Groundwater Barriers and the Water Table Groundwater barriers are impermeable materials, either naturally located or artificially placed underground that seek to raise the water table by preventing groundwater from draining downstream. Natural groundwater barriers are the materials that create aquifers. An aquifer is an underground source of water, underneath it is a material that water cannot pass through, such as bedrock. Above the aquifer is usually the top of the water table. However, there are aquifers that are trapped between two groundwater barriers. These are the most pure, and can travel for thousands of miles untouched by surface contaminants. Artificial groundwater barriers are put in place to protect the water table and to raise it in certain locations. There are several reasons for doing this. In regions with low water tables and minimal surface water, irrigation can be very expensive. A groundwater barrier can raise the water table to the level where it can be easily used for irrigation or natural watering of fields. They are also called subsurface dykes. It is an underground dam placed within the flow zone of an aquifer. Controlling the Water Table In densely populated areas, with yearly wet and dry seasons, conserving groundwater during the dry periods is very important. A groundwater barrier placed in the right location will raise the water table in that spot, and keep the aquifer from draining the water away. They are put in place in a manner similar to tunnel construction, where a trench is dug large enough for the barrier to be lowered into. This must be done from the surface to the nearest, natural groundwater barriers. In most places, this natural barrier is the bedrock upon which buildings are constructed. Once the structure of the barrier is in place, the most common method is to sheath the structure in the impermeable material, usually plastic, from the bedrock to the surface. This will slow the drainage of water and raise the water table. There are risks associated with this method. If the wet season has higher than average rainfall amounts, the region with the artificial barrier will definitely experience flooding. This does not outweigh the cost of a permanent, easy to maintain irrigation system. Groundwater Collection and Where the Water Goes Groundwater collection is the use of containers that store rainwater, preventing this water from rejoining the water table. They are useful in the same regions where you put a groundwater barrier, and they can supplement each other to ensure that both your fields and homes have water. Groundwater collection can be used anywhere, from big cities to rural farmlands. Collection systems are typically made up of a tank to collect rainwater, a natural filter system, like sand, to remove large contaminants, and a main storage tank that overflows into the water table. These systems can be used to raise the water table in a field when there is little rain, or to keep you house from having to pay for city water. This article about groundwater barrier is written by the author who has great deal of knowledge about Groundwater collection.