ABSTRACT in Albanian Coastal Area There Are Developed Mainly Two Important Aquifers; Gravelly Allu - Vial and Karst Aquifer
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SOME CONSIDERATIONS ON SEAWATER-FRESHWATER RELATIONSHIP IN ALBANIAN COASTAL AREA R. Eftimi ITA Consult, Rr. Rreshit Collaku, pll.10/3/18, Tirana Albania ABSTRACT In Albanian coastal area there are developed mainly two important aquifers; gravelly allu - vial and karst aquifer. In the alluvial aquifer the sea water intrusion is developed either by natural conditions or by water extraction. About 15 to 55 % of the surface of different coastal gravelly aquifers is affected by seawater intrusion. Most coastal karst area is affected by sea - water intrusion. In some places where the carbonate structures overthrow to impermeable clayey formation fresh water karst springs issue. As a case studies the seawater intrusion in the alluvial basin of Mat River is described as well as the intake structure of the Uji Ftohte karst springs. 239 ALBANIA INRODUCTION which is located about 30 km far from the coast, the population of Adriatic coastal area is more Albania is situated in the southwestern part then 1,5 million persons, equal to more than 50 % of Balkan Peninsula on the eastern coasts of of country’s population. In the Adriatic coastal Adriatic and Ionian Seas. Otranto Channel width area is concentrated also more then 80 % of the about 80 km separates Albania by Italy. T h e industry and more then 70 % of agriculture. A Albanian coastline has a total length of 476 km, massive tourism is under fast development in this of which two thirds border Adriatic Sea and one area. In the Ionian coastal area there are only third the Ionian Sea, (figure 1). The Adriatic and small traditional villages or towns. This area rep- Ionian coasts have different orientations and resents most valuable tourist resource for Alba- morphologies which reflect their geological nia, especially because of the many places of d i v e r s i t y. unspoilt natural beauty. The northernmost part of the Adriatic coast- The groundwater resources of Albania have line could be considered the continuation of the been found to be abundant, with an uneven geo- Dalmatian coastline. From Shengjin (near Lezha) graphical and to a lesser extend to a seasonal dis- to the Gulf of Vlore the coast is characterized by tribution. Traditionally in Albania appears a clear lowlands and wide coastal plains, created in part separation between irrigation, which rely on sur- by sediments of Mat, Erzen, Shkumbin, Seman face water, and drinking and industrial water, tak- and Vjosa rivers. Some sandstone, clayey and en from groundwater. This tradition based on a conglomerate hills separate wide bays. Some controlled and centralized management is not large lagoons are located along the Adriatic coast- popular any more. The farmers more and more line. The morphology of the coastline in the Gulf like to have the "own" water well for irrigation. of Vlore marks the boundary between the Adriat- So the gravelly aquifers, the most important ic lowlands and Ionian coastline of high relief. aquifers in the Adriatic coastal area, are threaten- The Ionian coast is mainly rocky and ing by the saline intrusion. coastal alluvium occurs only at the small valleys, In most of Ionian coastal area the salt-water like in Dukat, Qeparo and within Butrinti Lagoon. head exceed that of karst fresh water and sea- Most of Ionian coastline is characterized by cliffs water flow into aquifer. Most of karst springs are cut in limestones backed steep slopes that, within brackish or salty and only in restricted areas and a few kilometers, reach heights of over 1500 m at certain geological conditions some karst fresh above sea level. water springs issuer. At Holocene transgressive maximum, some 5000 years ago, the sea level is believed to have reached many of the uplands which today form the GEOLOGICAL CONTEXT landward limit of the coastal plain. The Ad r i a t i c Sea line at that time has been about 15 to 20 km The geology of Adriatic coast area differs east to the existing one. From the time of trans- essentially from that of Ionian coast area. The gressive maximum, under what became largely northernmost sector of Adriatic coast area is a stable sea level conditions, it was the input of sed- part of Dalmatian tectonic Zone, which in Alban- iments from the rivers rather than a rise in sea lev- ian territory is represented by Renci anticline. el that dominated the coastal morphody-namic This structure is overthrown on west and consists regime (BGR 1995). of Cretaceous and Paleogene carbonate rocks. The population and economic activities of The biggest part of Adriatic coastal area geologi- Adriatic and Ionian coastal areas are very differ- cally belongs to the Periadriatic foredeep Basin, ent. The Adriatic coastal area is densely populat- (Meco & Aliaj 2000). It extends from Lezha to ed. Including Tirana City, the capital of Albania Vlora and consists of a number of anticlines and 240 SOME CONSIDERATIONS ON SEAWATER-FRESHWATER RELATIONSHIP IN ALBANIAN COASTAL AREA into two formations; the Helmesi clayey Forma- tion and the Rrogozhina sandstone-conglomerate Formation. The Quaternary, mainly alluvial deposits usually fill the river valleys and some Periadriatic lowland plain synclines (Eftimi 1966, 1975, Eftimi & Tafilaj 1979, Eftimi et al. 1985, Eftimi et al. 1999). The Ionian coast area belongs mostly to Ionian Zone and only Karaburun peninsula and Sazani Island belongs to Preapulian Zone. The main structural characteristic of this area is the presence of a series of carbonate anticlines in a sub-meridian orientation. Most important struc- tures are the anticlines of Tragjasi, Karaburuni, Cika, Kudhesi, Ftera and Saranda. Generally, the anticlines are overthrown to the west; therefore the contact with neighboring syncline structures is always tectonic. The core of these structures, mostly not visible at the surface, are constructed of Permo-Triassic evaporates, which are covered by thick carbonate formation. Starting with Trias- sic dolomites the carbonate rocks follow with Jurassic algal limestone and bituminous schists, Cretaceous porcelain and phosphate limestones and Eocene stratified limestones. CHARACTERIZATION OF COASTAL AQUIFERS As shown in figure 1, the main coastal aquifers of Albania are the following: a) Porous gravelly aquifers; b) Carbonate fissured and karstified aquifers. Porous gravelly aquifers Figure 1. Location of main coastal aquifers of Albania and Most of the rivers in Albanian flow from case study areas. 1. Porous gravelly aquifer; 2. Carbonate east to west, to Adriatic Sea. After their debauch- fissured and karstified aquifer; 3. Karsr spring average ment into the plain area the seaward intensive discharge more then 100 l/s. sedimentation created vast deltas and low head- synclines formed by two marine molasse cycles, lands of Tertiary rocks. The bigger energy rivers namely one during Middle to Upper Miocene and like Mat, Erzen, and Vjosa have created bigger the other in the Pliocene. The Miocene molasse deltas filled with thick and heterogeneous coarse are represented mainly of clayey sediments, mas- deposits. Other rivers like Buna, Shkumbin and sive sandstone, gypsiferous clays, sandstone and Seman only fine materials have deposited in the siltstone. The Pliocene sediments are divisible coastal area after having deposited the coarse 241 ALBANIA materials inland. Some smaller rivers like Dukat Erzen, Vjosa and Pavlla river which have low- (south to Vlore) and Pavlla (the southernmost riv- rate groundwater movement. er) have small but thick sediment deltas. The Concerning the water resources of the grav- main parameters of the gravelly aquifers widely elly aquifers one can distinguish the natural differ related to their geometry, hydraulic param- water resources and the exploitable water eters and water resources. In the biggest alluvial resources. The natural water resources are identi- delta, that of Mat River, the total thickness of the fied with groundwater flow, which could be esti- alluvial deposits is about 270 m and there are up mated using Darcy formula. The exploitable to four gravelly aquifer layers. The total thickness water resources are identified with the sustain- of the alluvial deposits of the other deltas varies able water quantity (with acceptable quality dete- about 100 to 150 m and there are usually one or riorations) which can be extracted from a certain two gravelly aquifer layers. aquifer. The exploitable water resources could be Mostly, the hydraulic parameters of the even some times bigger then the natural water coastal gravelly aquifers of Albania are high to resources. It depends on the aquifer recharge very high as is shown in table 1. conditions. The induced infiltration of surface water as a source of recharge is intensively Parameter Mat Erzen Vjosa Dukat Pavlla developed in watercourse aquifer system areas. The water resources are extracted more inten- Maximal sively in the gravelly aquifers of Mat and Vjosa thickness, m 150 15 30 80 100 Rivers, table 2. Permeabi- Lity, m/d 90-260 1 -50 50-500 50-350 10-100 Parameters Mat Vjosa Transmissi- bility, m2/d 2000-10,000 100-700 2000-9000 1000-5000 300-3000 Natural ground-water flow, m3/s About 4.5 About 1.3 Capacity of wells, l/s 5-150 2-10 5-150 5-100 1-20 Groundwater Table 1. Some averaging values of the hydraulic parameters of Extraction 2.45 0.95 coastal gravelly aquifers of Albania (named after the rivers). Main use Water supply and Water supply The recharge of the alluvial aquifers occurs irrigation mainly by the infiltration of the rivers in the areas of the debouchments of the rivers into the plain. Table 2. Natural groundwater resources and groundwater extraction in the gravelly aquifers of Mat and Vjosa Rivers. The main groundwater flow direction is from the outlet areas of the rivers to the sea. Usually near Most of the extraction wells are used for the outlet areas the groundwater is unconfined drinking and industrial water supply and mostly but in short distances from these areas it become are located far from the sea coastline and in areas confined and even free flowing.