The development of water quality methods within ecological Reserve assessments, and links to environmental flows

Abstract

In the South African National Water Act (NWA, No 36 of 1998), the ecological Reserve is defined as the quality and quantity of water required to ensure appropriate protection of water resources, so as to secure ecologically sustainable development and use. Aquatic ecosystems are recognised as the core location of water resources, and although considerable progress has been made in developing methods for quantifying environmental flow requirements, this paper describes and discusses the first agreed method for quantifying environmental water quality requirements in an ecological Reserve assessment. Integration of flow and water quality is emphasised, and is based on the philosophy that environmental flows should be motivated to provide ecologically important flow-related habitat, or geomorphological function, but should not be motivated to solve water quality problems by dilution. Water quality is multivariate, and not all variables can be considered in an ecological Reserve assessment, but core water quality variables include: system variables (salts, dissolved oxygen, turbidity, temperature), nutrients (phosphate, nitrite, nitrate) and toxic substances (those listed in the South African Water Quality Guidelines for Aquatic Ecosystems, including toxic metal ions, toxic organic substances, and/or substances from a chemical inventory of an effluent or discharge). In addition, biological indicator data (e.g. SASS data), chlorophyll-a (e.g. phytoplankton and periphyton data) and toxicity test data may be used. For each variable, a concentration range or response is linked to a class within a water resource classification system, where classes range from minimally to severely modified. There are five main stages in the environmental water quality method:• Initiate study and determine scope of assessment.• Delineate water quality sub-units.• Select sites and collect data and information.• Determine benchmarks, including generic boundary values (literature-based concentrations related to classes); the unimpacted, natural or reference condition; the present ecological state; and the contribution of water quality to the overall ecosystem importance and sensitivity. • Provide quantified and qualitative water quality objectives for each ecosystem health class, and each variable in each resource unit. These steps are integrated with environmental flow assessment procedures. After environmental flows have been recommended to achieve a selected level of protection (class), flow-concentration relationships are modelled, and the likely water quality consequences of modified flows are provided to resource managers, who then decide on whether to allocate water for dilution and/or to address the pollution problem directly using source controls.

Linking Flow Regime and Water Quality in Rivers: a Challenge to Adaptive Catchment Management

“…So far, the vast majority of work on environmental flows has concentrated on the magnitude of flow and its variation (Tharme 2003) and direct links between flow and ecosystem responses; indirect links between flow, water quality aspects, and ecosystem responses are less studied. The South African National Water Act (NWA) of 1998 is probably the most advanced act so far in defining integrated management of the flow regime and the water quality (Scherman et al 2003, Palmer et al 2005a. It has recognized that to sustain the goods and services that are provided by rivers it is essential to safeguard the entire riverine ecosystem (Department of Water Affairs and Forestry (DWAF) 1999, Malan and Day 2003).…”

“…The scientific understanding of these relationships and the resulting effects on ecosystems are limited. Hence, the integration of water quantity and water quality variables in protecting water resource management is still in its infancy (Palmer et al 2005a).…”

“…Originally, this concept had its focus on more static hydrologic conditions, but it has successively been developed to encompass a dynamic view of water flow, specifically how a certain (minimum) mass of water could be shared out over the year to become most useful (Tharme 2003). An important aspect that has not been much dealt with until recently is how flow variation interacts with variation in the physicochemical characteristics of the water, especially when these are affected by waste discharge and non-pointsource pollution (Palmer et al 2005a). An associated applied question is how water extractions and releases can be designed to reduce ecological and sanitary problems that might arise from inappropriate combinations of flow dynamics and physicochemical characteristics of water.…”

A review of aspects of hydrological sciences research in Africa over the past decade

“…Many studies deal with agriculture and agronomy (Adimo et al 2012, Traore et al 2014 Another practical focus area in which hydrological modelling has been linked with ecological systems is the quantification of environmental water requirements (King and Brown 2006, Mazvimavi et al 2007, Hughes and Louw 2010, McClain et al 2013 A c c e p t e d M a n u s c r i p t 13 has always been linking water quantity and quality in integrated assessments of the ecological status of aquatic systems (Palmer et al 2005, Hughes 2009 …”

Little boats and big concerns? Seeking a balance between ecotourism and motorboat use in Tortuguero, Costa Rica.

“…freshwater, sediments) (Palmer, Rossouw, Muller, & Scherman, 2005;Walling & Fang, 2003). In response to increasing human use, proper management of waterways is vital.…”