Texas Administrative Code › Title 30 - ENVIRONMENTAL QUALITY › Part 1 - TEXAS COMMISSION ON ENVIRONMENTAL QUALITY › Chapter 298 - ENVIRONMENTAL FLOW STANDARDS FOR SURFACE WATER › Subchapter D - COLORADO AND LAVACA RIVERS, AND MATAGORDA AND LAVACA BAYS › Section 298.325 - 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 21 separate measurement locations in §
										298.330
				  of this title (relating to Environmental Flow Standards).
(b) Subsistence flow. The applicable
				  subsistence flow standard varies depending on the seasons as described in
				  §
										298.305 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 under severe
				  hydrologic conditions, unless the flow at the measurement point is above the
				  applicable subsistence flow standard for that point. During severe 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 level
				  varies depending on the seasons as described in §
										298.305 of
				  this title and the hydrologic condition described in §
										298.320
				  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 except those on the Colorado River below Lake Travis,
				  the water right will be subject to one of the following: a dry, an average, or
				  a wet base flow standard. For all measurement points on the Colorado River
				  below Lake Travis, the water right will be subject to either a dry or an
				  average base flow standard. For all measurement points, the dry base flow
				  standard applies during severe hydrologic conditions. 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.
(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 on the Colorado River below Lake Travis, two pulses per
				  season, one pulse per 18 months, and one pulse per two years are to be passed
				  (i.e., no storage or diversion by an applicable water right holder), if
				  applicable, and as described in §
											298.330
				  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 the daily average flow at the applicable measurement point equals
				  at least the 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.
(2) For measurement points on the Colorado
				  River above Lake Travis, tributaries of the Colorado River, and in the Lavaca
				  River Basin and the Colorado-Lavaca and Lavaca-Guadalupe Coastal Basins, one or
				  two pulses per season and one pulse per year are to be passed (i.e., no storage
				  or diversion by an applicable water right holder), if applicable, and as
				  described in §
											298.330
				  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.
(3) 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.
(4) Each
				  season is independent of the preceding and subsequent seasons with respect to
				  high flow pulse frequency.
(5) High
				  flow pulses are independent of the hydrologic conditions set out in §
											298.320
				  of this title.
(6) If a high flow
				  pulse requirement for a one-per-season pulse is satisfied for a particular
				  season, one of the two-per-season pulse requirements is also considered to be
				  satisfied. When a pulse flow requirement for an annual pulse is satisfied in a
				  particular season, the one-per-season pulse requirement and one of the
				  two-per-season pulse requirements are also considered to be
				  satisfied.