Problems confronting in Drilling of Borewells/Tubewells in different Geological formations in India.

It is common practice to observe that only DTH rigs are operating in Hard rock areas, Direct Rotary drilling machines in unconsolidated or alluvial formations and Percussion drilling machines in the areas where boulders, gravel and karst topography(limestone solution cavities) are prevalent. Percussion drilling also can be taken up in consolidated and unconsolidated formations but the drilling rate is slow and financially not viable compared to DTH and Direct rotary drilling methods. But the problem arises when alluvial formations or unconsolidated formations encountered in predominantly dominated Hard rock areas.Similarly,several problems occur when the local boring methods are being used instead of Direct Rotary drilling method   in unconsolidated formations,particularly when the depth of Tubewells increases from 25 feet to more than 100 feet  due to increase in utility of groundwater.

Reference: http://welldrillingschool.com/courses/pdf/DrillingMethods.pdf

Common problems in Hard Rock Areas

(http://cgwb.gov.in/District_Profile/AP_districtProfiles.html)

1.    Problems due to occurrence of unconsolidated formations

The alluvial formations occur in hard areas in patches due to buried river channels, along stream courses, floodplains, palaeo-channels etc or lake beds which are encroached for building construction. As only DTH rigs are available in hard rock areas,(as  Direct Rotary drilling or local hand boring methods are not available )drilling for bore wells in this area taken up by DTH rigs have to be abruptly stopped due to collapse of unconsolidated formations and as such drilling could not be proceed beyond 12 to 15 meters. And the owners of the buildings who have no other option except to satisfy with these shallow bore wells having very limited quantity of water. But later few years, the residents of the building face water scarcity as the shallow bore well goes dry. Direct Rotary drilling rigs or combination Rigs(combination of DTH and  Rotary  drilling) are not available in these areas to take up drilling under such conditions.

     2. Problems due to occurrence of Limestone Karsts topography:

In Singanamala mandal of Anantpur district, drilling of bore well came to an abrupt end at 100 feet as the DTH rig could not proceed further as continuation of granite rock is missing. This area is transition zone for Archaean Granite Gneisses and Kadapa rock formations. In fact Limestone formation having solution cavities (Karst limestone) struck at 100 feet. In Karst topography, Percussion drilling rigs could be able to drill bore wells but such rigs are not available in this area.

    3. Distance criteria not followed in urban areas:

In urban areas like Hyderabad large number of bore wells are drilled for drinking water

purposes. Due to increase in number of Apartments, the prescribed distance criteria between two Bore wells are not being followed. With the result, certain problems cropped up in the performance of Bore wells.  Some of the important problems are -lowering of water table, reduction in discharge of bore wells, and hampering of drilling progress. In the areas where bore wells are located close to each other I:e distance between two bore wells is about 20 meters and less-when drilling is under progress for new bore well, the Air that is emanating from Air Compressor- instead of adding to the  progress of drilling, Air get leaked through adjacent bore well/Dug well and hinder the progress of new bore well. The drilling process has to be stopped at this stage and make a retreat.

4. Effect of thick clay layer on the success of Bore well:

In one of the villages of Srikakulam district, it was observed that a bore well was drilled up to 150 feet which was located in highly favorable location turned out to be a unsuccessful well. Nearby river is flowing by the Bore well location has good catchment area and weathered rock existing up to the depth of 90 feet. The reasons for failure of Bore well could not be traced out easily. After a detailed investigation of the area, it was observed that one meter thickness of Clay is overlying the weathered rock and not allowing surface water to percolate to sub surface. There is one big Lake located in the village having abundant water. It was reported by villagers that throughout year, water exists in full capacity of the lake as underlying clay material will not allow any percolation to subsurface water. There is only evaporation of lake water and no recharge to groundwater. Thick clayey material is common in hard rock areas particularly in Kadapa formations, Deccan trap areas and in Achaeans.

    5. Highly weathered formation: In few locations, highly weathered (loose soil) formations from 80 to 100 feet struck in few bore wells. Generally Rig operators lower casing pipe up to 25 to 40 feet and complete the construction of bore well. In such cases, after few days of pumping it will be noticed that discharge of bore well has decreased. The reason for reduction of discharge is collapse of bore well from 40 feet onwards till the hard rock strikes. Casing pipe should cover the entire thickness of highly weathered rock formation.

Problems confronted in unconsolidated formations:

1. About 2 decades back, in Deltaic areas, Coastal areas, along stream courses and sometimes in command areas of Water bodies, filter points and shallow Tube wells depth up to 25 to 35 feet used to be ground water abstraction structures. Of late dependence on groundwater has increased in these areas, consequently, the depth of filter points and shallow tube wells in these areas has increased to 100 feet and some places the depth is more. But in these areas, though the depth of shallow tube wells increased, the same old methods of hand boring methods are still being practiced. It is a simple way of constructing shallow tube wells in alluvial formations without lowering slotted pipes or gravel  filling as  per the subsurface geological conditions. For shallow depths, these hand boring methods were working satisfactorily due to abundant groundwater. But for the deep tube wells (above 100 feet) certain problems encountered during the operation of these tube wells drilled by local boring methods. Main problems are, low discharge, muddy water and collapse of bore well etc. When number of tube wells are increased and depth of wells increased, it is necessary to follow proven technical methods while taking up the construction of wells. But the cost of construction of Tube wells on proven technical methods is high and the Direct rotary drilling methods with mud circulation are so far employed by government agencies only. The drilling process includes delineation of subsurface litho logical data, selection of gravel packing material as per geological formations, selection of slotted pipe, blank pipe, and development of Tube well until the water become free from clay, silt and Sand. In few locations, farmers constructed the tube wells lowering the casing up to the bottom of tube well without using slotted pipe and gravel packing etc. In such cases wherever sand zones are struck, the drilling will be stopped and lower the casing up to bottom. In such cases full potential of groundwater sources could not be exploited due to inadequate application of required technical methods.

2. Inadequate knowledge while encountering saline water. The quality of groundwater problem occurs along the coastal belt and in deltaic areas. The salinity problem is very complex and there is no uniformity in the pattern of occurrence of saline water. In the coastal areas of Andhra Pradesh and Tamilnadu states generally, fresh water occurs on upper shallow zone and saline Water encounter below the fresh water. In cities like Chennai and small towns located along the coastal area, utmost care is to be taken to pump out fresh water overlying the saline water. Any overexploitation or overdraft in this area will yield saline water particularly during summer season. The situation is so delicate in Chennai city, in the western portion of the city fresh water occurs up to 70 feet below ground level and  towards east(towards Sea)in intermittent zone, fresh water is available up to 50 feet and near coast fresh water is available up to 20 to 25 feet only.  More new number of wells and more exploitation of water lead to discharge of saline water.  Thanks to the efforts of state government which made Rain water Harvesting structures compulsory in all the Apartments of Chennai city which makes the situation better, as far as the availability of fresh water is concerned.

  In rural areas of coastal area, agricultural activities and fish pond culture has increased the exploitation of fresh water which caused yielding of saline water in few locations. This has resulted severe drinking water problem along the coastal area. In such areas, local authorities supplying drinking water through tankers.

  In deltaic areas of Godavari, Krishna and Cauvery rivers, shallow tube wells are generally drilled up to 70 to 100 feet which gives high yield of potable groundwater.  In addition, along River courses, along canals, potable groundwater is available in shallow tube wells.

The situation is quite different in west Bengal where in few major stretches like Diamond Harbour-Namkhana track , Saline water occur on upper zones and fresh water in lower zones. The same situation continues up to major part of Orissa state but near Puri Town,  the position changes where fresh water occur on upper zone and saline water underlying it. In coastal Gujarat both the conditions exists, i.e some places saline water occurs on upper zones and in lower zones fresh water and in other areas, reverse positon is existing.

In the areas where groundwater quality problem exists, the drilling units should be capable of carrying out Packer tests and cement sealing tests so as to seal the saline water and tap only fresh ground water. These techniques are so far used by government agencies and ordinary farmers should be able to follow these techniques. Government agencies or NGOs involved in such activities should guide the farmers when they go for Tube wells in their areas.

The problems which encounter in hard rock areas due to occurrence of unconsolidated formations, thick clayey layers and construction of Tube wells by local boring methods are prevalent in large part of Southern India and Deccan trap areas of Maharashtra, parts of M.P and Gujarat. In remaining parts of the country also similar problems occur though extent of hard rock areas is limited. There should be some agencies which should take care of such problems by taking extra efforts as the cases reported are few in number from Taluka and district level. Or some system should be evolved to register the cases from different areas and chalk out a plan to tackle the situation.

C Satyanarayana

Retd.Dy.Chief(Hydrogeology)

REC.

http://groundwaterindia.blogspot.com/

ARTIFICIAL RECHARGE OF GROUNDWATER-A TOOL FOR SAVING OF POWER

Large scale exploitation of groundwater resources particularly after 1970 has enabled us to meet the requirement of water for different purposes like irrigation, industrial and domestic needs. But due to lack of proper management and monitoring of groundwater resources, following undesired effects have crept in.

In the hard rock terrain of Andhra Pradesh, Karnataka, Tamil Nadu, Maharashtra and parts of Madhya Pradesh and Gujarat States, steep decline of water levels forced the farmers to go for deep bore wells upto the depth of 500 meters. The successful wells which were constructed within the weathered rock and upper portions of jointed hard rock during 1970’ and 1980’became defunct. After 1980’s the bore wells are  being located in deep Fractured zones.  But the success rate of such bore wells is very low and even in the case of successful bore wells, they became dry after 2-3 years of operation.  All these things led the farmers to undergo a lot of hardships.  In addition, there is burden on power sector due to transformation of shallow wells to deep wells, in as much as the consumption of power has been increased considerably. The state wise and district wise areas affected by over exploitation of groundwater are given below:

1.       Andhra Pradesh— Karimnagar, Warangal, Nalgonda, Mahaboobnagar, Nizamabad, Chittoor,  Anantpur and parts of Kurnool and Kadapa districts.

2.       Tamil Nadu-- Coimbatore,Salem,Dindigal,Erode districts.

3.       Maharashtra—Ahemadabad,Solapur,Osmanabad,Pune,parts of Sathara and Sangli districts.

4.       Karnataka---  The area covered by Precambrian hard rocks.

5.       Madhya Pradesh- Malwa plateau comprising of Indore, Rathlam, Ujjain, Jabua, Nimach districts  and parts of eastern M.P covered by Precambrian hard rocks.

In the above districts, however, the areas coming under canal command, valley fill areas, tanks and Lake command areas, buried river channels , along stream courses are not affected by over draft conditions.

Under the above circumstances, the  artificial groundwater recharge  assumes significance as an effective tool for mitigating water scarcity in the over exploited areas.  In this context, Rural                    Development Ministry attaching due priority has allocated considerable amount for this purpose. One of the main beneficiaries of the artificial recharge of groundwater is the power sector. Once the water levels improve, the power consumption of irrigation wells will be reduced appreciably.

Following is an attempt to work out the benefits on the power front due to artificial recharge

of groundwater schemes watershed wise.

 To calculate the effects of Watershed Development through artificial recharge of groundwater, a watershed is assumed to be comprising of 25 villages with 120 number of irrigation wells per village.

Parameters assumed:

1.       Watershed               ----                     1

2.       No. of villages          -----                  25

3.       No of existing irrigation wells --  120

4.       No of working hours of each

irrigation well annually           -- 1000                            

Discharge of well                    -- 5 lps

Cost of energy                        -- Rs.1.79 per unit

With the above parameters the input power required for the pumpset in KW has been

calculated using the following formula.

                              Q    X    H   X 0.746

            KW   =     -------------------------------------------

                              76  X   Pumpset effi  X  motor effi   

Where          Q is discharge of irrigation well in LPS

                       H is total head in meters

                       Pump efficiency has been taken as 70%

                       Motor efficiency has been taken as 80% 

As an example, average hydrogeological conditions of Mahabubnagar district have

been taken. The average discharge of irrigation well has taken as 5 lps, total head

of 17 meters. The values substituted in the formula:

                          5 x 17 x 0.746    

KW      =           ------------------        =    1.51 KW     

                         0.7 x 0.8 x 75

     It is assumed at this stage, artificial recharge (water harvesting) of groundwater project has taken up and after few days there is improvement in water levels of irrigation wells located In the watershed. Along with water level improvement, the discharge of wells also increases. For 1M improvement the discharge increase has taken as 5%, for 2M,8%,for 4M,20% and for 8M,50% increase in yield of well has taken. The input of power in KW is calculated for 1m, 2m, 4m and 8m as given below:

         

                    5.25 x 16 x 0.746

      1M =    ----------------------         =     1.492 KW

                     0.7 x 0.8 x 75  

                                

Similarly, KW values calculated for 2M,4M and 8M.

The number of units (Kwh) saved for 1M, 2M, 4M and 8M calculated using the following formula.

               E =   P x N x W

             E is energy in lakh units (L.U) saved          

 P is the difference of connected load in base level and at 1M

N is average working hours per well annually

W is No of wells in watershed.

The above procedure adopted for 2M, 4M and 8M.It is observed that with 1M water level improvement, 0.60 L.U, for 2M improvement 2.10 L.U, for 4M improvement 3.90

L.U and for 8M 9.30 L.U are saved.

Sl.No	Improvement in water level (M)	No.of units(Kwh)saved in L.U	Cost of energy per unit in Rs.	Cost of energy saved in Rs.Lakhs
1	1	0.60	1.79	1.07
2	2	2.10	1.79	3.76
3	4	3.90	1.79	6.98
4	8	9.30	1.79	16.65

Taking the saving of connected load in KW for 1M, 2M, 4M and 8M, total connected load for 3000 wells is calculated. From these values additional number of wells feasible in watershed are shown in the following table:

Sl.No	Water level improvement in (M)	Saving In KW	No of wells in wateshed	Total KW for 3000 wells	Addl no of wells feasible taking 3.73Kw per well
1	1	0.02	3000	60	16
2	2	0.07	3000	210	56
3	4	0.13	3000	390	104
4	8	0.31	3000	930	249

The above values may differ with the actual field conditions, like actual discharge, static water level, improvement in water level, number of pumpsets, working hours etc. The amount spent on artificial recharge of groundwater project can be realized to some extent due to savings in power consumption.

If three watersheds of same size as above are developed through artificial recharge of groundwater, about 30 lakh units can be saved which is equivalent to one MW of installed capacity. It is worthwhile to mention here that for 1MW installed capacity, 5 crores investment is required not to speak of the gestation period of 3-4 years.

ARTIFICIAL RECHARGE PROJECTS IN WATERSHED vis-à-vis INVESTMENT SAVED IN POWER SECTOR.

As per the data published in the paper “Central Sector Scheme-Artificial Recharge to Groundwater” published in the workshop on Rainwater-Harvesting conducted during 15^th to 16^th December 2001 in IIT Chennai, the cost of Rainwater Harvesting Structure ranges from 4.0 to 13.50 lakhs giving an average of Rs 8 to 9 Lakhs per village. For  a watershed of 25 villages, the cost will be about 200 lakhs and for 3 watersheds it is about 6 crores.

Though the above investment appears to be same as that required for additional generation, investment in Artificial Recharge of Groundwater is preferable for the following reasons.

Gestation period is small, compared to the setting up of unit for additional generation of power.

The associated problems of fuel products, higher degree of maintenance and administrative problems are avoided in the case of artificial recharge of groundwater schemes.

Though the additional generation of power will enable energisation of additional agricultural pumpsets, the depletion of water levels in the existing wells leads to drying of wells. Artificial recharge of groundwater schemes not only help adding more no of feasible wells due to saving of power, it can also sustain the satisfactory working of existing wells due to improvement in water level and yield of wells.

The Artificial Recharge of Groundwater methods can save the power and thereby help the power utilities to improve financially. In view of this, the financial institutions which are financing power utilities for various categories of schemes can also extend the finances to Artificial Recharge of Groundwater Schemes.

Finally, to quantify the actual benefits derived from Artificial Recharge of Groundwater Schemes, the following data is to be collected before and after implementation of schemes.

Measurement of water levels and Discharge of Irrigation wells in watershed before and after implementation of artificial recharge schemes.

All the irrigation wells in the watershed should have meters to monitor the power consumption before and after completion of projects.

The net and gross irrigated area per irrigation well before and after construction of artificial recharge schemes to be recorded.

                                                                                                                                                                                                                                                                          

             -----********-------

SUMMER DRINKING WATER PROBLEMS IN ANDHRA PRADESH- PROBABLE SOLUTIONS

Dwindling of fresh water supplies, inequitable access to water and Corporate control of water poses greatest threat to present and potential unrest in low income groups of rural and urban population of Andhra Pradesh.

Economically well off people get the scarce commodity by paying the premium, but it is a considerable burden to the middle class(the scale of impact on low income groups can only be left to imagination) to buy water for domestic needs.  In this process, water bottling companies are doing a brisk business in the name of “hygiene”. The tried and tested process of boiling and filtering provides water whose quality is considerably higher than the “run of mill” bottled water. Boiling of water removes the dangerous bacteria and filtering gets rid of mud or silt.  In a few isolated locations, harmful minerals like fluorides, arsenic and phosphorus, etc., may be present in the water in a dissolved form which is very difficult to identify.  To identify such mineral contaminated water, greater efforts from Government and Scientific institutions are necessary. This may sound cynical but majority of the branded Mineral water gives no assurance of such mineral absence from their products. Numerous reports in media have indicated the harmful chemicals in soft drinks manufactured by biggest multinational companies known to mankind; Water is the primary source of this contamination.

The scourge of drinking water problems across the state only aggravates with each passing summer. Following are the general problems encountered every year for getting potable drinking water.

In urban cities and towns, the common problem is decline of water levels in reservoirs, lakes and high capacity bore wells.  The authorities find it difficult to maintain the supply of water during summer season in required quantity as used to be supplied during other seasons.  Similarly, the domestic bore wells also fail to discharge water sufficiently during summer season due to steep decline of water levels in these urban areas.

In rural areas, hundreds of hand pumps operating on bore wells are under repair or the bore wells go dry.

Due to the failure of domestic bore wells, the residents of villages go to Irrigation bore wells for fetching drinking water.  It is not an easy job to get water from irrigation bore wells as the power supply is available in night time and sometimes these residents particularly women get snubbed by farmers.  It is also reported that in a few villages the public goes to lakes, ponds and rivers to get water.  In that process they dig small pits on the bed of these minor irrigation sources.

In a few villages of Nalgonda and Khammam districts where there is no nearby potable water source, villagers are forced to consume fluoride rich groundwater.  In a few localities government agencies are supplying potable water through tankers.  Though protected water schemes are implemented in a good number of villages, the schemes became non-functional in some villages for want of minor repairs.

In coastal villages, the limited quantity of fresh water floating on underlying saline

Water gets exhausted during summer season. If this limited water is utilized for

Drinking water purposes only, no problem would have arisen but the increased irrigation activities besides fish ponds and prawn culture in this belt aggravated the problem.

All the above mentioned problems repeat every summer season.  If government agencies take appropriate measures with the cooperation of local public just before the onset of summer season, most of the above problems can be solved. 

The fluoride problem and decline of water levels in reservoirs and lakes that are meant for supplying drinking water to towns and cities would still remain. For tackling water problem in these areas, bigger plans with high budgets are required.  To solve the fluoride problem in Podili, Kanigiri and Darsi Taluks of Prakasam district, water from Nagarjunsagar Dam was transported to this area and lakes and ponds were filled with fresh water.  A similar approach can be followed in the case of fluoride affected areas of Nalgonda and Khammam districts.  Similarly, bigger schemes are required to enhance the storage of water sources in urban cities and towns by transporting water through pipe line from rivers or bigger streams wherever feasible.

Drying up of domestic bore wells in towns and cities and shallow bore wells with hand pumps in villages and small towns owing to decline of water levels is a serious problem.  The main reason for this is energization of agricultural pump sets in a big way from 1980 onwards.  As a result, the depth of bore wells gradually increased from 150 to 300 feet.  The pumpset energisation programme was so intense particularly in Telangana districts of Karimnagar, Warangal, Nalgonda and Nizamabad where about 30,000 to 50,000 pump sets were existing in each district by 1980, but subsequently the pump set energization has increased with great speed and today, the number of agricultural pumpsets in Karimnagar district are more than 2.75 lakhs and in the other 3 districts, more than 2.0 lakshs.  Similarly,in the districts of Medak and Mahabubnagar too the number of pumpsets are more than 1.5 lakhs (in each district).  In view of the large number of agricultural pumpsets with deep bore wells, the shallow bore wells drilled for domestic purposes ran dry.  In some places where water source is good, hand pumps are under repair.  People seem to be suffering everywhere for want of drinking water for some reason or the other!

It is reported in the newspapers that as the domestic bores have gone dry, the villages depend on irrigation bore wells for drinking water purposes.  It indicates that water is available at greater depths.  Hence authorities can drill deep bore wells in suitable locations and install power driven Jet Air pumps. For drinking water purpose shallow bore wells were drilled in rural habitations along with hand pump installation due to lack of power supply but after 90’s , cent percent electrification has been achieved at village and hamlet level. In view of this particularly in villages with hard rock belt, hand pumps should be dispensed with and bore wells may be drilled equivalent to the depth of existing irrigation wells in the same village or nearby villages. These drinking water bore wells should also be energized with electric pump sets as the depth of borewells
is quite deep and handpumps may not be able to lift water to such higher discharge head.It is a common scene   in the rural areas to see that majority of handpumps are under repair wherever depth of borewells are more than 150 feet. Also it involves lot of physical labour to fetch water from handpump borewells.It is advisable to remove all the handpumps on borewells wherever the depth of borewells are beyond 150 feet and replace with power driver pumpsets in phased manner.

In Adilabad, Khammam, parts of Karimnagar (Manthani, Mahadevpur) and Warangal (Gudur,Narsampet), semi-consolidated rock formations like sandstone and shale are predominantly existing.  If shallow bore wells have gone dry, there is scope for construction of deep borewells for drinking water purposes.  Similarly, there are reports that in a few parts of Srikakulam, Vizianagaram and Visakapatnam districts there is problem for drinking water.  Exploitation of groundwater in this region is comparatively in low key and the rock formations are almost equivalent to granite terrain of Telangana region (from groundwater point of view, hard rock terrain consists of Khondalites, Charnockites, etc).  In this region too if shallow bore wells have gone dry, the authorities can go in for deep borewells.

In the above regions if the authorities intend to go in for drilling deep borewells, after successful completion of wells, instead of hand pumps, Jet Air pumps may be installed so that water can be stored in nearby storage tanks which are erected on cement structures.  It will be easy for villagers to fetch water.  If discharge of water from these borewells is medium to poor, Air compressor pumps can be installed.

This transformation from shallow bore wells to deep bore wells with power driven pumpsets takes considerable time to implement.  In the meantime, teams of mechanics with all the necessary repair equipment in suitable vehicles should be made available at the district level so that they can attend to the repairs immediately.  Similarly, there are reports that in protected water supply schemes too, schemes are non-operative due to minor repairs.  For undertaking repairs to such schemes, a team of mechanics with repair equipment loaded in a vehicle should be made available at district level.  Close monitoring of such activities by some nominated officers at the district level and water user associations will greatly help in getting the work done early.                                                

Besides all that has been said above, the most important and dangerous problem faced by some sections of population is ‘pollution’ of water through industrial pollutants, leakage of sewerage pipes, mixing of groundwater and drainage water in the areas where shallow groundwater conditions exist particularly during rainy season. This mixing of drinking water in shallow bore wells and drainage (sewerage)water is common during rainy season in the areas located along major rivers like Godavari and Krishna, in canal command areas and  deltaic areas.  Most of the villages located in such areas do not have underground drainage and toilets are constructed with local pits.  Lack of connectivity of pits and locations of final disposal in far off places causes mixing of drinking water with sewerage flow.  In such localities, particularly during rainy season, several diseases like diarrhoea, jaundice will affect the population.  Priority should be given to schemes dealing with sanitation and water.

To restore the deep groundwater levels to shallow levels and to increase the discharge of wells, artificial recharge of groundwater should be taken up in areas like  Karimnagar, Warangal, Nalgonda, Nizamabad, Mahabubnagar and Chittoor districts which are densely populated with agricultural pumpsets.  Artificial recharge methods like induced recharge through borewells, construction of ponds, etc., should be taken up in suitable locations.   The source of water for this artificial recharge can be from the flood canal being constructed from Sriramsagar project and the irrigation canals being constructed under phase-I and II of the same  project.  It is also not out of place to mention that during the construction of canals in these districts, provision may be made in certain selected locations for 2- to 3-metre pits which may be constructed using the filtering arrangement so that some part of canal flow  can be utilized for artificial recharge of groundwater in Karimnagar, Warangal, Nalgonda and Mahabubnagar districts as well as in the upland areas of West Godavari and East Godavari districts.  In all the proposed irrigation projects, to the extent possible, more number of ponds may be constructed along the route of canals in higher altitudes compared to the location of irrigation wells so that recharge of water can be done to improve the water levels and discharge of wells.

To improve the water levels and discharge of borewells, water harvesting methods in Hyderabad city and restoration of existing lakes, desilting of lakes and construction of new lakes in high altitude points should be taken up so that these lakes can recharge the borewells to improve water supplies.

There are many areas where unconsolidated sediments like sand, silt and clay formations are existing like deltaic areas and along the rivers.  In a few locations in Gandepalli and  Rangampet mandals of  East Godavari district, there are  recent Tertiary geological formations which are characterized by sand, silt, loose soil,and sandstore etc., for considerable depths.  They are not suitable for the normal down-the-hole-hammer drilling method and construction of which is generally deployed in hardrock formations.  In these areas, rotary drilling may be taken up.  Technical opinion may be taken for lowering the tubewell assembly which consists of casing pipe, slotted pipe, bailplug, size of gravel, etc.  It was observed that in these areas, tubewells are drilled and the casing pipe is lowered upto bottom  without any gravel packing and slotted pipes.  Without these additional precautions, the full benefits of tube wells cannot be realised. 

In  the extreme conditions of drought, services of experienced Hydrogeologists who might have worked for more than 2 to 3 years in groundwater survey and drilling of bores in a similar district should be utilised.  Such experienced hydrogeologists know subsurface geology, groundwater conditions of aquifers, etc., and would be able to give proper guidance for solving the water problems.

During summer season, due to decline of water levels and reduction in discharge of

borewell water, problems arise with regard to the setting position of submersible pumpsets.  When the discharge of a borewell reduces, the water level will go down within a few minutes after starting of the pumpset.  There is likelihood that the water level may go down below the submersible pumpset.  If the pump runs without water coloumn, the pumpset gets damaged.  Submersible pumpsets function well when there is good yield and a better recuperation rate.  If discharge of water is low and steep drawdown is recorded in deep borewells, air compressor pumps may be installed.  If the borewells are shallow and yield is poor, jet air pumps may be used.

In the case of exhaustion of most of the water sources in the villages, demarcation of

buried river channels, valley fill areas and highly favourable groundwater zones may be demarcated on mandalwise maps utilizing satellite imagery and aerial photography.  If such maps are available, it is easy to identify suitable locations for exploitation of groundwater in the times of accurate shortage of drinking water.

There should be a consumer center in every district for giving advice regarding the

drilling of borewells, selection of pumpsets, quality of groundwater, etc.  The center should consist of a Hydrogeologist, a Mechanical Engineer who had experience in drilling of borewells for water and pumpset selection and mechanics who can undertake repairs to pumpsets and borewells.