Impact of weather and climate scenarios on conservation assessment outcomes

Abstract

Selected watershed studies of the Conservation Effects Assessment Project (CEAP) are reviewed and findings are interpreted from the perspective of potential conservation outcomes due to climate change scenarios. Primary foci are runoff, soil erosion, sediment transport, and watershed sediment yield. Highlights, successes, and challenges with regards to climate change impacts on soil erosion, runoff, and watershed sediment yield are presented. The covered information adds to the existing knowledge base of climate change impacts and provides another piece of information that may be useful in the planning and management of agricultural watersheds; assessment of conservation needs; and development, funding, and implementation of conservation programs. The selected conservation assessment studies include, among others, a thought experiment on the sensitivity of soil erosion, runoff, and sediment yield to changes in rainfall; a computer-based investigation of potential climate change effects on runoff and soil erosion in a southeastern Arizona rangeland; the complex response of northern Mississippi watersheds to runoff variations and channel stabilization measures; the impact of conservation practices and a persistent pluvial period on watershed runoff and sediment yield in Oklahoma; and stream bank erosion during major flooding in Iowa and river corridor management. A study of rainfall-runoff in an north-central Missouri watershed and a curve number analysis in a northern Appalachian experimental watershed are included herein. Findings showed that climate change scenarios of increased precipitation intensity lead to an exponential increase in soil erosion, runoff, and watershed sediment yield, thereby stressing current conservation practices or future practices designed with present day practice standards. This diminishes conservation practice effectiveness and increases sediment supply to the stream network. The sensitive response of the watershed hydrologic system may lead to renewed soil erosion that is large enough to offset the reduction in soil loss achieved by current conservation practices. However, in alluvial-floodplain environments with noncohesive bed and bank material, watershed sediment yield is controlled by channel discharge and energy slope, neither of which is influenced by traditional in-field conservation practices or channel bank stabilization structures. Thus, control of sediment yield will gradually shift in the downstream direction from sediment supply to sediment transport capacity and blur any existing relation between a climate change signal, in-field conservation outcomes, and sediment yield at watershed outlets. Targeting conservation practices to erosion prone areas, expanding conservation coverage, and adapting agronomic practices may be necessary to prevent excessive soil erosion and downstream sedimentation under climate change scenarios that include intensified precipitation.Key words: conservation effectiveness-Conservation Effects Assessment Program-climate impacts-runoff...

Model analysis of check dam impacts on long-term sediment and water budgets in Southeast Arizona, USA

“…Traditional models cannot consider all the watershed-scale erosion and sediment transport processes at once due to knowledge and/or data limitations (De Vente and Poesen 2005). However, there are many models that have been applied to develop estimates of runoff, erosion, and sediment yield and to mimic how check dams and rock structures might influence those (Martín-Rosales et al 2007;Remaître et al 2008;Boix-Fayos et al 2008;Norman et al 2010a;2010b;Garbrecht et al 2014). In this study, we simulate the hydrologic processes documented in riparian areas treated with check dams using the Soil and Water Assessment Tool (SWAT; Arnold et al 1998;Neitsch et al 2009) to extend the hydrologic budget and describe the fate and transport of sediments.…”

Reducing current and future risks: Using climate change scenarios to test an agricultural conservation framework

“…Given that increased precipitation increases erosion risk and increases in erosion impacts under climate change have been emphasized in recent climate change research papers and guidance documents (e.g., Delgado et al, 2013;Garbrecht et al, 2014;Nearing et al, 2004;Soil andWater Conservation Society 2003, 2007), we expected that the substantial increases in precipitation in the two wet spring scenarios would produce consistent increases in surface flows and sediment loading that would drive reductions in fish IBI. Instead, while sediment loads did increase in both Wet scenarios for the Rifle and for the Wet-Wet scenario for the Pigeon Pinnebog, sediment loading declined in other watersheds, and changes in IBI maximum were more often driven by changes in organic P at the subbasin scale.…”

“…Achieving water quality and stream health standards in agricultural landscapes remains a persistent challenge, despite substantial research and investment in agricultural conservation practices (Sowa et al, 2016;Tomer et al, 2014). In watersheds across the US Great Lakes region, a variety of stakeholders are developing and testing innovative solutions to increase the effectiveness of conservation investments, including new or improved practices, multi-scale targeting, and new financial mechanisms (e.g., Bosch et al, 2013;Douglas-Mankin et al, 2013;Kalcic et al, 2015aKalcic et al, , 2015bLegge et al, 2013;Tomer et al, 2013).…”

“…In watersheds across the US Great Lakes region, a variety of stakeholders are developing and testing innovative solutions to increase the effectiveness of conservation investments, including new or improved practices, multi-scale targeting, and new financial mechanisms (e.g., Bosch et al, 2013;Douglas-Mankin et al, 2013;Kalcic et al, 2015aKalcic et al, , 2015bLegge et al, 2013;Tomer et al, 2013). While these innovations represent important advances, there is increasing evidence that the performance of many agricultural conservation practices can be influenced by climatic factors (Delgado et al, 2013, Garbrecht et al 2014Hatfield et al, 2013).…”

Riparian catchments: A landscape approach to link uplands with riparian zones for agricultural and ecosystem conservation

“…The availability of extensive, highresolution landscape data, with information on soils, land use, and topography, enables technologies for visualizing hydrologic pathways, and locations along those pathways where "trap and treat" conservation practices can slow flows and retard move-ment of sediment and nutrients (Tomer et al 2013). However, conservation aimed at water resource protection may require multiple practices, placed in series along water flow pathways, to account for tradeoffs among contaminants (Joosse and Baker 2011;Sharpley et al 2009) and for increasing risks associated with extreme precipitation events under a changing climate (Garbrecht et al 2014). In short, effective coupling of upland and riparian conservation as a system of practices, may become necessary to ensure water quality, water supply, agricultural sustainability, and ecosystem biodiversity and integrity.…”