The need to enforce minimum environmental flow requirements in Tanzania to preserve estuaries: case study of mangrove-fringed Wami River estuary

Abstract

The importance of restoring and maintaining environmental flows for sustaining the ecosystem integrity of rivers has been recognized in policies and legal frameworks in many countries. However this is routinely not implemented in Tanzania as exemplified by the case of the Wami River estuary, which plays a vital role in processing riverine nutrients, trapping sediment, recycling nutrients in the mangroves, and supporting the ecology of the Saadani National Park and the livelihood of the local communities. Our study reveals that currently the estuary is ecologically healthy but it is threatened by both increasing sedimentation and declining freshwater flow caused by decreasing rainfall – possibly linked with climate change – and by increasing water demand in the watershed for artisanal and large scale agriculture and irrigation schemes. Environmental flow assessment for the Wami River (with exclusion of estuary) has been done and the minimum flows were recommended but they are not enforced. We recommend that the responsible authority (Wami-Ruvu Basin Water Office) enforce its own environmental flow recommendations in order to maintain a healthy estuarine ecosystem and regulate water usage in the watershed. A similar recommendation also holds for all other rivers and estuaries in Tanzania.