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(1) Substantial credible information must be provided showing there is surface water physically available at the flow rate and volume that the applicant seeks to appropriate for the proposed period of diversion.

(2) If actual stream gaging records are available, or the source has been otherwise measured and quantified by a public entity, the records shall be used to estimate the median of the mean monthly flow rates and volumes for the stream gaging station period of record during the proposed months of diversion at the source of supply in the amount the applicant seeks to appropriate.

(3) If actual flow rate and volume data are not available to estimate the monthly median flows, then the department shall use an accepted method for estimating surface water flow rates and volumes in conjunction with discharge measurements to validate the estimation technique used. Some accepted methods are listed in (5).

(4) When stream flow gaging station data are not available and monthly median flow estimation techniques are used, the following stream discharge data must be collected:

(a) Stream flow measurements in cfs or gpm must be collected at least once every month during the proposed period of diversion at the most suitable location on the source of supply, and at or directly upstream of the proposed point of diversion.

(b) If it is not possible to take measurements every month due to high spring flow conditions or other limiting conditions approved by the department, at least one measurement must be collected during the lowest flow period.

(c) Measurements must be submitted on Form 649 in electronic format with all information and data provided.

(5) The following reports may contain accepted methods for estimating surface water flow rates and volumes:

(a) "Methods for Estimating Monthly Stream Flow Characteristics at Ungaged Sites in Western Montana," USGS Open-file Report 89-40;

(b) "A Method for Estimating Mean and Low Flows of Streams in National Forests of Montana," USGS Water Resources Investigation Report 85-4071;

(c) "Stream Flow Characteristics of Mountain Streams in Western Montana," USGS Open-File Report 84-244;

(d) "Estimated Monthly Percentile Discharges at Ungaged Sites in the Upper Yellowstone River Basin in Montana," USGS Water Resources Investigation Report 86-4009;

(e) "A Method for Estimating Mean Annual Runoff of Ungaged Streams Based on Characteristics in Central and Eastern Montana," USGS Water Resources Investigation Report 84-4143;

(f) "Estimates of Monthly Flow Characteristics at Selected Sites in the Upper Missouri River Basin, Montana, Base Period Water Years 1937 - 86," USGS Water Resources Investigations Report 89-4082;

(g) "Mean Annual Runoff and Peak Flow Estimates Based on Channel Geometry of Streams in Southeastern MT," USGS Water Resources Investigation Report 82-4092;

(h) "Mean Annual Runoff and Peak Flow Estimates Based on Channel Geometry of Streams in Northeast and Western Montana," USGS Water Resources Investigation Report 83-4046; and

(i) "Estimates of Mean Monthly Stream Flow for Selected Sites in the Musselshell River Basin, Montana," USGS Water Resources Investigation Report 89-4165.

(6) Other professionally documented hydrologic methods for estimating stream flow or annual runoff which may be applicable and acceptable to the department, including the Orsborn method, Mannings equation, U.S. Natural Resources and Conservation Service-developed mean annual runoff data, and drainage area information paired to gaged streams in similar type basins may be acceptable. The department will determine the acceptability of other methods on a case-by-case basis.


History: 85-2-113, 85-2-302, MCA; IMP, 85-2-302, MCA; NEW, 2005 MAR p. 264, Eff. 1/1/05; AMD, 2012 MAR p. 2071, Eff. 10/12/12.

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