بررسي ارتباط بين خشكسالي اقليمي و مكان گزيني روستاها (مطالعه موردي: استان زنجان)

The relationship between climatic drought andlocation of rural areas(Case Study: Zanjan Province)

خشكسالي اثرات متفاوتي بر زندگي و معيشت انسان ها دارد. تحقيق حاضر به روش كريجينگ و با هدف بررسي ويژگي هاي خشكسالي و پهنه بندي آن در سطح استان زنجان انجام شده است تا اثرات آن بر مكان گزيني روستا بررسي شود. با اين هدف، شاخص SPI كه شاخصي اقليمي است و براي تعيين كمبود بارش در مقياس هاي زماني كاربرد دارد و مي تواند در مقياس هاي زماني اثرات خشكسالي را بر مكان گزيني روستاها نشان دهد، انتخاب شد. اين پژوهش از نوع كاربردي و رويكرد حاكم بر آن تحليلي است كه در آن با بهره گيري از نرم افزار SPSS و ARC GIS10 به تجزيه وتحليل نقشه هاي اقليمي به شيوه زمين آمار و محاسبه ضريب همبستگي پيرسون بين خشكسالي و مكان گزيني روستاها پرداخته شده است. نتايج نشان مي دهد كه مدل بهينه براي پهنه بندي خشكسالي در استان زنجان، مدل كريجينگ معمولي كروي با ضريب -تعيين 89/0 است. همچنين، 615 روستاي استان زنجان كه درحدود 256016 نفر جمعيت دارند، در خطر خشكسالي واقع شده اند. افزون براين، روستاهاي استان زنجان تمايل به مكان گزيني در پهنه هاي مناسب تر را دارند كه اين نتيجه ازلحاظ كمّي، كاهش 31 روستا و 15730 نفر به ازاي هر طبقه را نشان مي دهد. علاوه-براين، يافته ها نشانگر اين است كه بين خشكسالي با تعداد روستاهاي منطقه و جمعيت آن ها رابطه معنا داري وجود دارد كه با توجه به عدد p-value كه مقدار صفر را نشان مي دهد، ارتباط دو متغير يادشده در سطح فراتر از 01/0 معنادار است. نتايج آزمون پيرسون نشان دهنده ارتباط معنادار قوي ميان متغيرهاي خشكسالي با تعداد روستاها و جمعيت آن ها است.

1. INTRODUCTION About half of the country is located in arid and desert areas. Understanding the drought phenomenon, knowledge of resources, capabilities of an area in on hand, and providing short and long term solutions on the other hand force surface water management authorities to make necessary preparations to reduce drought losses. The scientific study of this natural disaster is one of the basic needs of agriculture planning and water resource management in arid and semi-arid climates (Mohamadi yegane, et al. 2008:267) .Climate drought as a type of drought could increase the vulnerability of rain-fed agriculture and its continuation can end in poverty of rural communities. Therefore, it is necessary to identify locations where there is high risk of climatic drought. One of the ways of identifying and location based analysis of drought is zoning operation and estimating drought in rural areas, so that one can assess the extent and severity of drought in rural areas with regard to location of rural areas. In this study, the relation between climatic droughts and location of rural areas in Zanjan province will be examined using Kriging analysis method. 2. THEORETICAL FRAMEWORK In public perception, drought is a serious deviation from the normal conditions of water resources, a deviation which calls for public reactions to reduce its negative effects. Drought depends on conditions of raining time (such as rainy season precipitation, delaying start of the rainy seasons and occurrence of rain with regard to agricultural product development) and its effectiveness (for example, number of days with precipitation and its strength). Other climatic factors such as high temperature, high winds and low humidity, frequently accompany this phenomenon in many parts of the world, and they can considerably intensify the drought (Lashti zand, 2003:14). One drought index alone cannot be used to reliably predict the onset of drought. Sometimes the use of insufficient statistics results in false and unreal estimations. For example, if precipitation is the lower than normal for a long time, the conditions are favorable for the occurrence of meteorological drought. However, a rainfall less than average does not necessarily lead to a shortage in water supply (Kaviani, et al, 1998:195). Climatic drought is usually defined based on the degree of dryness (in comparison with some average or normal values) and the length of the dry period (Farajzade, 1998: 25). 3. DISCUSSION For analysis and classification of rainfall in GIS, it is necessary to provide appropriate indicators in order to use the raster map location. In this study, an SPI index was calculated for each region based on its long-term rainfall records. The records of droughts were obtained using the SPI index and precipitation statistics for every weather station. For the analysis of data, semi-log model was used by ARC GIS10. The results show that ordinary spherical Kriging with the determination coefficient of 0/89 had the highest correlation compared to other models and was selected as the optimal model for zoning of drought .According to studies, drought zoning of the province in the south and the north east are located in severe and very severe drought zone, and a large area of the province is located in moderate drought zone. According to studies, in Zanjan province, of 1031 inhabited villages, 135 villages with a population of 75178 are in the zone of very severe drought, 150 villages with a population of 55955 people are in the zone of severe drought, 330 villages with a population of 154883 are in moderate drought zone, 264 villages with a population of 96409 are in normal zone and 152 villages with a population of 51872 are in wet zones. The results show that there is a significant relationship between drought and number and population of rural areas. The p-value of 0 indicates that the relation between the two variables in levels higher than 0/01 is significant and the results of Pearson correlation test show a highly significant relation between variables of drought, and the number and population of rural areas. 4. CONCLUSION This study investigated droughts in Zanjan province and employed zoning by Kriging method to show that drought in which parts of the province could have more damaging effects. The results show that the optimal model for drought zoning in the province is ordinary spherical Kriging model with a determination coefficient of 0/89. Studies show that approximately 256016 people in 615 villages of the province are located in the risk area of drought, which include the southern, north-eastern and central regions of the province. The rural areas of Zanjan province tend to locate in more suitable zones. This was confirmed by reduction of 31 villages and 15730 people per category.