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Estimation of Evapotranspiration Using Budget Model.

Dr. M. H. Ali
SSO
BINA

H. Paul
Graduate student
IWM, BAU

M.R. Hoque
Prof.
IWM, BAU

Abstract/ Executive Summary:

The estimation of crop water requirement is one of the principal steps in the planning, design and operation of irrigation and water resources systems. Simulation model is a useful tool to estimate water balance in the crop field. In this study, the BUDGET model is used to evaluate its performance to simulate water balance in wheat field. The simulated values fall close to 1:1 line, indicating better performance. The statistical parameters such as standard deviation (SD), standard error (SE), coefficient of variation (CV) of simulated and actual evapotranspiration values are found 21.07 and 29.23; 4.49 and 6.23; and 38.03 and 50.75, respectively. The value of Index of agreement (IA) is 0.918 which indicates a very good performance of the model. The overall statistical parameters of simulation period are in satisfactory level. Therefore, the BUDGET model is able to predict actual evapotranspiration for any level of soil moisture with reasonable accuracy. The model can be used in planning, management and operation of an irrigation project for judicial use of water with the limited inputs, especially suitable for countries where modeling of crop yield is needed under water stress conditions.

Keywords: Evapotranspiration, Water balance, Wheat, Simulation model

Location: BINA, Mymensingh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: , Water management, Water management

Objectives:

To evaluate its performance to simulate water balance in wheat field.

Methodology:

BUDGET calculates the water storage in a soil profile as affected by the infiltration of rain and irrigation water and withdrawal of water by crop evapotranspiration and deep percolation for a given period. The climatic data option in BUDGET consists of daily, mean 10-day or monthly ET₀ (reference crop evapotranspiration) and rainfall observations. At run time, the 10-day and monthly data are processed to derive daily ET₀ and Rainfall data. By specifying and selecting a few appropriate crop parameters in a menu driven environment, the program creates a complete set of parameters that can be displayed and updated if additional information is available. The soil profile may be composed of several soil layers, each with their specific characteristics. BUDGET contains a complete set of default characteristics that can be selected and adjusted for various types of soil layers. More details about BUDGET model can be found in Raes (2002) and Raes et al. (2006).

Climate input (ET₀ and Rain data)

For each day of the simulation period, the program requires information concerning the weather conditions. The climatic conditions are given by:

Evaporative demand of the atmosphere for the given weather conditions. The atmospheric demand is given by the evapotranspiration from the reference surface (ETo),
Rainfall depth, which is the amount of water collected in rain gauges installed on the field or at a nearby weather station.

The data consist of daily, mean 10-day or mean monthly ETo and Rainfall observations. Simulations can run with climatic data of a specific year, mean average data not linked to a specific year, or even with ETo or Rainfall levels than are expected with a given probability (dependable ETo or Rainfall). At run time, the 10-day and monthly data are processed to derive daily ETo and Rain data.

Source of Information: J. Bangladesh Agril. Uni. 9(2): 257-266, (2011)

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Based on the graphical display and statistical indicators, it can be concluded that the simulation model BUDGET is able to predict actual evapotranspiration with reasonable accuracy. Thus, the model can be used in planning, management and operation of an irrigation project for judicial use of water.

Knowledge Management: Journal