Groundwater Resources Withdrawal and Depletion Estimation Methods (Part 1: Methods Based on International Experiences)

Food and water demand have increased as a result of population growth, economic development, and dietary changes. As a result, it is imperative to consider how to manage groundwater resources under existing and possible future conditions. Methods to assess groundwater depletion and withdrawal include volume-based methods (based on hydraulic head data, remote sensing with Gravity Recovery and Climate Experiment (GRACE) and (global) groundwater models), water balance methods (based on global hydrological models and remote sensing of fluxes beside the models) and indirect geodetic or geodetic estimates. Different methods of assessing groundwater depletion and withdrawal have advantages and disadvantages. The methods based on hydraulic head data are somewhat old and if there are possible human errors in the measurement system, the uncertainty of these methods increases. On the other hand, indirect methods and the use of global models have evolved, which bring significant improvements and accuracy. However, the use of these methods depends on the existence of observational data. In fact, with the development of data collection facilities and increasing accuracy in simulation and data collection, it is possible to change the method to more accurate methods, but without having partial data, the use of these approaches is not recommended. On the other hand, this study shows that both the estimation of current depletion rates and the future availability of non-renewable groundwater in the future is very uncertain. To reduce the uncertainty in the near future, significant data and research challenges must be resolved so that the sustainability plan of groundwater resources in the country can be formulated in order to improve the sustainability program of groundwater resources considering the hydro-economics of these resources.