Connectivity of Ephemeral and Intermittent Streams in a Subtropical Atlantic Forest Headwater Catchment

Alondra B A Perez,Pedro L B Chaffe,Camyla Innocente Dos Santos,João H M Sá,Pedro F Arienti

doi:10.3390/w12061526

Alondra B A Perez, Pedro L B Chaffe + Show 3 more

Open Access

https://doi.org/10.3390/w12061526

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Journal: Water	Publication Date: May 27, 2020
Citations: 7	License type: CC BY 4.0

Affiliation: Universidade Federal de Santa Catarina

Abstract

Stream network extension and contraction depend on landscape features and the characteristics of precipitation events. Although this dependency is widely recognized, the interaction among overland-flow generation processes, drainage active length, and frequency in temporary streams remains less understood. We studied a forest headwater catchment with wide variation in soil depth to investigate the runoff generation processes that lead to the occurrence of ephemeral and intermittent flow and connectivity between hillslope and outlet. We used low-cost equipment to monitor the variation in the length of the active drainage network and to measure the water table development. The flow in the channels can develop even under light rainfall conditions, while the connectivity is controlled by antecedent wetness, total precipitation, and active contribution area thresholds. Runoff permanence and fragmentation were related to soil depth variation; flow being usually more disconnected due to deeper water tables in deeper soil locations. Our findings emphasized the impact of soil structure on runoff generation in hillslopes and can be useful in the management of the most active areas and their impact on the quality of available water.

Highlights

The estimation of runoff depends on our understanding of the flow paths that water takes to the catchment outlet [1,2,3]
Based on Zimmermann et al [3], we made the following assumptions: If one overland-flow detectors (OFDs) was active and the adjacent downstream one was empty, we considered that the flow occurred up to the first OFD; if an OFD was empty and the adjacent downstream one was full we considered that flow started from the downstream full OFD
The connected drainage network (CDN) remained below the active drainage network (ADN) in 16 of reach these was active in 36 that events

Summary

Introduction

The estimation of runoff depends on our understanding of the flow paths that water takes to the catchment outlet [1,2,3]. Among the headwater’s drainage network, many channels that control the hillslope hydrological connectivity [2] are ephemeral or intermittent [4]. The quantity and the quality of the streamflow may be influenced by the hydrographic network expansion rate [10] as it influences the transport of water, sediments, and nutrients in small catchments [11] and shapes local biodiversity and ecosystem processes [12]. The refilling of ephemeral channels can affect the path of nutrients and organic matter that accumulate during dry periods, releasing large amounts of dissolved organic carbon [13]

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