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TITLE 30ENVIRONMENTAL QUALITY
PART 1TEXAS COMMISSION ON ENVIRONMENTAL QUALITY
CHAPTER 298ENVIRONMENTAL FLOW STANDARDS FOR SURFACE WATER
SUBCHAPTER DCOLORADO AND LAVACA RIVERS, AND MATAGORDA AND LAVACA BAYS
RULE §298.325Schedule of Flow Quantities

(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.

(e) Stored water. A water right owner that has stored water in accordance with the terms and conditions of its water right, including any applicable environmental flow requirement in effect at the time the water was stored, may divert, release, or use this water, even if the applicable environmental flow requirement is not met at the time of the subsequent diversion, release, or use of that stored water.


Source Note: The provisions of this §298.325 adopted to be effective August 30, 2012, 37 TexReg 6629

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