Sensitivity analysis of selected methods predicting reference crop evapotranspiration | |
| Author | Arif, Muhammad |
| Call Number | AIT Thesis no.WA-87-4 |
| Subject(s) | Plants--Water requirements Evapotranspiration |
| Note | A thesis study submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Abstract | A reliable estimate of crop water requirements is one of the key design criteria required for the planning, designing and operation of irrigation schemes. This in turn requires accurate estimation of reference crop evapotranspiration for which a variety of equations are widely used. The sensitivity analysis of 5 selected methods was conducted. Sensitivity coefficients were computed by approximating the derivatives by finite differences. A sensitivity coefficient (relative sensitivity) ∆ET○ / ∆Xi *Xi /ET○ was calculated to compare the relative importance of the different input variables. The sensitivity coefficient defines the change in computed ETo due to change in the variable. The mean monthly sensitivity coefficients were determined by applying 10 years data (1974-983) obtained from agrometeorological stations of Thailand. Annual graphs of the mean monthly sensitivity coefficients of input variables showed their seasonal trends, reflected their changing relative importance to the computed ETo values and variation both with time and space. The sensitivity analysis indicates that the Penman method appears to provide more realistic estimates of the importance of the various climatological factors. The Jensen-Haise method is more sensitive to temperature as compared to other methods. The results indicate that the sensitivity coefficients of input variables exhibit the same seasonal trend at all stations except Kho Hong. The results also show that there is less variation in the sensitivity coefficient values of temperature over Thailand and high variation for the values of wind velocity. A technique is also proposed for the preference of a method for a region with homogenous climatic conditions. |
| Year | 1987 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Structural Engineering (STE) /Former Name = Structural Engineering and Construction (ST) |
| Chairperson(s) | Loof, Rainer |
| Examination Committee(s) | Nielsen, Steen Asger ; Paudyal, Guna N. |
| Scholarship Donor(s) | The Government of Australia |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1987 |