An Overview on Techniques Involved in Recharging Ground Water and Its Impacts

Abstract

The movement of water from the surface of the earth into the sub surface areas are said to be as a hydrologic process which helps in improving the water table at the ground level. This process of water movement towards downward direction is said to be as Groundwater recharge or deep drainage or deep percolation. Ground water recharge could be achieved either by natural method or by artificial methods which involves anthropogenic processes. The ground water recharge has a superior impact while in consideration of various complexities such as climate, land surface and biosphere processes, and characteristics in the unsaturated and saturated subsurface. So in this chapter, we would like to briefly explain about the techniques involved in recharging the ground water table and also about the methods involved in estimating the ground water available along with the importance of agriculture globally along with the policies incorporated to maintain the ecological demand and also about the impacts caused to the environment due to the insufficient water at the ground water table.

1. Introduction

We all know that, in order to lead a peaceful life, we are in need of three basic things such as food, water and shelter. The main source of water for all living beings is through the fresh water which has reliable pH and also for the growth of nutritious food through agriculture. Ground water is one among the largest fresh water supply at the world for potable water, irrigation water etc. [1, 2]. At the other hand, Ground water is in need to recharge periodically through recharging methods for the replenishment of resources, since they are available as a limited resource i.e. not in an infinite manner. Hence, for the purpose of avoiding scarcity and to cope up with the need of ground water, it is really essential to recharge the ground water table as it is linked to the water resource sustainability and resilience amidst the changing climatic conditions and demand. For the purpose of planning and managing the sustainability of recharging the water table, it is necessary to consider the conditions such as total volume, location and timing according to the demand of water. Though the recharge of ground water table is one among the complex process which needs to quantify the requirement in an appropriate manner which is a tedious challenge to meet out at the hydrology. As the quantification of water cannot be done through the already exiting direct measurement methods, hence we need to adopt indirect observations for the purpose of monitoring the processes involved, properties and its quantities.

The water flow that takes place from downhill from surface water to aquifer is known as ground water recharge. This otherwise known as deep percolation or deep drainage. The most common method of recharging the ground water table is through entering the aquifer. The water recharge happens at the vadose zone which is located below the plant roots and is always denoted as flux to water table. At this process, the movement of water from water table into the saturated zone is said to be as ground water recharge. Recharging of water can be done through two methods that is through natural method and through manmade process. Some of the man made process are artificial recharge methods which are carried out through rain water harvesting where the rain water is channeled into the subsurface zone by bore holes.

The ground water recharge has a greater impact while in consideration of various complexities such as climate, land surface and biosphere processes, and characteristics in the unsaturated and saturated subsurface. The components such as Groundwater abstraction, artificial groundwater recharge and irrigation, management of hydraulic structures, infrastructure, and flood management are all manmade variables plays a vital role in the ground water recharge [1, 3]. Hence, for measuring the recharge of water table has been devised through several estimating methods (Figure 1).

Figure 1.

Sprinkler irrigation with groundwater.

2. Why ground water recharge is necessary?

For the purpose of utililization of water depending over the demand, the ground water is pumped out from the aquifer which leads to the depletion of it. For instance, due to the usage of water for the purpose of irrigating plant in agriculture sector, approximately 50 billion gallons per day is extracted from ground water table. Hence, due to the extraction of ground water as an enormous amount may lead to dry wells, poor water quality, soil subsidence and even deviation in plate boundaries. This over pumping of ground water from the soil causes the ground to sink as the soil compacts and also the soil is not capable to support the land above it. As the water table has been over pumped, the level of water at the ground decreases and necessitates deeper well drilling for the source.

The agriculture sector is dependent over the ground water for the purpose of irrigating at all over the world, as surface water availability is limited for irrigation and due to the depletion of ground water table it has become a serious threat to the farming. Though the surface water availability is low, for the places far from the availability is dependent over the water conveyance system which is a cheaper and quicker mode to transport.

Simply put, climate change disrupts the water cycle, causing less precipitation than normal, while population growth and increased food demand push agricultural businesses to pump more water out of the ground. This is known as water stress and warrants artificial groundwater recharge [4].

Ground water depletion is also caused due to the availability of surface water at lakes and streams in a reduced manner. As we all know that, the source of ground water is also achieved through surface water in an intricate way, less groundwater may imply less water flowing into wetlands and other ecosystems that rely on it. Hence the result will be less vegetation and less water quality which has high impact on Farmers and ranchers who often rely heavily on groundwater. Figure 2 shows the process of ground water recharge [5].

Figure 2.

Groundwater recharge.

3. Irrigation trends, potential and risks

The crop yield is usually dependent over the ground water as it is responsible for strengthening and radiating the cropping system which has an upper hand over household food security and income of Farmers In larger parts of Asia, North Africa and Middle East locations depends over Groundwater as it has boosted agricultural production in an enhanced manner. Due to the vast usage of land and private wells in an unregistered condition, the ground water usage has become unsustainable leading to a serious threat in rural and urban areas in the forms of pollution and over exploitation of resources that has an impact over socio economic benefits.

Due to the risk caused under the exploitation of ground water has lead to the need of developing Groundwater development research centers and policies that quantify both the potential and the risks, pooled with innovative management and policy solutions which can help guide future reliable and flexible groundwater use.

4. Global

The world is surrounded by 99% of sea water, at which only one percentage covers the water which could be adopted as potable water. This 1% of potable water covers the fresh water that is available at the streams and the ground water which is stored under the aquifers. Among which the 40% of ground water is currently utilized for the world’s irrigation purpose alone, as it provides about 13% of total food production and also 44% of irrigated food production globally [6, 7].

Though the food production and agricultural crop yield has significantly increased, at certain parts of the world the depletion of ground water has been occurred leading to replenishment levels.

An estimated amount of 14 to 17 percent of food produced with groundwater relies on unsustainable mining of groundwater resources globally. Regionally, the reliance on depleting groundwater sources for food production is greatest in South Asia, the OECD countries, East Asia, and the Near East and North Africa (MENA), where 15 percent, 16 percent, 21 percent, and 25 percent of total crop production from groundwater, respectively, is unsustainable [6].

Overexploitation causes groundwater tables to descend, water quality to depreciate, environmental dilapidation, pumping costs to ascend, and crop yields to plummet. Additionally, overreliance on depleting groundwater resources poses momentous risks, jeopardizing prospect food production and global food security as agricultural land becomes less prolific, if not nonproductive. These issues are progressively more being discussed at the national and international levels, such as at the World Food and Agriculture Organization’s Global Forum for Food and Agriculture.

5. Optimizing groundwater policies to boost sustainable groundwater use

Effective groundwater use has been constrained due to incorrect policies. The ground water is underutilized in many parts of India since there is abundant seasonal rainfall in the Indian states. The electric tube well pumps method were allowed to take by farmers in order to preserve the state ground water underground water legislation which was enacted in mid 2000s.the agriculture growth estimated to be 5% per in the year 1980s and 1990s, it fell to 2% in 2000s due to legislation where farmers has limited access to electric pump which consumes high expensive diesel pumps and electricity. State’s actual abundance of groundwater was reflected by scientist and state officials, who reviewed the changing policies which was done few years later after amendment of ground water legislation. The smallholder farmers are encouraged to use to use available water to boost agriculture productivity by relaxing the electric pump processing and flat electric connection were introduced to farmers. This policy change was implemented in the year 2011 under the recommendation of farmers. This policy results in higher net returns, better water quality and higher value outputs as this policies brought modification where over 140,000 new electric connections for tube well were established. This improves the irrigation on 250,000 ha for approximately 1.3 million water users [8]. Researchers and officials are now reviewing the policy to see if any additional changes are required to protect the state’s interests [6, 9].

6. Managing groundwater via incentives from the energy sector

Apart from water source, for sustainable groundwater irrigation incentives can be helpful to the poor farmers. In India, Ground water is considered to be the critical factor for crop growth, since the implementation farm power subsidies in 1970s, most farmers have electric connections. This leads to depletion of ground water. Solar power is considered to be climate change mitigation strategy which was introduced recently. This solar power is considered to be green alternative to electric pumps and versatile power. If carefully designed programmes are not implemented, it may endanger groundwater sustainability due to the drastic reduction in pumping cost. Effectively treated solar power is considered to be a ‘cash crop’. The intervention of solar power results in production of excess power which urges the state’s local electricity company to buys back the excess power from farmers. These profits of farmers can be used as an economic incentive to irrigate their crops effectively where groundwater and energy can conserved.

In India carbon emissions has been cut down by 4–5 percent per year by the use of solar power. The world’s first solar cooperative was formed in Gujarat where researchers recently testing the ‘smart solar pump” model. At the same time excess solar power can be purchased back at transaction costs than purchasing power from individual farmers. Sustainable groundwater use can be ensured if the model is scaled up. This model also helps in increasing the agricultural productivity and profitability, which reduces the demand for fossil – fuel energy and reduces the carbon emission into the atmosphere. Figure 3 shows the application of technology and incentives achieved through them [10].

Figure 3.

Incentives via energy sector.

7. Supporting urban aquifers via inter- sectoral water transfers

Researchers are studying the business of rural–urban water transfers and aquifer recharge with wastewater to address the significant challenges that urbanization poses to aquifers and their management. In Bangalore, India, groundwater recharge is done by directing the urban wastewater into reservoir called peri-urban tank. The revitalization reservior had been dry for more than 18 years, now it is making groundwater accessible to peri-urban and urban users once again. The Llobregat delta near Barcelona in Spain and the Mashhad plain in Iraq follows the same trend, where the freshwater is exchanged with treated wastewater by farmers and city people, while wastewater also replenishes the city’s aquifer. Researchers are investigating various models to increases the efficiency in exchanging the freshwater with treated water.

8. Enhancing community management through experimental games

To preserve the surface irrigation, forests, and protected areas, there are numerous successful models available but there is lack of models to validate the ground water. Many experimental games has been introduced by researchers in Andhra Pradesh, India to understand the social and biophysical contextual variables to solve groundwater challenges which influences the crop production and daily needs of people. The farmers refused to follow the legislation of groundwater use as a result the aquifers are used excessively which leads to reduction of water in water table. Researchers found out this due to lack of information among farmers, who believes the depletion of ground water is due to no proper rainfall, but they had not realized that crop choosing also plays major role in reduction of water in aquifer, since few crops need lot of water contribution. The experimental games plays major role in allowing the farmers to understand the connection more clear. Water management is improved by implementing by this games which proves to effective starting point [6, 11]. Figure 4 shows about the management of ground water [12].

Figure 4.

Management of ground water.

9. Estimation methods

In order to maintain the sustainability, the process of ground water recharge is adopted at which the recharge rates are usually difficult to measure. The difficulty in quantifying the rate of ground water recharge has become a tedious process because [13], it is in need to measure the related processes such as transpiration, evaporation and infiltration for achieving balance in the environment. Figure 5 shows the cycle of water flow [14].

Figure 5.

Cycle of water flow.

9.1 Physical

For the purpose of estimating the recharge at the ground water table, it is necessary to employ physical methods for determining soil physical principles. The direct physical methods are also incorporated to quantify the amount of water that passes through the soil pores below the root zone. While the indirect methods depend on determining or identifying soil parameters, which is used for measuring the potential of actual ground water recharge. At this method, the quantified ground water denotes that amount of drained ground water during no rain season and if the area of catchment is already known, then the recharge rate could be identified through the base flow itself.

9.2 Chemical

This kind of method could used while the ground water is found at a deeper zone, where the chemicals like chloride, isotropic tracer [15] are utilized in presence of relatively inert water soluble substance poignant through the soil.

9.3 Numerical models

The ground water recharge is identified using numerical codes such as Hydrologic Evaluation of Landfill Performance, UNSAT-H, SHAW, WEAP, and MIKE SHE. HYDRUS1D, a 1D programme that is available online. These kinds of codes usually use datas obtained by monitoring climate and soil to determine the amount of recharge to be done. At these numerical models, the flow of water at the vadose zone in the aquifer could be modeled with the consideration of Richards’s equation.

10. Techniques involved ground water recharge

There are two methods to recharge water table or ground water (Figure 6).

Figure 6.

Methods recharge.

10.1 Natural method

The Natural methods involve precipitation on soil, which enters into the soil. The other form of natural recharge occurs when there is leakage of water from lakes, ponds, streams etc.

10.2 Artificial method

This is efficient method in comparison with natural method, the amount of water consumed per capita is decreasing day by day and to increase the ground water recharge we need artificial method. This artificial methods involves various techniques (Figure 7).

Figure 7.

Artificial recharge.

10.2.1 Basins or percolation tank

A percolation tank is a anthropogenic method which consist of highly permeable land in its reservoir, which allows the excess runoff water to percolate and it will increase the storage of ground water. The percolation tank should be constructed using second to third order steams, particularly on extensively fractured and worn rocks with lateral continuity downstream; and the recharge area downstream should contain enough wells and cultivable land to benefit from the increased ground water. The percolation capacity in the tank bed determines the tank’s size. Percolation tanks are designed in a way to store 0.1 to 0.5 MCM capacities. There is also a column of 3 and 4.5 cm provided for ponded water.

The objective of percolation tank is ground water recharge; it allows leakage under bed’s seat. The majority of percolation tanks are earthen dams, with masonry structures serving only as spillways. For dams up to 4.5 m in height, keying and benching between the dam seat and natural ground is sufficient, and cut off ditches are not necessary (Figure 8).

Figure 8.

Percolation tank or basins.

10.2.2 Ditch and furrow system

Shallow, flat-bottomed, and closely spaced ditches or furrows provide maximal water contact area for recharge water from the source stream or canal in locations with variable topography. This technique is less sensitive to silting and preparation of soil is very less [16].

10.2.2.1 Lateral ditch pattern

The surface runoff water is streamed into a feeder canal/ditch, from which smaller ditches at right angles are formed. The flow rate from feeder cannal to ditiches is monitored by Gate valves .the uniform. The factors such uniform velocity, maximum wetted surface and furrow depth are determined by topography. A return canal transports the excess water, as well as any remaining sediment, back to the main stream.

10.2.2.2 Dendritic (tree-like) pattern

The water is streamed into the main canal. This pattern is continued until all the water are infiltrated into the ground through smaller ditches which are connected with main canal in tree like pattern.

10.2.2.3 Contour pattern

Ditches are excavated in accord with the area’s ground surface outline. The ditches are designed in such way to move front and back to navigate the spread area multiple times and switchback if ditch get close to the stream. The ditch joins the main stream to downstream at its lowest point, returning extra water to it.

10.2.2.4 Steam augmentation

The most important source of ground water reservoir is leakage that occurs from natural streams or rivers. When the total available water supply in the stream/river exceeds the rate of infiltration, the excess is lost as runoff. The infiltration can be increased by installing check bunds where runoff water can be stopped when the total available water exceeds the infiltration range.

To recharge the stored water in short span of time, there must be check dam with sufficient thickness of porous bed or weathered formation. The Height of the structure should be less than 2 m and the stored water in the structures are restrained to stream course. Series of check dams are constructed at various places to control the maximum runoff.

10.2.3 Recharge well

The main important components of groundwater recharge are:

• Catchment

• Conveyance

• Filtration

• Recharge well

10.2.3.1 Catchment

The area used for collection of water is called catchment the area can be smooth or unsmooth surface, such as rooftop, plot (garden, driveway etc). the water flowing through catchment need not to be clean, once they percolates through soil the dirt particles in water can be removed since soil acts a natural filter. The only care should be taken when using chemical residues, even small amount would have impact on whole ground water. Utmost care must be given while considering gardens and farmlands since there are high chances of using fertilizers and pesticides (Figure 9).

Figure 9.

Catchment.

10.2.3.2 Conveyance

There are different conveyances for different surfaces. Gutters or downpipe acts as conveyor for rooftops. Channels/pipes are used to carry water for plots. Storm water drains in layouts, campuses, and large residences convey runoff from various land use catchments (Eg: parks, roads, other paved areas, gardens and excess rooftop runoffs). As a result, storm water drains are an important conveyance system for recharge (Figure 10).

Figure 10.

Conveyance.

10.2.3.3 Filtration

Filtration is a process to remove the dirt or residual. In this method, soil act as filtration medium.

10.2.3.4 Recharge well

There are multiple ways to incorporate Recharge wells in the real estate development. The run off rain water, the catchment area decides the design and number of recharge well. Large numbers of recharge wells has to built in valley points, since they get highest rainfall. The valley point can be identified from topography study.

10.2.4 Recharge pit

Recharge pits are constructed for recharging a trivial aquifer. They can be circular rectangular or square. They are generally 1–2 m wide and 2–3 m deep. The Water that is diverted to ground water table should be residual free. In order to achieve that condition the pits after excavated are filled with stones, sands and boulders which act as a filter medium. Cleaning of the pit area should be done from time to time. Small buildings can have roof top area up to 100 m². If the pit is trapezoidal, the side slopes should be steep enough to avoid silt deposition [17].

10.2.5 Recharge shaft

A recharge shaft may be dug or drilled. The recharge shaft are filled with pebbles, sand and boulders, where cleaning can be done by removing the top layers alone and refilling it. This type’s ground water recharge is most commonly seen in area where the shallow aquifer is located. They are constructed where there is low permeability and ends in more permeable layer. Usually the depth of the recharge shaft varies from 10 to 15 m below the ground level [17].

10.2.6 Dug wells

Dug wells are the most common method of extracting water from ground water table. Dug well are bored manually since the labour charges are minimal. in this methods the dug well are bored deep down until it reaches the ground water level from where water can be obtained with the help of pumps and by other means. The diameter at initial phase is 1.5 meters and at final stage after lined with stones, bricks, or tiles to prevent disintegration, it is 1.2 meters but in some cases the diameter at initial phase is 15 meters. Since the excavation cannot do beyond the ground water table it will be only 10 to 30 feet deep. There are also high chances of contamination, since the well are shallow. In order to prevent the contamination there must be certain features (Figure 11).

Figure 11.

Dug well.

10.2.6.1 Dug well construction features

In order to prevent the contamination, the well needs to be covered with cap or concrete curb that stand above the ground level and also the land surface around the well should be slope in nature so that water runs from the well flows into land and will not form pool near the well. The well needs to be cased with concrete and a cement grout or bentonite clay to avoid disintegration of well. The pump of the well should be separately placed rather than placing it near the well.

10.2.7 Induced recharge

It is an indirect method of artificial recharge involving pumping from aquifer hydraulically connected with surface water, to induce recharge to the ground water reservoir. When the cone of depression intercepts river recharge boundary a hydraulic connection gets established with surface source which starts providing part of the pumpage yield. In such methods there is actually no artificial build up of ground water storage but only passage of surface water to the pump through an aquifer. In this sense, it is more a pumpage augmentation rather than artificial recharge measure.

Usually the ground water recharge is possible in a proper way as the abandoned channels in the hard rock regions act as a good site for the induced process of recharging. For this process, the check weir at stream channel helps in infiltration of water from surface reservoir to the abandoned channels which are then directed towards the aquifers.

During the unfavorable hydro geological conditions, induced recharge process has a greater advantage and also it helps in improving the quality of surface water which is generally improved due to its path through the aquifer material before it is discharged from the surface. Also, for the purpose of obtaining very high water supplies from the river bed deposits or waterlogged areas, collector wells are constructed. In India, these kinds of collector wells are constructed in the river bed such as Yamuna bed at Delhi and also in other places in Gujarat, Tamil Nadu, and Orissa as these wells are economical due to large discharges and lower lift even though initial capital cost is higher as compared to tube well. If the phreatic aquifer is situated near the river of limited thickness, then instead of horizontal wells, the vertical wells could be adopted which is rather effective than the other [17].

11. Creation of resilience to the environment

For agricultural production, the groundwater has the capability to improve the potentially of resilience in food-insecure areas around the world. Due to this the rural income of the farmers can increase and also to withstand climate shocks and water variability. However, in order for groundwater to contribute to the sustainable intensification of agriculture, it is critical to understand where to invest in groundwater development and how to manage groundwater resources in a sustainable manner. WLE has identified potentially usable groundwater resources in Africa, supported important policy changes to improve the sustainable use of groundwater in eastern India, and created maps and new tools that can be used to implement new groundwater policies [6].

12. Conclusion

Hereby, we conclude that the ground water recharge through artificial method is effective while compared to that of natural method. Though the installations of artificial methods are cost consuming rather than natural methods, the rate of ground water recharge level is in an increased manner along with the consideration of water quality. Since, the water consumption rate per capita area is increasing day by day; the need for creating the source of ground water recharge is mandated in order to satisfy the demand.