Final answer:
The variability of water in a drainage basin is influenced by precipitation, the dynamic water table, land use, soil characteristics, and climate changes, which all affect the hydrologic cycle and river discharge.
Step-by-step explanation:
The amount of water in the drainage basin varies over time due to several factors that affect the hydrologic cycle and river discharge. First, precipitation patterns have a significant impact, with rain and melted snow entering rivers through surface runoff and groundwater seepage. Following heavy rain, river discharge often spikes due to increased runoff. Conversely, the base flow, or normal flow, of a river is predominantly maintained by groundwater sources. Secondly, the water table, an important component in this cycle, fluctuates with the topography and is dynamic in nature - it rises during wet periods and falls during droughts, affecting the discharge into rivers and streams.
Additional elements such as vegetation cover, land use, and soil characteristics influence how much precipitation is absorbed versus immediately running off. Human activities, like intensive cultivation, can alter the natural water retention capacity of soil, potentially leading to enhanced runoff and flooding events. Finally, changes in climate, such as increased storm frequency and altered precipitation timing and type, also contribute to the variability of water within drainage basins.
SUMUP of key points: