded deficit constant loss methods. |
| SATURATION FRACTION | The percentage of the soil layer that is saturated in the deficit and constant or soil moisture accounting loss methods. |
| SOLAR RADIATION | Manually entered time-series of solar radiation for a time-series gage. |
| STAGE | Computed stage for an element when the optional elevation-discharge curve is used. Also, manually entered time-series of stage for a time-series gage. |
| STAGE-CHANNEL | Stage computed in the channel at a diversion element. |
| STAGE-FLOW | A manually entered elevation-discharge function defined in the paired data manager. |
| STAGE-OBSERVED | Observed stage for an element using the optional observed stage time-series gage. |
| STAGE-RESIDUAL | Residual stage for an element with observed stage. The residual is calculated as computed flow minus the observed flow. |
| STAGE-SIM | Stage at a reach using the modified Puls or Muskingum Cunge routing methods computed using the simulated flow depth. |
| STAGE-TAILWATER | The computed tailwater stage at a reservoir element. |
| STAGE-TW-AUX | The computed tailwater stage at the auxiliary discharge from a reservoir element. |
| STORAGE | Computed storage for a reservoir element. |
| STORAGE-CANOPY | Computed storage depth of the canopy layer in the soil moisture accounting loss method. |
| STORAGE-ELEVATION | A storage-elevation curve defined in the reservoir element. No longer used in the current program version. |
| STORAGE-FLOW | A manually entered storage-discharge function defined in the paired data manager. |
| STORAGE-GW | Computed storage depth of a groundwater layer in the soil moisture accounting loss method. |
| STORAGE-SOIL | Computed storage depth of the soil layer in the soil moisture accounting loss method. |
| STORAGE-SURFACE | Computed storage depth of the surface layer in the soil moisture accounting loss method. |
| SWE | Computed snow water equivalent in snowmelt. |
| SWE-OBSERVED | Observed snow water equivalent for a subbasin element using the optional observed SWE time-series gage. |
| SWE-RESIDUAL | Residual snow water equivalent for a subbasin element with observed SWE. The residual is calculated as computed flow minus the observed SWE. |
| TEMPERATURE | Computed temperature for a subbasin elevation band in snowmelt. Also, manually entered time-series of temperature for a time-series gage. |