Severe Watershed Degradation Escalates Sri Lanka's Climate Risks 📈

• Macro & Baseline Risks: Over two-thirds of forest cover lost in 100 years. >50% of agricultural land degraded, and 1/3 of national land is landslide-prone. 3.6–3.8M people face poor groundwater quality. • Agricultural Impact: Unprotected slopes in tea plantations lose up to 75 tonnes/ha/yr of soil (vs 2 t/ha/yr on managed plots), with 30 cm of topsoil stripped over a century. Decades of chemical usage dropped soil pH below 4.0, threatening the tea sector which already saw a 30-year yield low in 2020. • Energy & Infrastructure: High erosion feeds directly into reservoirs generating 35–50% of hydropower. Forest cover in the Mahaweli catchment dropped from 44% to 24% (1956–1992), causing Rantembe reservoir to lose 72% storage capacity within 3 years of construction. Key dams (Victoria, Kotmale, Randenigala, Moragahakanda) face accelerated siltation, reducing grid resilience and flood buffers. • Coastal & Marine: >50% of mangrove cover lost since the 1980s; shorelines retreating by 3.5–4.0m annually due to sand/coral mining (historically sourcing 90% of domestic construction lime). • Proven Fixes & Action Plan: Terracing with vetiver grass reduces soil loss to 0.17 t/ha/yr; IAEA isotope-based mapping cut erosion by 42%. A 5-point action plan highlights source protection at Horton Plains, slope erosion control, soil pH recovery, reservoir dredging, and setting up a unified inter-agency watershed authority to bridge data integration gaps.