GROUNDWATER CONDITIONS IN THE COASTAL REGIONS OF THE DRY ZONE OF SRI LANKA. A.P.G.R.L. Perera C.R. Panabokke

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1 GROUNDWATER CONDITIONS IN THE COASTAL REGIONS OF THE DRY ZONE OF SRI LANKA A.P.G.R.L. Perera C.R. Panabokke

2 Shallow Karstic Aquifer Deep Confined Aquifer Shallow Aquifers on Coastal Sands Alluvial Aquifer MAJOR AQUIFERS OF SRI LANKA REGOLITH AQUIFER OF SMALL TANK CASCADE REGION OF NCP AND NWP LEGEND Shallow karstic Aquifer Deep Confined Aquifer Shallow Aquifers on Coastal Sands Laterite (Cabook) Aquifer Alluvium Aquifer Metamorphic Hard Rock Aquifer Regolith Aquifer of Hard Hard rock Metamorphic Rock region with Small Tank Cascades Shallow Aquifers on Coastal Sands Laterite Aquifer INTERMEDIATE ZONE WET ZONE DRY ZONE

3 AQUIFERS ASSOCIATED WITH THE COASTAL REGIONS OF THE DRY ZONE 1. Shallow Karstic Aquifer of Jaffna Peninsula 2.Deep Confined Aquifers MAJOR AQUIFERS OF SRI LANKA REGOLITH AQUIFER OF SMALL TANK CASCADE REGION OF NCP AND NWP LEGEND Shallow karstic Aquifer Deep Confined Aquifer Shallow Aquifers on Coastal Sands Laterite (Cabook) Aquifer Alluvium Aquifer Metamorphic Hard Rock Aquifer Regolith Aquifer of Hard Hard rock Metamorphic Rock region with Small Tank Cascades 4. Alluvial Aquifers INTERMEDIATE ZONE 3. Coastal Sand Aquifers WET ZONE DRY ZONE

4 [1]. SHALLOW KARSTIC AQUIFER Confined to Jaffna Peninsula Shallow karstic Aquifer Jaffna

5 GROUNDWATER CONDITIONS IN THE JAFFNA PENINSULA

6 GROUNDWATER CONDITIONS IN THE JAFFNA PENINSULA 1 2 a 3 GWL 5 4 MSL FWZ b BWZ c (a)- Red Earth, (b)-jaffna Limestone, (FWZ) Zone of fresh water saturation, (BWZ) Probable zone of brackish water, (1) Dry well, (2) Well of Puttur type, (3) Ordinary successful well, (4) Spring of Keerimalai type, (5) Solution cavern, (MSL) Mean sea level, (GWL) Groundwater level

7 GROUNDWATER MONITORING PROGRAMME In Jaffna Peninsula, well Monitoring programs are being conducted by WRB Results of well monitoring and water sample analysis revealed a high concentration of NO3 in groundwater exceeding maximum permissible level of WHO for drinking water in the western part of the Jaffna Municipal Area. Higher values of EC observed in southern and western part of Jaffna Municipal Area.

8 RESULTS OF WELL MONITORING PROGRAMME Electrical Conductivity May Electrical Conductivity July

9 [2]. DEEP CONFINED AQUIFER Found in the Coastal Regions of North and North-West which extends from Puttalam to Jaffna and towards Mulativu. Sedimentary rocks (miocene limestones /Sandstones) REGOLITH AQUI OF SMALL TANK CASCADE REGION OF NCP AND NWP Deep Confined Aquifer

10 DEEP AQUIFER BASINS Eight distinct deep aquifer basins Average depth of wells m Yield lpm Electrical Conductivity Values moderate to high Vanathavilluwa Basin intensively used for irrigated agriculture Mannar C A Paranthan - Kilinochchi D B MULANKAVIL BASIN MURUNKAN BASIN KONDACHCHI BASIN PARANTHAN BASIN Vavuniya Mulaitivu MULAITIVU BASIN N Palavi & Madurankuliya Basins intensively used for prawn culture farms. Puttalam VANATHAVILLU BASIN Palavi Basin Madurankuliya Basin

11 MURUNKAN AQUIFER A Cross Section along A-B Line B Confined Aquifer

12 C CONCEPTUAL MODEL OF THE VANATHAVILLUWA AQUIFER Cross Section along C-D Line Main Recharge Area D Main Limestone Aquifer Recharge from rain Lagoon Piezometric level Saline tank Sandstone Sedimentary Limestone Metamorphic Hardrock

13 [3]. COASTAL SAND AQUIFERS CO- TERMINUS WITH REGOSOLS OF SOIL MAP Regosols on Recent Beach and Dune Sands - Flat Terrain Regosols on Recent Beach and Dune Sands - Flat Terrain Regosols on Recent Beach and Dune Sands - Flat Terrain

14 SOIL MAP - COASTAL SAND AQUIFER

15 Mannar Island Kondachchi Kalpitiya [3] 3 MAIN TYPES OF COASTAL SAND AQUIFER JAFFNA Poonery MANNAR COASTAL SAND AQUIFERS OF SRI LANKA Mulankavil MULLAITIVU Shallow DRY Aquifres ZONE on Coastal Spits Shallow aquifers on Coastal Beaches Kokkilai Pulmoddai Kuchchaveli Nilaveli TRINCOMALEE LEGEND Shallow aquifers on coastal spits Shallow aquifers on coastal beaches. Moderately deep aquifers on old coastal plain Distributed all over the coastal regions. 3 Types of aquifers a). Shallow Aquifers on Coastal Spits and Bars Eg : Kalpitiya, Pooneryn, Mannar Kalpitiya Peninsular -Spit Chilaw Katunayaka Negombo COLOMBO PUTTALAM Battulu Oya Panadura Moderately Deep Aquifers of Prior beach Plains WET ZONE INTERMEDIATE ZONE Kalkudai BATTICALOA Kalladi Kalmunai Pottuvil b). Shallow Aquifers on Coastal Beaches Eg: Pulmuddai, Nilaveli, Kalkuda, and Low Sand Dunes Eg: Hambantota c). Moderately Deep Aquifers of Prior beach Plains Eg: Katunayake, Chilaw The total extent KALUTARA Bentota Ambalangoda DRY ZONE Yala Palatupanna Kumana Type 1 & Type 2 estimated 140,000 ha GALLE Tangalla Koggala MATARA Dondra HAMBANTOTA Pocket Beaches

16 3.1. SHALLOW AQUIFERS ON COASTAL SPITS Mainly confined to the coastal spits Pooneryn mesopeninsula JAFFNA Coastal spit type sand aquifer is best expressed in the Kalpitiya Peninsula located in west coastal region of SL Mannar Island Mannar Island Poonery MANNAR Mulankavil M A similar formation is found in the Mannar Island and also in Pooneryn meso-peninsula. Also Batticaloa, Kalladi Kalpitiya Peninsula Kondachchi Kalpitiya Kalpitiya Peninsular -Spit DRY ZONE PUTTALAM Battulu Oya

17 3.2. SCHEMATIC SECTION KALPITIYA AQUIFER KALPITIYA Sea Main Land Sea Land Surface FreshWater Sea Sea Lagoon Puttalam Salt Water sand Sand Bounded by the sea on both western and eastern flanks A thin fresh water lens occur in the sand and is present at depths of 1-3 m. EC of this shallow ground water varies us/cm

18 3.2. GEOLOGICAL CROSS SECTION ON KALPITIYA PENINSULA DEPTH (MAMSL) Sea SAND AQUIFER Area under intensive cultivation Wells WATER TABLE Lagoon CLAYS MIOCENE LIMESTONE Fresh & Saline water Interface metres 1000 CROSS SECTION ACROSS KALPITIYA PENINSULA Consists of coarse sand to a depth of m underlain by clays and miocene limestone

19 3.3. SHALLOW AQUIFERS ON COASTAL BEACHES Kondachchi Kalpitiya Peninsular -Spit Chilaw Mannar Island Kalpitiya Katunayaka Negombo COLOMBO KALUTARA JAFFNA Poonery MANNAR PUTTALAM Battulu Oya Panadura Bentota Ambalangoda COASTAL SAND AQUIFERS OF SRI LANKA Mulankavil WET ZONE DRY ZONE GALLE Tangalla Koggala MATARA Dondra MULLAITIVU Kokkilai Pulmoddai Kuchchaveli Nilaveli INTERMEDIATE ZONE DRY ZONE TRINCOMALEE HAMBANTOTA Kalkudai Yala Palatupanna LEGEND BATTICALOA Kalladi Kumana Koggala Shallow aquifers on coastal spits Shallow aquifers on coastal sand raised beaches. Moderately Deep aquifers on old coastal plain Kalmunai Pottuvil Nilaveli Pasikuda Kalkudah Mainly confined to the numerous narrow strips of raised beaches and low sand dunes. Distributed all round the Island where ever the coastal geomorphology permits such build up. They lie well above the present sea level and usually m above msl Typical examples are the beaches of Nilaveli, Pasikuda,Kalkudah and Koggala etc

20 SCHEMATIC SANDY REGOSOL SOILSCAPE EAST COAST HIGHLAND REGOSOLS ON BEACH PLAIN DUNE SANDS Lagoon Beach Sea 2-4 Km 30 m

21 SHALLOW AQUIFERS ON THE BARRIER BEACHES OF THE EASTERN COASTAL REGION Kalkuda Co-terminus with the Soil map of Sri Lanka Regosols on Recent Beach Batticaloa Kalmunei

22 3.3. NILAVELI COASTAL SAND AQUIFER Land surface Wet season Water Table Mud Flat Lagoon Basement Rock Fresh Water Dry season Water table Bed rock Brackish water Sea Salt Water Located on the eastern coastline The Nilaveli sand aquifer is bounded by the sea on its eastern flank and by the lagoon and mud flat on it western flank Studied period of by WRB Water levels at the end of the dry season : 2-4 m depth EC of well water normal range

23 SEASONAL VARIATION OF ELECTRICAL CONDUCTIVITY July 2000 July 2001

24 3.4. KOGGALA COASTAL SAND AQUIFER A barrier beach is bounded by the Koggala lake in the north and sea in the south This barrier beach is made up of coastal sand, weathered shell and coral fragments, and is little more than 3m above mean sea level. Incipient dunes which are typical of the wet zone coast forms a patch behind the beach. Main aquifer is located within the sand and coral sand admixture. The depth to basement is in the range of meters. Wet Zone Recharge both monsoons

25 LOCATION MAP OF THE STUDY AREA Koggala Lake Koggala Sea

26 3.4. GEOLOGICAL CROSS SECTION WEST-EAST EAST KOGGALA C 4 0 SEA X 01 X 103 X 105 Lake Lake 4 Sand Clay Clayey Sand Sand with Shell Shells Sand 8 12 Clay 16 Weathered Rock Weathered Rock m Main aquifer consists of sand and sandy clay and thickness of this aquifer is ranging from m

27 VARIATIONS OF ELECTRICAL CONDUCTIVITY OF GROUNDWATER IN KOGGALA EPZ Pre and Post Tsunami Before Tsunami P-05 P-06 P-07 P-08 P-09 P-10 P-11 X-102 X-109 X-123 X-141 X-142 X-143 X-144 X-145 X-146 X-147 X-148 X jan feb mar apr may jun jul aug sep oct nov dec jan feb mar apr may jun jul aug sep oct nov dec jan feb mar apr may jun jul aug sep oct nov dec jan feb mar apr may jun jul aug sep oct nov dec jan feb mar apr may jun jul Year Electrical Conductivity (Us/cm)

28 CONDUCTIVITY VARIATIONS SELECTED WELLS IN KOGGALA 9000 EC - March Electrical Conductivity (Us/cm) X-142 Habaraduwa Malalagamduwa Magaltota X-143 X-144 X-146 X-145 X-142 X-123 X-141 X-148 X-147 X-102X-109 X-141 X-149 P-05 Koggala P-07 P-08P-09P-10 P jan feb mar apr may jun jul aug sep oct nov dec jan feb mar apr may jun jul aug sep oct nov dec jan feb mar apr may jun jul aug sep oct nov dec jan feb mar apr may jun jul aug sep oct nov dec jan feb mar apr may jun jul P-11 P-13P-14 P-06 Koggala P-06 Madolduwa Gurukanda FREE TRADE ZONE Kataluwa West ElectricalConductivity NoData Before Tsunami P-06 X-141 X Year

29 3.5. MODERATELY DEEP AQUIFERS OF OLD BEACH PLAINS M a h a O y a ar -Spit Battulu Oya NEGOMBO Kochchikade Kibulapitiya Oya Welisara Divulapitiya Chilaw Negombo Lagoon LEGEND Katunayaka Seeduwa Kandana Wattala Ekala Roads Streams Old beach plain Minuwangoda D i e y a a l l O Gampaha y a K e l a n i G a n g a Katunayaka Negombo Confined to the old beach plains that covers the area from Chilaw southwards to Kochchikade Negombo- Katunayake Seeduwa- Ja ela Kandana This old coast sand plain lies adjacent to several river system such as Kimbulapitiya oya and Dandagam oya, thus provide additional recharge to the aquifer

30 [4]. Alluvial Aquifers One of the largest carriers of groundwater among the sedimentary formation is river alluvium. Rivers such as Mahaweli ganga, Kelani ganga, Deduru oya, Mi oya, Kirindi oya and Malwathu oya have broad and deep alluvial beds in their lower reaches. Old buried river beds with high groundwater yields are present in the lower Kelani river aspects. This river alluvium may vary from 10 to 30 m in thickness Part of Puttalam water supply is drawn from alluvium of the Mi-oya.

31 ALLUVIAL AQUIFER OF MI-OYA

32 UTILIZATION OF GROUNDWATER IN COASTAL REGIONS Water supply to Jaffna is drawn 100% of the total requirement from shallow karstic aquifers. Water Supply to Mannar, Baticalloa and smaller towns are drawn from high yielding coastal sand aquifers Hambantota drew a part of its water supply from the sand dunes which occur very prominently around the town. Water suppiles to Koggala Free Trade Zone are drawn from high yielding coastal sand aquifer. The Katunayake moderately deep aquifer is now being fully exploited for both the requirement of the IAP and also industrial enterprises in Katunayake FTZ

33 SAND DUNES - HAMBANTOTA Koggala Lake Lagoon MSL Basement Bed Rock

34 MAIN TYPES OF AQUIFERS IN THE COASTAL DRY ZONE AND THEIR PRESENT STATUS Type 1. Shallow Karstic aquifer - Jaffna Present Status Agriculture 80%, Domestic 20% Re-charge 90,000 AF/y, Discharge to sea 50,000 AF/y Highly exploited, NO 3 pollution very high 2. Deep Confined Aquifer Miocene Base 3. Coastal sands Raised beaches Spits, bars, dunes 4. Alluvial Aquifer Partial Use Presently underutilized, No pollution threats Earlier Mainly Coconut Now Tourism, - Intensive agriculture Kalpitiya Increasing pollution threats Being exploited at varying degrees of extraction without experiencing major draw-down hazard.