HYDROGEOLOGICAL STUDIES

ON AND AROUND

BARAZAN PLATEAU, NORTH GOA

DISTRICT, GOA STATE

Advanced Center for Water Resources Development and Management (ACWADAM)

acwadam@vsnl.net / www.acwadam.org

ACWADAM technical report no.

ACWA/Hydro/2015/H39

November 2015

HYDROGEOLOGICAL STUDIES

ON AND AROUND

BARAZAN PLATEAU, NORTH GOA DISTRICT, GOA STATE

Principal authors

Jairaj Rajguru Rakesh Gupta

Associate author Dr. Himanshu Kulkarni

Technical Report: ACWA/Hydro/2014/H39

Advanced Center for Water Resources Development and Management Plot 4, Lenyadri society, Sus road, Pashan, Pune – 411021 Phone: +92 20 25871539 Email: acwadam@vsnl.net Website: www.acwadam.org

Table of contents

Background 1

Introduction 1

Location, geomorphology and drainage of the area 2

Geology of the area 5

Hydrogeology of the area 7

Bibliography 11

Glossary – some explanation of concepts 13

Salient photographs 15

1

Hydrogeological status of Barazan plateau

Background

Villagers surrounding Barazan plateau requested ACWADAM to conduct a rapid

hydrogeological assessment of the Barazan plateau particularly with regard to the impact

of the proposed airport and related infrastructural activities on the natural systems,

especially springs, around the plateau. This report is a result of a rapid study of the area,

based on a short visit and analysis of available data in the form of spring inventories,

toposheets and Google Earth imageries. A buffer of 10 km radius around the proposed

airport at Mopa village is considered for preparation of most of the maps. The report

derives from ACWADAM’s extensive experience of working on springshed management

programmes across various mountain ranges in India.

Introduction

Large parts of the country suffer from acute water scarcity. Most responses to tackle this

scarcity include construction of new wells, deepening pre-existing wells, drilling deeper

(borewells / tubewells), installation of pumps of high capacities on these wells and locating

wells in river beds. In addition, many responses also include construction of village ponds,

construction of irrigation tanks and provision of water by the tankers, which is just another

form of groundwater extraction. All of these are supply-side mechanisms and do not always

involve scientific approaches. Planning at village level by preserving the recharge zones of

ground water becomes an integral part of resolving the crises of water scarcity in the

country.

Perennial streams flow because groundwater remains above the streambed / riverbed

throughout the year. If the aquifer is in a healthy condition, then only is one able to see the

perennial streams. Base flow is the water-contribution of an aquifer to streams and rivers.

Stream flow, therefore, depends upon the status of base flows to stream and rivers.

Arguably, the most important factor regarding the fate of aquatic life in surface water is the

amount of sustainable flow in the channel, often determined by such base flows. Since

groundwater temperatures are nearly uniform year-round, groundwater discharge also

provides a measure of temperature stability in surface water. This ecological consideration

becomes a must when we try to study anything about the biodiversity richness around a

plateau such as Barazan plateau.

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Location, geomorphology and drainage of the area:

Barazan plateau is located in Pernem block of North Goa district in northern-most Goa,

along the Maharashtra border. Plateau encompasses six villages of Varconda, Casarvanem,

Chandel, Mopa, Uguem and Amberem in Goa and Netarde village in Maharashtra. The

residents of these villages (total number of over 7000 persons), especially those living in

settlements on the slopes of the plateau besides the streams originating from the springs

above, are dependent on the springs for their drinking and domestic water needs. This

spring water is also use for cattle rearing and irrigation of large plantations as well as the

paddy fields below.

Google earth image of Barazan plateau and villages around plateau with 10km buffer

These villages also receive piped water from the 10 MLD treatment plant at Chandel, which

lifts water from Kalne river for treatment and distribution. However, the dependency on

the springs remains high even today, since the water is released only for limited durations

(about an hour or two), and because the villagers prefer the spring water for drinking and

cooking, and also because the significant water supply is needed for irrigation and cattle

rearing. It can be said that Barazan plateau is acting as a water tower for surrounding

ecosystems and villages.

The land surrounding the proposed airport site is predominantly forest-land. The northern

and eastern side of the proposed site is reserve forest area, whereas the western side is

cultivated land within the surrounding villages. More than half of the land of plateau is

covered with scrub and scrub forest. Average annual rainfall of the area is 2932 mm.

Regional morphology of the study area comprises plateau at the center, which gives way to

highly undulating terrain as one moves away towards the rivers. The Digital Elevation

Model (DEM) below shows topography of the land in the study area. Highest elevation of

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the study area is 185 m and the lowest surface elevation is 4m above mean sea level,

implying an overall gradient of 181 m over a straight distance of 4 km, a slope of 0.0452.

The study area is mostly rural and is occupied by agricultural fields with thin soil

thicknesses.

Northwestern part of study area is drained by Terekhol river system and southeastern part

by Chapora and Kalna river systems and there tributary streams. Rivers flow in the

southwesterly direction, following the slope of the area. River and most of the streams are

perennial because most of the springs that are feeding these streams are perennial. Many

first order streams and two second order streams flowing westward are there over the

proposed airport site.

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5

Geology of the area:

The geology of the area is dominated by laterite (Cenozoic in geological age), which is

underlain by meta-basalt (Archaean to lower Proterozoic in geological age) and a volcanic

intrusions in the form of a dyke. Laterite rock is rich in iron and aluminium and is

commonly considered to have formed in hot and wet tropical areas. Laterites are formed

through the residual weathering of an original rock such as basalt or granite. Soils formed

from laterite are called lateritic soils, also rich in iron and aluminium. Nearly all laterites

are of rusty-red coloration, because of high iron oxide content. They develop by intensive

and long-lasting weathering of the underlying parent rock. Tropical weathering

(laterization) is a prolonged process of chemical weathering which produces a wide variety

in the thickness, grade, chemistry and ore mineralogy of the resulting rocks and soils.

Laterites, in large regions of western Maharashtra and northern part of Goa are formed

from the leaching of parent meta-basalt rock; which leaves the more insoluble ions,

predominantly iron and aluminium. The mechanism of leaching involves acid dissolving the

host mineral lattice, followed by hydrolysis and precipitation of insoluble oxides and

sulphates of iron, aluminium and silica under the high temperature conditions of a humid

sub-tropical monsoon climate. An essential feature for the formation of laterite is the

repetition of wet and dry seasons. Rocks are leached by percolating rain water during the

wet season; the resulting solution containing the leached ions is brought to the surface by

capillary action during the dry season. These ions form soluble salt compounds which dry

on the surface; these salts are washed away during the next wet season. Laterite formation

is favoured in low topographical reliefs of gentle crests and plateaus which prevents

erosion of the surface cover. The reaction zone where rocks are in contact with water from

the lowest to highest water table is progressively depleted of the easily leached ions of

sodium, potassium, calcium and magnesium. A solution of these ions can have the correct

pH to preferentially dissolve silicon oxide rather than the aluminium oxides and iron

oxides.

Meta-basalt is the rock which formed due to metamorphism of basaltic rock during

Archaean to lower Proterozoic ages. Metamorphism is the change of geologic texture

(distinct arrangement of minerals) and recrystallisation of the minerals in pre-existing

rocks in solid phase. The change occurs primarily due to heat, pressure, and the

introduction of chemically active fluids.

A dyke, in geology, is a type of later, vertical rock emplacement between older layers of

rock. Technically, it is any geologic body, which cuts across: flat wall rock structures, such

as bedding (sedimentary rock) or massive rock formations that are usually igneous in

origin. In this area, dyke rock is basalt formed during upper Cretaceous to lower Eocene

ages.

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ACWADAM’s fieldwork (Barazan Plateau and its slope towards the south-eastern half)

included the area that is entirely underlain by thick and firm mass of laterites with small

patches of meta-basalts in-between; these patches were too small to be called ‘mappable’

and hence are not shown as isolated polygons in the map below. Meta-basalt units are hard

and highly jointed. Laterites that were observed in the field are porous and permeable as

compared to the meta-basalts. One NW-SE trending dyke (of ?meta-basalt) is also marked

by on the eastern slope of the plateau. Almost all the springs (numbering 12) are observed

at the contact between laterites and underlying Meta-basalts.

Overlay of Geology on Google earth imagery of the area

7

Hydrogeology of the area:

A ‘spring’ is the point or area of emergence of groundwater onto the surface of the earth.

The emergence of groundwater on the surface in the form of springs around Barazan

plateau is mainly controlled by the lithological sequence of the area and the water bearing

laterite aquifers above. Laterites observed on and around plateau are thick, porous and

hence they are having considerable water holding and transmission capacity. These

laterites are underlain by the impervious meta-basalt. Due to its porous nature, the laterite

aquifer recharges rapidly with the monsoon rains and the water table recedes slowly from

this laterite mass. Hence, laterites not only act as the storage zones for aquifers feeding

springs, but their tops act as recharge zones for the aquifers that support such springs.

Laterite allows water to slowly percolate and, after reaching the impervious meta-basalt

and the dyke (laterally), it emerges on the ground in the form of contact springs. During

ACWADAM’s visit in the month of July, though the regional water-table of the area was

deep - about 10 meters below ground (155 m above mean sea level) - there was clear

evidence of a perched water table in portions observed at the top of plateau at a height of

about 170m. Such a perched aquifer system had also resulted in seeps and springs forming

a lake. This perched aquifer have formed a unique ecosystem, supporting the rarest of

forms of floral and faunal diversity and also traditionally used for irrigation of paddy fields

through a channel cut in the harder portions of the laterite rock, allowing water from the

lake to flow into the paddy fields on the plateau surface to the south of the lake. This lake is

a large water body which is dry only after March.

All the springs studied by ACWADAM were perennial with discharge ranging from 10

liters/minutes to about 100s of liters/minutes even in the dry season. This system of

springs constitutes a sustainable source of water to the villagers living in and around this

locality. This spring water flows down the slope, some portion of it seeps down into joints

and fracture of the Meta-basaltic flows and adding to the recharge of the regional aquifers

in the plains. These springs occur in areas with high topography, above village settlements

and hence, they are essentially gravity-fed systems with no energy inputs while already

constituting economically viable and ecologically sustainable sources of water for domestic

and livelihood needs.

8

Overlay of Springs on Google earth imagery of the area

9

Post monsoon cumulative discharge was found to be about 6000 liters/minutes. As this

study will proceed further we will try to measure actual pre-monsoon discharge of the

springs. While considering the local setup and geology of the area one can estimate the pre

monsoon cumulative discharge to the tune of 2500 liters/minutes. Based on this

assumption average year-round cumulative discharge can be taken as 4250 liters/minutes.

Normalised over a year, this amounts to more than 2.2 million cubic metres of water every

year. This figure reflects the fact that Barazan plateau is playing the pivoted role in local

hydrology of the area by recharging about 2233800m3 of water year-round. Considering a

catchment area of about 15 km2, this is equivalent to about 150 mm of water, not a small

quantity of fairly pristine, natural water supply.

The slow percolation of water through laterites filters the water and ensures a steady

supply of pure water year-round, long after the end of the monsoon. As a result

groundwater quality was found to be good. This was in stark contrast to the quality of

surface water, which was found to be deteriorated in terms of TDS, hardness, chlorides,

sulfates and presence of coliforms around the plateau.

Source: EIA for the proposed greenfield international airport at Mopa, Goa; prepaired by Engineers India Limited

Due to thin soil cover and highly rugged topography, in spite of heavy rainfall, the drainage

system tends to be lean during the summer months. Likewise, due to steep hydraulic

gradient and highly permeable phreatic aquifers, the dynamic ground water resource also

gets depleted, quickly rendering scarcity even for drinking water during summer months.

Therefore, there is need for augmenting recharge in the region.

Now-a-days it is seen that many infra structural projects including proposed greenfield

international airport project at Mopa is coming in this area. Such large-scale infrastructure

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footprints are likely to disturb the recharge zones for the aquifer system feeding the

natural springs of Barazan plateau. Such disturbances will significantly affect the laterite

aquifer feeding the spring system, thereby imperiling the integrity and safety of the natural

public drinking water sources. Either which way, it is important to recognize the recharge

zones for springs as well as the spring source areas themselves and ensure that these are

protected from various activities and interventions. Spring areas should be protected from

tree cutting, over grazing, and construction for the sustainability of springs.

Physical changes in the land morphology, land-use, land-cover and modification of drainage

networks in the catchment areas may hamper recharge that will affect the springs of the

area in terms of magnitude and seasonality of discharge and often lead to their complete

disappearance. Given that nearly 150 mm of water is discharged through this spring

system. Any changes to its recharge zones and aquifer storage is will not only hamper

spring discharges but may have negative impacts on the flow of streams and rivers and

will, in the longer run pose a severe threat to the related ecology downstream and also to

the livelihoods of downstream populations.

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BIBLIOGRAPHY

ACWADAM, 2014. Hydrogeology of the Kirunde springs. Submitted to GRAMPARI

ACWADAM (2009) Kulkarni, H., Badarayani, U. and Upasani, D. (eds) “Groundwater

management –typology of challenges, opportunities and approaches.” Arghyam-ACWADAM

publ. ACWA H-09-2.Compilation of papers from the Groundwater Conference, Pune, May 2009.

Bryan , K (1919) classification of springs. Jour. Geo. v. 27, pp. 522-561.

Buono, J., Thomas.R.(year unknown). Lateritic springs: A vital threatened resource along

the Western Ghats.

Central Ground Water Board (CGWB).(2013). Groundwater information booklet, North Goa

district, Goa state.

Chow, V. T., Maidment, D. R. and Mays, L. W. (1964) Handbook of Applied Hydrology.

McGraw-Hill, NewYork.

Driscoll, F. G. (1986) Groundwater and wells, 2 edition. Johnson division, Minnesota, 1108p.

Engineers India Limited.(2015). Environmental Impact Assesment for the proposed

greenfield international airport at Mopa, Goa. Fetter, C. W. (1980) Applied Hydrogeology. Charles E. Merrill Publishing Company, 488p.

Freeze, R. A. and Cherry, J. A. (1979) Groundwater. Prentice Hall Inc., Engelwood Cliffs, New

Jersey, 604p.

Kulkarni, H. (1998) Watershed Development and Management - a movement seeking

inputs in Earth sciences. Jour. Geol. Soc. India, v52(2), pp.239-241.

Kulkarni, H., Vijay Shankar, P.S (2009). “Groundwater: Towards an Aquifer Management

Framework”,Economic and Political Weekly, Mumbai, February 7.

Kresic, N and Bonacci, O. 2010.Groundwater Hydrology of Springs, Chp.4; p129-162.

Kresic, N. 2010. Groundwater Hydrology of Springs, Chp.2; p31-83.

Kresic, N. 2010.Groundwater Hydrology of Springs, Chp.5; p165-226.

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Negi, G. C. S and Joshi, v. (2002) Drinking Water Issues and Development of Spring

Sanctuaries in a Mountain Watershed in the Indian Himalaya. Moun. Res. Dev. v. 22, no. 1,

pp. 29-31.

Oliver, Cliff D., H.C. Sheth. (2008): The High Deccan duricrusts of India and their

significance for the ‘laterite’ issue. Journal of Earth System Science, Volume 117, Issue 5, pp

537-551.

Vashisht, A. K. and Sharma, H. C. (2007) Study on hydrological behaviour of a natural

spring. Curr. Sci. v. 93,no. 6, pp. 837-840.

Weight, W. D. and Sonderreger, J. L., (2001) Manual of Applied Field Hydrogeology.

McGraw-Hill, 608p.

Wisler, C. O. and Brater, B. F. (1959), Hydrology. Wiley, New York, 408p.

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Glossary – some explanation of concepts and meaning of terms

1. Aquifer: It is a water-saturated rock or rock-material (sand, silt, gravel) formation

that has capacity to store groundwater and transmit it to wells and springs.

2. Basalt: It is an igneous rock formed from the cooling of lava of basalt composition.

The lava is extruded at the surface through volcanic eruption through cones and/or

fissures on the surface of the earth.

3. Base flow: It is the part of stream flow that has been discharged from aquifers (into

the stream). In other words it is the ‘contribution’ of groundwater to streams and

rivers. Hence, in monsoonal climate regions, the water that one observes in streams

during the dry season is usually base flow.

4. Contact spring: Springs that are emerging at places where relatively permeable

rocks overlie rocks of rocks of low permeability.

5. Depression spring: Springs emerging at topographic lows where water table

intersects the ground surface.

6. Discharge: loss of water from an aquifer through springs or pumping out

groundwater

7. Hydrogeology: It is the science of ‘groundwater’

8. Karst spring: Water moving through cavities and openings developed in rocks to

form a spring.

9. Metamorphism: Process of metamorphic rock formation due to changes in physical

and chemical conditions, pressure and heat.

10. Perched aquifer: Locally saturated portion of the subsurface strata is referred to as a

perched aquifer.

11. Permeability: Also referred to as ‘hydraulic conductivity’, it is the property of rocks

or soils to allow the flow or movement of fluids (including water) through their pore

space.

12. Recharge: addition of infiltrated water to an aquifer

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13. Recharge zone: Recharge zones are the areas from where rainfall (or any other

natural precipitation) that infiltrates the ground surface leading to an addition to

the groundwater storage.

14. Spring: Point of groundwater discharge.

15. Total Dissolved Solids: It is the total amount of minerals, salts and metals dissolved

in a given volume of water, expressed either as milligrammes/litre (mg/l) or parts

per million (ppm).

16. Water table: The water table is the upper surface of an unconfined aquifer,

representing the uppermost surface of the zone of ‘water saturation’. The water

table is usually visible in shallow wells.

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Salient photographs:

Thick and firm mass of Laterites on the plateau Jointed meta-basalts observed in patches

Depression spring behaving like a Karst spring due to high weathering in laterites

Springfed stream; villagers are depended on such streams for their day to day needs

16

Well on the plateau showing Deep water-table Perched water-table on the plateau that forms a

unique ecosystem

17

Spring inventory sheet of mapped springs on and around Barazan plateau