Poor water quality is hindering water resource development in the Orange River system. It is therefore imperative to manage water quality. This is where water quality models play an important role in resource planning, operation, pollution control and reservoir dynamics. Salinity models have long been integrated in the planning process via the Water Resources Planning Model (WRPM) and Water Quality TDS (WQT) models. Eutrophication is also assuming serious proportions and should be incorporated in the planning process. There is also a need for models to encapsulate the planned operation of systems with regulated river reaches. The main product of this report comprises the development of algorithms for the inclusion of river and reservoir phosphate and chlorophyll-a in the WQT and WRPM planning models. The high level requirements for water quality operating models and possible development routes have also been considered.

The following recommendations have been made:

• The phosphate and chlorophyll-a modelling algorithms that have been developed should incorporated in the WQT and WRPM models.
• Water quality operating model requirements should be examined in detail and tested on key system elements.
• Ongoing improvements to the WQT and WRPM salinity modelling routines should proceed.