Ecohydrologic structure and function of stream networks with earthen upstream and concrete-lined downstream

Abstract

Concrete-lined streams are one of the most extreme forms of river regulation. This study investigated an urban stream network with concrete-lined (C) and earthen (E) sections. The C sections were positioned downstream of the E sections. This abrupt change of stream type due to concrete lining was compared with the predictions of river continuum concept and process domain concept. River continuum concepts predictions on the macroinvertebrate functional feeding group fractions against stream order and energy sources showed disagreements in this study. Furthermore, other than abundance of pollution intolerant species variation, most of the species responses did not support the process domain concept predictions. Correlations between explanatory variables (stream hydraulics or water quality) and response variables (macroinvertebrate composition and vegetation) observed to be dependent on stream lining and seasons. Stream discharge showed positive correlations with the pollution representative species in both section types but was more obvious in C sections. Water budget estimations showed that wastewater accounted for at least 5% of stream discharge of the C sections in the dry season. pH was the most important and significant water quality parameter of the C sections. Against expectations, nitrogen species and soluble reactive phosphorus did not have a major impact on species variables. Hydraulic variables that represented stream heterogeneity were more useful in explaining species variables of the E sections. Similar explanatory powers by the hydraulics and water quality variables of the C sections demonstrated the importance and interdependency of stream hydraulics and water quality in rehabilitating of this unique ecosystem.