2006 Annual Report 4d.Progress report. This report documents research conducted under a Reimbursable Agreement between ARS and the Idaho Natural Resource Conservation Service (NRCS), Boise, Idaho. This project is one of eight special emphasis national projects funded by NRCS. Its major emphasis is an irrigated agriculture watershed. Additional details of research can be found in the report for the parent project 5368-12130-009-00D, Water Quality Protection in Irrigated Cropping Practices and Systems. The overall objectives of this project are to evaluate the change in water and salt balance for an irrigated tract, and determine the effect of overhead irrigation systems on return flow water quality using multiple micro-watersheds within the irrigated tract. Field sampling studies will measure suspended sediment, total and soluble nutrients, and flow rates for irrigation inflows and outflows from irrigation tract and each sub-basin. This data will be related to land practices and types of irrigation systems within tract and sub-basin. Water quality monitoring was initiated in January 2005 at 23 return flow sites in the irrigation tract and at six sub-basins when the irrigation season started in April 2005. Data collection continues in the 2006 calendar year. A third season (year) will be obtained if sufficient funds remain in Agreement.