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<br />@ <br /> <br />Reach 6, NAPI, consisting entirely of reservation land, was evaluated thoroughly <br /> <br /> <br />~ during the '89-'91 study, and no deep percolation was found. Because of active <br /> <br /> <br />~ drainage flow from the area of Reach 6, sprinkler system data were gathered <br /> <br /> <br />~'1 during this current study to estimate whether changes had been made in the <br /> <br /> <br />irrigation practices evaluated by New Mexico SCS during the '89-'91 study. The <br /> <br />acreage and water data from the evaluations on the NAPI were not used in <br /> <br /> <br />developing the salt and water budgets displayed later in this report. <br /> <br />To estimate sprinkler irrigation efficiencies and the amount of deep percolation <br /> <br />on center-pivot and side-roll sprinkler systems on the NAPI, evaluations were <br /> <br /> <br />conducted on five fields operated by two cooperating land Users. Fields were <br /> <br />selected to include loamy fine sand, fine sandy loam, and loamy sand for the <br /> <br /> <br />center-pivot sprinklers, and silt loam for the side-roll sprinkler. It appears <br /> <br /> <br />that no deep percolation or surface runoff occurs with present management. <br /> <br /> <br />Therefore, it may be that the drainage flow originates in a nonfarming area. <br /> <br />However, photographic evidence and water records have led Some to suspect the <br /> <br /> <br />presence of a mound built up over a past period of ten to fifteen years of over~:0' <br /> <br />irrigation and deep percolation. In essence, the suspicion is that even in the <br /> <br />absence of present-day deep percolation, return flow is continuing. <br /> <br />The 1989 evaluation by New Mexico indicated a significant amount of salt loading <br /> <br /> <br />from all reaches, but evaluations conducted during the 1990 and 1991 irrigation <br /> <br /> <br />seasons led the investigators to conclude that the evaluated lands were not <br /> <br /> <br />contributing significant amounts of salt. <br /> <br />Coincidental data gathered from Reach 4 reservation lands indicated that they, <br /> <br /> <br />like the non-reservation lands, were not significant contributors of salt. <br /> <br /> <br />However, for the lower basin, the brief nature of the data gathered on Reach 4 <br /> <br /> <br />reservation lands and the complete lack of data for Reach 5 precluded the drawing <br /> <br /> <br />of accurate conclusions. Additionally, salt-loading estimates developed by the <br /> <br /> <br />U.s. Bureau of Reclamation, using U.~. Geological Survey gage records, show <br /> <br /> <br />unaccounted-for salt pick up in the river. The origin of a portion of the salt <br /> <br />has been assumed to be irrigated land. <br /> <br />6 <br />