Saltwater intrusions can be an important environmental problem, which can degrade water supplies required for drinking or irrigation. Saltwater intrusions are caused in places near the ocean where there are excessive withdrawals of underground supplies of fresh waters. This allows underground saltwaters to migrate inland, and spoil the quality of the aquifer for most uses. Saltwater intrusions are usually caused by excessive usage of ground water for irrigation in agriculture, or by excessive demands on freshwaters to supply drinking water to large cities.