Texas Administrative Code › Title 30 - ENVIRONMENTAL QUALITY › Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY › Chapter 298 - ENVIRONMENTAL FLOW STANDARDS FOR SURFACE WATER › Subchapter G - BRAZOS RIVER AND ITS ASSOCIATED BAY AND ESTUARY SYSTEM › Section 298.475 - Schedule of Flow Quantities

Current through Reg. 49, No. 28; July 12, 2024
(a)
				  Schedule of flow quantities. The environmental flow standards adopted by this
				  subchapter constitute a schedule of flow quantities made up of subsistence
				  flow, base flow, and high flow pulses. Environmental flow standards are
				  established at 20 separate measurement locations in §
										298.480
				  of this title (relating to Environmental Flow Standards).
(b) Subsistence flow. The applicable
				  subsistence flow standard varies depending on the seasons as described in
				  §
										298.455 of
				  this title (relating to Definitions). For a water right holder to which an
				  environmental flow standard applies, at a measurement point that applies to the
				  water right, the water right holder may not store or divert water unless the
				  flow at the measurement point is above the applicable subsistence flow standard
				  for that point. If the flow at the applicable measurement point is above the
				  subsistence flow standard but below the applicable dry condition base flow
				  standard, then the water right holder must allow the applicable subsistence
				  flow, plus 50% of the difference between measured streamflow and the applicable
				  subsistence flow, to pass its measurement point and any remaining flow may be
				  diverted or stored, according to its permit, subject to senior and superior
				  water rights, as long as the flow at the measurement point does not fall below
				  the applicable subsistence flow standard.
(c) Base flow. The applicable base flow level
				  varies depending on the seasons as described in §
										298.455 of
				  this title and the hydrologic condition described in §
										298.470
				  of this title (relating to Calculation of Hydrologic Conditions). For a water
				  right holder to which an environmental flow standard applies, at a measurement
				  point that applies to the water right, the water right holder is subject to the
				  base flow standard for the hydrologic condition prevailing at that time. For
				  all measurement points, the water right will be subject to one of the
				  following: a dry, an average, or a wet base flow standard. For a water right
				  holder to which an environmental flow standard applies, at a measurement point
				  that applies to the water right, when the flow at the applicable measurement
				  point is above the applicable base flow standard, but below any applicable high
				  flow pulse levels, the water right holder may store or divert water according
				  to its permit, subject to senior and superior water rights, as long as the flow
				  at the applicable measurement point does not fall below the applicable base
				  flow standard for that hydrologic condition except during dry conditions as
				  described in subsection (b) of this section.
(d) High flow pulses. High flow pulses are
				  relatively short-duration, high flows within the watercourse that occur during
				  or immediately following a storm event.
(1)
				  For all measurement points, one, two, three, or four pulses per season are to
				  be passed (i.e., no storage or diversion by an applicable water right holder),
				  if applicable, and as described in §
											298.480
				  of this title, if streamflows are above the applicable subsistence or base flow
				  standard, and if the applicable high flow pulse trigger level is met at the
				  applicable measurement point. The water right holder shall not divert or store
				  water until either the applicable volume amount has passed the applicable
				  measurement point or the duration time has passed since the high flow pulse
				  trigger level occurred except during times that streamflow at the applicable
				  measurement point exceeds the applicable high flow pulse trigger level. A water
				  right holder can divert water in excess of an applicable pulse flow trigger
				  requirement as long as its diversions do not prevent the occurrence of the
				  pulse flow trigger level of an applicable larger pulse.
(2) If the applicable high flow pulse trigger
				  level does not occur in a season, then the water right holder need not stop
				  storing or diverting water to produce a high flow pulse. The water right holder
				  is not required to release water lawfully stored to produce a high flow
				  pulse.
(3) Each season is
				  independent of the preceding and subsequent seasons with respect to high flow
				  pulse frequency.
(4) High flow
				  pulses at the applicable measurement point are dependent on the hydrologic
				  conditions set out in §
											298.470
				  of this title.
(5) For measurement
				  points in the Brazos River Basin described in §
											298.480(7)
				  - (8)  of this title, if a pulse flow
				  requirement for the large seasonal pulse is satisfied for a particular season,
				  one of the smaller pulse requirements is also considered to be satisfied for
				  that season.