Quantification of environmental flows in integrated water resources management

An important challenge of Integrated Water Resources Management (IWRM) is balancing water allocation between different uses. 'Environmental flows' has emerged as a promising new approach to bringing Water-for-Nature to the water agenda on equal terms with other uses. This paper examines the potentials for quantifying environmental flows in an IWRM context and presents a conceptual model for incorporating environmental flows into the decision-making process. Such a model requires knowledge of the links between environmental now, ecosystem goods and services and their economic value. A literature review is undertaken to identify the most appropriate methods for environmental flow assessment and economic valuation. While the holistic and interactive DRIFT methodology is found to be the most attractive for assessing environmental flows, it cannot be readily applied. A simplified, operationalised 'desktop-DRIFT' is recommended. Market and non-market values of ecosystem goods and services are best assessed using a combination of cost-based valuation and dose-response methods. These methods are then linked to an existing river basin simulation model, MIKE Basin. By including all relevant water uses, various water allocation scenarios can be explored and the socio-economic and ecological implications evaluated. Ultimately, however, it is the responsibility of decision-makers to select the water allocation scenario to be adopted, and thus to quantify environmental flows in IWRM. The tool described in this paper serves to inform such decision-making processes and place due value on Water-for-Nature.