Measurements of water circulation in mangrove swamps in Zanzibar

Field investigations of water circulation and flushing in Chwaka Bay, Zanzibar were carried out as part of a UNESCO/COMARAF training workshop on mangrove ecosystems and estuarine processes, held June 5-16 1989. Three sites M1 (tide pole site in the centre of Chwaka Bay), M2 (at the entrance to the mangrove creek) and X1 (in the mangrove creek)An echo-sounder measured depth along east-west transects in the bay and in the mangrove creek on the south-western side. Measurements were taken (using a mud probe) of longitudinal distribution of temperature, salinity and turbidity. A current meter which sampled at 5 min intervals was deployed for a day at sites M1 and M2. Tidal height was recorded 15 min intervals at M1 while surface temperature, salinity, dissolved oxygen concentration and nutrient concentrations were simultaneously recorded at M2.For use in the two-dimensional model, the Bay was divided into 32 cells adapted to the local bathymentry (depth measurements). To train workshop participants in aspects of field techniques to investigate water circulation and flushing, and in data analysis. For training purposes, the model was also applied to Tudor Creek, Mombasa, Kenya (but no field data are available for this).

1989年6月5日至16日，联合国教科文组织（UNESCO）与印度洋海洋与海岸研究委员会（COMARAF）联合举办红树林生态系统与河口过程培训讲习班，针对桑给巴尔岛查瓦卡湾（Chwaka Bay）开展的水循环与水交换野外调查，即为该讲习班的实践环节之一。
本次调查共设置3个采样点位：M1（查瓦卡湾中心验潮站点位）、M2（红树林溪入口处）与X1（红树林溪内部）。研究团队利用回声测深仪（echo-sounder），沿查瓦卡湾内及西南侧红树林溪的东西向断面开展水深测量；采用底泥探针（mud probe）获取了温度、盐度与浊度的纵向分布数据。
在M1与M2点位部署采样间隔为5分钟的海流计（current meter），连续观测时长为1天；在M1点位以15分钟间隔记录潮高，同时在M2点位同步记录表层水温、盐度、溶解氧浓度与营养盐浓度。
为支撑二维数值模型的应用需求，研究团队依据实测水深地形（bathymetry）数据，将查瓦卡湾划分为32个贴合局地地形的计算单元格。
本次工作旨在培训讲习班学员掌握水循环与水交换野外调查技术及数据分析方法，为此还将该模型应用于肯尼亚蒙巴萨的都德溪（Tudor Creek），但该点位无配套实测野外调查数据。