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 298.320 - Calculation of Hydrologic Conditions

Current through Reg. 49, No. 28; July 12, 2024
(a)
				  For new water right authorizations which increase the amount of water
				  authorized to be stored, taken, or diverted as described in §
										298.10
				  of this title (relating to Applicability), the determination of the hydrologic
				  condition for a particular season shall be determined once per season. The
				  conditions present on the last day of the month of the preceding season will
				  determine the hydrologic condition for the following season. For each
				  measurement point specified in this section, either cumulative streamflow for
				  the previous 12 months, combined storage in major reservoirs, or reservoir
				  elevation will determine the hydrologic condition, as described in subsections
				  (b) - (d) of this section.
(b) For
				  measurement points located on the Colorado River above Lake Travis and
				  tributaries of the Colorado River, and in the Colorado-Lavaca and the
				  Lavaca-Guadalupe Coastal Basins, cumulative streamflow for the preceding 12
				  months and the corresponding hydrologic conditions are:
Attached
					 Graphic
(c) For
				  measurement points located on the Colorado River below Lake Travis, the
				  combined reservoir storage in Lakes Travis and Buchanan and the corresponding
				  hydrologic conditions are:
Attached
					 Graphic
(d) For
				  measurement points located in the Lavaca River Basin, the reservoir elevation
				  of Lake Texana and the corresponding hydrologic conditions are:
Attached
					 Graphic
(e) For
				  purposes of water availability determinations, for measurement points on the
				  Colorado River above Lake Travis and tributaries of the Colorado River, and in
				  the Lavaca River Basin and the Colorado-Lavaca and Lavaca-Guadalupe Coastal
				  Basins, hydrologic conditions used in the commission's water availability
				  models shall be calculated such that severe conditions occur approximately 5%
				  of the time, dry conditions occur approximately 20% of the time, average
				  conditions occur approximately 50% of the time, and wet conditions occur
				  approximately 25% of the time.
(f)
				  For purposes of water availability determinations, for measurement points on
				  the Colorado River below Lake Travis, hydrologic conditions used in the
				  commission's water availability models shall be calculated such that severe
				  conditions occur approximately 5% of the time, dry conditions occur
				  approximately 45% of the time, and average conditions occur approximately 50%
				  of the time.
(g) The hydrologic
				  condition indicators set out in subsections (b) - (d) of this section govern
				  the operations of permits subject to this subchapter during the initial period,
				  of not longer than ten years, until the environmental flow standards in this
				  subchapter are reevaluated. Those indicators were calculated to achieve
				  compliance with the percentages of time stated in subsections (e) and (f) of
				  this section. The hydrologic condition indicators set out in subsections (b) -
				  (d) of this section will be recalculated, no less frequently than once every
				  ten years, in order to achieve, to the greatest extent possible, compliance
				  with the percentages of time stated in subsections (e) and (f) of this
				  section.