Geospatial and Multi-Index Assessment of Urban Lake Water Quality: Insights Into Pollution Sources and Irrigation Suitability in Udaipur, the Lake City of India.

Urban lake water quality is increasingly threatened by rapid urbanization and unregulated anthropogenic activities. This study evaluates the spatial and seasonal water quality of four major urban lakes in Udaipur-Fateh Sagar, Swaroop Sagar, Pichola, and Goverdhan Sagar-using an integrated approach that combines multiple water pollution indices (WQI, CPI, OPI, and EI) and irrigation suitability indices (SAR, KR, Na%, PI, TH, MH, RSC, and RSBC). An interlake comparative analysis was employed to examine spatial-temporal variations, while land use/land cover (LULC) mapping and principal component analysis (PCA) were applied to identify dominant pollution sources. Results reveal significant spatial-temporal variation, with Goverdhan Sagar showing the highest pollution levels (WQI > 300, CPI > 1, OPI > 2.5, and EI > 0.01) due to sewage and industrial discharges, while Fateh Sagar had comparatively better water quality. Although irrigation suitability remained largely acceptable, elevated SAR and RSC levels pose long-term risks to soil health. PCA highlighted organic pollution, nutrient enrichment, and industrial effluents as key contributors to degradation. The study presents a replicable multi-index geospatial framework to support sustainable urban lake management and inform targeted pollution control strategies. SUMMARY: The present study evaluates pollution and irrigation suitability in Udaipur's four major lakes using multiple indices (WQI, CPI, OPI, EI, SAR, KR, Na%, and so on). The methodology includes an interlake comparative analysis, LULC analysis, and PCA to identify pollution hotspots and dominant pollution sources. Goverdhan Sagar exhibited the highest pollution (WQI > 300 and CPI > 1), while Fateh Sagar had the least contamination. Eutrophication was highest in Goverdhan Sagar. PCA identified organic pollution, nutrient enrichment, and industrial discharge as primary contributors to water quality degradation. The study recommends improved wastewater treatment, controlled fertilizer use, and land-use regulations to mitigate pollution and ensure sustainable freshwater ecosystems.