Land system transformations govern trophic status of urban wetland
ecosystem: Perspectives from remote sensing and water quality analysis
Abstract
Globally, urban wetlands are facing immense pressure of land use land
cover changes (LULCCs) and associated water quality degradation that is
severely affecting the trophic status of these pristine ecosystems. This
study analyzed water quality degradation resulting due to the land
system changes in the vicinity of Khushalsar, an urban wetland, in
Srinagar city from 1980-2017. The analysis of satellite data indicated
that the wetland has lost ~18.1 ha from 1980-2017.
During the same period the urban area within the wetland increased from
0.2% to 16.5%. The land cover changes assessed in the immediate
vicinity of wetland indicated an increase of 119% in built-up and
62.8% in roads. The analysis of surface water quality of the wetland
showed much greater degradation of Khushalsar wetland. The Trophic State
Index (TSI) ranged from 73.4-84.6 thereby indicating the hyper-eutrophic
nature of the wetland. A snapshot of comparative water quality data from
2002-2018 revealed that the mean concentration of NO3–N increased from
219-433 µg L-1 and total phosphorus (TP) increased from 135.4-1236 µg
L-1 indicative of continuous nutrient enrichment. Hierarchical cluster
analysis (HCA) clustered 8 sampling sites into 4 groups based on
likeness of water quality characteristics. Similarly, discriminant
analysis (DA) showed the formation of similar patterns of clusters,
authenticating the outcomes of HCA. Wilk’s λ quotient dispersion
highlighted the role of nutrients and ions in the development of
clusters. Principal component analysis (PCA) formed three principal
components (PC’s) accounting for a cumulative variance of 90.61%.