Banjir Kanal Barat (BKB) and Banjir Kanal Timur (BKT) are widely used for various community activities such as residential areas, industry, fish cultivation, and auction. Community activity around BKB and BKT will affect N and P nutrient inputs, which further affects phytoplankton abundance. In this study, phytoplankton biomass was estimated through chlorophyll-a (chl-a) measurements. The purpose of this study was to determine the distribution of the chl-a and determine the influence of phosphate and nitrate in front of the estuary from BKB and BKT. Sampling was carried out at 8 stations from each estuary and was carried out in the dry season. The concentration of chl-a, phosphate, and nitrate is further described in the form of a distribution pattern based on the interpolation method with ArcGIS 10.2 software. The results showed that the average ± sd of chl-a, respectively was 15,781 ± 16.90 mg/m3 and 17,710 ± 15.31 mg/m3, phosphate was 0.0174 ± 0.0057 ppm and 0.0096 ± 0.0164 ppm, nitrate was 2.9086 ± 1.1824 ppm and 1.6919 ± 1.6316 ppm. The distribution pattern of chlorophyll-a and phosphate decreases in concentration towards the sea, while nitrate forms an irregular pattern and has a different pattern in each estuary. Nutrient phosphate has a positive correlation with chlorophyll-a.