Groundwater banking is a

water management Water resources are natural resources of water that are potentially useful for humans, for example as a source of drinking water supply or irrigation water. 97% of the water on the Earth is salt water and only three percent is fresh water; slightl ...

mechanism designed to increase water supply reliability.Semitropic Water Storage District. FAQs. .

Groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...

can be created by using dewatered

aquifer An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials (gravel, sand, or silt). Groundwater from aquifers can be extracted using a water well. Aquifers vary greatly in their characterist ...

space to store water during the years when there is abundant

rainfall Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...

. It can then be pumped and used during years that do not have a surplus of water. People can manage the use of groundwater to benefit society through the purchasing and selling of these groundwater rights. The surface water should be used first, and then the groundwater will be used when there is not enough

surface water Surface water is water located on top of land forming terrestrial (inland) waterbodies, and may also be referred to as ''blue water'', opposed to the seawater and waterbodies like the ocean. The vast majority of surface water is produced by prec ...

to meet demands.Maliva, Robert G. "Groundwater Banking: Opportunities And Management Challenges." Water Policy 16.1 (2014): 144-156. Academic Search Complete. Web. 18 Nov. 2015. The groundwater will reduce the risk of relying on surface water and will maximize expected income. There are regulatory storage-type aquifer recovery and storage systems which when water is injected into it gives the right to withdraw the water later on. Groundwater banking has been implemented into semi-arid and arid

southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural region of the United States that generally includes Arizona, New Mexico, and adjacent portions of California, Colorado, Ne ...

because this is where there is the most need for extra water. The overall goal is to transfer water from low-value to high-value uses by bringing buyers and sellers together.

Groundwater storage concepts

The bank is an aquifer used as an underground storage tank, and the recharge of water causes an increase in the volume of water stored in the aquifer to have increasing water levels. In the case of a withdrawal there would be a decrease in water levels. The amount of water depends also on a couple of other factors including groundwater pumping by other users, leakage, and natural recharge. The recharge of water by land application or injection increases the volume of water, and then some of the water will be used at a future time. It can be looked at as inputs of water minus outputs is equal to the change in water storage. Another aspect is the

hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...

which is the difference between dynamic and static response to recharge and abstraction. The water levels will rise or fall in the well during recharge and recovery. Once recharge and recovery stops the water levels return to background levels, and one of the main issues is the change in static water levels after the dynamic response from recharge or recovery disappears. There can be some technical issues with the aquifer response to manage recharge and recovery. If the aquifer is hydraulically connected to body of water on the surface there are increases in the water table elevation as the result of managed recharge. This could increase the rate of discharge or decrease the amount of induced recharge, and both of these cause water to leave the basin. The recharge and recovery could also affect the lateral and vertical groundwater flow into the aquifer. There is not always a one-to-one correspondence between the volume of water and the change in storage.

Methods of groundwater banking

Groundwater banking is accomplished in two ways: through in-lieu and direct recharge. In-lieu recharge is storing water by utilizing surface water "in-lieu" of pumping groundwater, thereby storing an equal amount in the groundwater basin. In-lieu recharge is the renewable surface water used to irrigate the farmland in place of using regular groundwater. This is helping to save more groundwater because the water stays in the aquifer to be used later. Direct recharge is storing water by allowing it to percolate directly to storage in the groundwater basin. With direct recharge it floods an area so that water seeps through the ground to get to the

s. The water is then pumped out when there is more of a demand with the use of recovery wells.

Pros and cons

There are some disadvantages to retrieving this groundwater. As groundwater is withdrawn from below the surface, the ground above settles. This settling of land, known as subsidence, can fracture roads and building foundations and can burst water, sewer, and gas lines. This method hasn't been well tested yet, so there could be some negative impacts on the environment. Water is a public resource and this could make water become a private industry. Groundwater banking can be compared and contrasted to the use of surface reservoirs. Groundwater banking has many advantages over the use of surface reservoirs. The projects do not cost as much to construct and store the same amount, if not more, than the surface reservoirs. The bank will have less of an impact on the environment than a surface reservoir. The water that is in the bank will no longer be exposed to

evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when humidi ...

, but several feet per year of water is lost in the reservoirs. It is more reliable to use when the

climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologic ...

is changing and can respond to seasonal changes better to manage the water than the surface reservoirs. There are also some disadvantages to groundwater banking over surface reservoirs. There are energy costs to recovering the water and these costs are usually more than the reservoirs. There is also a pumping capacity and when the demands change during the year the productiveness can be limited. Not all groundwater is used when sold. Some groundwater is being studied for its benefits. Groundwater banking and aquifer storage systems are being explored to control flooding during times of high precipitation.http://www.cpo.noaa.gov/sites/cpo/Projects/SARP/CaseStudies/2013/Russian%20River%20Basin%20CA_Case%20Study%20Factsheet_Extreme%20Weather%20Events_2013-2-6v1.pdf The groundwater is being traded in many regions. There are trades even in the United States. The city of

San Antonio ("Cradle of Freedom") , image_map = , mapsize = 220px , map_caption = Interactive map of San Antonio , subdivision_type = Country , subdivision_name = United States , subdivision_type1= U.S. state, State , subdivision_name1 = Texas , s ...

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

is the largest city in the United States that relies solely on groundwater for its municipal supply.

Feasibility of groundwater recharge on agricultural land

There have not been many successful trials of groundwater banking on agricultural land since the land is usually privately owned. The owners have to be on board with the practice of groundwater banking knowing what the risks and best practices entail. A study was done to find a Soil Agricultural Groundwater Banking Index (SAGBI) which evaluates

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

suitability for the use of groundwater banking in

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

. There are five factors that determine the feasibility of groundwater recharge on agricultural land: deep percolation, root zone residence time,

topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

, chemical limitations, and soil surface conditions. The five factors were modeled using

United States Department of Agriculture The United States Department of Agriculture (USDA) is the United States federal executive departments, federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, ...

Natural Resources Conservation Service (USDA-NRCS) digital soil survey data. For the deep percolation factor a high rate of water transmission through the

soil profile A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath. Horizons are defined in many cases by obvious physical features, mainly colour and texture. ...

and into the aquifer below is the key to successful groundwater banking. It becomes more important when there is flooding since it could be used as the main water source. It is derived from the saturated hydraulic conductivity of the limiting layer. Saturated hydraulic conductivity measures soil permeability when the soil is saturated. When looking at root zone residence time factor it was found that a prolonged duration of saturated conditions in the root zone has the possibility to cause damage to perennial crops. If the soil causes a bud break it is more likely that the crop will become damaged. Most crops are not able to withstand long periods of saturated conditions in the root zone. The root zone residence time estimates the likelihood of having good enough drainage within the root zone once water is applied. The topography of land for spreading water across fields has the best outcome when there is level topography. Level topography works the best because it holds water better on the landscape which allows infiltration across large areas.

Infiltration Infiltration may refer to: Science, medicine, and engineering *Infiltration (hydrology), downward movement of water into soil *Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings *Infiltration (me ...

reduces ponding and minimizes

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

by runoff. The chemical limitations factor is related to the

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

which is a threat to the

sustainability Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livi ...

agriculture Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to ...

and groundwater. This factor was determined by

electrical Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by ...

conductivity (EC) of the soil which measures the

soil salinity Soil salinity is the salt content in the soil; the process of increasing the salt content is known as salinization. Salts occur naturally within soils and water. Salination can be caused by natural processes such as mineral weathering or by the ...

. The best soil has the lowest levels of salinity. Soil also has

pesticide Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampri ...

s and nitrate, but it is unable to be evaluated due to the dependency on management history. The surface condition factor is when banking by flood spreading can change the soil surfaces physical conditions. Infiltrations limits can be caused by quality and depth of water that could lead to the destruction of aggregates, the formation of physical crusts, and compaction. To determine soil condition two factors were examined: soil erosion factor and sodium absorption ratio (SAR). To determine the feasibility of groundwater banking each of the five factors were assigned a weight to how significant it was, and then a SAGBI score was calculated. The weights were 27.5% deep percolation, 27.5% root zone residence time, 20% topography, 20% chemical limitations, and 5% surface conditions. Of the 17.5 million acres of agricultural land examined only 5 million acres were considered soils with excellent, good, and moderately good suitability. Agricultural groundwater banking can be associated with financial risk which may cause crop loss, so in the end, the loss may exceed the benefits of water saving. Adoption of this practice would require support to protect growers from risk of crop failure.

Groundwater accounting system

The

accounting Accounting, also known as accountancy, is the measurement, processing, and communication of financial and non financial information about economic entities such as businesses and corporations. Accounting, which has been called the "languag ...

system tracks the recharge and withdrawals of stored water and it can include a market system to reserve the storage of water. Depositors could earn credits for the recharge of water which can be used later on for the water recovered from the bank. The banking system could then be set up to allow trading of credits. There are several objectives of the water bank accounting system: track water deposits, withdrawals, and to control the amount, timing, and location of withdrawals by the participants. If groundwater is not regulated there is more of a chance for freeriding and overuse. There needs to be sustainability of the system in order to continue with the operation of the system or there would be no point to using it. The accounting method that will be used is the double-entry accounting method, so every transaction is recorded as a debit and a credit in separate

ledger A ledger is a book or collection of accounts in which account transactions are recorded. Each account has an opening or carry-forward balance, and would record each transaction as either a debit or credit in separate columns, and the ending or ...

accounts. This also allows for tracking of

inventory Inventory (American English) or stock (British English) refers to the goods and materials that a business holds for the ultimate goal of resale, production or utilisation. Inventory management is a discipline primarily about specifying the shap ...

in asset accounts and claims to inventory in ownership accounts. Deposits happen when more water is stored in an aquifer than there is supposed to be. The recharge of water by a member would be a credit in a member's account and a liability in the bank's account. For the bank to be successful then both ledgers have to be balanced, so the right to water in a member's accounts should be equal to the amount of water that can be recovered from the system. If the right to water is greater than liabilities then the bank is insolvent, and this will become a problem when a drought occurs. There are some issues that could arise from using this water bank accounting system. These problems were evaluated for the Las Posas Basin groundwater bank and Fox Canyon Groundwater Management Agency (FCGMA) has jurisdiction over the project. FCGMA reported that the accumulation of credits has been increasing for banks. What can happen is the accumulated credits can become greater than the annual abstraction rate. The volume of credits accumulating exceed the amount of water that can be taken out during a short-time period. This will cause a threat to the regional groundwater resource or even depressions in groundwater elevations, land subsidence, and seawater intrusion.

Regulatory framework

The banking systems need regulatory control over the basin to implement the withdrawal rates and to ensure that other participants will not extract too much stored water. The best scenario would be that the bank owner or participants would be the main users to ensure that abstractions are controlled. If this is not the case, then there must be another way to control the number and amount of abstractions happening. It needs to be clear who has priority over stored water, so that when abstractions are constrained it is known who will get the water first. There can be problems when multiple entities have jurisdiction over a project, and this can cause regulatory and organizational challenges. There are some generally accepted rules and also many of the issues are handled through state-specific concepts. One of the main requirements is an action needs to be in place so that the stored water is not being abstracted by other users who are not involved in the system. These frameworks rely on the knowledge of

hydrogeology Hydrogeology (''hydro-'' meaning water, and ''-geology'' meaning the study of the Earth) is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust (commonly in aquif ...

to determine the success of a system, and the systems need to provide benefits to prove it was worth building.

Economics

The different projects can become economically efficient by maximizing the benefits of the limited resource (water). To maximize efficiency the users need to find where

marginal cost In economics, the marginal cost is the change in the total cost that arises when the quantity produced is incremented, the cost of producing additional quantity. In some contexts, it refers to an increment of one unit of output, and in others it r ...

is equal to

marginal benefit In economics, utility is the satisfaction or benefit derived by consuming a product. The marginal utility of a good or service describes how much pleasure or satisfaction is gained by consumers as a result of the increase or decrease in consumpti ...

. It is important for supply to equal demand like in the figure below. The use of water becomes a negative

externality In economics, an externality or external cost is an indirect cost or benefit to an uninvolved third party that arises as an effect of another party's (or parties') activity. Externalities can be considered as unpriced goods involved in either co ...

when there is rivalry and the property rights are not well-defined. The way to eliminate some of the negative externality is there can be a

tax A tax is a compulsory financial charge or some other type of levy imposed on a taxpayer (an individual or legal entity) by a governmental organization in order to fund government spending and various public expenditures (regional, local, or n ...

placed on the resource to increase the marginal cost. When they tax the right amount the user will use the resource at the socially acceptable level. The other way to affect the externality is to create a

subsidy A subsidy or government incentive is a form of financial aid or support extended to an economic sector (business, or individual) generally with the aim of promoting economic and social policy. Although commonly extended from the government, the ter ...

. A subsidy will increase the marginal benefit in order to get to the socially accepted level of use for the resource. Simple supply and demand

Water is not a homogeneous

commodity In economics, a commodity is an economic good, usually a resource, that has full or substantial fungibility: that is, the market treats instances of the good as equivalent or nearly so with no regard to who produced them. The price of a comm ...

for several reasons which include sensitivity to location, time of use, form of the water, and administrative responses. The use of groundwater banking can make water a more homogenous commodity. This can create a market value which will enhance private investment increasing the benefits. It will also align marginal benefit with marginal cost causing the market to come to an economically efficient level. Water has high transaction costs and create market barriers which devalues the use to society restricting the reallocation of resources. The demand does not change when there is a market barrier so there will be many unpleasant people if they do not get their share of water. If a bank is in the process of being made the removal of market-access barriers can be part of the negotiations, but it is not necessarily the bank itself that is the cause. Groundwater banking could reduce transaction costs because each individual won't have to analyze each transaction.

References

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External links

How groundwater banking is done: A look at three groundwater banking operations
Civil engineering