Groundwater Replenishment Methods
 
Matthew Nier niermm@uwec.edu
 
Part of Water is Life, a class website on water privatization and commodification, produced by students of Geography 378 (International Environmental Problems & Policy) at the University of Wisconsin-Eau Claire, USA, Spring 2004.

     

Water is a renewable resource, to a point. The current population of the world is using water at an alarming rate, and nature cannot keep up. You may think there is enough water on earth for everybody, but when you look at the numbers, the amount readily available for consumption is very little. Of the Earth's water, 97% is salt water and 3% is fresh water, but of that 3%, only 0.003% is available for human consumption. In industrialized countries, urban sprawl is increasingly paving over land, forcing rainfall to flow to surface water, rather than seeping back into underground aquifers. This is why groundwater replenishment programs are very important to the survival of the Earth and all of its inhabitants.

    Artificial Recharge

    Artificial recharge is a very common process to replenish groundwater. One example of artificial recharge is the use of "reclaimed municipal wastewater" through infiltration basins or direct injection. Some other examples of artificial recharge are water traps, cutwaters, drainage wells, septic tanks and effluent disposal wells, and sinkhole injection of excess surface flows.

    Reclaimed Municipal Wastewater

    Reclaimed municipal wastewater is defined as any surface water that is not drinkable. Obviously there are drawbacks to replenishing the groundwater with this type of water. The biggest drawback to this style of artificial recharge are the health risks. It is essential that the water go through a certain number of pretreatment steps before the water can be introduced to the groundwater. This will prevent any contamination that may occur. There are two main ways to introduce the pretreated water into the groundwater, infiltration basins and direct injection. Takashi Asano, Ph.D., P.E.

    Infiltration Basin

    An infiltration basin is where "recharge waters such as treated municipal wastewater percolates from spreading basins through the unsaturated groundwater zone." This form of replenishment is the oldest, most easily used, and most widely used in the world. The reason infitration basins are so popular is because they are the most efficient and require the least maintenance. This form of recharge is best in huge open areas where plant an animal life is undisturbed.Takashi Asano, Ph.D., P.E.

    Direct Injection

    Direct injection is where the treated water is put directly into the groundwater. Direct injection is used where the topography of the land is not suitable for large infiltration basins, such as in the Rockie Mountains. Takashi Asano, Ph.D., P.E.

It is important to remember that both these forms of recharge are not limited to reclaimed municipal wastewater. They are used by many different communities across the world along with many other forms of artificial recharge.

Water Trap

A water trap is a mini-dam used to increase infiltration. Water traps are constructed perpendicular to riverbanks at a height of 1-3 meters. Water traps are constructed every 70-100 meters and have a holding capacity between 250 and 400 meters cubed. 1.9 Artificial recharge of aquifers

Cutwaters

Cutwaters are areas of excavated land, at varying dimensions, built in "low-lying areas." Cutwaters are built in areas with very few rivers or streams and are primarily used to harvest the available surface water. Cutwaters are built on permeable ground in order to replenish the groundwater or on impermeable ground to act as reservoirs.1.9 Artificial recharge of aquifers

Drainage Wells

Drainage wells, or "suckwells" as they are sometimes referred to, are used to dispose of drainage waters. These drainage waters include agricultural runoff, industrial runoff, runoff from pavement, etc. The water is sent through a series of tubes to the well that has an area of about 16-36 square feet. 1.9 Artificial recharge of aquifers

    Septic Tanks and Effluent Disposal Wells

    Effluent disposal wells are "very similar to suckwells in design and construction, except that they are used in conjunction with septic tanks and are always covered." 1.9 Artificial recharge of aquifers

    Sinkhole Injection of Excess Surface Flows

    Water is treated before it is allowed into the groundwater. This process is primarily done with salt water. The water is continuously monitored to make sure the saline level (saltiness) is not too high. 1.9 Artificial recharge of aquifers

    These types of artificial recharge styles are common throughout the world. In the Argentinian provinces of San Juan, Mendoza, and Santa Fe, infiltration basins have been installed; cutwaters are being used in the Paraguayan Chaco; and Caribbean island of Barbados is using drainage wells. The rainfall of these different comunities is not a sustainable amount. Artificial recharge is saving these communities from extinction and preserving their way of life. Even though artificial recharge seems to be a good idea, there are advantages and disadvantages you have to take into account before a community can make the decision to install one of them. 1.9 Artificial recharge of aquifers

    Advantages:

    • The technology is appropriate and generally well understood by both the technicians and the general population.
    • Very few special tools are needed to dig drainage wells.
    • Because of the structural integrity of the coral rock formations, few additional materials are required (concrete, softstone or coral rock blocks, metal rods) to construct the wells.
    • Groundwater recharge stores water during the wet season for use in the dry season, when demand is highest.
    • Aquifer water can be improved by recharging with high quality injected water.
    • Recharge can significantly increase the sustainable yield of an aquifer.
    • Recharge methods are environmentally attractive, particularly in arid regions.
    • Most aquifer recharge systems are easy to operate.
    • In many river basins, control of surface water runoff to provide aquifer recharge reduces sedimentation problems.
    • Recharge with less-saline surface waters or treated effluents improves the quality of saline aquifers, facilitating the use of the water for agriculture and livestock. 1.9 Artificial recharge of aquifers

    Disadvantages:

    • In the absence of financial incentives, laws, or other regulations to encourage landowners to maintain drainage wells adequately, the wells may fall into disrepair and ultimately become sources of groundwater contamination.
    • There is a potential for contamination of the groundwater from injected surface water runoff, especially from agricultural fields and roads surfaces. In most cases, the surface water runoff is not pre-treated before injection.
    • Recharge can degrade the aquifer unless quality control of the injected water is adequate.
    • Unless significant volumes can be injected into an aquifer, groundwater recharge may not be economically feasible.
    • The hydrogeology of an aquifer should be investigated and understood before any future full-scale recharge project is implemented. In karstic terrain, dye tracer studies can assist in acquiring this knowledge.
    • During the construction of water traps, disturbances of soil and vegetation cover may cause environmental damage to the project area. 1.9 Artificial recharge of aquifers

    Current Project

    Orange County, California, is currently running "one of the finest state-certified water quality laboratories." Orange County is treating municipal waste water and using it as the main water supply for its residents. This municipal wastewater treatment is producing about 70,000 acre-feet of water per year. To give you an idea of how much water is being produced, one acre-foot of water is enough to feed the water needs of two Orange County families per year. The goals of this project are:

    • Orange County needs more reliable, high-quality water in the future to replenish the groundwater basin, to protect the groundwater basin from seawater intrusion, and for industrial uses.
    • The Groundwater Replenishment System reduces the amount of treated wastewater released into the ocean and delays the need for another ocean outfall.
    • The Groundwater Replenishment System decreases Orange County's reliance on imported water from northern California and the Colorado River.
    • The Groundwater Replenishment System's locally-controlled water helps drought-proof Orange County.
    • The Groundwater Replenishment System's new water will help meet statewide water objectives.
    • The Groundwater Replenishment System helps reduce mineral build up in Orange County's groundwater by providing a new source of ultra-pure water to blend with other sources, including imported water. Groundwater Replenishment System

This groundwater replenishment project is an expensive one that many communities around the world could not afford.

Another way that a community could help replenish the groundwater is to help prevent the contamination of it. By doing this, the community is assured that the water it is drinking is pure and safe. The Wisconsin Department of Natural Resources (WDNR) is instituting grounwater replenishment regulations on new construction sites, to prevent sedimentation, and require "sinks" to allow rainfall and snow melt to seep back into the local aquifer. You have to get a permit before you can build on your land, and there are a few requirements to get that permit:

  1. Develop an Storm Water Pollution Prevention and Erosion Control Plan describing the best management practices that will be used on-site for erosion control.
  2. Submit a Construction Site Notice of Intent form to the Department at least 14 working days before construction will begin. To avoid potential construction delays, DNR staff recommend submitting a Notice of Intent as early in the project design process as possible.
  3. Submit the $200 fee.
  4. Implement best management practices, as described in the Storm Water Pollution Prevention and Erosion Control Plan, to help control erosion and prevent contamination of storm water.
  5. Conduct weekly on-site inspections through the duration of the project. Construction Water Management

For more information about the rules and regulations of construction sites and other water management issues in Wisconsin, visit the Storm Water Staff. If you have any questions regarding any of state rules, just go to your local DNR website.

Groundwater replenishment is a major factor in the survival of every species on the planet. If we keep using groundwater at our current rate and contaminating the sources that replenish the groundwater, there will be no way for us to survive. There are plenty of options out there to replenish your local groundwater. Just remember that groundwater replenishment is a problem affecting everyone, but there is something you can do about it.

 

Sources

Name of website: Takashi Asano, Ph.D., P.E.

Name of website: 1.9 Artificial recharge of aquifers

Name of website: Groundwater Replenishment System

Name of website: Construction Water Management