Water quality and sediment assessment of Manchar Lake, Sindh, Pakistan: after effects of the super flood of 2010

Abstract

Public attention to the preservation of the environment in recent decades has been increased and the present study covers the principal water of the Manchar Lake, a fresh water resource of Pakistan, which has received less fresh water for a decade. The accumulation of agricultural runoff through the Main Nara Valley Drain (MNVD) has changed its fate of salty water. The super flood event of 2010 in the Indus River and the receiving MNVD passed through Manchar Lake, affecting the lake water and sediments. The study, covering the period earlier than the monsoon season (April–June) of 2012, includes the physicochemical characteristics of water quality and sediments. Two bodies, the water and sediments, were monitored for more than 30 parameters: TDS, EC, DO, COD, BOD, chloride, hardness, alkalinity, nitrate, nitrite, ammonia, sulfate, orthophosphate, total phosphate, Na, K, Ca, Mg, Fe, Cd, Pb, Cr, Ni, Co, Cu, Mn, and Zn. The total extractable salts in sediments were determined by EDTA or mixed acid. The trend of EDTA-extractable metals was in a decreasing order Ca > Mg > Na > K > Fe > Mn > Pb > Ni > Zn > Cu > Cr > Cd. Most of the acid-extractable metals indicated similar pattern but the values were lower than EDTA. The water and sediments of the lake indicated less contamination compared to that reported before the Indus river super flood 2010, despite causing many causalities and economic loss. The study explained factor analysis (FA), hierarchical cluster analysis (HCA), Pearson correlation coefficient, and geo contamination index for the quality parameters of the water and sediments.