Future Impacts of Freshwater Resource Management: Sensitivity of Coastal Deltas

We present an assessment of contemporary and future effective sea level rise (ESLR) using a sample of 40deltas distributed worldwide. Forany delta, ESLR is a net rate defined by eu~tatic sea-level rise, natural gross rates of fluvial sediment deposition and subsidence, and accelerated subsidence due to groundwater and hydrocarbon extraction. Present-day ESLR, estimated from geospatial data and a simple model of deltaic dynamics, ranges from 0.5 to 12.5 mm year⁻¹. Reduced accretion of fluvial sediment from upstream siltation of reservoirs and freshwater consumptive irrigation losses are primary determinants of ESLR in nearly 70% of the deltas, while for only 12% eustatic sea-level rise predominantes. Future scenarios indicate a much larger impact on deltas thanpreviously estimated. Serious challengesto human occupancy of deltas worldwide are conveyed by upland watershed factors, which have been studied less comprehensively than the climate change and sea-level rise question.