UTILISATION OF AQUIFER CHARACTERISTICS FOR SELECTION OF AGRICULTURAL PUMP SETS IN ANDHRA PRADESH AND TELANGANA.
* C.SATYANARAYANA
Selecting an agricultural pump set of appropriate size and installing energy efficient pumping system for these pump sets avoids wasteful consumption of power. Shortage of power can be mitigated to a great extent by adopting an efficient pumping system to the existing pump sets since increasing the generation capacity is both capital intensive and it requires a long gestation period. Electrical pump sets used by farmers in Andhra Pradesh and Telangana states are, in majority of the cases, inefficient and therefore result in considerable wastage of energy. Installation of new energy efficient pumping system will definitely save the valuable power to some extent but to save more energy, the pump specifications should match the well characteristics like discharge, total head etc. Aquifer characteristics like discharge, drawdown, transmissivity, specific capacity, specific yield or storage coefficient varies depending on the type of rock formations, topographical conditions, recharge conditions, soil cover etc. The study on Hydrogeological conditions of different rock formations existing in Andhra Pradesh and Telangana state enable us to understand the above mentioned characteristics which are useful for the selection of correct size of agricultural pump sets.
To overcome the problems of low efficiency and low power factor of pumping system, following measures are to be followed.
· Efficient pumping system adopting BIS mark pumps, motors, piping system and foot valve etc
· Correct estimation of Discharge (Q), Total Head (H) of groundwater abstraction structures (Bore well, Tube well, Dug well, etc.) so as to select correct size of pumping system.
Ø Efficient Pumping system: - Regarding the installation of efficient pumping system, several field studies were carried out since last 20 years. The studies include
1. Replacement of foot valve with frictionless foot valve
2. Replacement of GI piping with PVC and HDPE pipes
3. Replacement of Motors and Pumps with energy efficient Motor and Pump sets.
Of late, some state governments like Andhra Pradesh and Maharashtra are going for complete replacement of existing pumping system with new energy efficient pumping system. Energy efficient pumping system adopting the following BIS standards are to be installed.
*Groundwater specialist, retired from RURAL ELECTRIFICATION CORPORATION.
Equipment
|
Relevant Indian Standard
|
Centrifugal pump
|
IS 6595
|
Mono set pumps
|
IS 9079
|
Submersible pump set
|
IS 8034
|
Electric Motor
|
IS 7538
|
Suction and Delivery or Piping system
|
IS 4984 and 4985
|
Pipe fittings PVC fittings
|
IS 10124
|
Ø Correct estimation of Discharge (Q) and Total Head (H):-,
Though installation of new energy efficient pumping system will definitely save the valuable power to some extent but to save more energy, the Pump specifications should match the well characteristics like discharge and total head etc. Generally, the farmers select the agricultural pump sets as per the advice of pump dealer without considering the discharge, static water level, pumped water level etc. In order to maintain higher efficiency of pump set, well characteristics should be taken into account, mainly discharge and total head. If the discharge and total head are appreciably lower or higher than the pump specifications for which pump is selected, low efficiency and reduction in power factor results. Therefore, there is a need for optimum selection. Due to large seasonal variation in ground water level and discharge, pump sets operate under varying load conditions. Under loading of motor results in lower efficiency, Power factor reduction and ultimately higher power consumption. Due to power cuts, farmers try to get maximum water in less time by opting for higher ratings of motors. In such cases, motors are operating between 50 and 75 per cent of rated load. Higher rating of motors lead to over loading of distribution transformers and together with existing higher HT and LT ratio, results in high line losses and fluctuations in voltage conditions.
Aquifer characteristics like discharge, drawdown, transmissivity, specific capacity, specific yield or storage coefficient vary with the type of rock formations, topographical conditions, recharge conditions, soil cover etc. Weathered and fractured zones in hard rock’s under favorable soil, recharge and topographical conditions yield adequate ground water potential. Sandstones belongs to Gondwana and Tertiary formations yield large quantity of water and it is observed that though number of Tube wells increased many fold in these rock formations since last 30 years but there is no significant decrease in transmissivity of Sandstone aquifers unlike in Granitic Gneissic rock formations where discharge and transmissivity decreased considerably results in steep decline of water levels. Though large area in Godavari, Krishna and Penna River Delta area is underlain by alluvial formations, the wells are restricted to shallow depth only, due to quality problem in higher depth. But along stream courses and in canal command areas, the filter points yield adequate ground water without quality problem.
HYDROGEOLOGICAL CONDITIONS OF DIFFERENT ROCK FORMATIONS IN ANDHRA PRADESH AND TELANGANA
Geological formations for the purpose of ground water availability can be divided into 3 main categories.
1. Hard rocks or consolidated rock formations
2. Sedimentary or Semi-consolidated rock formations
3. Unconsolidated formations.
In Andhra Pradesh the Hard rock, comprising of Granitic Gneisses, Schist, Khondalite, Charnockite, consolidated Shale, Quartzite, Limestone, Dolomites etc., occupies about 82% of the total area. The Sedimentary or Semi-consolidated formations occupy 6% and unconsolidated (Alluvial) formations cover 12%.In the Geological history of the state, the Hard rock formations are the oldest rocks(3500
million years)and hardness of rock formations gradually decreases with age, leading to Schist, Quartzite, Lime stone, Dolomite, Sandstones, Shale etc and finally recent alluvial formations. Similarly the water bearing zones also improve from old age to recent formations. But the quality of ground water is affected by other factors like chemical composition of rocks, sea water intrusion, water logging conditions etc.
THE GEOLOGICAL SUCCESSION IS GIVEN BELOW
SL.NO
|
PERIOD
|
ROCK FORMATIONS
|
AGE Mil Years
|
1
|
Recent
|
Alluvium/Laterite
|
0-2
|
2
|
Tertiary
|
Rajahmundry Sand stone
|
25-2
|
3
|
Post Cretaceous
|
Deccan Traps
|
70
|
4
|
Permian-Early Cretaceous
|
Gondwana formations
|
270-85
|
5
|
Late Proterozoic
|
Kurnool formations
|
1100-600
|
6
|
Middle Proterozoic
|
Kadapa formations
|
1700-1100
|
7
|
Early Proterozoic
|
High grade
Schist,Charnockite,Khondalite and low grade Schist
|
2350-3000
|
8
|
Late Archaean
|
Granitic Gneisses
|
3000-
|
9
|
Early Archaean
|
Peninsula Gneiss
|
3750
|
HARD ROCKS OR CONSOLIDATED ROCK FORMATIONS
EASTERN DHARWAR CRATON (EDC)-(In the above map shown as Archaean formations).
The EDC is one of the six cratons which are part of Indian shield made up of Archaean rock formations comprising of Granitic Gneisses, Green schist, Fold belts, intrusive dykes, sills etc. The EDC is bound in the north by the Deccan Traps and Bastar craton, east by Eastern Ghat Mobile Belt , south by Southern Granulites, and west by Closepet Granite and Western Dharwar craton. Between EDC and Eastern Ghat Mobile Belt, Kadapa type rock formations are occupied in the shear zone. The Eastern Dharwar craton occupied western portion of the state covering Telangana area except parts of Adilabad, Karimnagar, Khammam and Warangal districts.
There are two main rock types in EDC, which occupy major portion of the area
1. Granitic Gneisses
2. Green Schist
Granitic Gneisses occur as elongated plutonic belts running parallel to Schist belts. Origin and distribution of these rock formations have considerable impact on ground water potential of this region.
Origin of Granitic Gneisses (Dharwar Craton)
The Dharwar Batholith is a term first used by Chadwick et al.(2000) to describe a series of parallel plutonic belts. Previous works consistently used the term ‘Peninsular Gneisses’ to describe the majority of the EDC; however, it is compositionally different than the Western Dharwar Craton gneisses, more granitic than gneissic and hence the new terminology is more appropriate(Ramakrishnan and Vaidyanathan,2008). There are numerous elongated Granitic Gneisses running parallel to the Schist belts of the EDC. The plutonic belts are approximately 15-25 km wide, hundreds of km long and separated by greenstone belts. They trend NW-SE except for in the south where the trends become North-South.
These intruded Granites could have been originated from partial melting of the continental crust during subduction or during rise of mantle plume. The Dharwar batholiths then obliquely converged with the Western Dharwar Craton causing shear systems along the margins.
Origin of Green schist belts-In the above map shown as Dharwars.
The linear schist belts represent back-arc basin environment which were metamorphosed during accretion. Back arc basins are the submarine basins associated with island arcs and subduction zones. As per Plate tectonic theory, convergent plate margin is located at ocean trench where two plates converge and when denser of the two plates sink along an inclined plane below the other to be eventually absorbed into mantle. This process is called subduction.
Subduction of oceanic crust between two crystal blocks gives rise to back-arc basin, volcanic arc, fore arc basin and formation of ocean type crust. It is by subduction only that calc-alkaline volcanic and tonalite magma were generated. During Dharwar Orogeny the volcanics have been metamorphosed into Green schist, Amphibolites and higher grade basic Granulites while the associated sediments have recrystallised into Quartzites, Marbles etc. Another theory suggests that Green schist belts developed as a result of intra-arc basins associated with batholiths. Important Greenstone belts and Super groups are given below:-
1. Sandur schist belt,
2. Ramagiri-Penakacherla-Sirigeri-Hungund super belt (RPSH),
3. Kolar-Kadiri-Jonnagiri-Hutti super belt (KKJH), and
4. Veligallu-Raichur-Gadwal super belt (VRG).
Sandur schist belt is located north of closepet granite on the western side of EDC. RPSH consists of two discontinuous schist belts. These belts are intruded by granites and gneisses. It is located north of Ananthpur Town and in Kurnool district. KKJH schist belt is located in the southern portion of EDC and below kadapa basin in southern side. The Kolar region contains mostly amphibolite grade metamorphic rocks. The VRG super group is located north of Kadapa basin. The super group consists of granites, metabasalts which are typically formed during the early stages of subduction.
Intrusives of EDC-
Majority of intrusives include mafic dykes, kimberllites, lamproites and have the trends of NW-SE, E-W and NE-SW.
Five major intrusives are
1. Hyderabad cluster
2. Mahabubnagar
3. Bangalore
4. Anantpur
5. Tirupati.
Ø Hyderabad cluster is widely spaced NNE-SSW to N-S trending dykes transverse E-W oriented dykes. The majority of the dykes present are dolerites in composition.
Ø Mahabunagar dyke intrude local granitic gneisses. The mafic dykes are predominantly gabbroic and partly dolerite and metapyroxenite.They are oriented NW-SE with 50 km long and average 5-30 km wide.
Ø Anantpur dyke swarm and south of the Kadapa basin is the Tirupathi swarm.
Ø Anantpur dykes trends at NE-SW and ENE-WSW
Ø Tirupathi Dykes show E-W and NW-SE trends.
Groundwater conditions in Eastern Dharwar Craton
The major rock formation where high density of agricultural pump sets are concentrated is Granitic Gneisses occupying major portion of Telangana area, Chittoor, Anantpur, part of Kurnool district and few pockets in other districts of Andhra Pradesh. Weathered zone and fractured zones are favorable ground water areas. Another major rock formation is schistose rock where the ground water yield is limited as clay material is more compared to weathered zone of Granitic Gneisses rock. The other category of rocks is intrusive rocks which occur mainly as dykes and comprise dolerites and amphibolites. These rocks lack primary porosity and as a result, normally yield poor quantity of water. Wherever the dykes exist they act as barriers for ground water movement. Hence one side of dyke yields high ground water and other side poor yield or dry.
Highly to moderately weathered rock material:-This zone is restricted to shallow depths which generally vary up to 30m. Under favorable topographical and recharge conditions, this zone acts as shallow groundwater zone. Generally, Dug wells are feasible in this zone. Due to large number of wells constructed in this zone, groundwater in this zone is almost exhausted and water levels have gone down beyond this zone in major portion of the state except in few areas which are under the command areas of surface water bodies. Generally, under favorable conditions, the thickness of weathered zone is up to 15m in hard rocks.
Fractured rocks:-Fractures in hard rocks below weathered zone are prevalent in major portion of the Hard rock area. In such zones, dug cum bore wells were constructed wherever Dug wells failed to yield Water. This practice of construction of dug cum bore wells also continued for few years and due to intensive energisation of agricultural pump sets, these groundwater abstraction structures also failed to yield water. Finally, Bore wells started with the depth range of 150 to 200 feet in the initial days and continued to Increase the depth of bore wells up to 300 feet in general and depth of bore wells in some areas gone up to 1000 feet. In Hyderabad city the depth of bore wells have gone more than 1000 feet. The successful Bore wells are those which struck fractured, jointed and fissured rocks. It is generally believed that the weathered zone is restricted to maximum depth up to 15m and fractured zone usually up to 30m and in higher depth fractures/joints are absent. In continental crustal rocks like Peninsula Gneiss it may be correct but in Granitic Gneisses (Dharwar Batholith) of EDC which are formed due to partial melting of the continental crust during subduction or during rise of mantle plume, fracture/joints might have formed in higher depths also during the cooling history of Granitic Gneisses (Dharwar Batholith) and subsequent shrinkage of rocks. In the light of above theory, the fracture/joints encountered up to the depth of 1000 feet and above may be justified.
However, delineation of such fractured zones in higher depth is very difficult. If the thickness of water bearing strata is quite significant and yield large quantity of water, Geophysical methods like Resistivity survey can delineate the fractured zones at higher depth. But if the aquifers are very limited in thickness, it is difficult to identify such zones. It is common observation that deep bore wells up to 1000 feet are drilled without any technical guidance and whenever bore well is successful; others in the same locality also follow the same depth for construction of bore wells. But in such attempts, failure rate of bore wells is more and in several cases farmers tried more number of bore wells say 5 to 10 numbers to get success but they failed to get water and also miserably failed financially.
After 1980’s number of agricultural pump sets increased mostly in hard rock areas of Telangana area, chittoor district, Anantpur, Kadapa and Kurnool districts thereby increased the exploitation of Ground water resources. About 65% of Agricultural pump sets against the total 33 lakhs of existing pump sets are located in Granitic Gneisses and Schistose rocks (Hard rocks ).The highest number of 3.20 lakhs pump sets in Karimnagar district, 2.90 lakhs in chittoor district, 2.80 lakhs in Nalgonda district, 2.75 lakhs in Warangal district, 2.25 lakhs each in Nizamabad and Mahabubnagar districts,2.15 lakh in Medak and more than 2.0 lakhs in Anantpur district. This has resulted in decline of water levels, decrease in discharge rate and transmissivity values and increase in power consumption. The aquifer characteristics of Granitic Gneisses during 1980’s and in recent years are given below:-
Sl.No
|
year
|
Discharge(Q) m3/day
|
Transmissivity
(T) m2/d
|
Depth range
(m)
|
Depth to water level(M)
|
Power consumption (kwh/units)per pump set per year
|
Acres/pump set
|
v1
|
1980
|
516-691
|
68-254
|
DW 4-20
|
5-15
|
2500
|
1-8
|
2
|
2003 onwards
|
18-54
|
6-40
|
BW 50-120
|
20-38-14% wells
8-20-30% wells
5-10-32% wells
72 m DTW in Agali village in Anantpur
|
7000
|
1-2
|
As the hard rocks having low storage space (water bearing and transmitting capacity) increased exploitation of the groundwater over the last few decades has resulted steep decline of water levels. Hence access to Groundwater become difficult due to high cost and high risks of getting adequate water. Generally, it is observed that wells which can sustain 50 m3/day can be said to be moderate and sustainable. When Transmissivity ‘T’ of an aquifer is 100 m2/d or more, well yield can be adequate. The above data (in Table) indicate ‘T’ values are on very much on lower side and minimum discharge (18 m3/d) values are on lower side. Partial penetration and vertical heterogeneity might also be the reasons for low yields and transmissivity values.
As per the field observations, two decades back, density of wells used to be 5 wells per Sq.Km and at present increased up to 20 wells per Sq.Km. Hence, increased the possibilities of interference of wells and decline of water levels. As already mentioned that 85% of land area in Andhra Pradesh and Telangana states is underlain by Archaean basement rocks. Out of these 85% rocks, 20% area in major irrigation canal command area, 30% in poorly developed schistose rocks outside irrigation command area, and balance 35% area in deeply weathered and fractured hard rock aquifers outside canal command area.
Area under major irrigation canal command area
Groundwater conditions of hard rock areas falling under canal command area of Godavari, Krishna and Penna Rivers multipurpose irrigation projects is somewhat satisfactory. The existing and proposed major irrigation projects and the area covered under each project are given below.
1.Sriramsagar Project,Stage-1: Works started in 1963 to create a potential of 3.92 lakh hectares been partially completed to supply water to 2.87 lakh hectare and irrigate 1.28 lakh hectare in less developed districts of 1.Adilabad,2.Nizamabad,3.Karimnagar,4.Warangal districts. Except Adilabad district other districts are predominantly covered by hard rocks. In Karimnagar district highest number of agricultural pump sets is operating i.e. nearly 3.2 lakh pump sets. In Warangal district 2.75 lakhs and in Nizamabad district 2.25 lakhs pump sets are operating.
2. Sriramsagar, stage-2: This project was already sanctioned and works are yet to start. Under this project Warangal, Khammam and Nalgonda districts will be benefitted for irrigation purpose.
3. Sriramsagar flood flow canal:- This project envisaged to irrigate 2.20 lakh acres in Karimnagar, Warangal and Nalgonda districts.
4. Devadula Lift irrigation Project:- The location of the lift point on Godavari is 12 Km downstream of Ichampally Dam site, near Devadula village of Warangal district. It is proposed to irrigate large ayacut available in Karimnagar, Warangal, Nalgonda and Medak districts which are backward upland areas chronically affected under drought conditions. To bring this area under cultivation Lift is inevitable as the river flow at +90M level and the ayacut is at +360M and up to +500M contours.50 TMC of water is proposed to be lifted and supply for irrigation.
5. Nizamsagar Project: Already existing irrigation project benefit 0.97 lakh hectares in Nizamabad district.
6. Proposed Pranhita and Chevella Project is proposed to irrigate 16.4 lakh hectares in Nizamabad, Adilabad, Karimnagar, Medak, Rangareddy, Warangal and Nalgonda districts.
In all the above projects, the canal net work is located in hard rock terrain and these projects improves the groundwater conditions of the area wherever the canal net work spreads. Besides the canal net work, Artificial recharge of groundwater projects also can be proposed in suitable areas diverting the canal water to bring back the deep water levels to safe levels so that consumption of power will be reduced and beneficial to power utilities and individual farmers.
The Eastern Ghat Mobile Belt (EGMB)- (In the above map shown as Khon-
dalites and Charnockites)
EGMB is NE-SW trending arcuate Pre-Cambrian fold belt extending from Cuttack in Orissa to Nellore in Andhra Pradesh. Maximum width of 100 Km in North and less than 20 Km in South. EGMB is in contact with Singhbhum Craton in North, Bastar Craton in West, Dharwar Craton in South and East by Bay of Bengal. In western side with Bastar Craton the contact is marked by a shear zone and regarded as continuation of Sileru shear zone. The contact between EGMB and Singhbhum craton is marked by shear zone i.e. sukinda thrust.
East of EGMB also has one shear zone at which Chilka Lake is located.
EGMB is dissected by two prominent Rifts with infillings of Gondwana sediments.
1. Mahanadi Graben
2. Godavari Graben
Rifts trend NW-SE
Origin of EGMB-
EGMB has been divided into two segments namely North EGMB (NEGMB) and South EGMB (NEGMB) by NW-SE Godavari graben filled with Gondwana formations. Both northern EGMB and south EGMB have undergone high-pressure isobaric cooling (IBC) The isobarically cooled rocks of NEGMB have been uplifted by isothermal decompression (ITD) during an Orogeny. Basic magma is the source for high temperature heating of the deeper crustal rocks.
The SEGMB escaped the Orogeny as the rocks retain older ages and do not show isothermal decompression.
The prevailing NE-SW trend of the fold belt suggests a dominant E-W compression during the Eastern Ghats Orogeny. The compression is attributed to the collision between the continent of India (eastern part) and the Antarctica, giving rise to this Eastern Ghats fold belt.
Collissional processes have been responsible for the formation of mobile belts as well as thrust zones.
The folding events are thrust –related deformation.
The EGMB is supposed to have been juxtaposed against the East Antarctica in all Proterozoic reconstructions.
The deformation/fold phases have caused sufficient shortening of the crust which finally yielded to shearing and helped excavate the high-pressure granulites to shallower depth to be emplaced on the cratonic rock.
The last episode of deformation is marked by open folds, the axial plane of which is nearly parallel to the shear plane. The Granulite-Khondalite rock suite of EGMB was excavated along a shear zone.
The entire Charnockite rocks of EGMB have been exhumed by up thrusting along a ductile shear zone, the shear zone is found around the Proterozoic fold belt.
Godavari Graben is devoid of any igneous material but contain sediments of Pakhal Group and Gondwanas.
Ground water conditions in Charnockites and Knondalites
The area underlain by Khondalites and Charnockites are located in hilly and forest areas in Visakhapatnam, Vizianagaram and Srikakulam district inhabited mostly by Tribal population hence the exploitation of ground water resources is low to moderate. Up to 2000 year, mostly Dug wells were the main ground water abstraction structures and after the year 2000 onwards bore wells become common ground water abstraction structures but the density of wells are low to moderate. The yield of Bore wells ranges from 20-180 m3/d in Khondalite and Charnockite rocks and yield of dug wells was 18-90 m3/d. Valley fill area and foot hill zones are potential areas for ground water exploitation. Dominant E-W compression during the Eastern Ghats Orogeny results in development of fractures in the rock formations which are good source for groundwater. The depth to water level as on 2012 in Khondalite and Charnockite formations varies from 2-13m but in Guntur district the DTW is 27m and in West Godavari district is 19m.
KADAPA ROCK FORMATIONS OF ANDHRA PRADESH- (In the above map shown as Cuddapahs.)
The crescent shaped Kadapa basin with its convexity to the west occurs in the eastern dharwar craton underlain by basement rocks. The Kadapa super group of rocks consists of three sub-groups namely Papagni group, Chitravathi and Nallamalai groups.
Papagni and Chitravathi group of rocks occupied western portion of the basin while the Nallamalai group of rocks occupied eastern portion of the basin. The Papagni sub-basin in the western portion of basin marked by volcanic rocks in the form of sills and flows while the eastern side of the basin is marked by intensely folded and highly sheared Nallamalai group of rocks.
The equivalent of Kadapa basin rocks occur in either side of Godavari Graben. The Northeastern part of Kadapa basin where the different structural trends culminate is the site of maximum tectonic disturbanc.Thenumber of shear zones show the close relationship with the thrust boundaries of the Nallamalai basin.
SUBDIVISIONS OF KADAPA FORMATIONS:-
KURNOOL GROUP Banganapalli Quartzite etc.,
NALLAMALAI GROUP Bairenkonda Quartzite, Nagari Quartzite
----------- Tectonic Contact------
CHITRAVATHI GROUP Gandikota Quratzite, Tadipatri shale
Pulivendla Quartzite.
PAPAGNI GROUP Vempalli formations, Gulcheru Quartzite
It is assumed that extensional tectonics and compression played an important role in the evolution of Kadapa basin. Extensional tectonics followed by volcanic activity and normal faulting resulted in the formation of Papagni and Nallamalai basins. In general, the extensional tectonics is widespread, while the compressive deformation is restricted to narrow zones.
LOWER KADAPAS
Indications of marine, intertidal and sub-tidal origin observed in Vempalli, Chitravathi and Tadipathriformations. The following indications support the above theory.
1. Shelfal mud deposition in the upper part of Vempalli formation.
2. Laminated shales at the top suggest shore face inner-shelf deposition.
3. Algal laminites, Stromatolites and ripple sandstone suggest an intertidal, sub-tidal regime in Tadipathri formations.
4. Gandikota Quartzite represent a bar inter bar facies with tidal influence.
UPPER KADAPAS
1. Nallamalai group of rocks are folded and faulted
2. Consists of sandstone dominated Bairankonda Quartzite
3. Cumbum formation consists mainly of Shales with Limestone intercalations.
4. 4. Nallamalai fold belt has been regarded as major strike slip fault associated with Subduction and Transpression.
5. Nallamalai group show a tidal and storm influence indicating connection with open Sea.
Two numbers of cross fault that cut across the entire basin observed in the eastern part of basin.
1. Gudur-Kadapa fault
2. Veldurthi-kalva-Gani fault.
Ground water conditions in Kadapa and Kurnool formations
The kadapa and Kurnool system of rocks comprises of Quartzites, Shales, Slates and limestones also belongs to consolidated rock types as they have undergone large scale compaction, folding, faulting and metamorphism. The primary porosity and permeability of these formations have been very much reduced.However, the extensional tectonics and compression forces which played important role in the evolution of Kadapa basin might have produced large number of fractures which are good source for availability for groundwater. Under favorable conditions, the fractured shales and cavernous limestones yield moderate amount of water. Shelfal mud deposition in the upper part of Vempalli formation and other formations prevent rainfall recharge to groundwater and there is likely failure of Bore wells drilled in such areas. The Quartzite rocks in most of the areas exist as ridges and hilly terrain which acts as run-off zone. In Shales and Phyllites the DTW varies from 21 to 53m and in Kurnool formations the DTW varies from 14-38m.
GONDWANA ROCK FORMATIONS OF ANDHRA PRADESH – (In the above map shown as upper and lower Gondwanas.)
Gondwana land is part of Pangaea super continent that existed 510 to 180 M.Years ago Included Antarctica, South America, Africa, Madagascar and Australia. Some 170-180 M.Years ago many fissures were formed through which lava was outpoured to the surface giving rise to the Rajamahal Hills. This was probably the time of disintegration of Gondwana land. East Gondwana began to separate about 120 M.Years ago when India began to move north wards. The Madagascar block was broken off India. The separation (India-Madagascar) coincides with the eruption of Deccan Basalt.
Gondwana formation in Andhra Pradesh.
The Gondwana formations represent about 5000 m thick sequence ranges in age from Permo-Carboniferous to Early Cretaceous Gondwanas in A.P deposited in rift valleys or Grabens in NW-SE direction along River Godavari extending from Adilabad district to Eluru in West Godavari district.
These rocks lie unconformably on Proterozoic (Kadapa) formations in Pranhita-Godavari basin. The coastward extension of Godavari-Pranhita Graben (Gondwana) is terminated by NE-SW trending Bapatla ridge along the Eastern Ghats characterized by ridges and grabens which are the sites of sedimentation. The tilting of basins eastwards resulted in drowning of the coastal land. After Godavari-Pranhita
Graben, Gondwana formations lying on Archaean formations toward Delta region. Gondwana rocks are exposed in few locations but larger part lie concealed under younger deltaic and marine sediments of coastal and Off-shore shelf.
ORIGIN OF GONDWANA FORMATIONS
The Gondwana succession in south India represent glacial beds at base(Talchir) ,Coal measures In the middle(Barakars) and red beds at the top. Basement lineament, control the origin and evolution of sedimentary basins. The basement of Gondwana formations in Pranhita-Godavari is Proterozoic age was formed due to collision of various proto continent (Naqvi & Rogers, 1987). The Proterozoic sedimentation and merger of gondwana land in Carboniferous period initiate Gondwana sedimentation. Gondwana sedimentation begins with glaciations in northwesterly sloping valley. Subsequent deglaciation might have provided initial depression and controlled basin formation. Repeated rifting of Pre-gondwana basement took place in Proterozoic age in Pranhita-Godavari valley area. The gondwana basins of Peninsular India are therefore, bounded between two rift episodes of Early Permian and late Triassic/Jurassic respectively. The former initiated gondwana basin development following deglaciation whereas the later terminated sedimentation.(R.C. Tiwari and Watare Maejima,2010)
Groundwater conditions of Gondwana rock formations
Among the Gondwana formations the Sandstones are of importance from groundwater point of view. The impervious shale or clay layers form confined beds to give rise to semi-confined to confined conditions.
The sandstone of Kamthis stage located in Telangana area and its equivalent of Chintalapudi sandstone in West Godavari district are highly productive groundwater zones yielding high discharges throughout year.
Fluvatile deposits Coastal deposits
Upper ) Chikila stage -- --- --- Tirupathi Sandstone
Gondwana ) Kota stage Raghavapuram Shales
Maleri stage Gollapalli Sandstone
Kamthi stage -- --- --- Chintalapude Sandstone
Lower ) Barakar stage
Gondwana ) Talchir stage
In West Godavari district, Gondwana rock formations are prominently exposed in the upland areas in northern portion of the district. Chintalapudi sandstone equivalent of Kamthi sandstone of Lower Gondwana formations occupied the north western portion near Chintalapudi, Kamavarapukota villages Etc, followed by Raghavaram Shale occur in narrow elongated strip south of chintalapudi. Tirupathi .Sandstone occupied the area between Rajahmundry sandstone in south and Raghavaram Shale in north covering Dubacherla, Nallajerla, Polavaram, NW of Devarapalli and Gopalapuram villages.
LOCATION AND HYDROGEOLOGICAL CHARACTERISTICS OF GONDWANA FORMATIONS
SL.NO
|
Stage
|
Rock Type/Aquifer
|
Depth
m
|
Discharge
LPS
|
Drawdown
m
|
Transmissivity
m2/d
|
Locations/Areas
|
1
|
Gollapalli
sandstone
|
Sandstone U.C and Conf
|
600
|
8-60
|
--
|
80-900
|
|
2
|
Tirupathi
sandstone
|
Sandstone
|
300
|
10-40
|
6
|
86-1900
|
|
|
Raghavapu
|
ram shale
|
Has
|
Limited scope
|
for
|
Gr .water
|
development.
|
3
|
Barakar
|
Sandstone
|
--
|
3.30-
16.20
|
12-38
|
18-84
|
|
4
|
Kamthi
|
Sandstone
|
250
|
4-50
|
9-30
|
28-950
|
|
5
|
Chintalapu-di
|
Sandstone
|
50-150
|
7-16
|
7-13
|
150-303 flowing conditions
|
|
Comparison of aquifer characteristics like discharge and Transmissivity values during the period from 1980 to 2010 indicated that there is decrease in discharge and Transmissivity values in Chintalapudi sandstone in West Godavari district and in Kamthi Sandstones covered in Telangana area, almost no change in the values of Transmissivity but there is change in the discharge of wells. River Godavari is recharging the Gondwana formations in both Telangana and West Godavari districts besides precipitation annually. Large number of high capacity pump sets is operating in West Godavari district compared to Tube wells operating in Kamthis Sandstone area. The details are given below:-
SL.NO
|
YEAR
|
DISCHARGE ‘Q’ M3/D
|
TRANSMISSIVITY
‘T’ M2/D
|
DEPTH
RANGE (M)
|
DEPTH TO
WATER LEVEL(M)
|
|
|
KAMTHI SANDSTONE
|
TELANGANA
|
|
|
1
|
1980
|
1630-4197
|
50-957
|
Up to 250
|
2-10
|
2
|
After 2000
|
1000-1260
|
28-950
|
100-300
|
24-32
|
|
|
CHINTALAPUDI SANDSTONE
|
W.G.DIST
|
|
|
1
|
1980
|
176-2254
|
30-3540
|
30-150
|
2-7
|
2
|
After 2000
|
187-408
|
150-303
|
100-300
|
16-69m
In Koyyalagudem village the DTW is 69m
|
If the proposed Polavaram project canals are constructed from Polavaram to Buttayagudem,Koyyalagudem,Jangareddygudem and Chintalapudi instead of present layout of Polavaram to Devarapalli,Bhimadolu,Eluru and to Vijayawada( parallel to existing Doweleswaram project canals) there is good recharge to ground water aquifers in upland areas and could yield adequate water . As the canal works are under progress towards Bhimadolu area, separate canal net work could be designed from the proposed Polavaram Dam -if feasible- toward upland areas of west Godavari district. If this project is realized, the Gondwana formations in Telangana area, West Godavari district and Tertiary Sandstones in East and West Godavari district would be formed as Ground water Sanctuary’s. In case of severe drought conditions, these aquifers can meet the drinking water needs of neighboring areas. Or these formations could be one of the source for” Water Grid” –a concept which is actively under consideration by present governments taking the example of Gujarat model.
TERTIARY RAJAHMUNDRY SANDSTONE OF COASTAL ANDHRA PRADESH.
The highly potential rock formation for groundwater development is Tertiary Rajahmundry sandstone located on either side of Godavari River in East and West Godavari districts. Rajahmundry Sandstone is fluvial, unfossiliferous, ferruginous and feldspathic sandstone of Oligo-Miocene age equivalent to that of Ravva formation of Off-Shore area.
Resting unconformably on the older rocks including Khondalite and Charnockite rocks forms as small hills in the Coastal area. The 600 m thick succession of Rajahmundry Sandstone made up of coarse grained sandstone with subordinate clay stone and pebble beds, hence formed as the highly favorable Groundwater zone, next to alluvial formation in the state.
Location and occurrence of Rajahmundry Sandstone
SL.No
|
District
|
Main villages covered
|
Discharge LPS
|
Drawdown (m)
|
Transmissivity m2/day
|
1
|
East Godavari
|
Vemagiri, Rajahmundry, Dowleswaram
Balabhadrapuram, between Kadiam and Kasavaram, Peddapuram, Samalkot, Rangampet,Gandepalli.
|
10-128
|
6-15
|
86-576
|
2
|
West
Godavari
|
Eluru(S),Bhimadolu,Kovvur(W),Dwaraka Tirumala,Gopalapuram,Pedavegi,west of Nallajerla,Chagallu(W),Devarapalli(S)
|
-do-
|
-do-
|
-do-
|
3.
|
Krishna
|
Nuzuvidu,Gannavaram
|
-do-
|
-do-
|
-do-
|
The depth range of Tube wells ranges from 100-200m in East Godavari and from 100-300m in West Godavari districts. Transmissivity of aquifers ranges from 86-2500 m2/day .In West Godavari and Krishna district the Tertiary formations are noticed in the contact zone between Gondwana and Alluvial formations. The deep Tube wells in this area yield groundwater under confined (artesian) to semi-confined conditions. Even free flowing wells were also noticed few years back but at present free flowing conditions ceases to exist due to high density of Groundwater abstraction structures.
Comparison of the aquifer characteristic of Discharge and Transmissivity during the period from 1980 and after 2000 indicate that there is decrease in yield of Tube wells but there is no change in Transmissivity values as given below:-
TERTIARY SANDSTONE OF EAST AND WEST GODAVARI DISTRICTS
A. West Godavari District
SL.NO
|
YEAR
|
DISCHARGE ‘Q’ M3/D
|
TRANSMISSIVITY ‘T’ M2/D
|
DEPTH RANGE (M)
|
DEPTH TO WATER LEVEL(M)
|
1
|
1980
|
1368-4320
|
299-2550
|
Up to 300
|
7 and free flowing conditions.
|
2
|
After 2000
|
126-252
|
300-2500
|
100-300
|
|
B.East Godavari District
SL.NO
|
YEAR
|
DISCHARGE ‘Q’ M3/D
|
TRANSMISSIVITY ‘T’ M2/D
|
DEPTH RANGE (M)
|
DEPTH TO WATER LEVEL(M)
|
1
|
1980
|
NOT
|
AVILABLE
|
30-50 shallow TW’s
100-200 deep TW’s
|
|
2
|
After 2000
|
630-1260
|
36-2261
|
100-300
|
20-61m.In Gandepalli village the DTW is 61m.
|
The Seaward extension of Rajahmundry sandstone unconformably covering the Narsapur Claystone belongs to the Miocene to Pliocene temporal span. In the Off-shore regime, the Mio-Pliocene equivalent of the Rajahmundry sandstone is the Godavari clay stone, containing layers of sandstone.
The water quality of Rajahmundry sandstone deteriorates towards the coast while their equivalents of Cuddalore sandstone even near coast also, the quality of water is good.
DELTA FORMATION AND ALLUVIAL FORMATIONS.
Krishna Godavari basin/delta came into existence following rifting along eastern continental margin of Indian craton (Eastern Dharwar Craton in Andhra Pradesh) in early Mesozoic. The down to the basement faults which define the series of horsts and grabens are aligned NE-SW along Pre-Cambrian Eastern Ghats Mobile Belt trend. In the marine shelf, Carbonates and Clastic sediments formed a fan-shaped delta along the ridges and turbidites covered the slopes and graben floors. It could also be large prograding delta lobe over the coastal region where fluvial and marine sediments interfingered. In Godavari Delta fresh water samples are generally coarse to very fine sands confined to along the ridges and Estaurine samples are fine sand to clays rich in organic matter are confined to slopes and grabens yield saline water.
The chronological sequence of Delta formation are-
1 Rifting during permo-triassic
2. Followed by drifting results southerly, south-easterly tilt
3. Resulting marine transgression and deposition of shale sequence
4. Increased gradients for river systems and increased sediment load and significant sea level falls
5. Source for thick pile of sediment is long linear Gondwana belt located in Godavari graben.
Ground water conditions in Delta Area:-
Alluvial deposits concentrated in East and West Godavari, Krishna and Guntur districts and in few pockets in Prakasam, Nellore, Srikakulam, Khammam and Karimnagar districts.
East Godavari district- Southern portion of district where along the River Godavari and Delta area, vast thickness of Alluvium formed. Along the River Yeleru also alluvial deposits formed. Deeper aquifers in the above areas are yielding saline water.
West Godavari district: - Southern portion of district covered with highly thick alluvium. The basement rock struck at 3000m in this area compared to 500m in East Godavari and Guntur districts. Fresh water limited to shallow depth along canals, along River course. Shallow filter points are common in this area. Along Canals and Drains, small shallow pits are constructed to utilize the water for irrigation and during the non-flow of canal water shallow pits are used for fish ponds.
Krishna District: Shallow aquifers are yielding potable water and with depth, quality of water deteriorates. Krishna River between Ibrahimpatnam and Jaggayyapeta alluvial deposits comprising of sticky clay and silt occurred over a distance of 40 Km. It is observed that irregular nature of occurrence of alluvium. Hence a trial bore is necessary to ascertain the thickness of aquifer.
Guntur District; Along River Krishna, along Canals and in island areas of River, filter points are common. In Repalle, Tenali and in Bapatla fresh water is limited to pockets and lenses at shallow depths varying from 1m to 14m. Extensive fresh water aquifers at shallow depth are not possible in these areas.
ALLUVIAL FORMATIONS
SL.NO
|
District
|
Common Groundwater Abstraction Structures
|
Depth
Range
(M)
|
Areas covered with Alluvium
|
Quality of Ground-
water
|
1
|
East Godavari
|
Filter Points
Tube wells
|
12-20
100-150
|
Alamuru, Ramachandrapuram Kakinada and Kothapeta areas
Pitapuram and Chebrolu areas
|
Up to the average depth of 45m, quality of water is potable.
HP of p.sets up to 25 also common.
|
2
|
West Godavari
|
Shallow Filter points
|
Upto 60m
|
Tanuku, Kovvur, South of Tadepalligudem.
|
Saline areas-Bheemavaram,Narsapur etc.
|
3
|
Krishna district.
|
Filter points
Shallow Tube wells
|
Up to 20m
Up to 100m
|
Divi,Bandar,Gudivada,Kaikalur,
Gannavaram,Nandigama(part)
Vijayavada(south)
|
With the increasing depth quality of water deteriorates.
|
4
|
Guntur district
|
Filter points
Shallow Tube wells
|
20-50
40-100
|
Along Krishna River and along Canals.
Repalle, Tenali, Bapatla and partly in Chilakaluripeta, Duggirala, kothur and Amritalur areas.
|
With depth quality of water deteriorates.
|
SELECTION OF CORRECT SIZE OF AGRICULTURAL PUMP SET
Every pump set is manufactured for certain discharge (Q) and total head (H). Diameter of impeller and the speed (RPM) at which it is rotated decides the total Head (H). Area through which (impeller dia) the flow occurs and velocity of flow decides the discharge. Each pump set is manufactured with certain dia of impeller and fixed RPM. Hence Q and H are fixed for each category of pump set. For different requirement of discharge and total Head, the design of impeller and RPM changes.
To select the correct size of pump set, well should be tested for discharge, static water level, draw down etc. Maximum discharge (generally during winter season) and maximum total head (during summer season) are to be selected for calculating the HP of pump set.
Discharge measurement:- For new bore well while the drilling is in the final stage and when Air compressor is under operation, discharge of Bore well can be estimated roughly by using fixed volume Drum or by V-notch method. If possible after 24 hours, using the tape, the static water level of the bore well can be measured. Generally these details are not available at the time of installation of pump set. In such cases the discharge and Static water level of the neighboring Bore wells having the same depth and geological formations could be taken up for calculation. The discharge and Transmissivity details are also available in the reports prepared by Central Ground water Board and state Groundwater departments.
http://www.cgwb.gov.in/District_Profile/AP/Kurnool.pdf
Static water level:- Central Ground water Board is maintaining National net work observation well data throughout India
http://gis2.nic.in/cgwb/Gemsdata.aspx and state ground water department maintain the observation well and Peizometer’s data in their state jurisdiction
http://apsgwd.gov.in/swfFiles/reports/state/monitoring.pdf, . The static water level data during summer season of nearby observation well maintained by ground water departments can be utilized if there is difficulty in collecting same from the well under investigation for installation of pump set.
DRAW DOWN DATA:-The discharge and static water level data could be collected with some efforts but the data on draw down is very difficult to collect. Generally, Ground water departments conduct pumping tests like Step draw down and Aquifer performance test as a part of exploratory drilling activities and systematic ground water surveys. But such data is very limited compared to large number of wells fitted with pump sets which are likely to be replaced with energy efficient pump sets. Hence as mentioned above, an attempt has been made to calculate the draw down data using the empirical formulas.
For calculating the correct size of pump set and measure efficiency of pump set installed , the two parameters like discharge and total head of ground water abstraction structure(well/Bore well/Tube well ) are necessary. The total head includes depth to water well, maximum drawdown during summer season and fictional losses of piping system. Static water levels during summer month can be taken from National Net work observation well (CGWB) and observation well and piezometric water level data from state ground water department. Discharge details of wells during maximum utilization of ground water can be obtained from existing district wise/state wise reports/CGWB aquifer atlas/Ground water user maps of CGWB ground water reports.
But the data regarding drawdown of wells is not available in the above mentioned reports except for few wells where Aquifer performance tests were conducted. But the published data of such wells are limited to few locations. Considering the large number of Agricultural pump sets likely to be replaced with energy efficient pump sets, draw down data for different areas with different geological conditions are very limited. Hence it is decided to calculate the drawdown data using indirect methods.
Approximate formulas for estimating Transmissivity from Specific Capacity:-
FormuIa-1.
Discroll (1986) estimates Transmissivity(T) from specific capacity.
1. Metric system-
T= 1.385 X Q/s confined aquifer
T= 1.042 X Q/s unconfined aquifer
Where T Transmissivity in m2/d, Q discharge in m3/d/m, s draw down in metres
Formula-2
FPS system
T = 2000 X Q/s confined aquifer
T = 1500 X Q/s un-confined aquifer
Where T in us gal/d/ft, Q in gpm and s in metre
As the values of Transmissivity and discharge of the wells are available in the reports of CGWB, substituting these values in above formula, the value of‘s’ i.e. draw down can be calculated
Similarly the following formulas also used to calculate the drawdown.
Formula-3.
Vertical fracture model of Gringarten & Witherspon (1972) fractured hard rock areas. Assess Transmissivity from Specific Capacity.
T = 0.29(Q/s) 1.18
Where T in ft3/d/ft
Q in ft3/d
s in ft
Formula-4.
Modified Theim’s equation is used for determining permissible drawdown.
S = (528 X Q x log R/r )/ T
where T in gpd/ft
Q in gpm
S drawdown in ft
R radius of influence in ft
r radius of well in ft
Formula- 5.
Thomson etc calculated Transmissivity ‘T’ under steady state transient conditions.
T = Q/s x 1/2 x3.17x log R/r
i.e. T = (Q X 1 X log R/r)/( s X 2 X 3.72 )
Where T in ft3/min/ft
Q in ft3/min
s in ft
R radius of influence in ft
r radius of well
All the above formulas were used for calculating draw down substituting the values of Transmissivity and discharge and compared with the actual values of Draw down measured during the aquifer performance test. It is observed that sl.no 1 and sl.no 4 of above mentioned formula’s, the calculated draw down tallied with aquifer performance test value of draw down with 30% deviation in Kamthi formation , 20% in Granitic Gneisses formations , 80 to 100% in Chintalapudi sand- stone in West Godavari and 60% in Tertiary formations of West and East Godavari districts.
CALCULATION OF DRAW DOWN FROM EMPIRICAL FORMULAS
| |
| | | |
| | | | | | | |
|
SL.NO
|
LOCATION
|
DRAWDOWN VALUE AS PER PUMPING TEST IN FT.
|
FORMULA-1 CONFINED AQUIFER D/D IN FT
|
FORMULA-2 UNCONFINED AQUIFER D/D IN FT.
|
FORMULA-3 D/D IN FT.
| |
|
A
|
ALLUVIAL FORMATIONS
| | | | | |
|
1
|
Eturnagaram,Karimnagar dist
|
117
|
92
|
72
|
87
| |
|
2
|
Pedapudi,Krishna dist
|
7
|
4
|
3
|
3.5
| |
|
3
|
Narayanpura,East Godavari dist
|
11
|
7
|
5
| | |
|
4
|
Chodavaram,Visaka dist
|
27
|
23
|
17
|
21
| |
| |
Per cent deviation in Draw Down
| |
15-42
|
37-57
|
22-50
| |
|
B
|
TERTIARY,RAJAHMUNDRY SANDSTONE
| | | | |
|
1
|
Viravalli,West Godavari dist
|
28
|
21
|
16
|
19
| |
|
2
|
Takkapadu,West Godavari dist
|
59
|
26
|
20
|
24
| |
|
3
|
Chagallu,West Godavari dist
|
33
|
7
|
6
|
7
| |
|
4
|
Muppavaram,West Godavari dist
|
98
|
3
|
2
|
3
| |
| |
Per cent deviation in Draw Down
| |
25-97
|
43-98
|
32-97
| |
|
C
|
GONDWANA FORMATIONS
| | | | | |
| |
UPPER GONDWANA FORMATIONS
| | | | | |
|
1
|
Bhimadolu-II,West Godavari dist
|
102
|
55
|
42
| | |
|
2
|
Kavaluru,West Godavari dist
|
27
|
8
|
6
|
8
| |
|
3
|
Tirumalapalem,West Godavari dist
|
26
|
17
|
12
|
16
| |
|
4
|
Nimmalagudem,West Godavari dist
|
44
|
24
|
18
|
35
| |
| |
Per cent deviation in Draw Down
| |
35-70
|
54-78
|
8-35
| |
| |
LOWER GONDWANA
| | | | | |
| |
CHINTALAPUDI SST,EQUI OF KAMTHIS
| | | | | |
|
1
|
Kallacheruvu,West Godavari dist
|
42
|
9
|
7
| | |
|
2
|
Jangareddygudem,West Godavari dis
|
58
|
128
|
96
|
119
| |
|
3
|
Dharbagudem,West Godavari dist
|
91
|
170
|
128
|
158
| |
| |
Per cent deviation in Draw Down
| |
78-120
|
40-83
|
74-105
| |
| |
KAMTHIS, TELANGANA
| | | | | |
|
1
|
Narwa,Adilabad dist
|
92
|
111
|
83
|
103
| |
|
2
|
Kaleswar,Karimnagar dist
|
100
|
164
|
124
|
152
| |
|
3
|
Gangavaram,Khammam
|
57
|
50
|
37
|
46
| |
|
4
|
Narvavarigudem,Khammam dist
|
29
|
16
|
12
|
24
| |
|
5
|
Patwarigudem,Khammam
|
74
|
79
|
59
|
72
| |
|
6
|
Koyyuru,
|
61
|
27
|
20
|
25
| |
|
7
|
Yadlapalli,Karimnagar dist
|
74
|
40
|
30
|
37
| |
| |
Per cent deviation in Draw Down
| |
12-64
|
9-67
|
3-59
| |
| |
GRANITIC GNEISSES
| | | | | |
|
1
|
Damalacheruvu,Chittoor dist
|
44
|
60
|
45
|
50
| |
|
2
|
Gundlapalle,Chittoor dist
|
31
|
94
|
71
|
79
| |
|
3
|
Mattampalli,Chittoor dist
|
37
|
34
|
26
|
23
| |
|
4
|
Mogili,Chittoor dist
|
18
|
25
|
19
|
22
| |
|
5
|
Kalvagunta,Chittoor dist
|
30
|
33
|
25
|
28
| |
| |
Per cent deviation in Draw Down
| |
8-39
|
2-30
|
6-38
| |
DEVIATION OF CALCULATED VALUES OF DRAW DOWN COMPARED TO MEASURED VALUES OF DRAW DOWN DURING AQUIFER PERFORMANCE TESTS.
SL.NO
|
ROCK FORMATION
|
DEVIATIN RANGE IN PER CENT
|
AVERAGE VALUE IN PERCENT
|
1
|
Alluvium or Recent formations
|
15-57
|
36
|
2
|
Tertiary Sandstone(Rajahmundry sst)
|
25-98
|
62
|
3
|
UP Gondwanas (W.G. Dist)
|
35-78
|
56
|
4
|
Lower Gondwanas(Chintalapudi sst)
|
78-120
|
100
|
5
|
Kamthis (Telangana districts)sst.
|
9-67
|
38
|
6
|
Granitic Gneisses
|
2-39
|
20
|
The above data can be further modified by calculating the values of draw down using the latest pumping test data in different rock formations by Ground water departments who has access to voluminous aquifer performance test data. This exercise will enable to predict the draw down values up to mandal and village level. Wherever the discharge, Transmissivity and Draw down values are available, the data should be made available to farmers or to the agencies who are engaged in the installation of energy efficient pump sets as a part of energy conservation programme. Maximum benefits of energy conservation can be achieved if the energy efficient pump sets are selected based on aquifer characteristics like discharge and total head of the wells.
REPLACEMENT OF EXISTING OLD PUMP SET WITH NEW ENERGY EFFICIENT PUMP SET.
Many state governments are planning to replace the existing inefficient agricultural pump sets with new efficient pump sets. For such new pump sets using the old pump set, measure the discharge (preferably during winter) static water level and pumping water level to select the correct size of pump set. It is also advisable to calculate the efficiency of well using the old pump set. The details like discharge, total Head, voltage, current in amperes and power factor are to be measured using the old pump set. Due to inefficient pump set the values of Discharge, total head may be on lower side, hence 10 to 15% extra value may be added to these values so that it cover friction losses and compensation to inefficient pump set.
Out put
Efficiency = -------------
Input
Q X H X 0.746 X100
Efficiency = -------------------------
Kwh x 76
Q x H x 0.98
Efficiency = --------------
Kwh x 76
Where Q is discharge in Litres per second,
H is total head in metres.
Kwh is input energy. Kwh is calculated by measuring voltage, current in amperes and power factor.
Input energy = v3 x V x I x P.F
After installing the new pump set, Efficiency of pump set may be calculated measuring Q,H,V,I and power factor. With the new pump set, there will be improvement in the Efficiency value.
MATCHING OF PUMP CURVES AND WELL CHARACTERISTICS
Having known the discharge and total head, the correct size of pump set is selected on the basis of pump characteristic curves. These pump curves are plotted from the result of tests on a pump when running at its design speed. They show the relationship between discharge, head, efficiency and Brake horse power. Pump manufacturers provide characteristic curves or some time the details in tabular statement for the various models of the pumps. Each pump curve typically reflects a single model of pump made by manufacturer. It is usual to draw the discharge vs. drawdown curve of testing irrigation well on the same scale as the pump characteristic curve. The characteristics of the pump manufactured by leading manufacturer are matched with well characteristic curve (system head curve).This will lead to the selection of the pump which gives maximum efficiency and the desired discharge at the estimated total head. The point of intersection of head capacity curve of pump and well characteristic curve provide a point of selection. At the intersection of desired discharge (bottom scale) and head-capacity curve read the Head value on left side. In the Characteristic curve given below the value of Head at discharge intersection of head capacity curve is 11.5m. Divide this value into the total head to determine number of stages.
We have to select the make and model of pump which tallies with the well characteristics (discharge and Total head) and the efficiency curve reasonably flat at the top. The characteristic curve also shows the brake horse power of the driver of the pump. The Brake horse power can also be obtained from the following formula.
BHP = Q X H
--------------------------------------------------
76 X pump efficiency x motor efficiency
Where Q is discharge in lps,
H is total head in meters.
76 is work done by one HP (in Kg meters)in one second. One metric HP is the power to raise a mass of 76 kilograms against the earth’s gravitational force over a distance of one meter in one second. This is equivalent to 735.5 watts or 0.736 Kw. Brake horse power or pump input break horse power is the actual horse power delivered to the pump shaft.
Ideally pump should extract water at such a rate so that water level in the well stabilizes after some time and do not fall further. Within the stabilized water level (particularly during summer season) only submersible pump set should be installed. To monitor the water level in the well it is advisable to install 1 inch or 1.5 inch flexible PVC pipes in the bore well up to bottom of submersible pump set.
CONCLUSIONS
1. The Granitic Gneisses rock formation occupies major part of Telangana state, Chittoor, Anantpur and part of Kurnool district in Andhra Pradesh. Limited water bearing zone in the form of weathered and fractured zones in Granitic Gneisses. Sixty five per cent of 33 lakhs pump sets located in this area. The density of pump sets is more than 20 no’s pump sets per Sq.Km. Due to this, discharge of wells reduced and there is steep decline of water levels compared to the conditions existing 3 decades back.
Construction of Bore wells in the following Green schist belts and swarm dyke are not very productive from ground water point of view.
· Sandur schist belt
· Ramgiri-Penekacherla-Serigeri-Hungund super belt
· Kolar-kadiri-Jonnagiri-Hutti super belt
· Veligallu-Raichur-Gadwal super belt
Swarm dykes:
· Hyderabad dykes
· Mahabubnagar dykes
· Anantpur dykes
· Tirupathi dykes.
In these dyke areas one side exists good ground water potential and other side, poor to dry Bore wells. North east of Kadapa basin experienced tectonic disturbance and Western side of Kadapa basin on convex side, there has been sequence of tectonic events of extension and compression evolution of Kadapa basin.
Before taking up ground water extraction programme and installation of efficient pump sets all the above aspects are to be taken into account. Detailed survey of Hydro geological conditions is necessary in this area.
2. Ground water development in Khondalite and Charnockites belongs to Eastern Ghats Mobile Belt (EGMB) and Shales, Phyllites and Quartzites of Kadapa and Kurnool formations under safe conditions and the yield of Bore wells also low to moderate due to limited water bearing zones in the form of weathered and fractured zones. The EGMB area is covered with hilly and tribal areas and Kadapa formations also dotted with hilly and valley portions. Quartzite rocks form as hills and ridges and Shales, Phyllites and Lime stone in plain and valley areas.
The Tertiary and Gondwana formation are highly productive from ground water point of view and high capacity pump sets (up to 25 HP) are operating in these formations. The data on discharge and Transmissivity of last 3 decades indicates that though there is reduction in discharge of wells but there is no change in Transmissivity values in Kamthi formations of Gondwanas and Tertiary Sandstones.
3. Due to high density of pump sets in hard rock terrain, HT/LT ratio is quite high results in high line losses. In such cases to reduce the line losses HVDS system can be encouraged.
4. In high density pump set areas wherever steep decline of water levels and reduction in discharge values observed, artificial recharge of ground water projects are to be taken up. As several irrigation projects are under progress/proposal (in Godavari River) in Granitic terrain of Telangana state, irrigation wells located in Karimnagar,Warangal,Nizamabad, Nalgonda,Khammam and Medak district get benefitted wherever the area comes under canal command net work. Canal water also can divert to other neighboring areas to utilize the water for artificial recharge of ground water projects. In Mahabubnagar and Anantpur districts major portion of the area acts as catchment areas to major rivers. In Mahabubnagar district, Krishna River and in Anantpur district, Pennar River and its tributaries act as catchment areas. Run-off in this area is more than groundwater recharge, hence several check dams may construct across the tributaries of these rivers so as to increase the groundwater recharge. Major portion of Medak,Nizamabad,Rangareddy districts, the terrain looks like plateau with almost lying on 600m altitude (above sea level). In these districts revival of Tanks and Ponds and construction of new Tanks are helpful for the groundwater recharge. Up to Nagarjunsagar Dam the catchment area of Krishna river is surprisingly on northern side only i.e. in Telangana state and negligible portion in southern side. In this catchment area on northern side, check dams can be constructed on stream courses falling in the catchment of Krishna River so as to improve the groundwater recharge.
5. Ground water departments established net work of observation wells and water level measurement s taken quarterly to observe the fluctuation of water levels. It is advisable that in addition to water level monitoring, measurement of Specific Capacity values annually indicate the health of wells.
Specific Capacity (actual)
Efficiency of well ---------------------------------------
Specific Capacity (Maximum)
Where, Specific Capacity actual is the value measured during investigation
Specific Capacity Maximum is the value measured at the time of construction of well
Or first time investigation.
Specific Capacity is the ratio of Discharge to Drawdown. If Specific Capacity is high it means well is performing well and vice versa it is poor performance. In higher values of specific capacity Discharge is more and drawdown is less but if sp. capacity value is low, means Discharge is low and Draw down is more.
When Specific Capacity values are continuously recorded low, means there is decline of water levels. The reasons for the decline of water levels to be find out. One of the possible reason is interference of wells i.e. the distance between two wells is less than prescribed limit(less than 300m in hard rocks and 150m unconsolidated formations). In such areas artificial recharge of ground water projects are to be taken up.
For the selection of correct size of pump set to new irrigation wells and replacement of old pump sets with energy efficient new pump sets, service of Hydrogeologist and Electrical Engineers is very helpful in getting correct details of Discharge, Total head, sustainablity of groundwater yield, voltage regulatios, input energy and power factor which are useful in the calculation of efficiency of pump sets etc.
The hard work, devotion and the difficult field conditions under which the Geologists mapped the Geological formations, Geophysicists carried out the investigations and Drilling crew carried out the exploratory work and the valuable articles contributed by Geoscientists enable me write the article.
REFERENCES
Ø Aditi Mukherji, Tushar Shah and Shilp Verma; Electricity Reforms and their impact on Groundwater use in states like Gujrat,West Bengal and Uttarakhand, India.
Ø Aditi Mukherji, Tushar Shah and Mark Glordano; 2012. Managing Energy-Irrigation Nexus in India-2012, IWMI-TATA water.
Ø A.K.Jain, B.M.Muralikrishna Rao, M.S.Rama Mohana Rao, M.Venkataswamy; Groundwater Scenario in Andhra Pradesh-Dec. 2009
Ø A.M. Michael, S.D. Khepar; Water Well and Pump Engineering, Tata McGraw-Hill Publishing Company Limited, New Delhi.
Ø APGWD Report, Groundwater Estimation in 1993
Ø APGWD Report, Groundwater level Scenario in Andhra Pradesh-March, 2012.
Ø CGWB-1980, Groundwater Resources of Andhra Pradesh.
Ø CGWB-2003, Groundwater User Maps-Andhra Pradesh.
Ø CGWB, District Reports of Andhra Pradesh.
Ø CGWB-2012, Aquifer Atlas of India.
Ø Central Institute of Rural Electrification-Pumping Systems-Reading Material
Ø C.Satyanarayana-1994. Improper Matching of wells and pump sets-Need for carrying out Step draw-down test in representative wells, National Seminar on Conservation of Energy in Agricultural Pumping System.CIRE,Hyderabad.
Ø David Hundtley, Roger Nommensen and Duane Steffey. The use of Specific Capacity to assess Transmissivity in Fractured rock Aquifers.
Ø Dilip Saha,Vikash Tripathy; Palaeoproterozoic Sedimentation in the Kadapa basin in South India and Regional tectonics: a review.
Ø Hector Garudu fio, Stephen Foster, Pradeep Raj et. April 2009. Addressing Groundwater Depletion Through Community Based Management Actions in the Weathered Granitic Basement Aquifer of Drought-Prone Andhra Pradesh-India.
Ø Joseph G.Meert, Manoj K.Pandit, Vimal R.Pradhan et la; 2010. Precambrian Crustal Evolution of Peninsular India: 3.0 billion year Odyssey.
Ø Nisha Naid and Tushaar Shah, IWMI-TATA-2012. The other side of India’s Electricity-Groundwater Nexus.
Ø O.P. Pande and P.K.Agrawal-Lateral Zonation around Archaean Nucleus of the Dharwar Craton, India.Its deformation, segmentation and subsequent breakup.
Ø Ramachandra Tiwari and Wataru Maejima; Origin of Gondwana Basins of Peninsular India.
Ø REC-Best practices for Agricultural Pump sets and Rural Demand side Management (DSM), USAID, Ministry of Power, Drum training programme.
Ø Robert E.Mace; Determination of Transmissivity from Specific Capacity Tests in Karst Aquifer.
Ø R.S.Sharma; 2009.Cratons and Fold Belts of India, Lecture notes in Earth Sciences.
Ø T.R.K.Chetty, NGRI; Tectonics of Proterozoic Kadapa Basin, Southern India: A conceptual Model.
ANNEXURE 1 AREAS LOCATED IN GRANITIC GNEISS OF EASTERN DHARWAR CRATON IN ANDHRA PRADESH
SL.NO
|
District
|
Major portion/Small part.
|
If small part name of Tk/Mdl
|
If major part, name of other Tk/Mdl and rock type.
|
Remarks
|
1
|
Nizamabad
|
Complete district
|
-------
|
-----
|
|
2
|
Ranagareddy
|
Complete district
|
---------
|
-------
|
|
3
|
Nalgonda
|
Major part
|
--------
|
Devarakonda-SE portion,Miryalaguda-South,Zaheerabad-South.covered by Kadapa formations
|
|
4
|
Medak
|
Major part
|
------
|
Zaheerabad-partly by Deccan Traps
|
|
5
|
Mahabubnagar
|
Major part
|
--------
|
Achampet-SW portion covered by Kadapa formations.
|
|
6
|
Karimnagar
|
Major part
|
-------
|
Manthani and part of Peddapalli covered by Gondwana formations.
|
|
7
|
Warangal
|
Major part
|
--------
|
Narsampet,Mulug and Parkal partly covered by Kadapas etc.
|
|
8
|
Chittoor
|
Major part
|
---------
|
Srikalahasti and Vayalpadu covered by Kadapas.
|
|
9
|
Anantapur
|
Major part
|
-------------
|
Singanamala,Gooty and Kadiri covered by Kadapa formations.
|
|
10
|
Kurnool
|
Western portion of the district, Aler,Adoni,yemignur,Pattikonda Taluks etc
|
-----
|
Eastern part of district covered by Kadapas and Kurnool formations.
|
|
11
|
Khammam
|
Small part of district
|
Khammam,Yellandu,Burgampadu-SE,Nugur-SE,Kothagudem-E and W,Madhira.
|
Other formations-eastern part of district covered with Gondwanas(NW-SE),Western side with Dharwars and Archaean formations.
|
|
|
Adilabad
|
Small part of district
|
Luxettipet except eastern part,Adilabad-south,Mudhole-except North west.and Nirmal.
|
|
|
13
|
Nellore
|
Small part of district
|
Udayagiri,Atmakur and Rapur.
|
|
|
14
|
Prakasam
|
Small part of district
|
Podili-east,Ongole-west,Darsi-east,Addanki.
|
|
|
15
|
Guntur
|
Small part of district
|
Narsaraopet, Sattenapalli,Guntur partly
|
|
|
16
|
Krishna
|
Small part of district
|
Jaggayyapet,Vijayawada-North,Tiruvur,Nu-zuvidu-west, Gudivada-NW
|
|
|
|
|
|
|
|
|
ANNEXURE-2
AREA COVERED BY SCHISTS AND RELATED ROCKS OF EASTERN DHARWAR CRATON
SL.NO
|
District
|
Major portion/Small part.
|
If small part name of Tk/Mdl
|
If major part, name of other Tk/Mdl and rock type.
|
Remarks
|
1
|
Prakasam
|
Small part
|
Darsi-central,Podili-Central portion,Kanigiri Taluks
|
-------
|
|
2
|
Nellore
|
Small part
|
Udayagir,Atmakkur,Nellore-west,Gudur-West,apur-West,
|
|
|
3
|
Guntur
|
Small part
|
Vinukonda-south,Sattenapalli-part,Narsaraopet-part
|
|
|
4
|
Krishna
|
Small part
|
Nandigama-west,Vijayawada-part,Nuzuvidu-west,Gudivada-north west.
|
|
|
5
|
West Godavari
|
Small portion
|
Chintalapudi-west
|
|
|
6
|
Khammam
|
Small portion
|
Khammam-partly,Madhir-partly.
|
|
|
|
|
|
|
|
|
ANNEXURE-3
AREA COVERED BY EASTERN GHAT MOBILE BELT- CHARNOCKITES AND KHONDALITE ROCKS
Sl.No
|
District
|
Major part/Small part
|
If small part,name of Tk/Mdl
|
If major part,name of small part Tk/Mdl and rock type.
|
Remarks
|
1
|
Srikakulam
|
Major portion
|
---
|
Alluvium in Palakonda,Narasannapet,Patapatnam,Sompeta partly
|
|
2
|
Vizianagaram
|
Major portion
|
---
|
Alluvium in Parvathipuram partly
|
|
3
|
Visakapatnam
|
Major portion
|
----
|
Alluvium in Elamanchali and Bheemunipatnam Partly
|
|
4
|
East Godavari district
|
Small portion
|
Rampachodavaram,yellavaram,Prathipadu,Rajahmundry north,Peddapuram north,Tuni north
|
--------
|
|
5
|
West Godavari district
|
Small portion
|
Polavaram
|
|
|
6
|
Krishna
|
Small portion
|
Nandigama partly
|
|
|
7
|
Guntur
|
Small portion
|
Sattenapalli central
|
|
|
8
|
Prakasam
|
Small portion
|
Ongole patly
|
|
|
9
|
Nellore
|
Small portion
|
Kavali-west
|
|
|
10
|
Khammam
|
Small portion
|
Burgampadu SE portion,Bhadrachalam-SE portion,Kothagudem-East
|
|
|
ANNEXURE-4
AREAS COVERED BY KADAPA FORMATIONS IN ANDHRA PRADESH
SL.NO
|
District
|
Major portion/Small part
|
If small portion name of Tk/Mdl
|
If Major portion name of Small portion of Tk/Mdl and rock type
|
Remarks
|
1
|
Kadapa
|
Complete district
|
---
|
--
|
|
2
|
Prakasam
|
Small portion
|
Giddalur,Markapur
Podili-west,Darsi-west
|
|
|
3
|
Guntur
|
Small portion
|
Piduguralla,Macherla,
Gurjala,Vinukonda- north
|
|
|
4
|
Khammam
|
Small portion
|
Yellandu central,Burgampadu central,Nugur-NW portion,
|
|
|
5
|
Warangal
|
Small portion
|
Narsampet-east,Mulug-east,Parkal-north-east.
|
|
|
6
|
Adilabad
|
Small portion
|
Adilabad-north,Asifabad-west and north-east,Luxettipet-east
|
|
|
ANNEXURE-5
AREAS COVERED BY KURNOOL FORMATIONS IN ANDHRA PRADESH
Sl.No
|
District
|
Major portion/Small part
|
If small part name of Tk/Mdl
|
If Major portion, name of small portion of Tk/Mdl and rock type.
|
Remarks
|
1.
|
Kurnool
|
Half of the district in eastern part of district, covering Banganapalli,Allagadda,Nandyal
Atmakur, Nandikotkur, Kiolakuntla.
|
-----
|
Western part of district. east of Dhone, and Nandikotkur covered by Granitic Gneiss.
|
|
2
|
Chittoor
|
Small portion
|
Srikalahasthi,Vayal
Padu.
|
|
|
ANNEXURE-6
AREAS COVERED BY GONDWANA FORMATIONS IN ANDHRA PRADESH
Sl.No
|
District
|
Major part/Small part
|
If small part name of Tk/Mdl.
|
If major part name of small part Tk/Mdl and rock type
|
Remarks
|
1
|
Adilabad
|
Small portion
|
Sirpur,Chinnur
Asifabad except west and north west portion
|
-------
|
|
2
|
Karimnagar
|
Small portion
|
Manthani,peddapalli North east portion
|
|
|
3
|
Warangal
|
Small portion
|
Mulug except west portion,Parkal-eastern portion
|
|
|
4.
|
Khammam
|
Small portion
|
Yellandu-Eastern side, Burgampadu-north west portion, Kothagudem-central.
|
|
|
5
|
West Godavari
|
Considerable area
|
Lower Gondwana:-
Chintalapudi-except west,Kamavarapukota,Lakkavaram,
Jangareddygudem,Koyyalagudem,
Upper Gondwana:- Dubacherla,Nallajerla,Potavaram,North west of Devarapalli and Gopalapuram.
|
|
|
