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Cross-scale controls on the in-stream dynamics of nitrate and turbidity in semiarid agricultural waterway networks.

Abstract：

:Stream and riparian zone networks embedded in agricultural landscapes provide a potential intervention point to ameliorate the negative effects of agricultural runoff by reducing transport of nitrate (NO3-) and suspended sediments (SS) downstream. However, our ability to support and promote NO3- and SS attenuation is limited by our understanding of vegetative and hydrogeomorphic controls in realistic management contexts. In addition, agricultural landscapes are heterogenous on multiple management scales, from farm field to regional water management scales, and the effect of these heterogeneities and how they interact across scales to affect vegetative and hydrogeomorphic controls is poorly explored in many settings. This is especially true in irrigated agricultural settings, where stream and riparian networks are entwined with and sensitive to water management systems. To fill these gaps, we related the vegetative and hydrogeomorphic features of 67 waterway reaches across two water management districts in the California Central Valley to reach-scale NO3- and turbidity attenuation and district-scale water quality patterns. We found that in-stream NO3- attenuation was rare, but, when it did occur, it was promoted by shallow and wide riparian banks, low flows, and high channel-edge denitrification potential. Nitrate concentrations were consistently higher in upstream reaches compared to water district outlets, suggesting that while exports from the district were low, agricultural runoff may impair within-district water resources. Turbidity attenuation was highly variable and unrelated to vegetative or hydrogeomorphic features, suggesting that onfield controls are crucial to managing suspended sediments. We conclude that waterway networks have the potential to mitigate the effects of agricultural NO3- runoff in this setting, but that more effective monitoring and adoption of NO3- attenuating features is needed. Using our findings, we make specific management and monitoring recommendations at both reach and water district scales.

journal_name

J Environ Manage

journal_title

Journal of environmental management

authors

Webster AJ,Cadenasso ML

doi

10.1016/j.jenvman.2020.110307

subject

Has Abstract

pub_date

2020-05-15 00:00:00

pages

110307

eissn

0301-4797

issn

1095-8630

pii

S0301-4797(20)30242-5

journal_volume

262

pub_type

杂志文章

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Cross-scale controls on the in-stream dynamics of nitrate and turbidity in semiarid agricultural waterway networks.