2012 Annual Report 1a.Objectives (from AD-416): Principal focus of the CEAP Watershed Studies is to evaluate the effects and benefits of conservation practices at the watershed scale, in support of policy decisions and program implementation. 1b.Approach (from AD-416): The effects of conservation activities on water and soil quality will be assessed at the watershed scale using models such as ARS' Soil and Water Assessment Tool, in combination with ARS long-term watershed data sets, expertise, and resources. Associated with ONP Incoming Agreement Log 44374. 3.Progress Report: This agreement supports objective 3 of the in-house project by quantifying effects of irrigation in watersheds. Simple water balances were calculated for the Upper Snake-Rock Watershed in Idaho and the Upper Big Walnut Creek Watershed in Ohio. Irrigation water diverted from the Snake River supplied 80% of the water input into the Idaho watershed. Precipitation supplied 100% of the water input into the Ohio watershed. Potential crop ET was estimated to use 37 to 51% of the total annual water input in the Idaho watershed and 30 to 55% in the Ohio watershed. The relative volume of water potentially used by crops in these two watersheds was quite similar on an annual basis even though the hydrology throughout the year was quite different.