Dispersed urban-stormwater control improved stream water quality in a catchment-scale experiment

• DOI: 10.31219/osf.io/4j6vk
• Publication Date: 2021-12-16T01:14:01Z
• Authors: Christopher John ...; Moss Imberger; Matthew J Burns; Darren G Bos; Tim D Fletcher
• Keywords: Low-impact development; Urban stream; Catchment hydrology

Traditional approaches to urban drainage degrade receiving waters. Alternative have potential protect downstream waters and provide other benefits cities, including greater water security. Their widespread adoption requires robust demonstration of their feasibility effectiveness. We conducted a catchment-scale, before-after-control-reference-impact experiment assess the effect dispersed stormwater control on stream ecosystems. used variant effective imperviousness (EI), integrating catchment-scale runoff impact stormwater-control-measure (SCM) performance, as measure experimental effect. assessed response quality variables in 6 sites 2 streams, following SCM implementation catchments. compared changes those streams over 7 years, increased, 12 preceding 19 years 3 reference streams. SCMs reduced phosphorus nitrogen concentrations temperature, increased electrical conductivity; with size negatively correlated antecedent rain. SCM-induced reductions temperature were similar magnitude increases from development, when function change EI. Nitrogen observed, even though among not EI, being more influenced by septic tank seepage. had no suspended solids concentrations, which lower than This strengthens inference that contaminant demonstrates such impacts are reversible likely preventable. reduce reducing frequency uncontrolled flows augmenting baseflows. Increased EC result contribution groundwater The achieved did fully return or levels, but responses indicate an outcome is possible dominant conditions (up ~20 mm 24-h rain). would require nearly all impervious surfaces draining large retention capacity, thus requiring downslope space demand. EI predicts SCMs, allowing better catchment prioritization design standards for protection.