Texas Administrative Code › Title 30 - ENVIRONMENTAL QUALITY › Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY › Chapter 298 - ENVIRONMENTAL FLOW STANDARDS FOR SURFACE WATER › Subchapter F - NUECES RIVER AND CORPUS CHRISTI AND BAFFIN BAYS › Section 298.425 - Schedule of Flow Quantities

Current through Reg. 49, No. 28; July 12, 2024
(a)
				  Schedule of flow quantities. The environmental flow standards proposed in 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 19 measurement points in §
										298.430
				  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 §
										298.405 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 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 §
										298.405 of
				  this title. For a water right holder, 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) 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 §
											298.430
				  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. 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 flow
				  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 are applicable under both subsistence and base flow
				  conditions.
(5) If a pulse flow
				  requirement for a medium or large seasonal pulse or an annual pulse is
				  satisfied for a particular season or year, one of each of the applicable
				  smaller pulse requirements is also considered to be satisfied.