| (a) For new water right authorizations in the Rio Grande
Basin 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 the
applicable measurement point. For each measurement point, cumulative
streamflow for the previous 12 months will determine the hydrologic
condition.
(b) For purposes of permit special conditions related
to hydrologic conditions, for water right applications in the Rio
Grande Basin, which increase the amount of water to be stored, taken,
or diverted, the hydrologic condition shall be calculated using the
full period of record for the United States Geological Survey (USGS)
gage or the International Boundary and Water Commission (IBWC) gage,
as applicable, at each measurement point such that subsistence conditions
occur approximately 10% of the time, dry conditions occur approximately
15% of the time, average conditions occur approximately 50% of the
time, and wet conditions occur approximately 25% of the time.
(c) For purposes of water availability determinations,
for water right permit applications in the Rio Grande Basin, which
increase the amount of water to be stored, taken, or diverted, hydrologic
conditions used in the commission's water availability model shall
be calculated such that subsistence conditions occur approximately
10% of the time, dry conditions occur approximately 15% of the time,
average conditions occur approximately 50% of the time, and wet conditions
occur approximately 25% of the time, based on the period of record
and simulated flows of the water availability model.
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