**3.4 Land subsidence**

The primarily cause of land subsidence is a lack of support underneath ground surface. Sometimes, when groundwater is over-exploited, the soil collapses, compacts, and sinks. This depends on various factors, such as the type of soil, soil compressibility, physical attributes of the aquifer, water table levels and earth geology. It is most often caused by anthropogenic activities, mainly from the excess removal of subsurface water.

### **3.5 Deterioration of water quality**

Saltwater intrusion is the major cause and threat to contamination of fresh groundwater supplies. Available volume of water in the aquifers is not fresh water; much of the very deep groundwater and water below seas is saline. Under natural conditions the boundary between the freshwater and saltwater tends to be relatively stable while under excessive pumping conditions it may result saltwater to migrate inland and rising upward and it leads to contamination of the water supply.
