2012 Annual Report
Objective 1. ARS watershed data from Conservation Effects Assessment Project (CEAP) watershed were compiled into a database that is publicly available via the internet. This provides ARS customers/public better opportunities to review the scale of ARS CEAP research & specific monitoring results. A review of watershed research across ARS-CEAP watersheds was published to provide succinct information about watershed scale conservation assessments & factors that contribute to uncertainty in those assessments. Objective 2A. An inventory of conservation practices in the South Fork of the Iowa River provided an illustration of the importance of addressing transport pathways, because most conservation practices controlled surface runoff, but few practices address tile drainage, which contributed the most substantial hydrologic pathway, delivering nearly all nitrate & a substantial portion of P & E. coli. Historical sedimentation of the South Fork impacted flood severity & sediment loads in this watershed. Riparian zone management including rotational grazing & stabilized cattle crossings can promote stable banks to mitigate some impacts of erosion under flood conditions. Changes in shallow groundwater quality during establishment of prairie vegetation showed landscape patterns of nitrate & phosphorus differed, with clear implications & challenges for managing agricultural landscapes for improved water quality. Objective 2B. Analysis of an individual rainfall runoff event quantified the contribution of runoff, tile drainage, & in-stream processes to transport of nutrients, sediment, & E. coli. The importance of streambanks as a source of sediment was shown. Degradation of sulfamethazine in soil & stream sediment was described mathematically as a bi-phasic process, with initially fast then slowing as bioavailability is decreased. Bioreactors for nitrate removal were able to remove herbicides & antibiotics. The dynamics of E. coli populations in streams was assessed. Objective 3. The quality of tile drainage water can be improved with several practices including bioreactors, drainage water management (DWM), cover crops & wetlands. The efficacy of these practices were documented in several experiments and/or simulated in modeling studies. The potential reduction of nitrate loads to the Mississippi River by DWM & cover crops were estimated using simulation models. Results show these practices have the potential to achieve substantial reductions of nitrate loads at reasonable costs. The effects of long-term climatic trends & cycles on agricultural production & watershed hydrology were shown. Cyclic oceanic oscillations explained significant variations in crop production in Iowa. Long term climatic trends revealed that trend of increasing discharge & baseflow since the 1970s were linked to increasing precipitation & humidity, suggesting that climate change may have influenced the trend of increasing hypoxic zones in the Gulf of Mexico.
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