Relative Contribution of Phosphorus from Various Sources to the Upper Lake, Bhopal

An investigation on phosphorus loading from the point and non point sources to the Upper Lake, Bhopal and its contribution on eutrophication was undertaken at Indian Institute of Soil Science, Bhopal. Geo-referenced water samples from different entry points (15 locations), where water from different sources (agriculture and municipal water) enters to the Upper Lake, were collected and analyzed for various P fractions. The results showed that the total phosphorus (TP) content varied from 0.30 to 0.73 mg/L with a mean value of 0.47 mg/L having lowest and highest content from Kholukhedi (agriculture source) and Bhadbada (domestic wastewater), respectively. Among the P fractions, the bioavailable P fraction (total dissolved phosphorus-TDP) was highest in the water sample from the domestic source, whereas, the dominant P fractions in the water samples from agricultural source was particulate P (PP). The results shows that the total P in the sediment of post-monsoon stage samples ranges from 0.03 to 0.07% with a mean value of 0.04%. The mean sediment inorganic phosphorus (SIP) and the sediment organic phosphorus (SOP) is 68.01 and 31.98% of total phosphorus (TP), respectively. Among the inorganic P fractions in the sediment, Ca bound P was maximum and found to be in the range of 86.32–96.97% of total sediment inorganic P followed by Fe bound P (2.10–11.51%) and loosely sorbed P (LSP) (0.39–5.66%). To summarize, the source of water from the city (domestic wastewater) and at idol immersion location contains relatively higher total phosphorus (TP) and dissolved reactive phosphorus (DRP).