> Alongside flooding from rivers, Jakarta is also sinking about 5 to 10 centimeters each year and up to 20 centimeters in northern Jakarta mainland. From 2000 to 2050, the potential coastal flood extent is estimated to increase by 110.5 km2 due to both land subsidence and sea level rise.[44] Land subsidence in Jakarta is mainly caused by the overuse of groundwater.[45] At the same time, the groundwater has lost its capacity to recharge due to the lack of watershed areas and overpopulation in the capital. Without any groundwater regulation in place, buildings in Jakarta are drawing water from the ground at an unprecedented rate. For households, especially those at the bottom of the economic pyramid, access to piped water is considered a luxury. Not only must the customer pay for the tariff, which is higher than other Indonesian cities,[46] the installment fees often burden the poor households to connect to the tap.

> In addition, residents consider piped water (and to some extent groundwater) quality in Jakarta to be of poor quality, thus explaining why only 28 percent of Jakarta households drink piped water and groundwater compared to 95 percent in 2000.[47] It is important to note that apart from drinking, people in Jakarta still use groundwater, and to some extent piped water and wended water.[48] Such hydrological behaviour has led to the overuse of groundwater, thus contributing to the land subsidence.

That 28 percent seems concerning. Can someone explain more?