Comparison of kriging and cokriging for the geostatistical estimation of specific capacity in the Newark Basin (NJ) aquifer system.

Groundwater is a major water source in New Jersey; hence, accurate hydrogeologic data are extremely important. However, most measured data have inadequate spatial density and their locations are often clustered. Our study focuses on implementing geostatistical methods to generate the spatial distribution of specific capacity over the Newark Basin in New Jersey. Two geostatistical methods, ordinary kriging and cokriging, were employed and compared. Ordinary kriging was employed to estimate the spatial distribution of specific capacity by using measured values. Cokriging incorporated the spatial variability of fracture density into the estimation with the spatial variability of specific capacity, as groundwater flow in fractured rock aquifers depends on the fracture characteristics in the Newark Basin. Results indicate that cokriging manifested substantial improvements over ordinary kriging including a larger areal coverage, a more detailed variation of specific capacity, and reduction in the variance of its estimates.