1 THE EVALUATION OF DIFFERENT ARID CONDITIONS USING GEOGRAPHIC INFORMATION SYSTEMS IN YESILIRMAK BASIN Bilal Cemek Gaziosmanpasa Univ. Agricultural Fac., Dep. of Agric. Structures and Irrigation, 60240,Tokat/TURKEY, Yusuf Demir Ondokuz Mayıs Univ. Agricultural Fac., Dep. of Agric. Structures and Irrigation, Samsun/TURKEY, Mustafa Güler Blacksea Resarch Institute, Gelemen-Samsun, Sedat Karaman Gaziosmanpasa Univ. Agricultural Fac., Dep. of Agric. Structures and Irrigation 60240, Tokat/TURKEY, ABSTRACT The evaluation of arid condition was evaluated in Tokat Amasya, Corum ve Samsun provinces which composed of most of the yesilirmak basin. Arid condition was evaluated based on meteorological, agricultural, hydrologic and sociologicaleconomic conditions. The soil, water resources and agricultural activities with corporation of aridness of Yesilırmak basin must be investigated. The study was performed using long time data base of 48 meteorology station in Yeşilirmak basin. Keywords: Drought, GIS, Yeşilırmak basin INTRODUCTION Droughts are somehow different from other natural hazards in several aspects. Drought is a slow-onset, creeping natural hazard. Effects of drought generally accumulate slowly over a considerable period of time, and may linger for years. Therefore, the onset of drought is difficult to determine. The lack of a precise and universally accepted definition of drought also contributes to the confusion on drought and its severity. From a realistic perspective, definitions of drought must be region and application (or impact) specific. This is one explanation fort the scores of definitions developed. In addition, drought impacts are nonstructural, and spread over a larger geographical area than that of the damages result from other natural hazard. Since
2 PRACTICES ON RIVER BASIN MANAGEMENT 69 drought can affect such large areas, it is far more difficult to quantify impacts and respond [Wilhite 2003]. Meteorological drought is a result of the occurrence of persistent large-scale disruption in the global circulation pattern of the atmosphere. Drought exposure rates vary spatially, little can be done to alter the drought occurrence. Exposures are also determined by social factors such as population growth, population shifts (regional and rural to urban), demographic characteristics, technology, policy, environmental awareness, and social behavior. These factors change over time, and thus vulnerability will increase or decrease in response to these changes [Wilhite 2003, Hayes and Wilhite 2003, Topçuoğlu et all 2004]. MATERIAL AND METHOD Watershed of Yesilirmak covers the provinces of Tokat, Amasya, Samsun, Çorum, Gümüşhane Sivas, and Erzincan. In this study, four of the perovinces mentioned constituting significant portions of the watershed were selected. Location of provinces and meteorological stations were shown in Figure 1, and chracteristics of towns were presented in Table 2. Drought analysis were carried out based on Özgürel and Mengü , and evaluated based data given in Table 1. Climatic data were taken from Anonymous . ArcGIS 8.3 [ESRI 2003] software was used to visually analyze, compare and contrast the spatial patterns of the variables studied. Figure 1. The location of the study area and weather stations.
3 70 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT Lang, De Martonne, Erinc and standardised precipitation index (SPI) drought analysis methods GIS applications were used to determine the spatial and timely characteristics of droughts for Yesilirmak watershed. Study area composed of 4 provinces and 44 towns (Figure 1). Drought classification of the methods was given in Table 2. Maps were comprised based on classifications given in Table 2 and GIS tools. Table 1. Threshold values of different drought analysis methods Drought Index Climate 0-40 Dry Lang Semi-dry Humid 160< Very humid < 10 Very dry De Martonne Semi-dry Semi-humid 30< Humid <5 Very dry 5-10 Semi-dry De Martonne Semi-humid 20< Humid I<8 Dry 8<I<23 Semi-dry Erinç 23<I<40 Semi-humid 40<I<55 Humid I>55 Very humid 2 Very excessive humid Excessive humid Medium humid SPI 0.99-(-0.99) Normal (-1.00)-(-1.49) Medium dry (-1.50)-(-1.99) Excessive dry -2 Very excessive dry
4 Table 2. The sources and amounts of meteorological data used to examine the techniques for estimating drought analysis Longitude Altitude (m) Year No Province Town Latitude Longitude Altitude (m) Year No Province Town Latitude 1 Amasya Merkez Samsun Carsamba Amasya Aydinca Samsun Havza Amasya Dogantepe Samsun Kavak Amasya Goynucek Samsun Kolay Amasya Gumushacikoy Samsun Ladik Amasya Merzifon Samsun Samsun Amasya Saribugday Samsun Taflan Amasya Suluova Samsun Vezirkopru Amasya Tasova Tokat Almus Corum Alaca Tokat Artova Corum Bayat Tokat Bereketli Corum Bogazkale Tokat Boztepe Corum Buyuklacin Tokat Camlibel Corum Cemilbey Tokat Doganyurt Corum Merkez Tokat Erbaa Corum Iskilip Tokat Niksar Corum Kargi Tokat Pazar Corum Mecitozu Tokat Resadiye Corum Ortakoy Tokat Sulusaray Corum Osmancik Tokat Merkez Corum Sungurlu Tokat TokatTop,Su Corum Ugurludag Tokat Turhal Samsun Bafra Tokat Zile Samsun Bespinar Samsun Cakiralan
5 72 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT RESULTS AND DISCUSSION Annual average values were used, and De Mortenne, De Martonne1, Erinç drought index results were evaluated and mapped. Standard precipitation index were taken into consideration to evaluate the data of June, July and August with the highest drought possibility. Lang drought index indicates a semi-dry climate for the watershed. About 59% of the watershed was semi-dry, 35.5% was dry and 5.5% was humid. Humid parts occurred in Samsun and Tokat provinces. The driest parts were within the borders of Çorum (Figure 2). With regard to Erinç drought index, a semi-dry climate was dominant over more than half of the watershed (51%) and a semi-humid climate was dominant over 48% of the watershed. Significantly small (1%) humid part was located along the coastal part of Samsun. Based on De Martonne index, about 60% of the watershed was semihumid, 20.5% was humid and 19.5% was dry. De Martonne 1 index prevails a semi-humid climate for 89.5% of the water shed. Large part (10%) of the humid section was located in Samsun and semi-dry section occupies a small portion (0.5%) of the watershed. We evaluated Tokat, Amasya, Corum and Samsun provinces within the Yeşilirmak basin using 5 different arid indexes of geographic information systems. Results showed 86.4 % average, 12 % medium moist, 1 %excessive moist, 0.6 % middle arid in June. Results showed mostly mid-arid (82 %) conditions in July. The most arid month found to be August. Figure 1 shows the distribution of mid-arid areas. Overall, the edges of river has moist climate and as you go further away from river the climate changes to arid conditions. Yeşilirmak basin considered to have moist climatic conditions when used De Martonne arid indexes. However, most of the basin considered to have drought risk when lang, Erinc and standard rainfall indexes used by the help of GIS.
6 PRACTICES ON RIVER BASIN MANAGEMENT 73 Figure 2a. Spatial variability of drought analysis for De Martonne Figure 2b. Spatial variability of drought analysis for De Martonne
7 74 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT Figure 3. Spatial variability of drought analysis for Erinc Figure 4. Spatial variability of drought analysis for Lang
8 PRACTICES ON RIVER BASIN MANAGEMENT 75 Figure 5. Spatial variability of drought analysis for SPI
9 76 INTERNATIONAL CONGRESS ON RIVER BASIN MANAGEMENT CONCLUSION Drought has various impacts which ripple through the economy. Impacts are usually classified as direct or indirect impacts. Because of the number of affected groups and sectors associated with drought, its spatial extent, and the difficulties connected with quantifying environmental damages and personal hardships, the precise determination of the financial costs of drought is a complex task. Meteorological drought is generally defined on the basis of the degree of precipitation deficiency, compared to normal or average, and the duration of the dry period. That is why; intensity and duration are the key parameters of these definitions. Agriculture is often the first economic sector affected by drought since soil moisture supplies are quickly depleted. Agricultural drought links various characteristics of meteorological drought to agricultural impacts, especially focusing on precipitation shortages, differences between actual and potential evapotranspiration, and soil water deficits. Agricultural drought develops more quickly on sandy soils due to their lower soil water holding capacity. Plant water demand depends on prevailing weather conditions, biological characteristics of the plant, its stage of growth, and soil physical and biological characteristics. Then, a proper definition of agricultural drought should account for the variable susceptibility of crops at different stages of crop development. Hydrological droughts are often associated with the effects of periods of precipitation deficits on surface or subsurface water supply. Hydrological droughts are usually out of phase or lag the occurrence of meteorological and agricultural droughts. More time passes before precipitation deficiencies are detected in surface and subsurface water supplies. Then, impacts are out of phase with those in other economic sectors. Since water in hydrological storage systems is often used for multiple and competing purposes (e.g., power generation, flood control, irrigation, recreation), conflicts between water users increase significantly. Hydrological drought is also likely to continue long after the end of meteorological drought because of the time necessary to recharge surface and subsurface water supplies. From a realistic stand point, there is reason for optimism about drought risk management and reducing drought impacts in the future. However, it is also clear that responsible authorities around the world need to take proactive steps to develop comprehensive and integrated drought monitoring and early warning systems, to determine who and what is at risk to drought and why, and to create drought mitigation plans with specific actions that address these risks with the goal of reducing the impacts of future drought events. There is a growing perception that drought risk management is a critical ingredient of sustainable development planning and must be addressed systematically through risk-based politicies and plans [Wilhite 2003].
10 PRACTICES ON RIVER BASIN MANAGEMENT 77 REFERENCES Anonymous, Devlet Meteoroloji İşleri Gene Müdürlüğü, Ankara. ESRI, Using Arcview GIS 8.3. Environmental System Research Institute, Inc.Redlands, Calif. Hayes, M.J. and Wilhite, D.A., Drought Management. Encylopedia of Water Science Edited by B.A. Steward and Terry A.Howell. Marcel Dekker, Inc. Newyork- Basel. Ozgurel, M. and Mengu G.P, Tarımsal Meteoroloji. Ege Univ. Ziraat Fak.No:567, İzmir. Topcuoglu, K., Ozgurel, M. and Pamuk, G., Türkiye için yeni bir kuraklık indisi denemesi. Ege Univ. Ziraat Fak. Derg., 41 (3), , İzmir. Wilhite, D.A., Drought. Encylopedia of Water Science Edited by B.A. Steward and Terry A.Howell. Marcel Dekker, Inc. Newyork-Basel.