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ground water will result in depletions to a natural stream in excess of the specified <br /> rate. Withdrawal of ground water that is not hydraulically connected to a natural <br /> stream cannot result in depletions to a natural stream. <br /> In reaching his finding, the State Engineer considered as corroborating, but did not <br /> rely upon as determinative, testimonial evidence regarding Glover-Balmer analyses <br /> performed by Mark Levorsen for purposes of determining the timing of depletions to <br /> stream flow resulting from withdrawal of ground water from the subject formations. <br /> The State Engineer does not find it necessary to rely upon the Glover-Balmer method <br /> to determine the timing of depletions to stream flow, because of the convincing <br /> geologic evidence provided demonstrating the existence of a hydraulic disconnect <br /> within the subject formations between the outcrop areas and the delineated <br /> nontributary area. However, the State Engineer nonetheless finds that the Glover- <br /> Balmer analyses support the conclusion that the rule properly delineates areas where <br /> the State Engineer should consider ground water removed from the subject formation <br /> to be nontributary. <br /> For reasons previously stated, the State Engineer finds the Glover-Balmer method is <br /> an appropriate method for determining the timing of depletions to stream flow for <br /> purposes of C.R.S. §§ 37-90-103(10.5) and 37-90-137(7). The primary concern <br /> expressed regarding Mr. Levorsen's use of the Glover-Balmer method related to the <br /> permeability values input into the model. The State Engineer generally does not find <br /> merit in these concerns. The permeability values were based upon an extensive <br /> review of a detailed site-specific data obtained from numerous wells completed in the <br /> subject formations. A representative reservoir intrinsic permeability was then <br /> determined for each formation by calculating a geometric mean of all measured <br /> permeabilities. The objecting parties noted that the measured permeability values for <br /> each formation varied, and challenged the use by Mr. Levorsen of a single <br /> permeability value for each formation derived as a geometric mean of the numerous <br /> permeability measurements. The State Engineer finds that the use of such a <br /> geometric mean value was appropriate. It is undisputed that permeability within any <br /> formation will vary; however, ground water traveling through the formation will <br /> travel through areas of both relatively higher and lower permeability. As testified to <br /> by Willem Schreuder, Ph.D., a recognized expert in the fields of applied mathematics <br /> and groundwater modeling, to the extent that permeability numbers vary within a <br /> formation over a logarithmically-normal pattern, the effective permeability of the <br /> formation is accurately reflected through use of a geometric mean of the measured <br /> values. Here, the evidence was undisputed that the permeability numbers varied over <br /> a logarithmically-normal pattern. <br /> The objecting parties also noted that the permeability numbers were generally higher <br /> for wells outside of an oil and gas producing area known as the Greater Wattenberg <br /> Area, and argued that these higher permeability numbers were not adequately <br /> reflected in the permeability numbers input into the Glover-Balmer model. However, <br /> Produced Nontributary Ground Water Rules 2 CCR 402-17, Statement of Basis and Purpose <br /> -32- <br />