ABSTRACT
Low streamflow conditions occur around the world are becoming more frequent and have considerable economic, societal, and environmental impacts. As one of the most important indicators of drought, the factors that affect low flow include rainfall and snowmelt (climate change), land use/land cover, geological characteristics in the watershed, the groundwater flow recharge, the stream’s geometric characteristics, and human impacts. The possible environmental effects due to low streamflow are increased water pollution and sedimentation, and elevation of water temperature, which eventually lead to an unhealthy riverine ecosystem. To address the water quality issue under low-flow conditions, water quality criteria and critical low-flow conditions are defined. The characteristics of low streamflow and its effect on stream water quality are addressed. The low flow estimation methods at gauged and ungauged streams are described. Finally, environmental flow assessment methodologies are introduced.
