Section 298.470 - Calculation of Hydrologic Conditions(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 Palmer Hydrologic Drought Index (PHDI) value present on the last day of the month of the preceding season, as reported by the National Weather Service, and calculated for the geographic area as described in subsection (b) of this section, will determine the hydrologic condition for the following season. For each measurement point specified in this section, the PHDI Index will determine the hydrologic condition, as described in subsection (c) of this section.(b) The percentage of each climatic division within each geographic area, as defined in § 298.455 of this title (relating to Definitions), are: Attached Graphic
(c) For all measurement points, based on the geographic area in which the measurement point is located, as defined in § 298.455 of this title, the PHDI Index and the corresponding hydrologic conditions are: Attached Graphic
(d) The PHDI Index for the hydrologic conditions, as set out in subsection (b) of this section govern the operations of permits subject to this subchapter during the initial period, not longer than ten years, until the environmental flow standards in this subchapter are reevaluated. The PHDI Index was calculated to achieve compliance with the percentages of time for dry, average, and wet conditions of 25%, 50%, and 25%, respectively. The PHDI Index set out in subsection (c) 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 for dry, average, and wet conditions of 25%, 50%, and 25%, respectively.30 Tex. Admin. Code § 298.470
The provisions of this §298.470 adopted to be effective March 6, 2014, 39 TexReg 1416