Humans are changing the water cycle in multiple significant ways, both directly and indirectly. Key human influences include:

• Construction of dams for water storage and hydroelectric power, which alter natural river flow, sediment transport, and aquatic ecosystems. This causes imbalances in upstream and downstream water availability and impacts plants, animals, and fish migration.
• Water withdrawals for agriculture, industry, and domestic use, which reduce natural runoff and alter evapotranspiration patterns. Irrigation, especially, moves vast quantities of water and depletes groundwater reserves.
• Deforestation, which lowers transpiration and reduces atmospheric moisture, leading to drier conditions and changes in rainfall patterns. This also increases surface runoff, erosion, and flood risks.
• Global warming driven by greenhouse gas emissions that modify evaporation, precipitation, and the timing and distribution of water cycle processes on a global scale.
• Urbanization, where paving surfaces prevents water infiltration, causes rapid runoff, flooding, and water quality degradation from pollutants.

Together, these actions disrupt the natural water balance, causing regional droughts, floods, water scarcity, and ecosystem stress. Some river basins already face water shortages exceeding those induced by moderate climate change alone due to human activities.