Bangli Landfill is subject to operational and environmental pressures associated with waste accumulation, leachate generation, rainfall, and day-to-day site management. This study combines four types of evidence—water quality, stable isotopes, multitemporal vegetation greenness, and a 27-parameter operational-risk assessment—to identify management priorities without creating a new composite index. Sixteen water samples, consisting of one leachate-treatment-plant outlet sample, 10 groundwater samples, and five surface-water samples, were collected on 5 January 2026 and interpreted as a wet-season snapshot. The outlet effluent showed the strongest chemical signature, with chemical oxygen demand of 2,140 mg/L, biochemical oxygen demand of 42.50 mg/L, ammonium of 257.76 mg/L, chloride of 429.96 mg/L, sodium of 297.97 mg/L, and potassium of 603.68 mg/L. Groundwater generally differed from the outlet effluent. Surface water showed higher organic loads and isotope values that were numerically closer to the effluent, but this similarity was not taken as proof of mixing or leachate migration. Landsat-derived greenness fluctuated during 2015–2025 without a persistent downward trend. The nominal IRBA score was 599.75, within the moderate category (300–600), but the classification is sensitive to assumptions because groundwater depth and leachate TDS were not measured directly. Varying these two parameters produced scores of 579.75–630.00. Based on the combined evidence, the main priorities are improvement of leachate and stormwater control, better management of the waste mass, reduction of biodegradable waste disposed of at the landfill, repeated monitoring of water media, and improvement of baseline data for future risk reassessment. The contribution of the study is the use of these established methods together while keeping their results separate and making the limits of each line of evidence explicit.