Climate and erosion in the Ohrid - Prespa zone

Eglantina Bruci, Liri Muçaj, Vangjo Kovaçi Hydrometeorological Institute, Rruga Durresit Nr. 219 Tirana,

Abstract

In Albania as a part of Mediterranean countries, the erosion seems to be bigger than the neighbors, where the value varies from 20 up to 80 ton/hectare per year or up to 100 ton/hectare per year, in some specific area. This paper presents some results of the study on the impact of condition on soil erosion, taking into account the meteorological elements; especially heavy rain, temperature, drought, strong winds etc. which are the main contributors in this phenomenon. Heavy rain (intensity and amount) is one of the most hazardous weather phenomena that cause the emergency as well as the potential erosion risk. Universal Soil Loss Equation (USLE) that takes into consideration many factors (rainfall erosivity, soil erodibility, slope length and gradient, cropping management) is used to calculate the soil loss rate. According to scenarios of the expected climate change for Albania, an annual increase in temperature up to 1.8°C and to 3.6°C and the decrease in up to -6% and –12.5% respectively by 2050 and 2100 related to 1990 are expected. These changes are likely to cause increase in drought frequency, and the intensification of soil erosion, especially in the coastal zone, might be expected. Keywords: heavy rain, soil erosion, soil loss equation, climate change scenarios Intodruction The zone under study, according to the climatic division, belongs to the southeastern mountainous sub region, with cold winter and cool summer [Group of authors. 1975]. The mean annual temperature over this zone varies between 7.5°C and 12°C, the mean winter temperature between -2.3°C and 6.6°C, while the mean summer one varies between 10.5°C and 22.3°C. The absolute maximum temperature recorded is 39.6°C and the absolute minimum -14.5°C in Pogradec and in Sheqeras is -26.8°C which is the absolute minimum recorded over all the Albanian territory). The total precipitation over the zone varies between 608 mm to 890 mm, while the 24h maximum precipitation reaches 130 mm. The number of days with snow cover registers 22 days/year (Liqenas). Average values of global solar radiation and sunshine duration are respectively 1454 kwh/m2 and 2426 hours/year. According to the scenarios the expected climate change for Albania (UNDP, 2002) is likely to cause an increase in drought frequency, increase of temperature and changes in precipitation, which may affect water availability and other factors and intensification of soil erosion as well.

Method ¾ The mean monthly, seasonal and annual data of long term precipitation for stations Gorricë e Madhe, Liqenas, Korçë, Sheqeras, Bilisht and Pogradec are investigated to study the climatic conditions of this zone. ¾ Universal Soil Loss Equation (USLE) is used to predict the soil loss rate. A = R K L S C Where A - the soil loss (t/ ha / year)

Climate conditions

Air temperature As we can see in the fig.1, the maximum value of air mean temperature reached in the summer season (July, August, 20.8°C) and the lower one in the January 2.1°C. While the absolute maximum temperature reaches up to 40°C in June (Korçe) and the absolute minimum recorded varies from - 14.5°C (Pogradec) up to -26.8°C (Sheqeras) in the January. Figure 2 displays the annual average temperature distribution over the Ohrid - Prespa zone. Here we can see that the annual mean temperature over this zone vary from 9°C up to 10 °C.

25

20

15

10 temp.oC

5

0 I II III IV V VI VII VIII IX X XI XII months

Fig.1. The course of mean air temperature Fig. 2. The space distribution of air temperature over this zone

Wind Besides the above-mentioned climatic elements, wind regime plays an important role in the formation of climate conditions, soil erosion and in practice as well. To describe the wind regime over the area are used the wind data of Pogradec station. The area considered is characterized by calmness, with mean annual value of frequency 53%. Mean annual wind speed varies among 2.5 and 2.9 m/s while the maximum up to 20m/s. The main prevailing direction is North (with frequencies varying from 10 to 20% over the year). The mean values of wind speed after this direction vary from 2.4 m/s (May, June) to 4 m/s (winter time). As a second prevailing direction during the period October-April appears South, with frequencies from 10 to 12.8%.

Precipitation The total precipitation over the zone varies between 650 to 890 mm, while the 24h maximum precipitation reached up to 130 mm. In Pogradec the 24h maximum precipitation recorded is 87.2 mm in October and the number of snow days is relatively low (around 18.7 day/year), due to the mild influence of the Ohrid lake. The annual course of precipitation is presented in the figure 3. We may distinguish the following characteristics: winter is the wettest season with maximum precipitation in the November. The second maximum of precipitation in May indicates the presence of in this zone. Figure 4 displays the distribution of precipitation total (annual) over Ohrid-Prespa zone. Here we can see that the annual mean precipitation over this zone is below 800mm. 120 101.8 100

80 68.9

Prec. 60 (mm) 40 30.2

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0 IIIIIIIVV VI VII VIII IX X XI XII months

Fig. 3. The course of mean annual of Fig. 4.The space distribution of precipitation over precipitation. Ohrid - Prespa zone.

Estimation of soil erosion The relief of Albania it’s not uniform not only because of geologic construction of the earth, but also of the effect of non stop thousand years eroded from the erosion. 24% of our territory consists of predisposed soil to be eroded, 59 % of middle predisposed and only 17 % are not predisposed against erosion. To predict the soil loss rate is used the Universal Soil Loss Equation (USLE) in order. (Wischmeier , W. H. & Smith, D.D. 1978) A = R K L S C P Where A - the soil loss (t/ ha / year) R - rainfall erosivity factor K - soil erodibility factor L - slop length factor S - slop gradient factor C - cropping management factor, and P - the erosion control practice factor.

The “R” factor is a definition of the erosivity of rainfall events and is defined as a product of two rainstorm characteristics: kinetic energy and the maximum 30-minute intensity. (“R” = (E I30)/100) To calculate this factor is analyzed the heavy rain (intensity and amount) as a one of the most hazardous weather phenomena that cause the emergency as well as the potential erosion risk. As a first step is investigated the extraordinary rain falling down over all the territory, in order to find out the rain intensity during the intervals 30 minute. After that, it is prepared the map that shows the distribution of the 30-minute rain intensity over Albania. (Fig. 5)

¾ Calculation of the erosion index “R” is based on 10 years of data in 23 Albanian meteorological stations. Albanian territory is divided in three homogenous statistic areas in the term of index erosion value “R” (A, B, C group zones) fig.6. We can see that south part of the country, where Ohrid-Prespa catchments take part, is included in the C zones with the value of R index is bigger than in the zones A and B. ¾ The highest values of “R” factor belong to the C zone (average 47.8/year), subject of our study. The lowest belongs to the B zone (average 5.2/year). ¾ The estimation of the soil erodibility factor “K” is made by using the improvement monogram method (Wieschmeier, 1978). Twelve type of soils are considered to evaluate “K” factor. As a result was find out that the smallest value (0.16 - 0.22) of the soil erodibility factor “K”, belongs to the clay soils and the biggest one (0.56) to the sandy soil. ¾ Both slop length factor “L” and slop gradient factor “S” calculated as a single topographic factor (LS) are used to estimate the erosion. Seven experimental fields are built to estimate the “LS” value. It results that the influence of this factor in the soil erosion is considerable, about 2.93. ¾ The cropping management factor “C” is a product of percent of yearly erosion index and the ratio of soil lost according to the yield stage. This is evaluated for every stage of crops in every agriculture year. This factor has the high value in the A zone and the lowest in the C zone. ¾ The erosion control practice factor “P” is assumed to be equal 1, which do not has the influence in estimation value of erosion. ¾ The annual mean erosion of agricultural soil (A), calculated by Universal Equation A = R K L S C P is: A(A)= 52.5 ton/ha/year, A(B)= 14.8 ton/ ha/year and A(C)= 37.1 ton/ha/year, where A(A), A(B) and A(C) are the soil lost of agriculture soil in three zones respectively. (Kovaçi, V et al. 1997)

Fig. 5. The 30-minute intensity of rainfall Fig. 6. Distribution of ”R” value according to A, B, C group zones

Potential Impacts of expected climate change on erosion process.

Existing problems Some major environmental problems in these zones are: ¾ There are no restrictions on the use of chemical herbicides, pesticides and fertilizers in agriculture, resulting on the contamination of rivers, canals and ground water. ¾ Waste waters of industrial origin are usually directly discharged into lakes and rivers with any treatment. Wastewater of urban origin is also directly discharged into canals and rivers. ¾ Air quality is a very serious environmental concern, particularly around the industrial settlements and in urban areas. ¾ We are facing with the keen problem of overpopulation and construction of the new settlements without control. ¾ Taking into consideration all these impacts, this zone especially the lakes itself always has been problem for the Government, but in the erosion control and soil management very little work is made.

Fig. 7. The land erosion in Çerave.

Expected climate change The climate change scenarios for Albania lead to an annual increase in temperature up to 1.8°C and to 3.6°C respectively by 2050 and 2100 related to 1990. (UNDP), 2002. The decrease in precipitation is expected to reach to -6% and –12.5% respectively by 2050 and 2100 related to baseline. Severe summers with high temperatures (up to 4.1°C) and low precipitation (up to –27%) are expected to meet over the territory that may cause negative or positive impacts. Autumn seems to play the second role in annual changes. Milder winters and warmer springs are expected as well. These climatic changes by 2025 are not expected to have any significant impact. There is a possibility for all systems to adapt to new conditions. The possible changes should be expected also even in the behavior of some other climate elements very important to have in the consideration related to the erosion process like: ¾ Increase in the drought intensity, and frequency, due to temperature increase and precipitation decrease, particularly in summer; ¾ Increase in wind speed, particularly in summer, as well as a slight increase of storm frequencies and strong winds. ¾ Decrease in the number of snow days, due to the expected rise in the winter temperature; ¾ Increase in global radiation and hourly daily number of sunshine, etc.

Some recommendations suggesting to avoid, mitigate or adapt to the predicted negative effects of climate change related to the erosion. ♦ Study of the erosion and the dynamics of soil. ♦ Establishment of an artificial precipitation system to avoid the negative effects of drought on agriculture. ♦ Preparation of a landslide map predisposed to erode. ♦ Possible afforestation to help mitigate the impact of drought and strong winds. ♦ Construction of protective step walls or pipes in the areas prone to landslide affected due to erosion. ♦ Improved planning of the civil engineering works, including complete technical, economic and architectonic studies.

Conclusions 1. The improved Universal Soil Loss Equation (USLE) can be used in our climatic and orography condition. 2. The most potential erosion risk of rainfall occurs in October month (R=90.98) and the smaller in July 4.2. 3. The possible changes should be expected in soil erosion 4. The value of the agriculture soil lost estimated by USLE is 35.0 ton/ha/ year. 5. Climate change scenarios lead to an annual increase in temperature up to 1.8°C and to 3.6°C respectively by 2050 and 2100 related to 1990.

References: IHM 2004: “Archive” Tirana, Albania Demiraj E. et al., (2001), “Vulnerability assessment and adaptation options” UNFCCC. ALB/96/G32/A/1G/99

Group of authors. 1975, “Climate of Albania”, Hidmet , Tirana, 244-264.

Hulme M. et.al., (2000), “The use of simple Climate Models in Vulnerability and Adaptation Assessments”: MAGICC/SCENGEN Workbook .

Kovaçi, V et al. 1997. Estimation of soil erosion process in Albania and of the factors which have influence on it. Soil Search Institute, Tirana.

UNDP, 2002. The First Communication of Albania to the United Nations Framework Convection on Climate Change (UNFCCC), 94-97.

Wischmeier , W. H. & Smith, D.D. 1978. Rainfall energy and its relationship to soil loss.