Investigating the Spatial and Temporal Variation of Groundwater Quality Applying the Best Geostatistical Estimation (Case study: Kerman Plain)

Recognizing of critical zones of groundwater quality is one of the most important issues about researches in water fields. The goal of this study is to determine the spatial and temporal variation of groundwater quality factors such as electrical conductivity and chloride ion contents using the best suited geostatistical estimation in Kerman plain on 10 years period (1996-2006). Also, the best variogeram model and parameters related to model of EC and Cl contents will be determined. Findings of variography analysis for Cl contents of groundwater quality data in the beginning and the end of study period showed that the exponential structure is the best spatial model fitted to this parameter. Thus, its effect range increased from 101700 to 106200 meter and sill contents decreased from 2.246 to 1.698, during 1996 to 2006. The best model fitted to electrical conductivity spatial structure became exponential in 1995-1996 and spherical in 2005-2006. The results of geostatistical analysis show that effect range and sill contents of EC decreased from 79800 to 37500 meter and 0.84 to 0.608, during 1996 to 2006, respectively. Comparing of interpolation methods of groundwater quality data introduced log kriging method as the best approach for Cl and EC zonation maps. Cl zonation maps show an increasing trend of Cl content in all plain areas in 10 years period. Thus, Cl concentration in the input region of plain increased in the range of 3.03-13.01 in 2006.Intensity of Cl content occur in north outlet of plain near well numbers 27, 28, and 33, and Cl critical core of western south of plain near well number 19 show an increasing trend. Our findings showed an increasing in EC content, especially its spatial spreading in west and north outlet of Kerman plain and Kerman city in 10 years period.