Over the last 20 years there has been an enormous increase in the use of ground water resources all over the world.  Besides providing an important source of water for domestic and agricultural use, groundwater also plays a key role in supporting and maintaining the livelihoods of the poor.  This is because groundwater can be accessed relatively easily and cheaply and its quality is generally high. The intensity of groundwater exploitation has raised concerns that groundwater use and the livelihoods it supports - may not be sustainable.  Symptoms of over-exploitation include declining water levels and increasing competition between users for scarce supplies. Now a days due to over exploitation of ground water for irrigation purposes, the water table is falling by about 20-25 cm per year in good ground water quality regions of Punjab, Haryana & Gujarat (Source: CGWB). Therefore there is urgent need for recharging of groundwater resources. 

Artificial Recharge 

            Artificial recharge is an important aspect of groundwater management as it provides storage space free of cost avoids evaporation losses and allows use of stored water during dry period.  Artificial recharge is achieved by three methods, namely by:
    1. Spreading
    2. By induced recharge and
    3. By injection 

The suitability of a particular method is based on the hydro geological conditions, quality of source water and proposed use of recharged water.  These methods are explained below:

 
1.Spreading Methods:
This method is similar to that of surface irrigation with the difference that in recharge operation the water is allowed to stand on the field for a much longer period.  The following three aspects should be considered for spreading methods as shown in Fig1.  

Fig1 : Showing Infiltration-Recharge System

·   Getting the water into the ground. 
·  Getting the water down through
   the vadose zone to the aquifer.

·   Getting the water to move through the aquifer away from the infiltration site without undue build-up of groundwater mounds.

Thus, for successful infiltration of recharge systems, the following conditions are desirable:
   

Keeping in view the above-mentioned conditions and hydro geological set-up of Punjab State, the following areas offer suitable conditions:

• Kandi belt adjoining the Shivalik system where alluvial plains exist.
• Area of old river courses, which can be identified with the help of Landsat data.
• Areas around flood plains (in and along stream beds).
• Areas different than the above three categories and where unconfined aquifers predominate.

According to size soils are classified as clay (<2 microns), silt (2-50 microns), and sand (0.05-2 millimeters).  Particles larger than 2 mm in diameter are classified as gravel (fine, coarse, cobbles, and boulders).  Usually infiltration basin soils should be sandy loams or coarser to produce acceptable infiltration rates (for example, more than 20 cm/day).  Coarse sands and gravels can give very high infiltration rates.

 
Methods of water spreading involve:  

• Construction of Basins
• Stream channels
• Ditch and furrows
• Flooding
• Irrigation
• Pits and shafts

In this method, basins are constructed by excavation or by building dikes or levees.  Sizes and shapes are adjusted to fit topography, land ownership and available land.  Depending on topography, basins can have a surface area of 0.1 hac (0.25 acre) or less to 10 hac (25 acres) or more. Often, the first few basins are "sacrificed" as presedimentation facilities.

Water is then released to basins for infiltration.  Water released should have minimum sediment load so to reduce deposition and scaling of basin surfaces. This can be accomplished by three ways:  

• Diverting water to basins during non-flood periods when suspended sediment is low.
• Adding chemical flocculating agents to water to remove sediment.
• Providing sedimentation basins to hold water before releasing it into recharge basins.

Basin designs vary widely depending upon local conditions.  Basin width should be sufficiently wide to accommodate scrappers to remove sediment periodically.  Side slopes should be relatively steep so as to minimize sediment deposition.

In actual infiltration basins, suspended material in the water (silt, clay, organic particles, etc.) accumulates on the bottom.  Also bacterial and algae growth in the basins produces algae crests and organic deposits on the bottom.  These accumulations reduce infiltration rates, typically if the water contains high suspended solids content and the basins are flooded for a long time.  Thus, the hydraulic conductivity 'K' of the bottom soil gives an idea of maximum sustained infiltration rates in the basin.  Order of magnitude of hydraulic conductivity K for different soils are (in m/day):

These values give a general idea of K-ranges for different soils, hence, of the maximum infiltration that can be obtained to get more reliable estimates. In Punjab infiltration basins can be constructed close to rivers, and in areas of old river courses, and in wide channels.  Studies by Central Ground Water Board have shown that basins of 250 m X 60 m size and having depth of 2 m to 5 m can be constructed to carry artificial recharge.

 
Stream Channel Method:

Water spreading in stream channels involves operations to increase the time and area of water contact.  Activities typically require upstream storage facilities to regulate stream flows and channel modifications to enhance infiltration. Ideally, upstream reservoirs should limit flows to rates that do not exceed the absorptive capacity to downstream channels.  Types of stream channel improvements include:

• Widening leveling, scarifying or ditching of the channel.
• Permanent low check dams, which do not cause flood hazard.
• Temporary low check dams consisting of stream bed materials.
• L shaped finger levees constructed by bulldozer at the end of high-stream flow season.

In Punjab, this method is particularly suitable for Kandi area of District Ropar, Hoshiarpur, and Gurdaspur.  

Ditch and Furrow Method:

In this method continuous ditches and furrows are constructed throughout the field, which facilitates the infiltration rate by providing more surface area. Ditches and furrows are adaptable to irregular terrain where other methods of water spreading would not be feasible.  This method is not suitable for Punjab State and is mainly practicized in hilly regions with uneven topography. 

Flooding Method:

In flat land areas, water can be simply released over large area and allowed to infiltrate.  Velocities of flow should be minimal to avoid soil movement.  Usual practice is to leave vegetation of that area undisturbed. This method is the least costly of all spreading methods, provided the land is available without cost.  For maximum efficiency, hard labour should be employed to distribute the water over area as wide as possible.  This method has very limited scope in a state like Punjab where most of land is cultivated.

Water can be recharged on irrigated lands by three methods:

• Applying excess water during non-irrigation seasons.
• Applying excess water during irrigation (However, this can have adverse effects on leaching salts and removing soil nutrients). 
• Keeping irrigation canals full . 

This method is also not suitable to the conditions of Punjab except in last option i.e. keeping the irrigation canals full in central parts of Punjab having sweet water (District Ludhiana, Jalandhar, Kapurthala, Amritsar, Gurdaspur).  However, canal network is very little in Bist Doab Tract (Ludhiana, Hoshiarpur, Jalandhar).  As such this method has also very little scope in Punjab. 

Pit Method:

Pits are excavated into permeable formations, which serve as ideal facilities for artificial recharge.  Abandoned gravel pits are most economical for this purpose.  This method has also very little application in Punjab.

Induced Recharge:

Induced recharge occurs where groundwater is pumped from a location near a surface water body so that lowering of groundwater level induces water to enter the ground from the surface source.  

Fig 4 : Showing flow pattern with pumping well

The method is effective in permeable formations, which hydraulically connected between the stream and the aquifer (See Fig.4).  The amount of water depends on: pumping rate, permeability, type of well, distance from stream and natural groundwater movement.  The stream velocity should be sufficient to prevent sediment deposition from sealing the streambed.

Injection Methods:   Such methods are of particular interest where over drafting occurs in confined aquifers and areas are located close to major canals.  As water is available during monsoons, injection methods are suitable on account of clean waters available close to sites (See Fig.5).  Such methods can be tried areas having confined aquifers and suffering from over drafting of groundwater.

Other Measures:

• The other measures aim at reducing the ground water overdraft.  It is suggested that in severely over draft areas, new cropping patterns may be introduced.  Crops, which require less water than the existing crops, shall have to be promoted. e.g. wheat Rice-Rotation practice should be replaced in Punjab and Haryana as early as possible.
• In critical areas, legislative measures can be introduced.  Pumping patterns can be regulated keeping in view the available water supply in the canals.
• There is need to educate the farmers regarding optimum water utilization aspects, irrigation planning etc.  Public awareness regarding water conservation measures should be created through Celebration of  'National Water Day' and with the help of awareness programmes through people's participation and voluntary organizations.
• Recycling of water and reuse of water should be promoted especially in those areas where industries consume groundwater.  

By utilizing one or a combination of above-mentioned methods depending on its suitability to a particular area we can regenerate our groundwater resources to a great extent.

Source: Summarized from DFID News-Letter & Technical Report on Water Management by Punjab Irrigation Department.  
 

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