Impacts Of Conservation Buffers And Grasslands On Total Phosphorus Loads Using Hydrological Modeling And Remote Sensing Techniques

Catena 86 (2011) 121–129

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j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c a t e n a

Impacts of conservation buffers and grasslands on total phosphorus loads using hydrological modeling and remote sensing techniques
Myriam Larose a, Gary C. Heathman b,⁎, Darrell Norton b, Douglas Smith b
a b

School ofNatural Resources, University of Michigan, 440 Church St, Ann Arbor, MI 48105 USA National Soil Erosion Research Laboratory, USDA-ARS, West Lafayette, IN, 47907 USA

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To better assess the impacts of conservation buffers and grasslands on water quality at large spatial scales, development and integration of novel approaches are crucial to ensure thatthese land management practices are functioning properly and meeting their original goals. Recent developments in remote sensing technology have greatly enriched the availability of geospatial data that can be used in hydrological modeling to assess the potential hydrological response of conservation practices over larger areas. A methodology was developed using the object-based image analysisapproach with Landsat-5 TM imagery of the year 2005 and thematic layers of streams to quantify conservation buffers and grasslands (OBIA-2005). The OBIA-2005 land cover data was used in the Soil and Water Assessment Tool hydrologic model to assess the impacts of vegetative conservation practices on total phosphorus (TP) loads. The model was calibrated and validated for discharge and TP loads inthe Cedar Creek Watershed (CCW) in northeast Indiana. In general model efficiency for streamflow values was within acceptable statistical ranges. While calibration of TP loads was satisfactory for the total contributing area of two nested catchments within the upper CCW. Vegetative buffers of 30.5 m and 61 m combined with conservation grasslands generated from the OBIA-2005 resulted in a largereduction of TP loads as compared to no practices. The results also showed that including conservation grassland alone reduced TP loads by less than 2%. However, the combination of these practices with the width of edge-of-field buffer strips module of the SWAT model achieved the largest TP loads reduction. These findings demonstrate that improved representation of vegetative conservation practices ingeospatial land cover data sets are more effective in assessing the impacts of conservation buffers and grasslands on water quality through hydrologic modeling. Published by Elsevier B.V.

Article history: Received 28 September 2010 Received in revised form 25 February 2011 Accepted 13 March 2011 Keywords: Hydrological modeling Object-based image analysis Landsat-5 TM Conservation practicesVegetative buffers Total phosphorus load

1. Introduction Natural surface and ground water systems are crucial resources for our societal well-being. However, many of these systems have been severely jeopardized due to a variety of water quality issues that continue to persist. Agrochemical losses present one such issue which, unfortunately, is expected to continue to affect these valuableresources unless sustainable and innovative approaches are adapted that achieve effective water resource management. Phosphorus (P) is one of the major macronutrients needed for optimal crop yield that can also contaminate lakes, rivers, and coastal waters (Sharpley et al., 1993; Rabalais et al., 2002; Volf et al., 2007; Alexander et al., 2008; White et al., 2009). An excess of the soluble fractionof P (orthophosphate, inorganic polyphosphates, and organic phosphate compounds) in runoff can contribute to eutrophication of freshwater, a major water quality problem worldwide (Sharpley et al., 1993; Shikagi et al., 2006; Volf et al., 2007). In a study conducted in the Gulf of Mexico, Alexander et al.

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