California Rapid Assessment Method for Wetlands - State Water ...

California Rapid Assessment Method for Wetlands v. 5.0.2 – Chapter 4
C. Seasonality: Water source should be evaluated during the dry season.
D. Office and Field Indicators: The assessment of this metric is the same for all wetland types.
It can be assessed initially in the office using the site imaging, and then revised based on the field
visit. For all wetlands, this metric focuses on direct sources of non-tidal water as defined above.
The natural sources will tend to be more obvious than the unnatural sources. Evaluation of this
metric should therefore emphasize the identification of the unnatural sources or diversions that
directly affect the dry season conditions of the AA.
The office work should initially focus on the immediate margin of the AA and its wetland, and
then expand to include the smallest watershed or storm drain system that directly contributes to
the AA or its immediate environment, such as another part of the same wetland or adjacent
reach of the same riverine system within about 2km upstream of the AA. Landscape indicators
of unnatural water sources include adjacent intensive development, irrigated agriculture, and
wastewater treatment discharge.
The typical suite of natural water sources differs among the wetland types. The effects of
changing the natural sources or modifying them also differ among the types. The following
discussion may be helpful in understanding these differences and recognizing them in the field.
Estuarine: This metric is focused on the non-tidal water sources that account
for the aqueous salinity regime of the AA during the early and middle months
of the dry season, regardless of the time of year when these sources exist. The
focus is usually on the tidal water that enters and exits the AA across the
associated foreshore, as well as any local freshwater seeps or artificial sources
of non-saline water that enter the site across its backshore. To assess the water
source, the plant species composition of the wetland should be compared to
what is expected, in terms of the position of the wetland along the salinity
gradient of the estuary, as adjusted for the overall wetness of the water year. In
general, altered sources are indicated by vegetation that is either more tolerant
of saline conditions or less tolerant than would be expected. If the plant
community is unexpectedly salt-tolerant, then an unnatural decrease in
freshwater supply is indicated. Conversely, if the community is less salt-tolerant
than expected, than an unnatural increase in freshwater is indicated.
Slope Wetlands: Ground water is the source of water for seeps and springs
(i.e., slope wetlands). It is generally expected that the source is perennial and
relatively constant in volume throughout most years. The water source can be
assessed, therefore, based on plant indicators of its permanence and
consistency. The hydrologic needs of many plant species commonly found in
wetlands have been determined (Reed 1988).
Riverine, Depressional, Lacustrine, and Playas: The natural sources of
water for these wetlands are mainly direct rainfall, groundwater discharge,
runoff, and riverine flows. Whether the wetlands are perennial or seasonal,
alterations in the water sources result in changes in either the high water or low
water levels. Such changes can be assessed based on the patterns of plant
growth along the wetland margins or across the bottom of the wetlands.
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