River Management Decision Modelling in IQQM

The Department of Infrastructure, Planning and Natural Resources (DIPNR) is involved with the planning for theand management of rivers in New South Wales. DIPNR has developed a daily time-step integrated quantity/quality river basin model (IQQM) to investigate water-sharing issues and determine river basin flow management rules. IQQM can quantify the impacts of water resource management policy changes on stakeholders, including the environment and the irrigation industry. Recently Water Sharing Plans (WSPs) were developed for various NSW river systems. The WSPs were finalised after extensive consultation with the community and other stakeholders. During that consultative process numerous complex variations of water sharing rules were identified. IQQM was used to model those rules and quantify the likely impacts on the environment and water users under the different variations. The modelling of these complicated rules was made possible by the IQQM Decision Tree (IDT). The IDT is a device used by a subset of IQQM node types to make a decision based on defined conditions at any point in the river system. For example the releases from a dam may be dependent on: 1. The storage volume in the dam; 2. Flows at a single and/or multiple locations either upstream or downstream of the dam; 3. Time of the year; 4. Downstream demand. The IDT combines all of these criteria into a decision network to arrive at a single governing decision at every time-step of the simulation. The IDT is designed to avoid the need for changing and writing new and highly specific code for testing complex flow rule variations. The mechanisms and applications of IDTs for modelling various flow rules are described in this paper with some specific examples.