Model-based assessment of the effect of shading on river water quality WOK

Shading by riparian vegetation affects incident solar radiation and water temperature in
small- and moderate-size streams, and is thus an important component in the influence of
forested riparian buffers on streams. Thewater quality effects of riparian shading are largely
unknown. A simulation study was carried out to evaluate the effect of shading on six water
quality variables in a moderate-size Belgian river stretch. A dynamic modelling approach
making use of the RiverWater Quality Model No. 1 was chosen to represent the system. The
scenarios developed indicate that shading may be an effective tool in controlling stream
eutrophication (44% reduction in phytoplankton productivity in the simulated stretch) but
has a limited effect on dissolved oxygen, chemical oxygen demand, nitrates, ammonium
nitrogen, and phosphates. Results suggest that shading can effectively be implemented as a
direct management strategy to improvewater quality conditions in small and moderate-size
watercourses that are exposed to excessive algal growth during summer periods.