Influence of Groundwater Management on Land Subsidence in Deltas

This paper examines effects of groundwater management on land subsidence taking into consideration visco-plastic creep and delayed compaction. The method used in this paper decomposes total strain into a direct elastic contribution and a transient viscous contribution. It is applied to a conceptual model that is partially based on real data of geology, land subsidence measurements, and hydrogeology of northern Jakarta, Indonesia. The developed model is conditioned on land subsidence measurements (from 1974 to 2010) using the Maximum a Posteriori method. The calibrated model is used to evaluate effects of four groundwater management scenarios (from 2010 to 2100) on land subsidence. Maintaining piezometric heads at their values of 2010 has not stopped land subsidence while continuous drawdown has led to larger amount of land subsidence. Furthermore, although piezometric heads recovery decreases effective stresses along the subsurface profile, land subsidence continued (at a lower rate) over time due to creep and slow dissipation of excess pore water pressure. The paper also showed that contribution of creep compaction to total land subsidence could be significant. In addition, coupled processes of consolidation and creep compaction leads to a favorable condition where slow dissipation of excess pore water pressure reduces contribution of the creep compaction to total land subsidence at early times at which degrees of consolidation are small and creep rate is large.