The effects of a single freshwater release into the Kromme estuary Part 1: General description of the study area and physico-chemical responses

Abstract

The natural runoff from the Kromme River catchment area has been severely restricted by impoundments with storage capacities exceeding the mean annual runoff (MAR). As a consequence, freshwater input into the Kromme Estuary has been drastically reduced and the estuary itself has been labelled as ‘freshwater-starved’. The annual allocation of storage water to the estuary (2 x 106 m3) has been released from the Mpofu Dam as a single release. The impact on various physico-chemical parameters as well as inorganic dissolved nutrients (phosphate, nitrate, nitrite, ammonia) in the estuary has been investigated with regards to the magnitude, persistence and management of future releases. The impact on dissolved nutrient concentrations was short-lived (less than 7 d), and pre-release concentrations were quickly re-established. The release raised especially nitrate and nitrite concentrations temporarily because of elevated concentrations in the storage water, but slightly diluted phosphate concentrations in the estuary.

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