Optimization of observation well network for the estimation of groundwater balance using double water table fluctuation method

An estimate of the groundwater budget at the aquifer scale is particularly important for the sustainable management of available water resources. Water resources are generally subjected to over-exploitation for agricultural and domestic purposes in agrarian economies like Iran. Using water table fluctuations in dry and wet seasons of a hydrological year is a reliable method for calculating the water budget. In this method, the existence of a piezometric network with careful monitoring and measurements is essential. The objective of this study was to develop a methodology for optimizing the piezometric network so that the groundwater budget could be estimated accurately. In this method the priority of each well and its effects on estimation of water budget was determined by using geostatistics. Using this analysis an optimal network could be determined. In order to demonstrate the applicability of proposed methodology, the Astane-Koochesfahan aquifer with an area of about 1173 km2 in north of Iran was selected. Fifty seven observation wells were analyzed using geostatistical methods and results showed that spherical variogram model had the best performance. It was recognized that such an optimized network provides far fewer measurement points, i.e. 33 wells, without considerably changing the conclusions regarding groundwater budget.