 This study examined the effects of climate, soil type, and groundwater systems on hydrological droughts. It found that droughts are more common in certain climatic zones, such as the equatorial and temperate climates, compared to other climates like the arid and polar climates. Additionally, the duration of more severe droughts is shorter in the equatorial and temperate climates due to higher recharge rates. Soil type also plays a role in determining the frequency and severity of droughts. Permanently grassy soils have little effect while quicker responding groundwater systems have a greater effect. Finally, groundwater systems have a strong influence on hydrological droughts, especially in wetter climates where they can control the duration of more severe droughts. This article was authored by H. A. J. Van Lenen, N. Wonders, L. M. Talikson, and others.