Study of drought with SPI index (case study: Ghareh Chai and Karkheh basins)

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1 International Research Journal of Applied and Basic Sciences 2013 Available online at ISSN X / Vol, 4 (9): Science Explorer Publications Study of drought with SPI index (case study: Ghareh Chai and Karkheh basins) Mahtab. Safari Shad 1, Maryam.Dashti Marvili *2, Mohammad.Dashti Marvili 3 1- M. Sc. Graduate, Dept. of Natural Resource. University of Sari, Iran. 2-Hamedan Branch, Islamic Azad University, Hamedan, Iran 3- Borujerd Branch, Islamic Azad University, Borujerd, Iran *Corresponding author maryamdashti90@yahoo.com ABSTRACT: To geo location and climate condition of Iran, in recent years, some hydro meteorological problems have emerged for different parts of Iran because of Low rainfall, it s inappropriate distribution and drought. The goal of this study is the investigation of the Meteorological drought in Ghareh chaiand Kharkhe watershed in Hamadan province, location in Western part of Iran. In this study, flow and precipitation data series of hydrometric and climatology station with 37 years dataset was used. Then drought period were extracted using SPI index and the results were analyzed. Results showed that drought periods have taken place, and influenced water resources and few years were without drought, but in many years drought were occurred even for a short period. Finally assessment of SPI drought with using correlation between Runoff and SPI index show high accuracy SPI index. Keywords: Drought, SPI, Ghareh Chai watershed, Karkheh watershed INTRODUCTION Drought is a natural phenomenon which afflicts vast regions all over the world every year. According to statistics, 36 countries with a total population of 230 million are faced with chronic water shortage. There are currently 80 countries classified as arid or semi-arid, and they are home to 40%of world s population. It is estimated that 35 countries will be facing severe water shortage by the year Due to their particular geography and climate, many regions of Iran are constantly threatened by drought. Based on their origin, Hisdal et al 2000 & 2006 recognize four types of drought. These are meteorological, hydrological, agricultural, and socio-economical droughts. Droughts are measured based on a few indexes which are used to assess and monitor them within different time scales. One important index for monitoring droughts is Standard Precipitation Index or SPI. This index was developed by Mccoy et al in 1993 and is widely used in different countries including the U.S. Birdi et al (2001) used this index to compile sort-term, medium-term, and long-term monthly drought zoning maps of Italy. Brunini et al (2001) showed that using the SPI, it would be possible to quantify drought. They asserted that values obtained for this index shows very good conformity with the value obtained using water balance equations, especially when used for monthly time scales. They suggested that it would be possible through combined use of SPI and water balance equations, to adjust water shortage/surplus practices for each stage of growth of plants in a way that drought damage would be reduced drastically. In their study titled Decision Making Support System for Managing Water Resources in Romania, Adler & Anderson (2003) suggested that co-ordination between supervisory bodies and data collection systems can result in establishment of a unified water resource management system capable of making decisions which conform to meteorological predictions. Shirmohammadi et al (2002) used SPI in their study of temporal and spatial drought patterns in the Iranian province of Khorassan. They recommended the index for the monitoring of dry periods and mapping of the region s climatology. They used Krieging Model (which is a technique of spatial analysis and determination of spatial distribution of data points) to compile short term (3 months) and long term (24 month) SPI zoning maps. In their study titled Monitoring and Prediction of Drought in Eastern Iran, AshgarTousi&Alizadeh (2005) used SPI to quantify drought within different time scales and thus to investigate short-term, medium-term, and long-term drought situation. TayyebRazaei et al (2003) used SPI to study drought in central Iranian regions. They showed that in central Iran drought becomes

2 more intense to the east and it reaches highest intensity in the eastern regions of Yazd province. The current study will be dealing with drought and precipitation in Ghareh Chai and Karkheh basins of the Iranian province of Hamedan, in consideration of the very important role of these two basins in supplying water to the province. METHOD AND MATERIAL The Region under Study The current study will be dealing with drought and precipitation in Ghareh Chai and Karkheh basins of Hamedan province. The situation of these two basins (Ghareh Chai and Karkheh basins) can be seen in the map of figure1. Figure1. situation of Ghareh- Chai basin and Karkheh basin of Hamedan province, as well as other basins within Iran SPI Index Using drought indexes is one of the ways of studying droughts, and SPI is among the most widely used indexes. The index is calculated based on the probability of precipitation within certain time intervals. It can be calculated for intervals of different lengths and can be used for the prediction of future drafts and their intensities. This is a widely used index which is usually preferred to other indexes of similar use. SPI values reflect the effects of drought on water resources and groundwater as well as on soil moisture and surface water regime reasonably well. The method used here involves compiling the statistical distribution of precipitation data and transforming the distribution into the normal curve, in a way that the mean value of SPI would be set at zero. Precipitation data points greater than the mean are then assigned positive values and those smaller than the mean assigned negative values. Using the index, we can give a year or a particular time interval of any given length that any given starting point a precipitation rank reflecting the local climate condition of the time of the interval (Amin Alizadeh, 2007). Here we have used an interval of one year (which is a regularly used hydrological cycle length) for the calculation of SPI. Calculation of the values of the index was done using the following formula:

3 Equation 1 Here n is the number of months for which the accumulated precipitation is calculated; P0 is the normalized amount of precipitation of the current month, P iis the normalized amount of precipitation of the previous month; µn is the mean accumulated precipitation of the nth month; and on is the standard deviation of the precipitation values. Table 1. SPI index values and the drought intensity Climate situation SPI value Intensely moist 2 Very moist 1.5 x 1.99 Moderately moist 1 x 1.49 Low moisture 0 x 0.99 Borderline drought x 0 Moderate drought x -1 Severe drought x -1.5 Intense drought x -2 To determine the climate condition based on this index, we would notice that the drought has already set in when the value of the index is -1 or lower and it would persist up to the start of the interval for which the value of the index is calculated at 1; from which point we have entered a moist period. RESULTS AND DISCUSSION A Review of Alternation of Moist and Dry Periods inghareh Chai and Karkheh Basins of the Iranian Province of Hamadan As pointed out earlier, we have used SPI to get a picture of the alternation of moist and dry periods in the region under study. Figures 2 and 5 shows that the variation of the index over a 37 year spans from 1971 to A study of these figures and table 1 tells us that the periods and were intense dry spells for Ghareh Chai and Karkhehbasins respectively. We can also see that the drought persisted through subsequent years, albeit with less severity. Figure 2 and table 2 show negative values of the index for Ghareh Chai basin for the periods , , , , , , , , , , , , , ; and positive values for the periods , , , , It is evident from table 2 and figures 2 and 5 that the periods and constituted the onset of drought in Karkheh and Ghareh Chai respectively, and the onset of drought in Karkheh preceded that of Ghareh Chai by about 6 years. Values of the index for Karkheh basin were negative for the periods , , , , , , , , , , , , , , , and , and there has persisted a prolonged drought there. Considering the figures and the table, it can be asserted that the drought is a clear and present danger to agriculture there which can recur time and again at short intervals. Few droughts have been followed by moist periods in these two basins and this is an indication of how precarious the conditions are in these basins. Take a closer look at figures 3 and 6 for a better grasp of the situation. A Study of the Effect of Drought on River Debitsin Ghareh Chai and Karkheh Basins Investigation of changes of the volume of runoff (also called the flow ) of rivers in the two basins shows a steep downward trend readily indicative of the already severe effect of drought. This calls for effective and comprehensive management of water resources there (figures 3 and 6). The downward trend is more severe in the case of Ghareh Chai River. Correlation analysis of runoff data of each river against the obtained SPI values for the same river basin is indicative of high accuracy and reliability of the index (figures 4 and 7). Other studies have arrived at a similar conclusion regarding the accuracy of SPI.

4 Precipitation period Table 2 SPI Results for the Rivers Ghareh Chai and Karkheh Runoff (Million Cubic Meters) Yearly SPI Ghareh Chai Karkheh Ghareh Chai Karkheh Figure 2. pattern of changes of SPI value for Ghareh Chai basin during the studied 37 year span

5 Figure 3. pattern of changes of runoff volume (or flow volume) for Ghareh Chai basin during the studied 37 year span Figure 4. correlation between SPI values and runoff volume (or flow volume) for Ghareh Chai basin during the studied 37 year span; the lower curve was compiled through linear regression and the upper one through exponential regression Figure 5. pattern of changes of SPI value for Karkheh basin during the studied 37 year span

6 Figure 6. pattern of changes of runoff volume (or flow volume) for Karkheh basin during the studied 37 year span Figure 7. correlation between SPI values and runoff volume (or flow volume) for Karkheh basin during the studied 37 year span; the lower curve was compiled through linear regression and the upper one through exponential regression. CONCLUSION Water shortage resulting from droughts may become a food security issue and even a food security crisis if appropriate measures are not adopted and effective management of water resources is not put in place. Permanent rivers may turn into seasonal rivers and these into temporary rivers if there is prolonged and persistent drought. As a river s flow volume decreases, its water becomes more brackish and saline and more and more contaminated with toxics, microbes, and chemicals (Kardavani 2001). This is just happening to Ghareh Chai River. Flow curves which will be presented in the next research article (titled the Environmental Imperatives of the Ghareh Chai basin ) indicate that it has already become a seasonal river. Drought indexes present one effective way of predicting such events. Using these indexes, it would become possible to predict the intensity of the coming drought and put in place the appropriate preventive measures. Such measures may differ from region to region since they are determined, to a very large extent, by a region s physiographic situation and its climate. SPI values obtained for the two studied basins are indicative of their precarious situation regarding the supply of water. Hence it is imperative that the drought is alleviated and its consequences contained. Considering the studies conducted on the collection and preservation of water during droughts, and considering the conditions at the two studied basins, using permeable water collection surfaces seems a good idea. We recommend that such water collection

7 surfaces are contrived in the two basins and surface waters are collected and preserved during winter and spring for later use during dry seasons. While preserving the water needed to sustain agriculture, the measure can prevent irredeemable losses normally brought about by droughts. This can be a step in the right direction with respect to realization of the country s long term agricultural goals. In their article titled Drought Management and Planning in England and Wales, Denet and Atess (1999) discuss the framework and methods used in the management of droughts in England and Wales. The authors suggest that high population density and valuable resources of these territories have resulted in an effective and accurate resource management being put in place. They consider the following steps necessary in attaining to an effective drought management system: drought planning, content of a drought plan being compiled and prepared, appropriate regulations being in place, effective communications being in place. REFERENCES Adler Mary-Jeanne Glen D A Decision support system for integrated water management in Romania: recent development and future plans. Alizadeh A Application of a hydrological principles (edition 22) Institute Quds Razavi Press and Publishing, 804 p. Ashgr Toosi Sh, Alizadeh A "Drought monitoring and forecasting of the East Iran ', dryness and drought, agricultural magazine, No. 16. Pp Bordi I, Frigio S, Parenti P, Speranza A, Sutera A the analysis of standardized precipitation index in the Mediterranean area: large-scale patterns. Annali di Geofisica. Vol 44. pp ( Bronini OHS. Pinto Jr MT, Barbano MBP, camargo RR, Alfonsi GC, Blain MJ, Pedro Jr GQ, Pellegrino ND Drought quantification and preparedness in Brazil- the example of Sao Paulo state. ( 22 august Dent J, Glenn W Drought planning and management in England and Wales maintaining public water supplies, Department Of Environment, Transport and The Regions and The Welsh Office. 11 p. Hisdal H, Tallaksen LM, Randen F Regional low flow and drought Frequency analysis. Geophysical Research Abstracts. Vol. 7, l083 Hisdal H, Tallaksen LM Drought event definition. Technical Report to the ARIDE Project No.6 Kardavani P "Drought And The Contronting Way With it at Iran "Publications of Tehran University, Iran. Shir Mohammadi R, Kohi M, Golmakany T, Davoodi N "Application SPI in study spatial and temporal patterns of drought in the Khorasan province. "Bulletin of the Institute of Scientific Climatology". C. 2. No. 4. Pp T- Colleagues Rzyyy "Monitoring Phenomenon Drought At Central Iran With Use SPI Index " Third, this Conference Area and First Conference National Climate - Isfahan University, Iran.