Semarang City, Indonesia is plagued by a combination of widespread flooding during the wet season and a lack of fresh (potable) water during the dry season, the latter related to saltwater intrusion. The East Flood Canal (Banjir Kanal Timur = BKT) was built to address these problems by improving runoff (drainage) and increasing groundwater recharge. This research was conducted to reconstruct the history of environmental change, including seawater intrusion, along the coast of Semarang using pollen and diatom assemblages from a 190-cm-long, ²¹⁰Pb-dated sediment core extracted from the estuary at the mouth of the BKT. The age of the sediments within the core ranged over 160 years (the surface dated to 2014). The sediments could be subdivided into three zones on the basis of pollen assemblages and 2 zones on the basis of diatom assemblages. Lower zone assemblages, dominated by Sonneratia alba (mangrove), Acrostichum aureum (Pteridophyte), and Cocconeis pediculus (an epiphytic diatom), indicate that historically, the estuarine ecosystem was relatively open to the Java Sea and characterized by periods of marine and freshwater conditions. Thereafter, an upward increase in saline mangrove species of pollen and diatoms, combined with the loss of freshwater species (e.g., Avicennia and Rhizophora), indicates an increasing prevalence of marine conditions at the mouth of the BKT. Increasing salinity was associated with a landward shift in the mangrove ecosystem, a trend indicated by the progressive increase in mangrove plant diversity as statically manifested by the three pollen zones. This landward shift was associated with a “closing off” of marine flow in response to a significant (order of magnitude) increase in the estuarine sedimentation rates at about 1981. Increased sedimentation was presumably related to land-use changes that enhanced sediment delivery to the coast via the BKT. Inherent in these sediments were allochthonous fragments of Asterionella formosa, a freshwater species found in the upper sediment layers. The results of this study are consistent with the increased saltwater intrusion along the coast and a decline in groundwater quality.

印度尼西亚三宝垄市在潮湿季节遭受洪水泛滥，而在干旱季节则缺乏淡水（饮用水），这与海水入侵有关。东部洪水运河（Banjir Kanal Timur = BKT）旨在通过改善径流（排水）和增加地下水补给来解决这些问题。这项研究的目的是使用长度为190厘米，²¹⁰厘米的花粉和硅藻组合物重建三宝垄海岸的环境变化历史，包括海水入侵。从BKT口的河口提取的含铅沉积物芯。岩心内沉积物的年龄范围超过160年（地表日期为2014年）。根据花粉组合，沉积物可分为三个区域，基于硅藻组合物可分为2个区域。下部区域组合以白背海葵（Sonneratia alba）（红树林），金黄色古猿（Acrostichum aureum）（蕨类植物）和小球藻（Coccois pediculus）（附生硅藻）为主，表明从历史上看，河口生态系统相对向爪哇海开放，并具有一定时期的海洋和淡水条件。此后，花粉和硅藻的盐渍红树林物种的数量增加，而淡水物种的丧失（例如，紫薇）和Rhizophora），表明BKT口的海洋状况正在增加。盐度的增加与红树林生态系统的向内转移有关，这种趋势由红花粉植物多样性的逐步增加所表明，这是三个花粉区的静态体现。这种陆上移动与响应于大约1981年河口沉积率显着（数量级）增加的海洋流量“关闭”有关。沉积增加可能与土地利用变化有关，土地利用变化增加了向沙洲的泥沙输送。通过BKT沿海岸航行。这些沉积物中固有的是福尔摩沙菌的异源碎片是在上层沉积物中发现的淡水物种。这项研究的结果与沿岸咸水入侵增加和地下水质量下降是一致的。