**Preface**

Water is a crucial element on Earth for all living and non-living components. Climate change is an alarming issue for managing and sustaining life on Earth. Given climate change, water resources worldwide have been under drastically stressed conditions, as is evident from the uneven weather patterns, droughts, floods, and cloud bursts. Only three percent of the water resources on Earth are fresh, and two-thirds of the freshwater is locked up in ice caps and glaciers. Of the remaining one percent, a fifth is in remote, inaccessible areas. Much of the seasonal rainfall in monsoonal deluges and floods cannot be easily used. Only about 0.08 percent of all the world's freshwater is exploited by humankind, with an ever-increasing demand for sanitation, drinking, manufacturing, leisure, and agriculture. The ever-increasing water exploitation has intensively degraded freshwater ecosystems, notably rivers.

Furthermore, the climate extremes and water scarcity that are enhanced by climate change induce additional stress on the freshwater ecosystems and may stimulate conflicts among water users. In addition, we know that water is needed for several vital human activities, of which agricultural and industrial activities are the primary water consumers. In the context in which we observe more frequent droughts and incidences of water scarcity in the world, water systems' management requires the most advanced approaches and tools to rigorously address all of the dimensions involved in the sustainability of its development.

Therefore, this Topic Collection's main objective is to contribute to the understanding of water systems' management, and to provide science-based knowledge, new ideas/approaches, and solutions for water resources' management. Water demand for irrigation has been steadily increasing during in recent decades. However, other water users have simultaneously been competing with agricultural sectors for water resources. The conservation of freshwater ecosystems also needs special attention, such as the sufficient allocation of environmental flows. In addition, in terms of the projected climate change caused by warmer temperatures and shifting precipitation patterns, water availability is expected to decrease, and water demand to increase, in many areas of the world.

Consequently, soil productivity and, thus, crop production could be drastically reduced. These trends raise concerns highlighting the role of water and natural resources' management and their conservation to ensure the sustainability of irrigated agriculture. How well-irrigated agriculture adapts to water scarcity scenarios, particularly by increasing water use efficiency and better-estimating evapotranspiration, will directly affect the future and sustainability of the sector. The 89 papers published in this Topic Collection encompass a diverse range of critical issues and potential solutions concerning the sustainable management of water resources. We anticipate that this collection will serve as a source of inspiration for engineers, scientists, policymakers, and decision-makers worldwide, helping them to identify appropriate solutions and make informed decisions regarding their specific water-related challenges.

> **Alban Kuriqi and Luis Garrote** *Editors*
