Linking flow, water quality and potential effects on aquatic biota within the Reserve determination process

Abstract

Linking the potential effects of altered water quality on aquatic biota, that may result from a change in the flow (discharge) regime, is an essential step in the maintenance of riverine ecological functioning. Determination of the environmental flow requirement of a river (as well as other activities, such as classifying the resource) is known in South Africa as determining the "ecological Reserve". This paper describes the philosophy behind the incorporation of water quality concerns in, as well as the constraints that are likely to be in operation during a Reserve determination. Three simple, predictive tools that have been developed for routine use in ecological Reserve assessments are described in this paper. Flow-concentration modelling can be used to predict the water quality that is likely to result from a given, prescribed flow regime. The Biotic Protocol attempts to provide an assessment of the likely implications of the predicted water quality for aquatic macroinvertebrates. Concentration time-series modelling can be used to rank complex flow scenarios with regard to potential consequences for water quality. Finally, a framework is presented for incorporating predictions of water quality and the implications for the aquatic biota in ecological Reserve assessments.

Linking key environmental stressors with the delivery of provisioning ecosystem services in the freshwaters of southern Africa

“…). Impacts on freshwater systems are linked to the higher evapo‐transpiration rates of alien trees relative to those of the indigenous vegetation that they replace, resulting in reduced river flows and groundwater reserves (Malan and Day ). For river catchments receiving >800 mm rainfall per year, Cullis et al .…”

“…While the ecosystem services concept is rapidly establishing itself as a framework through which to implement the sustainable use of freshwater resources, many of its principles already exist within southern African water policy in the form of an older concept, integrated water resource management (IWRM). Both concepts approach the management of freshwater resources, by addressing competing interests such as socio‐economic needs, environmental concerns, and human health considerations (Jewitt ; Malan and Day ; Cook and Spray ). There remains, however, a significant knowledge gap in understanding the fundamental interactions between environmental stressors and freshwater resources that, if not adequately addressed, could result in ineffective implementation of sustainable water resource management objectives (Jewitt ).…”

Comparative Use of Hydrologic Indicators to Determine the Effects of Flow Regimes on Water Quality in Three Channels across Southern Florida, USA

“…Regression models have been developed to predict the behavior of the concentrations of constituents that affect water quality for specified flow regimes [17]. Specifically, several studies have used concentration-discharge (C-Q) relationship models to quantify the effect of flow on the behavior of water quality constituents within natural channel networks [12,15,16,[18][19][20].…”