Harman and Stewardson mentioned that only a

Harman and Stewardson (2005) mentioned that only a few published studies explicitly described the link between environmental flow targets and dam operating rules. To resolve the river management-driven issues and bridge the gap between a simple minimum stream flow target and the great complexity of the natural flow regime, the research proposed a realistic and feasible approach that incorporates the human demands with the most essential aspects of natural flow variability (such as the seasonal CMX001 flow requirements) as the key targets in searching for the optimal strategy of reservoir operation management.
The water resources planning process
Applications of reservoir planning During the past two decades, one of the most important advances made in the field of water resources engineering is the development and adoption of system analysis application methods for planning, design and management of complex water resource systems. The rapid evolution of computers together with their frequent use in management and control also contributed to the growth of system analysis applications in the field. System analysis cannot be defined with a single phrase as it involves several disciplines and a large number of actions. Stalnaker and Arnette (1976) define system analysis in brief as follows. “System analysis is a coordinated set of procedures that can be used to address issues of project planning, engineering design, and management. System analysis is a decision making tool. An engineer can use it for determining how resources can be used most effectively to achieve a specified goal or objective. For successful decision making, both technological and economic considerations must be employed in the analysis.”
Modelling water resources systems The modelling of water resources systems represents an essential component of the water resources planning process since it provides a testing environment for assessing the behaviour of a system under any number of selected scenarios prior to actual experience. Models therefore provide an important basis for testing the possible impacts of implementing planned infrastructure developments, management and operational options and other measures and thereby provide a reliable basis for making important decisions in diatomaceous earth regard. A great number of water resources modelling tools are applied across the world and most were developed based on the application of complex analytical techniques and computer programs (software) that simulate the behaviour of water resource systems with mathematical principals. However, due to their very nature, all of these models have certain limitations which may include some or all of the following:
Role of the model The Water Resources System Model (WRSM) was developed for the purpose of modelling complex water resource systems and is used together with other simulation models, pre-processors and utilities for the integrated management of water resources (uMngeni, 2008). Essentially, the model provides as a decision support system with the ability to evaluate the capability of existing and proposed water resource systems through simulation of the physical, statistical, operational and water quality aspects that influence the capability of such systems.
Model development and user support The WRSM is currently under development by the South African Department of Water Affairs and Forestry (DWAF) and combines the functionalities of three established water resources models that have been used for over 20 years for managing the country\'s water resources. These are: The DWAF, Directorate: Water Resource Planning Systems is the custodian of the model and is responsible for its on-going updating and refinement within a development framework which involves the maintenance of all hydrological and software systems used by the Department and its service providers. The development process involves a number of steps which include: