Below are products used to support CEFF. This page will be updated as the project progresses.

Hydrologic Stream Classification and Dimensionless Reference Hydrographs

Hydrologic Stream Classification
Hydrologic Stream Classification
Map of the Reach-Scale Hydrologic Classification of California National Hydrography Dataset Streams (excluding Strahler first order 380 streams).

Hydrologic classification is a strategy for distinguishing groups of stream reaches with similar streamflow characteristics for regional water management efforts. We developed a hydrologic classification for California that is specific enough to make critical distinctions between natural streamflow patterns (also called natural flow regimes), but general enough to support the development of environmental flow targets in altered stream reaches across the state. The classification identified nine natural stream classes with distinct streamflow patterns that are the result of several characteristics of rainfall-runoff response, including: dominant water source (snowmelt, rain, groundwater), hydrologic attributes (mean annual flow, extreme low flow duration and timing, etc), climate setting (mean annual precipitation, mean August and January precipitation, etc.) and topographic and geologic setting (slope, catchment area, dominant rock type, soils compositions, etc.).

The results of the hydrologic stream classification are available to view interactively and download here.  Further details about the classification are described in Lane et al 2018



Dimensionless reference hydrographs (DRHs) of the nine reconciled stream classes identified in California: Snowmelt (SM), Low-volume Snowmelt and Rain (LSR), High-volume Snowmelt and Rain (HSR), Winter Storms (WS), Rain and seasonal Groundwater (RGW), Groundwater (GW), Perennial Groundwater and Rain (PGR), Flashy Ephemeral Rain (FER), and High elevation Low Precipitation (HLP)
Dimensionless Reference Hydrographs

Dimensionless Reference Hydrographs (DRHs) refer to unimpaired daily streamflow time series non-dimensionalized by average annual flow. These summary hydrographs form the basis for reference-based flow targets for each of the nine stream classes in California. For each stream class, dimensionless hydrographs, with confidence intervals representing the range of natural inter-annual variability, have been constructed for each reference gage and for all gages within the class combined.  The unimpaired reference hydrographs represent seasonal stream conditions without impairments from anthropogenic land use or upstream diversions or storage. 

The DRHs are available to view interactively here. Further details are described in Lane et al 2018.


Predicted Reference Functional Flow Metrics 

The Functional Flows Calculator and Observed Functional Flow Metrics 

The Functional Flows Calculator. 

The Functional Flows Calculator (FFC) is a web tool for visualizing, downloading, and exploring California's unimpaired streamflow patterns, including natural stream classes, DRHs, and functional flow metrics. 


Explore the FFC here


Guidance for Accessing Alteration



Ecological Indicators and Flow Metrics

Regional Fish Species Assembles and Suites of Umbrella Species
Identifying desired ecological outcomes and taxa of concern across the state is a key step in developing ecological flow regimes. Based on a literature review of documented relationships between aquatic species response and flow conditions, we found that data directly linking individual species to quantifiable flow components and metrics are lacking (Yarnell et al., 2020). In order to relate streamflow conditions directly to aquatic species community composition and life history requirements for taxa of concern, we developed an approach to determine regional fish assemblages across California that are geographically distinct and, thus, are assumed to have evolved under similar historical hydrologic conditions. The purpose of this analysis was to provide a unit (i.e., fish assemblages and a suite of umbrella species) upon which to base flow management recommendations in order to reach a biological outcome broader than a single-species approach to the development of ecological flow regimes and environmental flow prescriptions.

The results of this analysis are displayed on the web map below and in the attached tables.

Benthic Macroinvertebrates and Functional Flows

Flow Form Function

Geomorphic Classification


Tradeoff Evaluation Tool

Impaired Stream Classification and Flow Alteration Assessment

Case Studies and Synthesis 

Metadata Template