Evaluating evapotranspiration Values in Rwanda while Using the FAO-56 PM, Turc and Hargreaves-Samani Equations.

Elizabeth Uwase Author

04/05/2021 Added

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This research study focuses on comparing reference evapotranspiration (ET) using the Penman Monteith FAO_56 and the temperature based methods - the Turc (Tu) and Hargreaves- Samani (HS), for the five provinces of Rwanda

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[00:00:01.710]Hi everyone.
[00:00:02.680]My name is Elizabeth Uwase and I am a senior student
[00:00:07.020]here at a University of Lincoln, Nebraska
[00:00:10.210]under the College of Agriculture and Natural Resources.
[00:00:13.400]It's been a great pleasure
[00:00:16.070]to have been part of the UCARE program
[00:00:18.370]for the year of 2020 or 2021.
[00:00:22.000]My research is about evaluating evapotranspiration values
[00:00:25.930]in Rwanda while using the FAO-56 Penman-Monteith,
[00:00:30.381]Turc and Hargreaves-Samani equations.
[00:00:34.150]The key features of my presentation today include
[00:00:37.000]an introduction, objective, methods, results,
[00:00:40.270]discussion, conclusion, acknowledgments and references.
[00:00:45.770]Rwanda is a landlocked country located in central Africa.
[00:00:49.400]And agriculture is the largest sector
[00:00:52.440]accounting for a total of 32% of GDP.
[00:00:57.210]The unique topography of the country defines
[00:00:59.460]why farming activities relies
[00:01:02.030]on a wide range of geographical landscapes
[00:01:04.660]and micro-climates.
[00:01:07.000]Rwanda highly depends on natural resources
[00:01:09.190]and it's climate variability is one of the most important
[00:01:12.820]factors that account for the country's
[00:01:15.310]year to year crop production.
[00:01:19.240]This study focuses on comparing reference
[00:01:21.800]evapotranspiration using the three equations,
[00:01:25.130]the Penman Monteith FAO-56,
[00:01:27.510]the Turc and Hargreaves-Samani
[00:01:29.080]for the five provinces of Rwanda.
[00:01:33.660]The map shows the different provinces of Rwanda
[00:01:37.120]the yellow is the Northern Province.
[00:01:45.717]The red is the Eastern Province,
[00:01:48.713]the orange is the Western Province
[00:01:50.483]and the blue is the Southern Province
[00:01:53.419]and green is for Kigali city.
[00:01:57.390]The main objective of this study is to evaluate the accuracy
[00:02:00.770]and efficiency of the three equations
[00:02:03.550]and
[00:02:05.450]to select the best simple, accurate
[00:02:08.170]and efficient method to use while calculating
[00:02:11.520]reference crop evapotranspiration
[00:02:13.460]using limited weather data by farmers,
[00:02:16.670]researchers in agriculturalists in Rwanda.
[00:02:21.010]So the climate data we used
[00:02:23.880]are minimum and maximum air temperature
[00:02:26.480]and the data was recorded for the past nine months
[00:02:30.660]by Rwanda Meteorology Agency.
[00:02:34.800]So the equations are the FAO-56 Penman-Monteith equation
[00:02:39.360]which is shown on the screen
[00:02:41.220]and the Hargreaves-Samani equation, the Turc equation
[00:02:44.180]as you can see on the screen
[00:02:45.700]those are the equations we use for the research.
[00:02:51.250]So after collecting the data
[00:02:54.300]and making calculations that were necessary
[00:02:58.460]to get reference crop evapotranspiration
[00:03:01.120]using the three questions
[00:03:03.005]data was analyzed and the graphs
[00:03:05.350]were plotted for visualization.
[00:03:08.060]And all three methods have shown to have performed well
[00:03:12.380]in some-humid and semi-arid environmental conditions.
[00:03:18.200]Below we have scatter graphs for the three equations
[00:03:23.810]showing their performances in the different provinces
[00:03:27.400]of the country.
[00:03:34.800]The first graph shows reference crop evapotranspiration
[00:03:39.580]for Kigali AERO in Kigali city
[00:03:43.470]with the Hargreaves-Samani equation.
[00:03:46.501]And the first graph shows for
[00:03:51.730]the Hargreaves-Samani equation.
[00:03:53.020]The second graph is showing for the Turc equation.
[00:03:57.220]So we're using the two equations to compare results
[00:04:02.170]and according to the graphs
[00:04:03.590]there's no difference in the results.
[00:04:07.470]Most of the results were very consistent.
[00:04:11.850]The last graph which is graph 11
[00:04:16.520]shows reference crop evapotranspiration for Kigali city
[00:04:20.560]using the Penman-Monteith equation.
[00:04:25.890]So the two graphs are comparing the performance
[00:04:28.510]of the three questions.
[00:04:30.250]The first graph
[00:04:32.390]is showing how the three questions performed
[00:04:36.130]and according to the graph the Penman-Monteith equation
[00:04:40.090]had high ET values.
[00:04:44.110]So the Turc and Hargreaves-Samani equation
[00:04:46.970]were underestimating the ET results
[00:04:53.890]for Kigali city.
[00:05:01.890]The average monthly reference evapotranspiration
[00:05:04.375]for the Turc and Hargreaves-Samani equation
[00:05:06.290]ranges from three to five millimeter per day.
[00:05:11.132]The Panman-Monteith equation had high ET in 2014
[00:05:14.760]accounting for 15 millimeter per day.
[00:05:17.860]And it's less ET values were in 2013
[00:05:21.420]with a maximum value of 7.8 millimeter per day.
[00:05:27.400]The Hargreaves-Samani graphs for all the five locations
[00:05:30.850]shows a low value of reference evapotranspiration
[00:05:33.398]between three to four millimeter per day
[00:05:37.500]for the year of 2018 compared to the previous years.
[00:05:40.880]The Turc method showed consistency in the results
[00:05:43.200]for the nine years but underestimated ET values
[00:05:46.940]compared to the Hargreaves-Samani
[00:05:48.120]and Panman-Monteith equations.
[00:05:51.880]Generally, there was consistency in the variation
[00:05:54.630]in the reference ET throughout the nine years
[00:05:57.650]for both equations.
[00:05:58.960]The Turc method underestimates reference ET value
[00:06:02.450]compared to the other two equations.
[00:06:08.170]Finally, more science and technology needs to be involved
[00:06:12.710]to account for better agriculture management decisions
[00:06:15.390]in the future.
[00:06:16.740]More recent and accurate climatic weather data
[00:06:19.790]needs to be used while calculating reference crop
[00:06:22.260]evapotranspiration to get more efficient
[00:06:25.090]and effective results.
[00:06:29.210]I would like to extend my thanks
[00:06:32.140]to people who helped me to finalize my research project
[00:06:37.290]and those people are Dr. Derek Heeren,
[00:06:41.430]Dr. Lameck Odhiambo and Sandeep Bhaati
[00:06:45.276]and Ankit Chandra.
[00:06:48.230]And thank you so much for your time.
[00:06:53.930]Bye.

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Evaluating evapotranspiration Values in Rwanda while Using the FAO-56 PM, Turc and Hargreaves-Samani Equations.

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