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Biological assessments of streams that have been adversely impacted by sediment runoff in Idaho, USA

100%
Mahler R. L., Barber M. E.
Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation
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2010
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tom 42
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nr 1
31-37
Sediments are the major source of pollution in surface waters of the Pacific Northwest Region of the USA. The purpose of this study is to evaluate the relationship between SMI water quality scores at 76 sampling sites in eight watersheds and the observed soil erosion rates on adjacent landscapes. The water quality SMI scores in streams were obtained using stream macro invertebrates as an indicator of water quality, while soil erosion rates were determined by observation on adjoining landscapes during periods of maximum precipitation. Soil erosion rates of <2, 2–5, 5–15, 15–25 and >25 mt/ha/yr were observed at 9, 20, 45, 14 and 12% of the sampling sites, respectively. Landscapes with erosion rates of less than 5 mt/ha/yr generally resulted in good water quality in adjacent streams; however, when soil erosion rates on adjacent landscapes exceeded 5 mt/ha/yr SMI water quality scores were less than good 86% of the time. Strong signifi cant relationships were observed between SMI water quality rating and observed soil erosion rates. Consequently, land management or rehabilitation practices that reduce soil erosion rates to levels below 5 mt/ha/ /yr should improve stream water quality.
2
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Ephemeral gully erosion from agricultural regions in the Pacific Northwest, USA

100%
Barber M. E., Mahler R. L.
Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation
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2010
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tom 42
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nr 1
23-29
Soil erosion continues to be problematic financially and environmentally with the USEPA ranking sediment as one of the top ten pollutants of concern in the USA. One aspect of erosion often overlooked is the role of ephemeral gullies in terms of quantity of sediment produced and amount exported to nearby waterways. Current physically-based and empirical models are inadequate for predicting this type of erosion particularly at the watershed scale. A new methodology for predicting the quantity and location of sediment delivery was developed and tested via a case study. Aerial ephemeral gully erosion rates varied from 33.6 mton/km2 (0.15 U.S. tons/acre) in the Big Bear Creek basin to 88.4 mton/km2 (0.39 U.S. tons/acre) in the Middle Potlatch Creek basin representing 2.3 to 7.7% of the total surface sediment load. This information was used to develop a predictive Erosion Potential Index (EPI) that uses LANDSAT aerial imagery combined with readily available soils information and a digital elevation model to identify the most probably locations of ephemeral gully development. High resolution aerial imagery was used to quantify actual ephemeral gully locations which were then compared to the EPI predicted locations to verify the procedure. High resolution aerial imagery was also used to quantify the amounts of soil erosion from ephemeral gullies in basins of the Potlatch River system.
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