This paper presents a study on the spatial and seasonal/temporal variation of the water quality of Dal Lake and its tributaries based on some physicochemical parameters (viz. temperature, pH, EC, TDS, NO3--N, NH3-N, total phosphorus, PO43-, Na+, K+, COD, DO, BOD, oil and grease, Ca2+, Mg2+, total hardness, SO42- and heavy metals (viz. Cu, Fe, Mn, Pb, Cd, Zn, and As). Four inlets (viz. Botkoul, Telbal Nallah, Pishpav Nallah, and Nallah Meerek Shah), two outlets (viz. Dal Lock Gate and Nallah Aamir Khan), and five sampling sites within Dal Lake (viz. Char Chineri, Nehru Park, Southeast SKICC, Northeast SKICC, and Near Karpora Lam) were selected as study sites during summer and autumn of 2020. The data reveals that in summer, temperature ranged from 14.10 - 23.60 oC, pH (6.71 – 8.18), DO (2.09 - 7.34 mg/L), total phosphorus (0.33 - 0.49 mg/L), orthophosphate (0.26 - 0.31 mg/L), COD (26.67 - 80.00 mg/L) and BOD (3.42 - 9.11 mg/L) and these levels were higher than recorded in the autumn at most of the study sites. Conversely, in autumn, higher concentrations of TDS (74.67 - 449.67 mg/L), EC (113.33 - 640.00 µS/cm), NO3--N (0.85 - 1.78 mg/L), NH3-N (0.79 - 2.18 mg/L), SO42- (39.33 - 218.53 mg/L), oil and grease (0.07 - 0.16 mg/L), Ca2+ (15.01 - 126.83 mg/L), Mg2+ (11.91 - 141.51 mg/L) and total hardness (96.58 - 755.56 mg/L) were recorded at most of the study sites. Iron, Manganese, and Lead were higher during the summer, whereas Copper, Zinc, and Cadmium were higher during the autumn. The seasonal variation between most locations (study sites) and among parameters was statistically significant (p ? 0.05) respectively. This implies the influence of spatiotemporal and environmental factors on the poor water quality of Dal Lake and its tributaries.

Keywords: Dal Lake; heavy metals; physicochemical; seasonal variation; summer and autumn; tributaries.