A review of 40 years of hydrological science and practice in southern Africa using the Pitman rainfall-runoff model

- We review 40 years of the use of the Pitman model in the context of IAHS PUB.
- Some of the Pitman model developments anticipated PUB, others learned from PUB.
- Recent developments are aligned with uncertainty issues that emerged during PUB.
- More efforts are required to make use of new hydrological (EO) data products.
- Key differences are associated with the emphasis on the practical use of the model.

SummaryThe 40th anniversary of the initial development of the Pitman rainfall-runoff (developed in South Africa and widely applied throughout southern Africa) approximately coincides with the end of the IAHS PUB programme and the start of a new decade focussing on hydrological change (Panta Rhei) and society. The paper reviews the developments and applications of the Pitman model in the context of the appropriate outcomes of PUB and the proposed future directions of Panta Rhei. The focus of development of the Pitman model has been dominated by practical applications, while PUB was largely dominated by science issues. While some of the PUB principles have been applied with the Pitman model, there are others that are deemed inappropriate for practical modelling and others that would almost certainly benefit the Pitman model applications in the future. The paper includes discussions of the model structure, input data, parameters and output evaluations - all in the context of uncertainty. The capabilities of the model to address societal development impacts are also discussed and a brief example of an uncertainty approach to applying the model is provided. The conclusions are that some developments of the Pitman model anticipated more recent international developments, while others have not been ignored even if further efforts are required to effectively implement them. Perhaps the largest gap in applying uncertainty principles in practice is how to use them in water resources decision making.