Investigation on drought impact on the depletion of spring discharge in western parts of Iran

Karstic springs, as the main resources of rivers such as Karkheh, have encountered scarcity in the western of Iran during past years. It is necessary to consider the effects of climatic and human co-factors to prepar a rehabilitation plan in watershed scale. The present study was carried out to evaluate this phenomenon in the case of Sarab-e Niloufar, in Kermanshah Province. Two methods including Standard Precipitation Index (SPI) and Moving Average (MA) are used in this study. Four wet and dry periods were occured, including wet periods from 1980-1981 to 1997-1998 and from 2003-2004 to 2005-2006, dry periods from 1998-1999 to 2002-2003, and from 2006-2007 to 2014-2015 water years. The SPI results showed two main periods from 1989 to 2015, include 1989 to 1999 and 2000 to 2015. The first period is wet or normal, but the second period is very dry to normal and is characterized by persistence and severity of dryness. Also, the results showed that spring discharge has been stable in a-29 years period from 1969 to 1988 with fluctuations by seasonal rainfall, but a sharp decrease over the second period. The average spring discharge was 1100 ls-1 during the first period, but 337 ls-1 in the next 19 years. Other results showed a harmony period between decreasing of the spring discharge with drought cycles resulted from MA and SPI, except for the wet period of 2003-2004 to 2005-2006. Nevertheless, the spring discharge had decreasing rate in the wet period of 2003-2004 to 2005-2006. In addition, spring decreasing discharge rate was greater than rainfall. Therefore, despite the fact that the effects of drought are recognized as a major factor of spring deficit, other factors such as decreasing in water table of adjacent aquifers are also important to consider for rehabilitation of the spring.