Monterey Initiative - Final Text Submitted to Printer
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Monterey Initiative - Final Text Submitted to Printer
UNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printercarlett3, M. Harman3, c.p. Duerdoth-', A. Hawczak*, J.L. Pretty*, A. Arnold6, c. Laizé3, D.D. HornbyS A.L. Collins^, D.A. Seal4. J.I. Jones6a Centre for Ecology and Hydrology, Wallingford, Oxfordshire, 0X10 8BB, UKb School of Biological and Chemical Sciences. Queen Mary University of London. London. Monterey Initiative - Final Text Submitted to Printer El 4NS. UKc Geography and Environment. University of Southampton. Southampton. SOI7 1BJ. UK' Sustainable Soils and Grassland Systems Department. RothMonterey Initiative - Final Text Submitted to Printer
amsted Research, North Wyke, Okehampton, Devon. EX20 2SB, UK* corresponding author1AbstractExcessive sediment pressure on aquatic habitats is of globaUNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printers analysed in relation to 20 potential explanatory catchment and channel variables. The most effective explanatory variable for the amount of deposited sediment was found to be stream power, calculated for bankfull flow and used to index the capacity of the stream to transport sediment. Both stream Monterey Initiative - Final Text Submitted to Printerpower and velocitycategory were highly significant (p«0.001), explaining some 57% variation in total fine sediment mass. Modelled sediment pressure, pMonterey Initiative - Final Text Submitted to Printer
redominantly from agriculture, was marginally significant (p<0.05) and explained a further 1% variation. The relationship was slightly stronger for erUNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printerplanatory variable (p<0.001) but velocity category, baseflow index and modelled sediment pressure were all significant (p<0.01); each provided an additional 2% explanation to an overall 50%. It is suggested that, in general, the study sites were transport-limited and the majority of stream beds were Monterey Initiative - Final Text Submitted to Printer saturated by fine sediment. For sites below saturation, the upper envelope of measured fine sediment mass increased with modelled sediment pressure.Monterey Initiative - Final Text Submitted to Printer
The practical implications of these findings are that (i) targets for fine sediment loads need to take into account the ability of streams to transporUNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printeremove fines may also be needed in order to effect an improvement in ecological status in cases where streams are already saturated with fines and unlikely to self-cleanse.Keywordsdeposited fine sediment; agricultural streams; agricultural sediment pressure; stream power;channel substrate; saturated Monterey Initiative - Final Text Submitted to Printerfine sediment fraction21. IntroductionExcessive sediment pressure on aquatic habitats has become of increasing concern for river systems around the woMonterey Initiative - Final Text Submitted to Printer
rld (Relyea et al., 2012). In particular, intensification of agriculture has increased fine sediment loading to rivers (Wilcock, 1986; Dearing et al.,UNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printerlids and, potentially, deposition of fine sediment. Evidence has also been accumulating, from both field survey and experiments, on the deleterious effects of excessive fine sediment on biota (Waters, 1995; Wood and Armitage, 1997; Matthei et al., 2006; Bilotta and Brazier, 2008; Larsen et al., 2011 Monterey Initiative - Final Text Submitted to Printer; Sutherland et al., 2012; Wagenhoff et al., 2012, 2013; Chapman el al., 2014). It is clear from this evidence that the impact of excessive fine sedimMonterey Initiative - Final Text Submitted to Printer
ent on biota is more often related to deposited rather than suspended material (Kemp et al., 2011; Jones et al., 2012a, Jones et al., 2012b; Jones et UNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printerl., 2008; Collins and Anthony, 2008; Bryce et al., 2010; Collins et al., 2011; Benoy et al., 2012). Yet, the relationship between deposited fine sediment and agricultural sediment pressure is still poorly understood.Sediment pressure has been variously quantified by catchment or local'network ripari Monterey Initiative - Final Text Submitted to Printeran land use (Sutherland et al., 2010), runoff-weighted percentage land use (Wagenhoff et al., 2011) and modelled sediment load apportionment (CollinsMonterey Initiative - Final Text Submitted to Printer
and Anthony, 2008). Catchment land use has been shown to be related to deposited fine sediment in specific cases of intensification of agriculture (e.UNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printeroad has potential to link fine sediment deposition with current or future projected land management and. thus, provide information on the likely effectiveness of mitigation measures for fine3https://khothuvien.cori!sediment delivery to rivers in terms of sediment deposition and its biotic impact. Th Monterey Initiative - Final Text Submitted to Printere ability to make this link is fundamental to supporting national policies regarding the protection of water resources and ecological status.RepresentMonterey Initiative - Final Text Submitted to Printer
ative field sampling of deposited fine sediment in agricultural streams across England and Wales, carried out as part of a wider national scientific pUNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printerediment pressure. Sampling was specifically designed to cover both the range of agricultural sediment pressure and different biological river types across England and Wales (following Davy-Bowker et al., 2008). The impact on biota is covered elsewhere (Murphy et al., 2015). The aim of this paper is Monterey Initiative - Final Text Submitted to Printerto analyse the sediment data in conjunction with a range of catchment and channel descriptors in order to investigate potential linkages between agricMonterey Initiative - Final Text Submitted to Printer
ultural sediment pressure and deposited fine sediment in streams. In particular, it is hypothesized that the mass of deposited fine sediment is directUNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printerch and methodsThe approach taken was a synoptic survey of streams in agricultural catchments across England and Wales. Sampling sites were selected from the 12,447 stream sites within the Environment Agency River Habitat Survey (RHS) database. Biological river types were based on the physical attrib Monterey Initiative - Final Text Submitted to Printerutes of catchment geology, distance from source, altitude and slope; with boundary values loosely based on those associated with RIVPACS IV super endMonterey Initiative - Final Text Submitted to Printer
groups (Davy-Bowker et al., 2008). Screening was undertaken to eliminate any sites with a4substantial influence from urban areas or sewage effluent (sUNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printerurse, the most downstream site meeting the screening requirements was selected. Full details regarding the site selection process are given in Murphy et al. (2015). Some 230 sites were sampled once in either spring or autumn between May 2010 and November 2011. Most samples were collected during low Monterey Initiative - Final Text Submitted to Printerto medium flows as necessitated by the technique and no samples were collected during or immediately after peak flow events. From data on water width,Monterey Initiative - Final Text Submitted to Printer
depth and velocity category at the time of sampling, approximately 90% samples were collected when the flow was less than 10% of the estimated medianUNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printer the same field team and in exactly the same manner between October 2009 and May 2011, was also available for model testing and to assess temporal variability.2.1 Deposited fine sedimentFine sediment deposited on, or in, the river substrate to a depth of about 10 cm was collected using the disturban Monterey Initiative - Final Text Submitted to Printerce technique (Duerdoth et al., 2015 adapted from Collins and Walling, 2007a,b). An open-ended, stainless steel cylinder (height 75 cm; diameter 48.5 cMonterey Initiative - Final Text Submitted to Printer
m) was carefully inserted into an undisturbed patch of stream bed to a depth of at least 10 cm, until an adequate seal with the substrate was achievedUNDERSTANDING THE CONTROLS ON DEPOSITED FINE SEDIMENT IN THESTREAMS OF AGRICULTURAL CATCHMENTSP.S. Naden3*, J.F. Murphy*, G.H. old3, J. Newman3, p. Sc Monterey Initiative - Final Text Submitted to Printeritated vigorously for one minute using a metal pole, without touching the stream bed. This established a vortex that brought any fine sediment into suspension. This was then immediately sampled, while the waler was still in vigorous motion, by plunging two inverted 50 ml tubes to the bottom of the c Monterey Initiative - Final Text Submitted to Printerylinder which then filled as they were turned5upright and brought to the surface. To sample the total (i.e. combined surface and subsurface) depositedMonterey Initiative - Final Text Submitted to Printer
fine sediment, the stream bed was then disturbed to a depth of about 10 cm, vigorously agitated for one minute to suspend any subsurface fines and aGọi ngay
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