Correct Answer - Option 1 : linear
Explanation
Isohyetal Method:
- It is used to estimate the average precipitation across an area by drawing lines of equal precipitation.
- Isohyets are contours of equal precipitation analogous to contour lines on a topographic map.
- In this method, precipitation values are plotted at their respective stations on a suitable base map and Isohyets are drawn to create an Isohyetal map.
- While constructing isohyets, it is assumed that rainfall between two stations varies linearly unless abrupt changes in topography indicate otherwise.
- The following formula can be used to calculate the average precipitation using the Isohyetal method –
Mean precipitation for a catchment \(̅ p = \frac{{{\rm{Total\;volume\;of\;rainfall\;}}\left( {\rm{V}} \right)}}{{{\rm{Total\;area\;of\;catchment\;}}\left( {\rm{A}} \right)}}\)
\(̅ p = \frac{{\mathop \sum \nolimits_{i = 1}^n {A_i}\frac{{({P_i} + {P_{i + 1}})}}{2}}}{A}\)
