Answer:
A rainfall hyetograph is a graphical representation of the intensity and duration of rainfall over a specific period of time. It shows the variation in rainfall intensity at different time intervals, typically in the form of a bar graph. The x-axis represents time, while the y-axis represents rainfall intensity. The elements of a rainfall hyetograph include the time intervals (usually in hours or minutes) and the corresponding rainfall intensity values.
On the other hand, a storm hydrograph is a graphical representation of the response of a watershed to rainfall. It depicts the variation of discharge in a river or stream over time, in response to a specific storm event. The x-axis represents time, and the y-axis represents the discharge of water in the river or stream. The elements of a storm hydrograph include the rising limb, peak flow, falling limb, and base flow.
Several variables or parameters can contribute to relative differences in outlet discharge and affect the corresponding storm hydrograph:
1. Rainfall intensity: Higher intensity rainfall over a shorter duration can lead to a steeper rising limb and a higher peak flow on the storm hydrograph, resulting in increased outlet discharge.
2. Rainfall duration: Longer duration rainfall events result in a prolonged rising limb on the storm hydrograph. This leads to a slower rise in discharge and extended flooding.
3. Watershed characteristics: The size, shape, and slope of the watershed influence the response of the hydrograph. Larger watersheds tend to have longer time lag between rainfall and peak discharge, whereas steeper slopes can cause faster response times.
4. Soil type and moisture content: Soil infiltration capacity affects how much rainfall is absorbed or runs off. If the soil is already saturated or has low infiltration capacity, more water will contribute to runoff, resulting in higher peak flows and greater outlet discharge.
5. Land use and vegetation: Urban areas with impervious surfaces, such as pavement and buildings, can lead to rapid runoff compared to vegetated areas. Vegetation can increase infiltration and decrease runoff, resulting in a less pronounced storm hydrograph.
By considering these variables and parameters, it is possible to analyze the relative differences in outlet discharge and understand the corresponding storm hydrograph in a watershed.