GROUNDWATER ARTICLE 12, Thesis of Groundwater Hydrology

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CENTRAL GROUND WATER BOARD

MINISTRY OF WATER RESOURCES

GUIDE

ON

ARTIFICIAL RECHARGE

TO

GROUND WATER

NEW DELHI

MAY, 2000

GUIDE ON ARTIFICIAL RECHARGE

TO

GROUND WATER

CONTENTS

Page No.

**1. INTRODUCTION 1 - 3

2. PLANNING OF ARTIFICIAL RECHARGE PROJECTS 3 - 9
3. ARTIFICIAL RECHARGE TECHNIQUES AND DESIGN 10 - 32
4. MONITORING, MECHANISM FOR ARTIFICIAL RECHARGE 33 - 36** **PROJECTS
5. CASE HISTORIES OF ARTIFICIAL RECHARGE IN INDIA 36 - 75**

Annexure 1 --Format For Preparation of Artificial Recharge Project

Annexure 2 --Planning Artificial Recharge Project -- Checklist

Annexure 3 –General Guidelines for the evaluation of Ground Water Recharge Projects with special reference to Basaltic Terrain

water would substantially improve in brackish and saline areas. The conduit function of aquifers thereby reducing the cost intensive surface water conveyance system. The effluence resulting from such sub-surface storage at various surface intersection points in the form of spring line, or stream emergence, would enhance the river flows and improve the presently degraded ecosystem of riverine tracts, particularly in the outfall areas. The structures required for recharging ground water reservoirs are of small dimensions and cost effective, such as check dams, percolation tanks, surface spreading basins, pits, sub- surface dykes etc.

1.1.2 Basic Requirement for Artificial Recharge Projects

The basic requirements for recharging the ground water reservoir are:

a) Availability of non-committed surplus monsoon run off in space and time.

b) Identification of suitable hydrogeological environment and sites for creating sub- surface reservoir through cost effective artificial recharge techniques.

1.1.3 Source Water Availability

The availability of source water, one of the prime requisites for ground water recharge, is basically assessed in terms of non committed surplus monsoon run off, which as per present water resource development scenario is going unutilised. This component can be assessed by analysing the monsoon rainfall pattern, its frequency, number of rainy days, maximum rainfall in a day and its variation in space and time. The variations in rainfall pattern in space and time, and its relevance in relation to the scope for artificial recharge to sub-surface reservoirs can be considered for assessing the surplus surface water availability.

1.1.4 Hydrogeological Aspects

Detailed knowledge of geological and hydrological features of the area is necessary for adequately selecting the site and the type of recharge structure. In particular, the features, parameters and data to be considered are: geological boundaries; hydraulic boundaries; inflow and outflow of waters; storage capacity; porosity; hydraulic conductivity; transmissivity; natural discharge of springs; water resources available for recharge; natural recharge; water balance; lithology; depth of the aquifer; and tectonic boundaries. The aquifers best suited for artificial recharge are those aquifers which absorb large quantities of water and do not release them too quickly. Theoretically this will imply that the vertical hydraulic conductivity is high, while the horizontal hydraulic conductivity is moderate. These two conditions are not often encountered in nature.

The evaluation of the storage potential of sub-surface reservoirs is invariably based on the knowledge of dimensional data of reservoir rock, which includes their thickness and lateral extent. The availability of sub-surface storage space and its replenishment capacity further govern the extent of recharge. The hydrogeological situation in each area needs to be appraised with a view to assess the recharge capabilities of the underlying hydrogeological formations. The unsaturated thickness of rock formations, occurring beyond three meters below ground level should be considered to assess the requirement of water to build up the sub-surface storage by saturating the entire thickness of the vadose up to 3 m. below ground level.

The upper 3 m of the unsaturated zone is not considered for recharging, since it may cause adverse environmental impact e.g. water logging, soil salinity, etc. The post- monsoon depth to water level represents a situation of minimum thickness of vadose zone available for recharge which can be considered vis-a-vis surplus monsoon run off in the area.

The artificial recharge techniques inter relate land integrate the source water to ground water reservoir. Two effects are generated by artificial recharge in ground water reservoir namely - (a) Rise in water level and (b) increment in the total volume of the ground water reservoir.

2.0 PLANNING OF ARTIFICIAL RECHARGE PROJECTS

2.1 Identification Area

The artificial recharge projects are site specific and even the replication of the techniques from similar areas are to be based on the local hydrogeological and hydrological environments. The first step in planning the project is to demarcate the area of recharge. The Project can be implemented systematically in case a hydrologic unit like watershed is taken for implementation. However, localised schemes are also taken to augment ground water reservoir. The artificial recharge of ground water is normally taken in following areas:

1. Areas where ground water levels are declining on regular basis.
2. Areas where substantial amount of aquifer has already been desaturated.
3. Areas where availability of ground water is inadequate in lean months.
4. Areas where salinity ingress is taking place.

2.2 Scientific Inputs

In order to plan the artificial recharge schemes following studies are needed

surface". Although a distinction is made between infiltration and percolation (the movement of water within the soil) the two phenomena are closely related since infiltration cannot continue unimpeded unless percolation removes infiltrated water from the surface soil. The soil is permeated by noncapillary channel through which gravity water flows downward towards the ground water, following the path of least resistance. Capillary forces continuously divert gravity water into pore spaces, so that the quantity of gravity water passing successively lower horizons is steadily diminished. This leads to increasing resistance to gravity flow in the surface layer and a decreasing rate of infiltration as a storm progresses. The rate of infiltration in the early phases of a storm is less if the capillary pores are filed from a previous storm.

There is maximum rate at which water can enter soil at a particular point under a given set of conditions, this rate is called the infiltration capacity. The actual infiltration rate equals the infiltration capacity only when the supply rate rainfall intensity less rate of retention) equals or exceeds.

Infiltration capacity depends on many factors such as soil type, moisture content, organic matter, vegetative cover, season, air entrapment, formation of surface seals or crusts etc. Of the soil characteristics affecting infiltration, non-capillary porosity is perhaps the most important. Porosity determines storage capacity and also effects resistance to flow. Thus infiltration tends to increase with porosity. Vegetal cover increases infiltration as compared with barren soil because (i) it retards surface flow giving the water additional time to enter the soil (ii) the root system make the soil more pervious and (iii) the foliage shields the soil from raindrop impact and reduces rain packing of surface soil. As water infiltrates soil under natural conditions the displacement of air is not complete even after many hours. Air spaces in the soil and intermediate zones interfere with infiltration as air is not pushed out by the infiltrating water but is gradually absorbed by water. Due to this phenomena infiltration rate may start rising towards a new high after a few days of continuous application of water. Surface conditions have a marked effect on the infiltration process and the formation of surface seals or crusts which forms under the influence of external forces such as rain drop impact and mechanical compaction or through staking reduces the rate of infiltration.

Infiltration of water through surface takes place generally over small periods of time and it is the process of redistribution of the soil water that goes on for most of the time and therefore predominates. When rainfall ceases the water wetted during the infiltration process starts to drain with the soil being wetted lower down the profile. The soil water conditions during the distribution periods are therefore those that primarily influence plant growth and agricultural husbandry and that also provide the buffer action in hydrologic cycle that the soil water zones has on the transport of water from the soil surface to the ground water aquifer. As such, infiltration is critically inter-linked with the phenomena of water evolution in the vadose zone which includes wetting front propagation.

In order to know infiltration rates of soils infiltration tests are carried out. Cylinder or flood infiltro-meters are common type of instruments which measure the infiltration as

the rate of water leaving the device. Map showing infiltration rates of soils are prepared. These help to design suitable artificial recharge structures and to assess the extent of recharge from these structures.

2.2.4 Hydrogeological Studies

A correct understanding of hydrogeology of an area is of prime importance in successful implementation of any Artificial Recharge scheme. A desirable first step is to synthesize all the available data on hydrogeology from different agencies. The regional geological maps indicate the location of different geological strata, their geological age sequence, boundaries/contacts of individual formations and the structural expressions like Strike, Dip, Faults, Folds, Flexures, Intrusive bodies etc. These maps also bring out correlation of topography and drainage to geological contacts.

The Map providing information on regional hydrogeological rock units, their ground water potential and general pattern of ground water flow and chemical quality of water in different aquifers are necessary.

Satellite Imagery maps provides useful data on geomorphic units and lineaments which govern the occurrence and movement of ground water.

A detailed hydrogeological study besides the regional picture of hydrogeological set up available from previous studies is therefore imperative to know precisely the promising hydrogeological units for recharge and correctly decide on the location and type of structures to be constructed in field.

The hydrogeological investigations required before implementation of an artificial recharge scheme are given below.

(i) Detailed Hydrogeological Mapping The purpose of hydrogeological mapping is to present the following maps which facilitate in the analysis of the ground water regime and its suitability to artificial recharge schemes.

a) Map showing hydrogeological units demarcated on the basis of their water bearing capabilities, both at shallow and deeper levels. b) Map showing ground water contours to determine the form of the water table and the hydraulic connection of ground water with rivers, canals etc. c) Map showing the depths to the water table are usually compiled for the periods of the maximum, minimum and mean annual position of water table. d) Maps that show amplitudes of ground water level fluctuations and the maximum position of the water table of considerable importance for artificial recharge studies. e) Maps showing piezometric head in deeper aquifers and their variations with time.

Using certain common geophysical methods, it is possible to model the

i) Stratification of aquifer system and spatial variability of hydraulic conductivity of the characteristic zone, suitable for artificial recharge.

ii) Negative or non-productive zones of low hydraulic conductivity in unsaturated and saturated zones.

iii) Vertical hydraulic conductivity discontinuities, such as dyke and fault zone.

iv) Moisture movement and infiltration capacity of the unsaturated zone.

v) Direction of ground water flow under natural/artificial recharge processes.

vi) Salinity ingress, trend and short duration depth salinity changes in the aquifers due to varied abstraction or recharge.

The application of proper techniques, plan of survey and suitable instruments will definitely yield better understandable results, but, of indirect nature.

2.2.6 Chemical Quality of Source Water

Problem which arise as a result of recharge to ground water are mainly related to the quality of raw waters that are available for recharge and which are generally require some sort of treatment before being used is recharge installations. They are also related to the changes in the soil structure and the biological phenomena which take place when infiltration begins, to the changes brought to the environmental conditions. The chemical and bacteriological analysis of source water besides that of ground water is therefore essential.

2.2.7 Suspended matter may clog the soil in two different ways

Suspended Solids and Clogging Problem: A major requirement for waters that are to be used in recharge projects is that they be silt-free. Silt may be defined as the content of undissolved solid matter, usually measured in mg/l, which settles in stagnant water with velocities which do not exceed 0.1 m/hr. To obtain still clearer water, with only 10 - 12 mg/l suspended solids, further additions of flocculants and, frequently, agitation of the water must be resorted to.

First, near the surface the interstices of the soil may be filled up and a layer of mud may be deposited on the surface, on the other hand suspended particles may penetrate deeper into the soil and accumulate there.

Methods to minimize the clogging effect by suspended matter can be classified into broad groups:

a) Periodical removing of the mud-cake and dicing or scraping of the surface layer.

b) Installation of a filter on the surface, the permeability of which is lower than that of the natural strata (the filter must, of course, be removed and renewed periodically)

c) Addition of organic matter or chemicals to the uppermost layer.

d) Cultivation of certain plant-covers, notably certain kinds of grass.

Providing inverted filter consisting of fine sand coarse sand and gravel at the bottom of infiltration pits/trenches are very effective.

Clogging by biological activity depends upon the mineralogical and organic composition of the water and basin floor and upon the grain-size and permeability of the floor. The only feasible method of treatment developed so far consists in thoroughly drying the ground under the basin.

2.3 Assessment Of Sub-Surface Potential For Ground Water Recharge

Based on the hydrogeological and geophysical surveys, the thickness of potential unsaturated zone for recharge should be worked out to assess the potential for artificial recharge in terms of volume of water which can be accommodated in this zone vis-à-vis source water availability. The studies should bring out the potential of unsaturated zone in terms of total volume which can be recharged.

3.1.1.1 Lateral Ditch Pattern

The water from stream is diverted to the feeder canal/ditch from which smaller ditches are made at right angles. The rate of flow of water from the feeder canal to these ditches is controlled by gate valves. The furrow depth is kept according to the topography and also with the aim that maximum wetted surface is available along with maintenance of uniform velocity. The excess water is routed to the main stream through a return canal along with residual silt.

3.1.1.2 Dendritic Pattern

The water from stream can be diverted from the main canal to a series of smaller ditches spread in a dendritic pattern. The bifurcation of ditches continues until practically all the water is infiltrated in the ground.

3.1.1.3 Contour Pattern

The ditches are excavated following the ground surface contour of the area. When the ditch comes closer to the stream a switch back is made and thus the ditch is made to meander back and forth to traverse the spread are repeatedly. At the lowest point down stream, the ditch joins the main stream, thus returning the excess water to it.

3.1.1.4 Site Characteristics and Design Guidelines

a. Although this method is adaptable to irregular terrain, the water contact area seldom exceeds 10 percent of the total recharge area. b. Ditches should have slope to maintain flow velocity and minimum deposition of sediments. c. Ditches should be shallow, flat-bottomed, and closely spaced to obtain. Maximum water contact area. Width of 0.3 to 1.8 m. are typical d. A collecting ditch to convey the excess water back to the main stream channel should be provided.

3.1.2 Percolation Tanks (PT) / Spreading Basin

These are the most prevalent structures in India as a measure to recharge the ground water reservoir both in alluvial as well as hard rock formations. The efficacy and feasibility of these structures is more in hard rock formation where the rocks are highly fractured and weathered. In the States of Maharashtra, Andhra Pradesh, Madhya Pradesh, Karnataka and Gujarat, the percolation tanks have been constructed in plenty in basaltic lava flows and crystalline rocks. A typical design of PT is given in Fig. 3 The percolation

tanks are however also feasible in mountain fronts occupied by talus scree deposits. These are found to be very effective in Satpura Mountain front area in Maharashtra. The percolation tanks can also be constructed in the Bhabar zone. Percolation tanks with wells and shafts Percolation tanks are also constructed to recharge deeper aquifers where shallow or superficial formations are highly impermeable or clayey with certain modification. Recharge wells with filter are constructed in the Percolation Tanks and the stored water is Moti Ranjan and Bhujpur, Mandvi Kutch district, Gujarat.

3.1.2.1 Important Aspects of Percolation Tanks:

a. A detailed analysis of rainfall pattern, number of rainy days, dry spells, and evaporation rate and detailed hydrogeological studies to demarcate suitable percolation tank sites.

b. In Peninsular India with semi arid climate, the storage capacity of percolation tank be designed such that the water percolates to ground water reservoir by January since the evaporation losses would be high subsequently.

c. Percolation tanks be normally constructed on second to third order stream since the catchment so also the submergence area would be smaller.

d. The submergence area should be in uncultivable land as far as possible.

e. Percolation tank be located on highly fractured and weathered rock for speedy recharge. In case of alluvium, the bouldary formations are ideal for locating Percolation Tanks.

f. The aquifer to be recharge should have sufficient thickness of permeable vadose zone to accommodate recharge.

g. The benefitted area should have sufficient number of wells and cultivable land to develop the recharge water.

h. Detailed hydrological studies for run off assessment be done and design capacity should not normally be more than 50% of total quantum of rainfall in catchment.

i. Waste weir or spillway be suitably designed to allow flow of surplus water based on single day maximum rainfall after the rank is filled to its maximum capacity.

j. Cut off trench be provided to minimise seepage losses both below and above nalla bed.

k. To avoid erosion of embankment due to ripple action stone pitching be provided upstream upto HFL.

l. Monitoring mechanism in benefitted as well as catchment area using observation

9. For the foundation for core wall a trench is dug 0.6 m wide in hard rock or 1.2 metres in soft rock of impervious nature. A core brick cement wall is erected 0.6 m wide to stand atleast 2.5 metres above nala bed and the remaining portion of trench is back filled on upstream side by impervious clay. The core wall is buttressed on both sides by a bund made up of local clays and on the upstream face, stone pitching is done.
10. Normally the final dimensions of the Nala bund are; length 10 to 15 metres, height 2 to 3 metres and width 1 to 3 metres, generally constructed in a trapezoidal form. If the bedrock is highly fractured, cement grouting is done to make the foundation leakage free.

The check dams are also popular and feasible in Bhabar, Kandi and talus scree areas of Uttar Pradesh, Punjab, and Maharashtra and have substantial impact on augmentation of ground water.

3.1.4. Gabion Structure

This is a kind of check dam being commonly constructed across small stream to conserve stream flows with practically no submergence beyond stream course. The boulders locally available are stored in a steel wire. This is put up across the stream's mesh to make it as a small dam by anchoring it to the streamside (fig 5). The height of such structures is around 0.5 m and is normally used in the streams with width of about 10 to 15 m. The cost of such structures is around Rs.10 to 15000/-. The excess water overflows this structure storing some water to serve as source of recharge. The silt content of stream water in due course is deposited in the interstices of the boulders to make it more impermeable. These structures are common in the State of Maharashtra, Madhya Pradesh, Andhra Pradesh etc.

3.1.5. Modification of Village tanks as recharge structure

The existing village tanks which are normally silted and damaged can be modified to serve as recharge structure. In general no “Cut Off Trench” (COT) and Waste Weir is provided for village tanks. Desilting, coupled with providing proper waste weir and C.O.T. on the upstream side, the village tanks can be converted into recharge structure. Several such tanks are available which can be modified for enhancing ground water recharge. Some of the tanks in Maharashtra and Karnataka have been converted.

3.1.6. Inter Watershed Transfer

The percolation tanks in a watershed may not have enough catchment discharge though a high capacity tank is possible as per site conditions. In such situations stream

from nearby watershed can be diverted with some additional cost and the tank can be made more efficient. Such an effort was made in Satpura Mountain front area at Nagadevi Jalgaon district, Maharashtra. The existing capacity of the tank of 350 TMC was never utilised after its construction. This could however be filled by stream diversion from adjacent watershed.

3.1.7 Dug Well Recharge

In alluvial as well as hard rock areas, there are thousands of dug wells which have either gone dry or the water levels have declined considerably. These dug wells can be used as structures to recharge (Fig 6 & 7). The ground water reservoir, storm water, tank water, canal water etc. can be diverted into these structures to directly recharge the dried aquifer. By doing so the soil moisture losses during the normal process of artificial recharge, are reduced. The recharge water is guided through a pipe to the bottom of well, below the water level to avoid scoring of bottom and entrapment of air bubbles in the aquifer. The quality of source water including the silt content should be such that the quality of ground water reservoir is not deteriorated. Schematic diagrams of dug well recharge are given in figures 6 &7.

3.1.8 Recharge Shaft

These are the most efficient and cost effective structures to recharge the aquifer directly. In the areas where source of water is available either for some time or perennially e.g. base flow, springs etc. the recharge shaft can be constructed (Fig 8). Following are site characteristics and design guidelines: -

(i) To be dug manually of the strata is non-caving nature. (ii) If the strata is caving, proper permeable lining in the form of open work, boulder lining are should be provided. (iii) The diameter of shaft should normally be more than 2 m to accommodate more water and to avoid eddies in the well. (iv) In the areas where source water is having silt, the shaft should be filled with boulder, good and sand from bottom to have inverted filler. The upper most sandy layer has to be removed and cleaned periodically. A filter be provided before the source water enters the shaft. (v) When water is put into the recharge shaft directly through pipes, air bubbles are also sucked into the shaft through the pipe which can choke the aquifer. The injection pipe should therefore be lowered below the water level, to avoid this

The main advantages of this technique are as follows: -

• It does not require acquisition of large piece of land like percolation tanks.

• There are practically no losses of water in the form of soil moisture and evaporation, which normally occur when the source water has to traverse the vadose zone

(b) With Injection Well

In this technique at the bottom of recharge shaft a injection well of 100 - 150 mm diameter is constructed piercing through the layers of impermeable horizon to the potential aquifers to be reached about 3 to 5 meter below the water level. (Fig.-9)

• Ideally suitable for very deep water levels (more than 15 meters)
• Aquifer is over lain by impervious thick clay beds
• Injection well can be with or without assembly
• The injection well with assembly should have screen in the potential aquifer at least 3 – 5 meter below the water level.
• The injection well without assembly is filled with gravel to provide hydraulic continuity so that water is directly recharged into the aquifer
• The injection well without assembly is very cost effective.
• Depending upon volume of water to be injected, number of injection wells, can be increased to enhance the recharge rate.
• The efficiency is very high and rate of recharge goes even up to 15 lps at certain places.

These structures have been constructed at following places.

♦ Injection Well Without Assembly

• Dhuri drain, Sangrur district, Punjab
• Issru, Khanna block, Ludhiana district, Punjab
• Lodi Garden, New Delhi
• Dhaneta, Samana Block, Patiala district, Punjab

♦ Injection Well With Assembly

• Dhuri drain, Sangrur district, Punjab
• Dhuri Link drain, Sangrur district, Punjab
• Kalasinghian, Jalandhar district, Punjab

3.1.8.2 Lateral Recharge Shaft

• Ideally suited for areas where permeable sandy horizon is within 3 meter below ground level and continues upto the water level - under unconfined conditions (Fig. 9 )
• Copious water available can be easily recharged due to large storage and recharge potential.
• Silt water can be easily recharged
• 2 to 3 meter wide and 2 to 3 meter deep trench is excavated, length of which depends on the volume of water to be handled.
• With and without injection well ( Details of structures already described in Section 3.1.8.1)

This structure has been constructed at following places.

• Dhuri drain, Sangrur district, Punjab - 300 meters ( with 6 injection wells)
• Dhuri Link drain, Sangrur district, Punjab - 250 meter (with 3 injection wells)
• Garhi Kangran, Baghpat district, U. P. - 15 meter (with 2 injection wells)
• Shram Shakti Bhawan, New Delhi - 15 meter ( 3 lateral shafts with 2 injection well in each)
• Dhanetha, Samana block, Patiala district, Punjab - 4 lateral shaft with injection wells
• D. C. Office complex, Faridabad, Haryana - with injection wells
• Lodhi Garden, New Delhi - with injection wells

3.1.9. Artificial Recharge Through Injection Wells

Injection wells are structures similar to a tube well but with the purpose of augmenting the groundwater storage of a confined aquifer by pumping in treated surface water under pressure (Figure 10). The injection wells are advantageous when land is scarce.

This techniques was successfully adopted at temple town of Bhadrachallam in A.P. during 1987 to provide safe drinking water to about 2 to 3 lakh pilgrims on the festival of Shriramanawami. The ground water aquifer had meager reserve and had to be necessarily replenished through induced recharge from Godavari River. The surface water could not be directly pumped to the distribution system due to turbidity and bacteriological contaminations. A water supply scheme was successfully executed by construction of 30 filter point wells of 90 cm dia which yielded about 60 cubic metre/ha of potable water, mainly the induced recharge from river with phreatic alluvial aquifer acting as filtering medium. Hydraulically the effectiveness of induction of water in injection well is determined by: -

(a) Pumping Rate (b) Permeability of aquifer (c) Distance from stream (d) Natural ground water gradient (e) Type of well

In alluvial areas injection well recharging a single aquifer or multiple aquifers can be constructed to normal gravel packed pumping well. An injection pipe with opening against the aquifer to be recharged may be sufficient. However, in case of number of permeable zones separated by impervious rocks, a properly designed injection well with inlet pipe against each aquifer to be recharged need to be constructed. The injection wells