Contents



Preface

) of

**Gabrijel Ondrasek** University of Zagreb, Faculty of Agriculture, Zagreb, Croatia

Annually, the global hydrological cycle circulates a large amount (~0.6 Mkm3

which is one of the most challenging tasks for humankind.

freshwater that is returned as precipitations (*blue and green water*) into the aquatic (~80%) and terrestrial (~20%) ecosystems, causing spatiotemporal distribution of readily available, fresh hydro-resources. The annual per capita availability of fresh water resources has sharply reduced during the last century, while over the same period water withdrawals and consumption has increased in the agri-/ domestic/industrial triangle. In the same period availability and quality of fresh (*blue/green*) water resources have been exposed to extreme pressures (pollution, population growth, urbanization, deruralization) and non-sustainable management (overexploitation, rising of *grey waters*), which, under global climate changes, further disturbs the water cycling/balance. As a consequence, global ecosystems are frequently experiencing negative water balance (-ΔW), that is, a scenario in which certain domain water inputs (precipitations, river/groundwater inflows) are substantially lower than water outputs (evapotranspiration, water abstraction, deep percolation). Although drought and aridity are not synonymous, both share –ΔW. However, while drought assumes a relatively short-term –ΔW (usually several weeks to months), that is, a temporary, recurring reduction of water level/volume/ flow in a certain domain (river, lake, catchment, aquifer), aridity implies long-term –ΔW, that is, permanent average climate condition with negative water balance. Irrespective of drought situations (hydrological, meteorological, agronomical), they jeopardize energy and food production, ecological value of certain domains, and limit *blue/green waters* for our basic needs. Thus, each particular drought type should be managed appropriately, often with costly integrative agro-hydrotechnical approaches. New and more sustainable approaches are being developed depending on environmental conditions. This book presents the most recent insights related to drought types, their detection, and their effects on food, energy, and municipal water supplies. It also examines some novel approaches to drought management,
