Spatiotemporal geostatistical modeling of groundwater in arid region
during dry and wet seasons: a case study The Experimental Station at
Hadat Ash-Sham Farm, Saudi Arabia
Abstract
Saudi Arabia lies in an arid region where groundwater has become main
resource. Due to the increase of water demand; therefore, it is
essential to understand groundwater dynamics for the best groundwater
management practice in Saudi Arabia. In Hadat Ash-Sham Farm Experimental
Station, Saudi Arabia, water table data from 11 wells and rainfall data
were monitored for 16 months. These water table data is analyzed using
the geostatistical method with ordinary Kriging technique, to generate
the best water table spatial distribution map for each month and the
expected flow direction. The cross-validation technique is used to
evaluate the quality of the developed water table maps. The Kriging maps
show two regimes: weak spatial dependence (WSD, the ratio of the nugget
to sill >75%) and strong spatial dependence (SSD, the
ratio of the nugget to sill <25%). The WSD regime happens
during dry seasons, while the SSD happens during wet seasons. The SSD
gives better results and better accuracy compared to WSD. The
root-mean-square error (RMSE) of water table varies between 0.26 – 3.4
m in the case of SSD, while it varies between 0.51-4.8 m in the case of
WSD. Water table maps show groundwater flow direction in the study area
is from East to West and South-East to North-West during the wet season
(SSD). This direction is parallel with the relative orientation of
surface stream with higher elevation to the surface stream with lower
elevation, where study area is between these surface streams. While
during the dry season (WSD), there is no preferred direction since there
is almost no flow.