The
performances of five empirical models, namely: Hargreaves-Samani, Makkink [1],
Makkink [2], Priestley-Taylor and FAO 56-PM in estimating reference
evapotranspiration (REF-ET) were separately compared with Epan data and FAO
56-PM, respectively. The predictive perBased on statistical analysis,
Hargreaves-Samani method compared best with daily and monthly Epan data, while
Makkik2 (1984) ranked first with FAO 56-PM. In terms of regression analysis,
Priestley-Taylor performed best with daily FAO 56-PM method while
Hargreaves-Samani ranked first with daily Epan data. Hargreaves-Samani also
correlated best with mean monthly Epan data. The quantitative evaluation of
cumulative daily and monthly reference-evapotranspiration (RET-ET) values
showed that Makkink [2] produced the least overestimation and percent relative
error against FAO 56-PM while Hargreaves-Samani performed best with Epan data
with the least overestimation and percent relative error. In terms of
cumulative monthly ETo totals for the farming season (Dec-April) over the study
period, Hargreaves-Samani ranked best with Epan data with the least
overestimation and percent relative error while Priestley–Taylor ranked best
with FAO 56-PM producing the least overestimation. Overall, Hargreaves-Samani
with its original coefficient was adjudged best, capable of approximating FAO
56-PM and Epan data in the Lower Niger River Basin, followed by Makkink [2] and
Priestley-Taylor. Penman-Monteith estimates were used to develop monthly
correction factors for adjusting Empirical models for their potential use in
Lower Niger Basin. A comparative study such as this has not been undertaken in
the Lower Niger River Basin. The models recommended in this study are
economical, lesser-data demanding and can be applied to predicting REF-ET in
remote agricultural areas. In other to create more computational skill in the
subject matter a number of illustrative example problems are presented in
Appendixes B and C, manually solved for easy comprehension.
Author(s) Details
Itolima Ologhadien
Department of Civil Engineering, Rivers State University of Science and Technology, Nkpolu, Port Harcourt, Nigeria.
Professor Ify L. Nwaogazie
Department of Civil and Environmental Engineering, University of Port Harcourt, Nigeria.
View Book :- http://bp.bookpi.org/index.php/bpi/catalog/book/176
Author(s) Details
Itolima Ologhadien
Department of Civil Engineering, Rivers State University of Science and Technology, Nkpolu, Port Harcourt, Nigeria.
Professor Ify L. Nwaogazie
Department of Civil and Environmental Engineering, University of Port Harcourt, Nigeria.
View Book :- http://bp.bookpi.org/index.php/bpi/catalog/book/176
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