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Showing 1 results for Sen’s Slope Test

Dr Hamid Ghorbani, Dr Abbas Ali Vali, Mr Hadi Zarepour,
Volume 6, Issue 2 (9-2019)

Drought is one of the most complex and unknown natural phenomena that causes a periodic water crisis in the affected areas. Increasing water demand on the one hand and the experience of droughts in the province in recent years have led to the water crisis. Knowing the drought is one of the requirements for water crisis management. The purpose of this study was to analyze the trend of the SPI drought index in Isfahan province using nonparametric Sen’s slope test, Pettitt’s change point test and Man-Kendall test. From the monthly climatic data of 10 synoptic stations with a length of 27 years (1990-2017) for time series    The results of applying  Mann–Kendall  and  Sen’s slope tests based on SPI Index for  9, 12, 18, 24 and 48 month time periods, shows drought trend is significantly increasing for all stations out of Ardestan, Esfahan and  Shahreza  stations. In Ardestan station, the drought trend is significantly decreasing for 9, 12, 18, 24 and 48   month time periods and in Isahan station, the drought trend is significantly decreasing for only 48 month time period, and in Shahreza statition, the drought trend is significantly increasingonly for only 18 month time period.
  Despite all stations, the drought trend for one month time period, is significantly increasing just  for Naein station.
   In addition, applying Mann–Kendall test  on monthly rainfall for all station  shows downward but  not significant trend.
   Finally, applying Pettitt’s change point test based on SPI  Index  for 9, 12, 18, 24 and 48   month time periods indicates  the existence of a  significant change point. For same periods we observe  no change point for the monthly rainfall  in all stations.
   In summation, considering the SPI drought index, about 59% of  all stations show significant downward trend bases on Mann-Kendall test and 60% of  all stations show significant slope  based on Sen's slope test and 75% of  all stations show significant change point based on Pettitt's test. In general, for drought analysis using different time periods for the SPI index, in a short time period. (such as 6 months) drought is more frequent but shorter, and as the period increases the duration of drought also increases but frequency decreases. All together, we are facing  a water crisis in Isfahan province and  we must manage water demand  very urgently.

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