| OCR Text |
Show PART IV METHODOLOGY AND ASSUMPTIONS ration rate is the net water loss rate obtained by subtracting the precipitation rate from the sum of the surface and evapotranspiration rates. The gross surface area multiplied by an annual fullness factor is defined as the net surface area. Water consumed by the animals was estimated by converting all live- stock (cattle, sheep, horses, dairy cows, pigs, and poultry) to animal units (AU) and multiplying that sum by the water-use coefficient of 10 gallons per day, or 0.0112 acre-feet per year. 1/ For example, in the Upper Main Stem Subregion there were 351,000 AU in 1965. Therefore: 351,000 AU multiplied by 0.0112 acre-feet per year equals 3,900 acre- feet. Animal units were developed from the OBE-ERS projections as region- ally interpreted by the Economic Base and Projections Workgroup. Evaporation from single purpose municipal and industrial reservoirs was determined by the same method as were the stock watering pond losses. Reservoir evaporation is treated as a collection system use and is not called a requirement per se in this appendix. Evaporation from multi- purpose reservoirs that serve municipal and industrial purposes is not included in this appendix. However, it is included in the total water resource requirements of the Region and listed in the Water Resources Appendix. The quantity of withdrawal water supplied by municipal systems in each subregion in 1965 was determined by the following equation: M - EN (Y) (P) + RE Where: M = Subregion municipal withdrawal in MG per year. Y « Weighted-average county municipal water-use rate in gpcy. P * County population served by municipal systems RE « Reservoir evaporation N * Number of counties in the subregion. The quantity of withdrawal water required by rural-domestic systems for each subregion in each target year was determined by multiplying the estimated average subregional rural-domestic water-use rate times the population served by rural-domestic systems. Quantities of water supplied by livestock systems are equal to the withdrawal requirements of the livestock sector. 1/ Source, U. S. Department of Agriculture Task Force. 53 |
