BALWOIS 2004 Ohrid, FY Republic of Macedonia, 25-29 May 2004
The Regionalisation Of Albanian Territory According To The Annual Specific Yield
Bardhyl Shehu Polytechnic University of Tirana Tirana, Albania Molnar Kolaneci Hydrometeorological Institute Tirana, Albania
Abstract Albanian territory is very reach in water resources. The spatial distribution of the water resources in Albanian territory is heterogeneous due to a high variability of climatic and land characteristics. The parameter chosen for the regionalisation is the specific yield. The long-term average of specific yield has a spatial variability of 10 to 100 l/s/km2 in Albanian territory. The data used include the period 1951-1990 of 80 hydrometric stations distributed in whole Albanian hydrographic network. The lower limit of catchment area (basin) of 100 km2 is accepted. As the result are established two maps. In the first one is presented the general regionalisation of water resources according to the concept of high and low water resources. The second one presents the more detailed regionalisation that includes 8classes. This is the first attempt of the regionalisation of the water resources in Albanian territory. Key words: Water resources, specific yield, regionalisation, Albania
The regionalisation of Albanian territory according to the annual specific yield.
Introduction Albanian territory is very reach in water resources. The spatial distribution of the water resources in Albanian territory is heterogeneous due to a high variability of climatic and land characteristics. Evaluation of water resources and their presentation in a comprehensive form is useful information for decision maker’s institutions, which are interested for a complex exploitation of water resources. The hydrologic maps give a good presentation of hydrologic information (water resources). These maps, compiled from real data received from hydrologic network, give opportunity to have hydrologic information for area with small data or without data. Three-dimensional presentation of watercourses parameters in a two-dimensional framework has specific problems and drawing of isolines becomes more difficult in case of Albanian territory. For this reason we are of the idea that the regionalisation of the territory according to the water parameters and drawing of isolines, is a difficult problem to be resolved, especially for mountain area, where the variation of land characteristics is very high. So this study is oriented towards the division of the territory in areas with determinate water parameter. The determination of spatial distribution of water parameters is not only scientific problem. The determination of the areas with high or low level of water resources gives the possibility to establish an action plan in the framework of sustainable economic development (for example the transfer of water from reach areas towards poor region).
Methodology The water parameters of the watercourse in one station, which are different from meteorological parameters (point representative), present the behaviour of a determinate area (watershed). The information used for this study, includes data of 80 hydrological stations from all Albanian rivers. After analyzing this data, was made the extension of the data series in a common period, which is 1951- 1990. The extension of short data series was made basically by correlation method between neighbour stations or analogue watersheds. In some cases the water parameters (ex. average annual discharge) are calculated with ratio or graphic method. As parameter, for an objective water resources evaluation, usually is used the annual specific yield, which express the water quantity gathered from the catchment area in the unit of time (m3/s/km2 or l/s/km2). Due to spatial character of this parameter, the values of the calculated parameters for all stations are located in “gravity center” of the catchment area, which belong. The attention is paid to the fact that in the value of a station down stream is included also the value of the upstream station. So, the value of the parameter for the upper station is
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taken twice in consideration, once in integral form (upper station) and secondly as pondered value for the down station. To avoid this phenomenon, in this study are calculated the parameters for the sectors between two stations, where is the case, meanwhile their integral value either are not taken in consideration, or are considered as consulting values. Our idea is that the presentation of water resources in a map by dividing the territory by areas with different values of water resources parameters is more significant for our physical-geographical conditions. As the border for these divided areas are accepted, in most of the cases, the borderline of the watersheds (basins). This criteria of drawing these borders, is not applied in every case because as it mention above the physical-geographical conditions including those of land surface (relief, geology, pedology and plant cover) may be approximate similar with neighbour watershed or part of them. The determination of the areas (regions) is made taking in account not only the water flow parameters (annual specific yield), which is the most important, but also the complexity of other factors in water flow. During the process of regionalisation we have tried that the border of the regions being more large as possible in order to avoid the drastic jumping from one region to the other. In a specific case like Kardhiqi and Benca streams, this attempt was not successfully completed due to high percentage of karstic formations in the catchment areas of these streams. In other side, the catchment areas of these streams are relatively small (<100 km2) and it is known the fact that the influence of karst formation is considerable for catchment area < 200 km2. This limit of 200 km2 is difficult to apply for Albanian rivers and tributaries due to their small surfaces of the catchment areas. So the lowest limit of catchment areas that are taken in consideration for the regionalisation is accepted 100 km2. This limit is conditioned also by heterogeneous distribution of the precipitation in Albanian territory and also by the high variation of physical-geographical condition of our territory.
Hydrologic regionalisation Generally the water quantity (discharge) of the rivers depends mainly on precipitation falling in the respective catchment area, evapotranspiration (climatic factors) and also land characteristics like permeability, slope, plant cover and others. The annual specific yield is a water parameter in which is included the effect of all mentioned factors. The territorial distribution of this parameter gives a good panorama of the level of the country’s water resources. Water resources in Albania are considered with high level of variability. The average annual specific yield has a spatial variation from 10 to 100 l/s/km2. This large diapason has imposed also a relatively large diapason in the division of the respective regions. Due to the influence of different factors it was not possible to find a define rule or function for the spatial distribution of water resources in Albania. Among these factors one of them, the karst formation, has created major problems, because they are relatively small surfaces where are concentrated important springs. Having limited dimension of the area, these karst formations are not presented as single areas. Nevertheless in territory of our country can be distinguished region with relatively small water resources and areas with high water resources. The first map presents the general regionalization of water resources according to the concept of high and low water resources fig. 1. As the criteria is accepted the value of 20 l/s/km2 of the specific yield, taking in consideration that the average annual specific yield for hydrographic Albanian territory is around 30 l/s/km2. In the region with small water resources (< 20 l/s/km2) is included mainly the Western Plateau of Albania. As its east border serves the line starting from Lezha, Miloti, Fushe Kruja in west of Tirana, Cerrik, Kucove up to Memaliaj. In this area the annual specific yield varies from 5 to 15 l/s/km2, growing from west to east. In this region is included also the upper and middle part of Devolli and Osumi rivers, where the annual specific yield varies from 10 to 20 l/s/km2, growing from north to south. In the second region, with high water resources, is included the central part of the country from North to South and the catchment area of Drini i Zi river. In this region the water resources decreases considerably from North to South up to the border of Devolli catchment areas where the water parameter varies from 100 l/s/km2 to 20 l/s/km2 (with predominance of 30-35 l/s/km2) growing after in south direction up to 50 l/s/km2 in Kardhiqi catchment area.
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BALWOIS 2004 Ohrid, FY Republic of Macedonia, 25-29 May 2004
Figure 1 General regionalisation of Albanian territory
Following is more detailed regionalisation of the territory according the distribution of annual specific yield, which is constituted by 8 regions (classes): A_ >70 l/s/km2. Include the most northern part of the country, the upper part of Valbona, Curraj and Lesniqe rivers (the catchment area of Vermoshi river is out of this region). In this region there are the most abundant precipitation of the country, around 3000 mm annually, and also strong underground springs.
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B) 50-70 l/s/km2. This region includes the area of Albanian Alps except rivers flowing in Shkodra Lake. As northern borderline of this region serves the southern borderline of class A and also the northern state border. The eastern borderline starts from state border through border between Gashi and Bistrica catchment areas rivers up to intersection with Drini River. As the southern borderline serves Drini River up to Vau i Dejes. 2 C) 40-50 l/s/km . This region is divided in three separated sub regions: C1 is an area with longitudinal extension from North to the Central Albania. His northern borderline is Drini River and eastern borderline is the left side of Drini i Zi River Basin. In this sub region are included mainly the upper parts of Fani and Mati Rivers. The C2 sub region has similar characteristics as C1 and it is located in south of the country, in Kurveleshi mountain area (Benca and Kardhiqi Rivers). C3 sub region includes the upper and middle part of Gostima and Radicina Rivers Basins in mountain area of Polisi. 2 D) 30-40 l/s/km . Also this region is divided in two sub regions: D1 includes the northern part of Western Plain, upper Shkodra, the middle parts of Kiri River basin, the basin of River Gjadri, the middle and lower parts of Fani and Mati Rivers, the basins of Zeza, Terkuza and Tirana Rivers and the upper part of Erzeni River basin. The sub region D2 is located in the south and includes the Basin of Drino River and the upper and the middle part of Kalasa and Shushica Rivers. E) 20-30 l/s/km2. This region is divided into two sub regions: E1, is a part of Central Albania, mainly the basin of River Shkumbini up to Paper station (except C3 sub region), the basin of Erzeni River up to Farka bridge and also the basin of Lana River. The E2 sub region includes the basin of River Vjosa from the state border to the interception with the main tributary, Drino River. F) 10-20 l/s/km2. This region has the largest area of the country. Is divided in three sub regions: F1, includes the eastern part of Western Plain and also the basin of Rivers Devoll and Osum: F2, includes the northeastern part of the country, the basin of Rivers Kruma and Luma. As the western borderline is region B and the south border line is River Drini: F3 is located in the extreme south part of the country and includes the lower part of the basin of Rivers Kalasa and Bistrica and the basin of River Pavla. In this sub region is excluded the important karstik spring of Bistrica, the Azure Eye, which is out of the classification due to the fact that the underground basin of this spring is several times bigger than the surface basin. G < 10 l/s/km2. Is located in the west part of region F and includes the western part of the Western Plain of the country. DE 25-35 l/s/km2. Is a specific region, in which the values of the annual specific yield are between 25 and 35 l/s/km2 and for this reason is named DE. Dividing this area in D region and E region will bring the non-justified fragmentisation of the area.
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A > 70 l/s/km2 B 50-70 l/s/km2 C 40-50 l/s/km2 D 30-40 l/s/km2 E 20-30 l/s/km2 F 10-20 l/s/km2 DE 25-35 l/s/km2
Figure 2 Regionalisation Map of Albanian territory according to the specific yield.
In this regionalisation of Albanian territory for the water resources, presented in this paper, is not pretended to have a high accurate regionalization. We are of the idea that as the first attempt in our
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studies, this regionalization will be useful for the planning of the exploitation of water resources in our country.
Table 1 Principal hydrographical characteristics of the Albanian rivers. Nr. River Surface of Precipitation Runoff Discharge Specific basin discharge ( km²) (mm) (mm) (m³/s) (l/s.km²) 1 Drini 14173 1450 780 361 25.8 2 Buna 5187 2170 1950 321 61.7 3 Mati 2441 1663 1331 103 42.2 4 Ishmi 673 1430 977 20.9 32.0 5 Erzeni 760 1470 753 16.1 21.2 6 Shkumbini 2446 1352 794 61.5 25.2 7 Semani 5649 1084 532 95.7 16.9 8 Vjosa 6706 1510 917 195 29.1
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