水文学：当前研究

The Need to Enforce Minimum Environmental Flow Requirements in Tanzania to Preserve Estuaries: Case Study of the Mangrove-Fringed Wami River Estuary

Abstract

Halima Kiwango, Karoli N. Njau and Eric Wolanski

The importance of restoring and maintaining environmental flows for sustaining the ecosystem integrity of rivers and estuaries has been recognized and given proper attention in policies and legal frameworks in many countries including Tanzania. The Wami River estuary is small but it plays a vital role in processing riverine nutrients, in trapping sediment, in recycling nutrients in the mangroves, and in supporting the ecology of the Saadani National Park and the livelihood of the local communities. The proper functioning of this estuary to a large extent depends on adequate supply of freshwater flows. Our studies reveal 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. However, like in many other rivers in the country, effective implementation of recommended environmental flows remains to be a challenge. In order to maintain a healthy estuarine ecosystem in the future, it is the obligation of the WRBWO now to stick to and enforce the recommendations of its own environmental flow assessment to regulate water usage in the watershed. A similar recommendation also holds for all other rivers and estuaries in Tanzania.