Enrol to start learning
Reading is open to everyone. Enrolling is free, and it is what unlocks the audio lessons, practice tests and progress tracking.
9. Theissen’s and Isohyetal Methods
Estimating average precipitation over a catchment area is vital for hydrological tasks such as flood estimation and water resource planning. This chapter discusses two primary methods for estimating rainfall spatially: the Theissen Polygon Method and the Isohyetal Method. Each method's construction, assumptions, advantages, limitations, and applications are explored, highlighting their importance in accurately assessing rainfall distribution.
Sections
This section discusses the Theissen Polygon and Isohyetal Methods for estimating average precipitation over a catchment area.
The Theissen Polygon Method uses geometric divisions to estimate average rainfall based on point observations.
The Isohyetal Method relies on drawing isohyets for superior accuracy, accounting for spatial rainfall gradients.
GIS tools can enhance the accuracy and efficiency of both methods by automating processes and reducing subjectivity.
Theissen Polygon Method
A geometrical approach to estimate area-weighted average rainfall from point observations at rain gauge stations.
Isohyetal Method
A contouring technique for estimating areal precipitation by connecting points of equal rainfall depth.
Isohyets
Lines that connect points of equal rainfall on a map.
Area-weighted average rainfall
A calculation that accounts for the area of influence of each rain gauge station in determining average precipitation.
Spatial interpolation
A method used to estimate values at unmeasured locations based on values from surrounding measured points.
Practice Exercises
Total Questions
2
Estimated Time
4 min
Passing Score
70%
Instructions
- Read each question carefully
- You can use hints if you need help
- Complete all questions before submitting
1 more question available
Enrol free