Model analysis for the selection of irrigation methods

Abstract

This study was conducted to arrive at a mathematical model which could be used as a rapid and easy procedure for deciding when farmers in the North East Ghor of the Jordan Valley should shift to sprinkler irrigation. This decision is to be based on both personal and national economic benefits. On a typical farm unitt the costs of surface and sprinkler irrigation were evaluated. The annual costs per dunum for surface and sprinkler irrigation were J.D. 4.711 and J.D. 7.502 respectively. The average volume of the water saved by using sprinklers was 312 m3/du per year at a cost of 8.9 fills/ m3. Considering the current water charges levied in the Jordan Valley, it was found uneconomical for farmers to shift to sprinkler irrigation on personal basis. However, the shift may be recommended on a national basis. A general model was developed from this typical case for other specific selections. This model was formulated by evaluating the separate influence of each factor involved in determining the cost of either method and was mathematically expressed as C = 8.9 (0.76 Xf + 1.00 Xs +2.38/I Xp - 1.48 L - 0.003 G) in which Xf, Xs and Xp are price indeces, L is the daily wage of labor, I is the infiltration rate of the soil and G is the volume of cut required for proper land grading. A method for estimating (G)t the land grading requirement was also developed. Expressed in cubic meters per dunum, it may be estimated by the relation G = 42 ΣDc where Dc is an easily determined topographic parameter. The model thus developed was applied on two different farm units, each having different physical conditions and under varying prices of fuel, equipment, labor and water charges. The application proved to be a rapid and easy technique for deciding on the shift to sprinklers.