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--></style><title>Saving streams and rivers for fish: How much shade
needed?</title></head><body>
<div><i>Water Resources Research</i><font face="Lucida Grande"
size="-1"> 27 May 2015</font></div>
<div><br></div>
<div>Seeing the landscape for the trees: Metrics to guide riparian<br>
shade management in river catchments</div>
<div><br></div>
<div>Matthew F. Johnson and Robert L. Wilby</div>
<div><br></div>
<div>Key Points:</div>
<div><font face=".LastResort">-</font>Temperature over long stretches
of river will not be affected by riparian shade</div>
<div><font face=".LastResort">-</font>Midreaches of headwater streams
are most responsive to riparian shade</div>
<div><font face=".LastResort">-</font>To offset a 1C temperature rise,
1 km of trees is necessary in UK small streams</div>
<div><br>
Abstract</div>
<div><font face="Lucida Grande"
size="-1"><u
>http://onlinelibrary.wiley.com/doi/10.1002/2014WR016802/full</u></font
></div>
<div><br></div>
<div>Rising water temperature (Tw) due to anthropogenic climate change
may have serious conse- quences for river ecosystems. Conservation
and/or expansion of riparian shade could counter warming and buy time
for ecosystems to adapt. However, sensitivity of river reaches to
direct solar radiation is highly heterogeneous in space and time, so
benefits of shading are also expected to be site specific. We use a
network of high-resolution temperature measurements from two upland
rivers in the UK, in conjunction with topographic shade modeling, to
assess the relative significance of landscape and riparian shade to
the thermal behavior of river reaches. Trees occupy 7% of the study
catchments (comparable with the UK national aver- age) yet shade
covers 52% of the area and is concentrated along river corridors.
Riparian shade is most ben- eficial for managing Tw at distances
5-20 km downstream from the source of the rivers where discharge is
modest, flow is dominated by near-surface hydrological pathways, there
is a wide floodplain with little land- scape shade, and where
cumulative solar exposure times are sufficient to affect Tw. For the
rivers studied, we find that approximately 0.5 km of complete shade is
necessary to off-set Tw by 1C during July (the month with peak Tw) at
a headwater site; whereas 1.1 km of shade is required 25 km
downstream. Further research is needed to assess the integrated effect
of future changes in air temperature, sunshine duration, direct solar
radiation, and downward diffuse radiation on Tw to help tree planting
schemes achieve intended outcomes.</div>
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<div><font size="-2" color="#000000">"</font><font face="Arial"
size="-1" color="#262626">Nothing an institution can do will prevent
misconduct altogether. This is not the goal. Rather, it is to support
the work of well-meaning scientists, to reduce the waste from biased
results, and to relieve some of the pressures that encourage sloppy
science."<br>
<br>
<i>Nature</i><b> 525,</b> 25-27 (03 September 2015)
doi:10.1038/525025a<br>
http://www.nature.com/news/robust-research-institutions-must-do-their<span
></span>-part-for-reproducibility-1.18259</font></div>
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