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_ Once again, abstractions, ie, means an increase soils resulting i runoff. runoff is equal to precipitation minus losses. An increase in the infiltration rate in the moisture holding capacity of the surface n a loss of precipitation available for surface Therefore, in determining the HSG for reclaimed lands at Colowyo, consideration should be given to actual data generated by CSU on infiltration rates and on standard reclamation procedures used by Colowyo to insure that compaction of surface soils does not occur. Both factors combined should allow Colowyo to justify the use of a HSG classification on reclaimed lands of at least HSG B. Derivation of Colowyo's CN=63 As agreed between MLRD and Colowyo, there are two distinct land conditions taken into account in the SEDCAD model, 1. Natural, undisturbed, semi-arid rangeland. 2. Fully reclaimed, grassland or range, brush, weed, grass mix. Natural, undisturbed semi-arid rangeland As has been previously accepted by MLRD, the BLM EMRIA Report • No. 3-1975 was used to determine a HSG D, semi-arid rangeland __.. Oak-Aspen (O-A), Pinion-Juniper (P-J), Sagebrush (S) cover in good condition. Utilizing SEDCAD's comprehensive listing of CNs, gives the following: O-A, good, CN = 48 P-J, good, CN = 71 S, good, CN = 55 Averaging all three values gives a CN = 58. Colowyo maintains that due to a policy of no domestic livestock grazing within the permit area, range conditions are classified as good. None-the-less, to be conservative, Colowyo chose to arbitrarily Berate the sagebrush from good to fair which gives S, fair, CN = 70 Averaging all three values gives a CN = 63, which is the value used in the model for natural, undisturbed, semi-arid rangeland. 2. Fully reclaimed, grassland or range (G-R). brush, weed. grass (B-W-G) mix • Once again, SEDCAD's comprehensive listing of CNs was utilized. Recalling Colowyo's justification for a good range