Kevin C. Petrone

Hydrologic and biotic control of nitrogen export during snowmelt: A combined conservative and reactive tracer approach

Hydrologic and biotic control of nitrogen export during snowmelt: A combined conservative and reactive tracer approach

The origin and function of dissolved organic matter in agro‐urban coastal streams

[1] Streams draining urban and agriculture catchments are often a source of inorganic nutrients to downstream aquatic ecosystems, but little is known about how changes in land use influence the quality and biodegradability of dissolved organic matter (DOM). We used parallel factor analysis of excitation‐emission fluorescence spectroscopy and biodegradation incubations to examine how DOM composition influences bioavailable dissolved organic carbon (DOC) in surface waters of urban and agricultural catchments during summer (low flow), winter (high flow) and spring (flow recession). Percent bioavailable DOC was variable for all catchments (2–57%) and negatively related to percent humic‐like fluorescence, but positively related to percent protein‐like fluorescence and simple fluorescence metrics of DOM precursor material (fluorescence index and b:a values). Conversely, highly variable DOC concentrations (2–140 mg L −1 ) were negatively related to protein‐like fluorescence and positively related to humic‐like fluorescence. Elevated concentrations of DOC (>30 mg L −1 ) in agro‐urban streams revealed fluorescence indices (<1.3) typical of wetland and forest‐dominated ecosystems, suggesting that enriched stream DOM is either derived from the destabilization of legacy soil carbon or currently produced from remnant wetlands and patches of native vegetation. Overall, we demonstrate that fluorescence characteristics can be used to predict bioavailable DOC in human‐dominated catchments to better understand the flow of carbon and nutrients in aquatic food webs for improved monitoring and management of coastal ecosystems.

Can stormwater harvesting restore pre-development flows in urban catchments in South East Queensland?

Increases in the impervious area due to urbanisation have been shown to have negative impacts on the physical and ecological condition of streams, primarily through increased volume and frequency of runoff. The harvesting and detention of runoff has a potential to decrease this impact. This paper describes the effects of urbanisation on catchment flow and of stormwater harvesting on reducing those adverse impacts on a stream in South East Queensland (SEQ), Australia. A largely undeveloped catchment located southeast of Brisbane city was calibrated and validated using the Stormwater Management Model (SWMM). This model was used to investigate the effect of a range of future increases in urbanisation (represented by impervious area) on stream hydrology as well as the potential of stormwater harvesting to return the catchments to predevelopment flow conditions. Stormwater harvesting was modelled according to flow frequency measures specified in current SEQ development guidelines. These guidelines stipulate the capture of the first 10 mm of runoff from impervious areas of 0-40% and the first 15 mm from impervious areas of 40% or greater for urban developments. We found that increases in the impervious area resulted in increases in the mean, frequency and duration of high flows, and an increase in the mean rate of rise and fall for storm events in the catchment. However, the predevelopment (non-urbanised) flow distribution was very flashy in comparison with all urbanised scenarios; i.e. it had the quickest response to rainfall indicated by a high rate of rise to and fall from peak flow volume, followed by a return to zero flow conditions. Capturing the runoff according to the development guidelines resulted in a reduction in flow towards the flow distribution of a lower impervious area, however this was insufficient to meet predevelopment conditions. This suggests a stronger influence of impervious areas in this catchment on the volume of runoff than flow frequency measures are able to ameliorate.