Stormwater Infrastructure Controls Runoff and Dissolved Material Export from Arid Urban Watersheds

Abstract

. (2015) 'Stormwater infrastructure controls runo and dissolved material export from arid urban watersheds.', Ecosystems., 18 (1). pp. 62-75. Further information on publisher's website:http://dx.doi.org/10.1007/s10021-014-9812-2Publisher's copyright statement:The nal publication is available at Springer via http://dx.doi.org/10.1007/s10021-014-9812-2.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. General commentsOverall I was quite happy with the quality and scope of this paper. It is very well written and contains some important findings. Some general and more specific comments are provided below. I think the authors should have the opportunity to think about a few of my comments below; this calls for minor revision.While the paper concerns both hydrology and water quality, I think more attention is given to the latter. I would have liked to seen more results on hydrology. Maybe you could provide a graph (with associated discussion in the text) showing mean event runoff coefficients for each catchment? Given that the paper is already fairly long, this might not be possible. In any case, I recon you could expand your hydrological findings in a separate journal paper.• Response: We are planning a separate paper that details the hydrologic results of this work. However, since both reviewers requested more hydrologic data, we have added a table in the appendix that provides more details on runoff and storm characteristics (Table A1) In the discussion, you present a conceptual model of urban watershed ecosystem function and describe four periods of change. You suggest that the model is for arid urban catchments. I think it would be worth fleshing this section out a bit more. In doing this, maybe you could firstly describe in a general way, what is natural arid catchment hydrology.• Response: We have limited space to add more discussion here, and we already have some information on arid hydrology in the introduction (lines 191-194), and we reference key literature (Osterkamp and Freidman, 2000. We have however, included a bit more discussion about how this model might differ in other regions (now lines 611-618).Where I'm from, the "third" phase in your diagram is very different. We have been installing distributed stormwater infrastructure for the last 15 years. But, our systems are generally designed for pollutant-load reduction-aimed to protect our largest receiving water (a bay). These systems are not designed to restore/protect natural hydrology. Because of this, runoff/ratios tend to still be c...

Sources and Transport of Nitrogen in Arid Urban Watersheds

“…Runoff coefficients in these study watersheds, in turn, were strongly and negatively related to retention basin density and watershed area and positively related to impervious cover and precipitation. 26 In these watersheds, therefore, retention basin density was associated with increased DIN retention at the watershed scale, whereas the imperviousness and precipitation was associated with decreased DIN retention at the watershed scale. Larger watersheds also had lower runoff coefficients and therefore retained more DIN, as noted by Lewis and Grimm.…”

“…The results of this study have significant implications for stormwater management in arid cities. Larson and Grimm 35 reported high rates of potential denitrification in stormwater retention basins in the Phoenix area, and Hale et al 26 reported that N delivery was negatively related to the density of retention basins in a watershed. However, our isotopic results suggest that, even though retention basins change the isotopic composition of NO 3 − in stormwater, the mechanisms driving N retention at the scale of rainfall-runoff events are primarily hydrologic, not biogeochemical.…”

“…However, other research has found that increasing hydrologic residence time increases opportunities for biogeochemical transformations across a range of ecosystem scales from individual small streams to large watersheds. 27−30 Furthermore, Hale et al 26 found that spatial and temporal patterns of event-specific N export can be variable. Wet N deposition is highly variable in both space and time; 31 yet how this variability in wet N deposition translates to spatial and temporal patterns of stormwater N export has not been evaluated.…”

“…We sampled rain and runoff from 10 nested urban watersheds that varied in stormwater infrastructure type and drainage area (see Hale et al 26 and Supporting Information for site information and descriptions of infrastructure designs). Because of the arid climate, these watersheds do not have baseflow and produce runoff only in response to rain.…”

Spatial and Temporal Variation in Local Stormwater Infrastructure Use and Stormwater Management Paradigms over the 20th Century

“…Urbanization has tremendous consequences for hydrological processes through the alteration of land cover [1], burial of streams [2], creation and destruction of lakes [3], re-plumbing of watersheds with stormwater infrastructure [4,5], and restoration and redesign of streams [6]. Depending on design, stormwater infrastructure can exacerbate or mitigate the effects of urbanization on the transport of water, nutrients, and other pollutants from urban watersheds [5][6][7][8][9][10].…”