Texas Administrative Code › Title 30 - ENVIRONMENTAL QUALITY › Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY › Chapter 298 - ENVIRONMENTAL FLOW STANDARDS FOR SURFACE WATER › Subchapter H - RIO GRANDE, RIO GRANDE ESTUARY, AND LOWER LAGUNA MADRE › Section 298.525 - 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 flows, and high flow pulses. Environmental flow standards are
				  established for five measurement points in §
										298.530
				  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 §
										298.505 of
				  this title (relating to Definitions) and hydrologic conditions, as described in
				  §
										298.520
				  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 may not store or
				  divert water under subsistence hydrologic conditions, unless the flow at the
				  measurement point is above the applicable subsistence flow standard for that
				  point. During subsistence hydrologic conditions, if the flow at the measurement
				  point is above the subsistence flow standard but below the applicable dry
				  condition base flow standard, then the water right holder may divert or store
				  water 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 standard varies depending on the seasons, as
				  described in §
										298.505 of
				  this title, and the hydrologic conditions, as described in §
										298.520
				  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 the hydrologic
				  conditions prevailing at the time, i.e., the water right holder will be subject
				  to one of the following: a subsistence, 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 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)
				  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 §
											298.530
				  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 independent of the hydrologic conditions set out in §
											298.520
				  of this title.
(5) If a pulse flow
				  requirement for an annual pulse is satisfied for a particular season or year,
				  one of the applicable smaller pulse requirements is also considered to be
				  satisfied in that season.