Intermittency as an indicator of drought in streamflow and groundwater

Under normal precipitation conditions, increasing water demand causes groundwater level to deplete and streamflow to decrease. This results in more frequent intermittency. The so-called intermittency cycle hypothesis is examined in this study. It is a vicious circle in hydrology making both surface and groundwater resources less efficient in supplying ever-increasing water demand. To test the hypothesis, a data-based analysis is applied to Gediz, Kucuk Menderes, and Ergene river basins in western Turkey. Results at basin- and station-scale show no change in precipitation while streamflow fluctuates with a tendency to decrease and groundwater steeply declines. Groundwater is used excessively to meet the drastically increased water demand. With the overuse of groundwater, water table descends, streamflow decreases and intermittency increases. Intermittency ratio of a river is found related to the decrease in streamflow and the drop in groundwater level. It can trigger drought in streamflow and groundwater. It is concluded that intermittency can be taken as a quantitative indicator of drought in streamflow and groundwater.