What factors influence river discharge and flow?

River discharge and flow are influenced by factors such as precipitation, evaporation, transpiration, and the physical characteristics of the river basin.

Precipitation is the primary source of water in rivers. The amount, type (rain, snow, sleet, etc.), and distribution of precipitation over time can significantly affect river discharge and flow. For instance, heavy rainfall can lead to a sudden increase in river discharge, a phenomenon known as a flood. Conversely, prolonged periods of low precipitation can result in reduced river flow or even drought.

Evaporation and transpiration also play a crucial role. Evaporation is the process by which water changes from a liquid to a gas or vapour, reducing the amount of water available for river flow. Transpiration, on the other hand, is the process by which water is carried through plants from roots to small pores on the underside of leaves, where it changes to vapour and is released to the atmosphere. Both processes can significantly reduce the amount of water available for river flow, especially in hot, dry climates.

The physical characteristics of the river basin, including its size, shape, geology, vegetation, and land use, can also influence river discharge and flow. Larger basins can collect more water and therefore have higher discharge rates. The shape of the basin can affect how quickly water flows into the river; a long, narrow basin will collect water more slowly than a short, wide one. The geology of the basin can affect how much water is absorbed into the ground and how much runs off into the river. Areas with permeable rocks or soils will absorb more water, reducing runoff and river flow. Vegetation can slow down runoff and increase evaporation and transpiration, reducing river flow. Finally, human activities such as deforestation, urbanisation, and agriculture can alter the physical characteristics of the river basin and therefore affect river discharge and flow. For example, deforestation can increase runoff and river flow by reducing evaporation and transpiration, while urbanisation can increase runoff and river flow by creating impermeable surfaces that prevent water absorption.