Florida Administrative Code › 40 - WATER MANAGEMENT DISTRICTS › 40C - St. Johns River Water Management District › Chapter 40C-8 - MINIMUM FLOWS AND LEVELS › Section 40C-8.021 - Definitions

Current through Reg. 50, No. 138; July 16, 2024
Unless the context indicates otherwise, the following terms
				  shall have the following meanings.
(1)
				"Black Water Creek" means that watercourse designated Black Water Creek within
				the Wekiva River Hydrologic Basin as defined by Rule
				 40C-41.023, F.A.C.
(2) "Determined minimum surface water flow"
				means a flow, expressed in cubic feet per second combined with a temporal
				element. The temporal element may be specifically expressed as a duration and
				return interval or may be generally expressed as a hydroperiod
				category.
(3) "Determined minimum
				surface water level" means an elevation in feet NGVD combined with a temporal
				element. The temporal element, for purposes of this chapter may be specifically
				expressed as a duration and return interval or may be generally expressed as a
				hydroperiod category.
(4)
				"Intermittently exposed" means a hydroperiod category where surface water is
				present throughout the year except in years of extreme drought. In most lakes
				this category does not typically support emergent vegetation and would be
				characterized as open water or floating-leaved deep marsh. Water levels causing
				inundation are expected to occur more than ninety percent of the time over a
				long term period of record.
(5)
				"Intermittently flooded" means a hydroperiod category where the substrate is
				usually exposed, but surface water is present with variable frequency and
				duration. Water levels causing inundation are expected to occur on average
				approximately once every ten years or more. Years may intervene between periods
				of inundation. On recharge lakes (sandhill type lakes), the dominant vegetation
				growing at this elevation can change as soil moisture conditions change, from a
				dominance of upland species to wetland species or the reverse. Duration of
				inundation is on the order of several months. Water levels are expected to
				inundate less than two per cent of the time over a long term period of
				record.
(6) "Long term" or "long
				term period of record" means at least a 30 year continuous period.
(7) "Minimum frequent high" means a
				chronically high surface water level or flow with an associated frequency and
				duration that allows for inundation of the floodplain at a depth and duration
				sufficient to maintain wetland functions.
(8) "Minimum infrequent high" means an
				acutely high surface water level or flow with an associated frequency and
				duration that is expected to be reached or exceeded during or immediately after
				periods of high rainfall so as to allow for inundation of a floodplain at a
				depth and duration sufficient to maintain biota and the exchange of nutrients
				and detrital material.
(9) "Minimum
				average" means the surface water level or flow necessary over a long period to
				maintain the integrity of hydric soils and wetland plant communities.
(10) "Minimum frequent low" means a
				chronically low surface water level or flow that generally occurs only during
				periods of reduced rainfall. This level is intended to prevent deleterious
				effects to the composition and structure of floodplain soils, the species
				composition and structure of floodplain and instream biotic communities, and
				the linkage of aquatic and floodplain food webs.
(11) "Minimum infrequent low" means an
				acutely low surface water level or flow with an associated frequency and
				duration which may occur during periods of extreme drought below which there
				will be a significant negative impact on the biota of the surface water which
				includes associated wetlands.
(12)
				"NAVD" means North American Vertical Datum of 1988.
(13) "NGVD" means National Geodetic Vertical
				Datum of 1929.
(14) "P25" means the
				percentile ranking represented by the elevation of the water surface or the
				flow of the spring or surface water that is equaled or exceeded 25 percent of
				the time as determined from a long-term water level or flow time
				series.
(15) "P50" means the
				percentile ranking represented by the elevation of the water surface or the
				flow of the spring or surface water that is equaled or exceeded 50 percent of
				the time as determined from a long-term water level or flow time
				series.
(16) "P75" means the
				percentile ranking represented by the elevation of the water surface or the
				flow of the spring or surface water that is equaled or exceeded 75 percent of
				the time as determined from a long-term water level or flow time
				series.
(17) "Permanently flooded"
				means a hydroperiod category where water covers the land surface throughout the
				year in all years. Vegetation, if present, is composed of aquatic
				macrophytes.
(18) "Phased
				Restriction" means the level or flow (based on the past 30 consecutive day
				average level or flow) at which a water use shortage phase (Phase I-IV as
				defined by Rule  40C-21.251, F.A.C.), is declared
				and its associated restrictions imposed.
(19) "Seasonally flooded" means a hydroperiod
				category where surface water is typically present for extended periods (30 days
				or more) during the growing season, resulting in a predominance of submerged or
				submerged and transitional wetland species. During extended periods of normal
				or above normal rainfall, lake levels causing inundation are expected to occur
				several weeks to several months every one to two years.
(20) "Semi-permanently flooded" means a
				hydroperiod category where surface water inundation persists in most years.
				When surface water is absent the water table is usually near the land surface.
				In many lakes with emergent marshes this water level is near the lower
				elevation that supports emergent marsh or floating vegetation and peat
				substrates, or other highly organic hydric substrates. This characterization
				may not be true for herbaceous wetlands around sandhill type lakes, which often
				have emergent vegetation that follows declining water levels to below the lower
				elevation of peat substrate. Water levels causing inundation are expected to
				occur approximately eighty percent of the time over a long term period of
				record. Exposure of these ground elevations is expected to re-occur, on
				average, about every five to ten years for extended periods (several or more
				months) during moderate droughts.
(21) "Temporarily Flooded" means a
				hydroperiod category where surface water is present or the substrate is flooded
				for brief periods (up to several weeks) approximately every five years. Plants
				of upland and wetland species are characteristic. The composition of the
				vegetation at this water level is dependant upon whether the flooding
				predominantly occurs in the growing season, whether seepage from higher
				elevations is pronounced, and the nature of the soil. Lake water levels are
				expected to equal or exceed this elevation five per cent of the time or less
				over a long term period of record.
(22) "Typically saturated" means a
				hydroperiod category where for extended periods of the year the water level
				should saturate or inundate. This results in saturated substrates for periods
				of one-half year or more during non-flooding periods of typical years. Water
				levels causing inundation are expected to occur fifty to sixty per cent of the
				time over a long term period of record. This water level is expected to have a
				recurrence interval, on the average, of one or two years over a long term
				period of record. Obligate wetland plant species are expected to be predominate
				near this water level.
(23) "Wekiva
				River" means that watercourse designated Wekiva River within the Wekiva River
				Hydrologic Basin as defined by Rule
				 40C-41.023,
				F.A.C.
Rulemaking Authority
					 373.044,
					 373.113 FS. Law Implemented
					 373.042,
					 373.103,
					 373.415
					 FS.
New 9-16-92, Amended 8-17-94, 6-8-95, 3-19-02, 6-25-14,
					 1-30-19, 9-28-21.