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.
Watershed-scale data were collected at the Walnut Creek Watershed, in Story County, Walnut Creek, Jasper County, and the Southfork of the Iowa River, Hamilton and Hardin County, Iowa. Measurements of water flow, dissolved oxygen, temperature and pH were made, as well as nitrate and phosphorus concentrations, E. coli and Enterococcus, and sediment. These data and meteorological data were placed in the Sustaining the Earth's Watersheds: Agricultural Research Data System (STEWARDS) database. The effect of temporal variability of nitrate loads over multiple years was analyzed with respect to estimating nitrate removal bioreactor installations in Walnut Creek and South Fork in Iowa and Cedar Creek in Indiana. These analyses suggest that cumulative watershed bioreactor volumes sufficient to achieve an HRT of 0.5 days will reduce at least 20% of the total annual nitrate loss in one watershed and 30% in the other two watersheds. The area required for wood-chip bioreactors would be 0.27% or less of the watershed area. A manuscript describing this research was prepared for submission to The Journal of Soil and Water Conservation in July of 2013.