Trophic State Assessment of a Freshwater Himalayan Lake Using Landsat 8 OLI Satellite Imagery: A Case Study of Wular Lake, Jammu and Kashmir (India)
Fayma Mushtaq, Mili Ghosh Nee Lala, Afaan Gulzar Mantoo
Abstract
Abstract A new version of Trophic State Index for freshwater Himalayan Lake (TSI FHL ) has been derived from Landsat 8 OLI to determine the aquatic health of the lake ecosystem. TSI FHL is based on chlorophyll‐a concentration ( C Chl‐a ) which has been retrieved from Landsat 8 OLI data and laboratory measurements using an empirical approach. Further, in situ measurements have also been taken with Secchi disk depth (Z SD ) in a freshwater Himalayan Lake (FHL). The derived C Chl‐a exhibited lower and upper limit of 25.81 and 207.96 μg/L, respectively. The modeled Z SD values ranged between 0.18 and 0.66 m with an average depth of 0.50 m. The best‐fitted regression model, developed for C Chl‐a with R 2 = 0.89, exhibited model error of 0.77 μg/L for the standard error of estimate (SEE). The mean absolute percentage error (MAPE), and Nash‐Sutcliffe coefficient ( E ) values were 5.83% and 0.98 μg/L, respectively. For the Z SD , the best‐fitted model showed errors of 0.11 μg/L (SEE), 13.93% (MAPE), and 0.77 μg/L ( E ) with R 2 = 0.84. The proposed model is useful for bio‐optical studies of Himalayan Lake ecosystems and could provide potential support for inland water management. Long term strategies like multisector monitoring and control of nutrient load entering the lake can be developed to alleviate problems of eutrophication.