A rapid rise in population and urbanization has caused excessive groundwater exploitation, which is a major concern. Therefore, technologies to replenish the groundwater are necessary for its conservation and sustainable development. Storage of freshwater in shallow aquifers using different techniques has become the practice worldwide to restore depleted groundwater and improve water quality.
The deliberate addition of water to an underground reservoir (aquifer) is referred to as recharge. This can be accomplished in two ways: artificially, by techniques like redirecting surface water into the ground, or naturally, by allowing rainwater to percolate into the ground. Aquifer recharge is done to replenish the water in underground aquifers so that there is a steady supply of groundwater. This is essential to maintaining the , especially in areas where groundwater is a significant source. Improved water quality, a stable water supply, and the prevention of land subsidence are all benefits of proper aquifer recharge.
There are various methods for aquifer recharge, such as:
Rainwater enters inside the soil through voids, and the recharge is natural recharge.
The conditions favorable for natural recharge are:
Causes of reduction in natural recharge:
Due to rapid industrialization, population increase, intensive agriculture, urbanization, etc., the use of water has been considerably increased. For this purpose, water is pumped from the groundwater sources.
The aquifers are not recharged at the same rate at which water is pumped out. Thus, the water table falls every year. To fulfill the needs, artificial recharge is carried out.
The goal of artificial groundwater recharge is to increase groundwater reservoirs by altering how surface water moves naturally while utilizing appropriate civil construction methods. Artificial recharge techniques have some of the following issues:
Artificial recharge can be done by some of the methods outlined below:
In this method, water is spread over the surface of permeable open land and pits from where it directly infiltrates a shallow aquifer.
In this method, water is stored in shallow ditches and spread over open areas by constructing low-earth dykes. The rate of recharging depends on the permeability of the spread area and the depth of water stored.
Common ways of spreading methods are-
This method of artificial recharge is more effective where the aquifer to be recharged is located very deep. In this method, water is directly injected into the aquifer by means of horizontal wells, galleries, or shafts.
The spacing of wells depends upon the following:
Common ways of injection method are –
In this method, the water table around the natural sources of water like ponds, streams, or lakes is brought down by pumping out of water before monsoon season. The lowering of the water table will increase the rate of infiltration of water during monsoon.
In this method, wells or galleries are constructed parallel to the river or around the lake or pond. From these wells or galleries, water is pumped out before the rainy season, and the water table is lowered.
A promising adaptation strategy to lessen vulnerability to climate change and hydrological variability is referred to as managed aquifer recharge (MAR). In India, managed aquifer recharge (MAR) has become very important due to the country’s water problems and rising demand for freshwater resources. The main goals of MAR initiatives in India are to restore depleted aquifers and guarantee a steady supply of groundwater. To raise groundwater levels, a variety of techniques are used, including the construction of check dams, percolation tanks, recharge wells, and artificial recharge structures.
To address the issue of water scarcity, MAR projects have been implemented in several Indian states. In order to recharge aquifers, these projects involve collecting rainwater during the monsoon season and directing it into the ground. Following the right purification procedures, treated wastewater is also increasingly being used to recharge aquifers, maximizing the use of the available water resources.
In recent years, local communities, NGOs, and government agencies have worked together to raise awareness of MAR techniques and encourage their adoption throughout different parts of India. These initiatives are essential for boosting water security, assisting agriculture, and giving millions of people in the nation access to clean drinking water.
Aquifer recharge projects offer several significant benefits such as:
There are various government initiatives for supporting Aquifer Recharge. Some of them are-
The Central Ground Water Board (CGWB) is responsible for carrying out the National Aquifer Mapping and Management Program (NAQUIM). In order to facilitate the sustainable management of groundwater resources, NAQUIM plans to map aquifers (water-bearing formations), characterize them, and create aquifer management strategies. In order to define and characterize the aquifers and create plans for groundwater management, NAQUIM was started as a part of the Ground Water Management and Regulation Scheme. States and UTs are provided with the NAQUIM study report and management plans in order to make the appropriate interventions.
The NAQUIM program was taken up with the following objectives:
Jal Shakti Abhiyan (JSA) is being implemented by the Indian government. The first JSA was launched in 2019 in water-stressed blocks of 256 districts, which continued during the years 2021 and 2022 (across the entire country, both urban and rural) with the primary objective to effectively harvest the monsoon rainfall by creating artificial recharge structures, recharge and reuse structures watershed management, intensive afforestation, and awareness generation, etc. JSA for the year 2023 was launched by the President of India on 4 March 2023 with the theme “Source Sustainability for Drinking Water”.
As per a report by the Press Information Bureau on July 20th, 2023, under Ministry of Jal Shakti, the Central Ground Water Board (CGWB), an organization under this Department, is implementing the Central Sector Scheme ‘Ground Water Management & Regulation’ in the country for delineation of aquifer disposition & their characterization for preparation of aquifer/ area specific groundwater management plans, Ground Water (GW) Monitoring, GW Resource Assessment, GW Regulation, etc. The information generated is shared with States/UTs for their suitable interventions.
The Ministry has distributed a Model Bill to all States/UTs in order for them to enact appropriate groundwater legislation, which includes provisions for rainwater harvesting. As of now, 21 States and UTs, including West Bengal, have enacted groundwater legislation in accordance with the Model Bill.
This depends mainly on the storage coefficient, availability of storage space, and permeability. Very high permeability results in loss of recharged water due to sub-surface drainage, as low permeability reduces recharge rate. In order to have a good recharge rate and to retain the recharged water for a sufficient period for its use during the lean period, moderate permeability is needed. Older alluvium, buried channels, alluvial fans, dune sands, glacial outwash, etc., are favorable places for recharge. In hard rock areas, fractured, weathered, and cavernous rocks are capable of allowing a high intake of water. The basaltic rocks, i.e., those formed by lava flows, usually have large local pockets, which can take recharge water.
Implementing aquifer recharge projects comes with several challenges, including understanding geological heterogeneity is essential because aquifers have a variety of different properties. It can be difficult to pinpoint ideal recharge sites and foresee how recharged water will move. A major problem is the contaminated recharged water caused by contaminants or chemicals in the soil. In order to avoid health risks, it is crucial to guarantee the quality of the recharged water. The efficiency of aquifer recharge may be impacted by shifting precipitation patterns brought on by climate change. Unpredictable weather conditions could cause an overreliance on aquifers during dry spells, further depleting them. It costs a lot of money to build the wells, basins, and pipelines needed to recharge aquifers. It cannot be easy to secure funding and guarantee that resources are available, particularly in areas that are economically disadvantaged.
It is necessary to maintain recharge structures on a regular basis and to continuously check the quantity and quality of groundwater. The project’s effectiveness may deteriorate over time if maintenance is neglected.
In the contemporary era, factors like population growth, concentration in urban areas, the requirement for increased food production, enhanced industrialization, and an increase in living standards have all contributed to groundwater depletion and contamination. Thus, the implementation of MAR, which refers to the techniques that are used to secure, maintain, and enhance groundwater systems, has become crucial. Rainwater was used as the primary source in India for several decades, but now, with the advent of MAR, even effluents from wastewater are being used to recharge the aquifers.
The processes of aquifer recharge (AR) and aquifer storage and recovery (ASR), which move water underground, are either created by humans or naturally occur but have been improved. The procedures replenish groundwater that has been kept in aquifers for advantageous uses.
Aquifers can absorb water at a rate of 50 feet per year to 50 inches per century, depending on their permeability.
The capacity of infiltration, the stochastic nature of rainfall, and climate factors all affect groundwater recharge.
Aquifers are layers of rock or sand under the earth that serve as water storage and transport systems. A recharge area is a location where there isn’t a confining layer, allowing water to seep into the ground and refill an aquifer. For an aquifer to be healthy, recharge zones are required.
The aquifers can be drilled into and water pumped out of. The porous rock of the aquifer eventually receives water (recharge) from precipitation. But when drawing water from a well, it is important to keep in mind that not all aquifers recharge at the same rate.
Water can remain in groundwater during the hydrologic cycle for just a few days or up to 10,000 years or more.
Groundwater is pumped upward and out of an aquifer during discharge, while groundwater is pumped downward and into the aquifer during recharge. Activities related to recharge and discharge are typically restricted to a specific area of an aquifer.
Sandstone, fractured limestone, conglomerate, and unconsolidated sand and gravel are examples of the types of rock that make up aquifers and must be both permeable and porous. Columnar basalts and other fractured volcanic rocks function well as aquifers.
Some of the types of Managed aquifer recharge are Infiltration ponds, Soil Aquifer Treatment, Excess irrigation, ditches, trenches, Reverse drainage, borehole or shaft recharge, Check dams, Riverbed scarification, Induced bank filtration, Aquifer storage (transfer) and recovery.
Read our Article:Water Management Techniques For Businesses