1. (1) A water right has several elements, one of which is the amount of water that is used for each purpose described in the right. A reasonable amount of water will vary with the type and location of the use and will depend on various circumstances such as:

   1. (a) soil conditions;
   2. (b) method of conveyance;
   3. (c) topography;
   4. (d) climate;
   5. (e) system efficiency; or
   6. (f) other conditions affecting the particular use.

2. (2) The department will use the following standards when reviewing notices or applications for new uses of water:

   1. (a) for domestic use, for one household, the standard shall be based on the residential wastewater treatment design flow rate standards used by the Montana Department of Environmental Quality, and calculated by the number of bedrooms served:

      1. (i) 1 bedroom 150 gpd;
      2. (ii) 2 bedrooms 225 gpd;
      3. (iii) 3 bedrooms 300 gpd;
      4. (iv) each additional bedroom add 50 gpd;
   2. (b) for lawn, garden, shrubbery, and shelterbelts, 2.5 acre-feet per acre per year;
   3. (c) for stockwater, a consumptive use of 15 gallons per day or .017 acre-foot per year per animal unit. Animal unit equivalencies for water consumption are set out in ARM 36.12.101 and the DNRC water calculation guide;
   4. (d) fire protection water needs shall be determined by the type of equipment used, diversion rate, the size of the area to be covered, the frequency of the water use and must be explained and documented.

   5. (e) For irrigation, the following table applies:

      Irrigation Standards

      Climatic Area 1 Acre Feet per Acre

      	I	II	III	IV	V
      Sprinkler Irrigation 70% Efficiency	2.63 - 3.04	2.30 - 2.69	2.08 - 2.41	1.76 - 2.07	1.26 - 1.48
      Level Border 60% Efficiency Design Slope Level	3.07 - 3.55	2.69 - 3.15	2.43 - 2.81	2.06 - 2.41	1.47 - 1.73
      Graded Border 70% Efficiency Slope Group Design Slope .10% Design Slope .20% Design Slope .40%	2.63 - 3.04	2.30 - 2.69	2.08 - 2.41	1.76 - 2.07	1.26 - 1.48
      Graded Border 65% Efficiency Design Slope .75% Design Slope 1.5%	2.84 - 3.28	2.48 - 2.90	2.24 - 2.59	1.90 - 2.23	1.36 - 1.60
      Graded Border 60% Efficiency Design Slope 3.0%	3.07 - 3.55	2.69 - 3.15	2.43 - 2.81	2.06 - 2.41	1.47 - 1.73
      Furrow 70% Efficiency Design Slope .10% Design Slope .20% Design Slope .40%	2.36 - 2.74	2.11 - 2.44	1.87 - 2.16	1.39 - 1.70	NA
      Furrow 65% Efficiency Design Slope .75%	2.54 - 2.95	2.27 - 2.63	2.02 - 2.33	1.50 - 1.83	NA
      Furrow 60% Efficiency Design Slope 1.5%	2.75 - 3.19	2.46 - 2.85	2.19 - 2.52	1.62 - 1.98	NA
      Contour Ditch 60% Efficiency Design Slope .75%	3.07 - 3.55	2.69 - 3.15	2.43 - 2.81	2.06 - 2.41	1.47 - 1.73
      Contour Ditch 55% Efficiency Design Slope 1.5% Design Slope 3.0%	3.35 - 3.87	2.93 - 3.43	2.65 - 3.07	2.24 - 2.63	1.60 - 1.88
      Contour Ditch 45% Efficiency Design Slope 6.0%	4.10 - 4.73	3.58 - 4.19	3.24 - 3.75	2.74 - 3.22	1.96 - 2.30

      1 The irrigation climatic areas are identified in the 1986 Irrigation Climatic Areas of Montana map. Climatic area I is high consumptive use, climatic area II is moderately high consumptive use, climatic area III is moderate consumptive use, climatic area IV is moderately low consumptive use, and climatic area V is low consumptive use.

3. (3) A permit is required when a reservoir is proposed to include fire protection purposes and the volume of water reasonably needed for fire protection must be explained and must reference reliable industry sources.
4. (4) For fire protection reservoirs located within a basin closure area, evaporation losses must be made up from nontributary water sources or addressed in a mitigation plan.
5. (5) The flow rate and volume of water for any uses not listed in this rule must be calculated, explained, and documented based on the beneficial use and operation of the project.
6. (6) Deviations outside the standards will require information supporting the requested amount.

Authorizing statute(s): 85-2-113, MCA

Implementing statute(s): 85-2-301 through 85-2-319, 85-2-321 through 85-2-323, 85-2-329 through 85-2-331, 85-2-335 through 85-2-338, 85-2-340 through 85-2-344, 85-2-350, 85-2-351, 85-2-401, 85-2-402, 85-2-407, 85-2-408, 85-2-410 through 85-2-413, 85-2-415 through 85-2-419, 85-2-436, 85-2-437, 85-2-439, 85-2-501 through 85-2-512, 85-2-601 through 85-2-606, 85-2-608, 85-2-804 through 85-2-806, MCA

History: NEW, 2004 MAR p. 3036, Eff. 1/1/05; AMD, 2008 MAR p. 1820, Eff. 8/29/08; AMD, 2025 MAR, Notice No. 2025-157, Eff. 10/1/25.