Spatial Estimation of the Risky Areas for Drainage and Salinity in Suluova Plain, Turkey Using Geostatistical Methods

Abstract

This study measured groundwater depths over the 2010 water year (from October 1, 2009 to September 30, 2010) and groundwater salinity in July 2010, when irrigation activities were most intense. Geostatistical methods were used to model variations in five groundwater properties (the highest groundwater depth (HGD), the lowest ground-water depth (LGD), groundwater depth in July (GDJ), groundwater elevation in July (GEJ), and groundwater salinity in July (GSJ), the month with the most intensive irrigation). Moreover, areas with drainage and salinity problems were determined with groundwater depths and salinity values using ordinary kriging and indicator kriging methods. Among the properties measured, GEJ showed minimum variability and GSJ maximum variability, whereas GSJ showed the shortest range of spatial variability and LGD the highest one. HGD and LGD were best described by a spherical semi-variogram model, whereas GSJ was best described by an exponential model. Measurements of the spatial distribution of the five groundwater properties using ordinary kriging indicated a drainage problem in 80.82% (7419 ha) of the research site, with groundwater depths ranging from 0.00-2.00 m in 35.24% (3254 ha) of the site. In addition, 16.11% of the research site was found to suffer from salinity problems (salinity levels above 5 dS m-1) and nearly 50% of the site was found to be on the verge of a salinity problem (salinity levels between 2.25-5.00 dS m-1). Indicator kriging was also applied and probability maps were generated giving the most exciting result. Areas with low groundwater elevations were determined to have more drainage problems.