Texas Administrative Code › Title 30 - ENVIRONMENTAL QUALITY › Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY › Chapter 298 - ENVIRONMENTAL FLOW STANDARDS FOR SURFACE WATER › Subchapter E - GUADALUPE, SAN ANTONIO, MISSION, AND ARANSAS RIVERS, AND MISSION, COPANO, ARANSAS, AND SAN ANTONIO BAYS › Section 298.375 - 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 for 16 measurement points in §
										298.380
				  of this title (relating to Environmental Flow Standards) and this
				  section.
(b) Subsistence flow. The
				  applicable subsistence flow standard varies depending on the seasons as
				  described in §
										298.355 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. For measurement points in the Guadalupe River Basin, if the
				  flow at the applicable measurement point is above the subsistence flow standard
				  but below the 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.
				  For measurement points in the San Antonio River Basin and the San
				  Antonio-Nueces Coastal Basin, during dry hydrologic conditions, if the flow at
				  the applicable measurement point is above the subsistence flow standard but
				  below the applicable dry 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 points 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
				  §
										298.355 of
				  this title, and the hydrologic condition described in §
										298.370
				  of this title (relating to Calculation of Hydrologic Conditions) for river and
				  coastal basins to which a hydrologic condition applies. For a water right
				  holder in the San Antonio River Basin or the San Antonio-Nueces Coastal Basin,
				  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, i.e., the water
				  right holder will be subject to one of the following: a dry, an average, or a
				  wet base flow standard. For a water right holder in the Guadalupe River Basin,
				  to which an environmental flow standard applies, at a measurement point that
				  applies to a water right, the water right holder is subject to a 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 trigger 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.
(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 measurement points in the Guadalupe River Basin, one or two 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 §
											298.380
				  of this title, if the flows 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 except during times that streamflow at the applicable measurement point
				  exceeds the applicable high flow pulse trigger level and until either the
				  applicable volume amount has passed the measurement point or the applicable
				  duration time has passed since the high flow pulse trigger level
				  occurred.
(2) For measurement
				  points in the San Antonio River Basin and the San Antonio-Nueces Coastal Basin,
				  one, two, or three 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 §
											298.380
				  of this title, if the flows are above the applicable base flow standard, and if
				  the applicable high flow pulse trigger level is met at the applicable
				  measurement point. For the measurement points described in §298.380(c)(12)
				  - (15) of this title, the water right holder shall not divert or store water
				  until the daily average flow at the applicable measurement point equals at
				  least the large high flow pulse trigger level on consecutive days equaling the
				  duration time, except during times that streamflow at the applicable
				  measurement point exceeds the applicable high flow pulse trigger level. For all
				  other measurement points in the San Antonio River Basin and the San
				  Antonio-Nueces Coastal Basin and for small seasonal pulses at the measurement
				  points described in §298.380(c)(12) - (15) of this title, the water right
				  holder shall not divert or store water except during times that streamflow at
				  the applicable measurement point exceeds the applicable high flow pulse trigger
				  level and until either the applicable volume amount has passed the measurement
				  point or the duration time has passed since the high flow pulse trigger level
				  occurred.
(3) If the applicable
				  high flow pulse flow trigger level does not occur in a season, then the water
				  right holder need not stop storing or diverting to produce a high flow pulse.
				  The water right holder is not required to release water lawfully stored to
				  produce a high flow pulse.
(4) Each
				  season is independent of the preceding and subsequent seasons with respect to
				  high flow pulse frequency and each time-period is independent of each other
				  time-period with respect to high flow pulse frequency.
(5) High flow pulses are independent of the
				  hydrologic conditions set out in §
											298.370
				  of this title, for measurement points for which a hydrologic condition is
				  applicable. For all other measurement points, high flow pulses are applicable
				  under both subsistence and base flow conditions.
(6) For measurement points in the Guadalupe
				  River Basin, the San Antonio River Basin and the San Antonio-Nueces Coastal
				  Basin, except those described in §298.380(c)(12) - (15) of this title, if
				  a pulse flow requirement for a large seasonal pulse is satisfied for a
				  particular season, one of the smaller pulse requirements is also considered to
				  be satisfied. For measurement points described in §298.380(c)(12) - (15)
				  of this title, if a pulse flow requirement for a large seasonal pulse is
				  satisfied, all smaller pulse requirements for the applicable season are also
				  considered to be satisfied.