together these regions accounts for about half of total groundwater depletion in the united states since scanlon et al as shown in figure both systems have been subject to serious groundwater overdraft with water tables lowered by up to fifty meters or more for some portions of the aquifer during the studied period however figure shows that the reduction in water levels depends on the location within the affected areas similarly in california the southern san joaquin sj and tulare t counties are the main hotspots for groundwater level reduction while the northern part of the valley with better water endowment and surface water is not really subject to groundwater depletion