Using of of CR index in the optimal design of furrow irrigation by SIRMOD model

Introduction

Today, water crisis is one of the most serious concerns in the world which is increasingly leading to the growing amount of dry lands in the most areas of the world, hence saving the amount of consumptive water in agriculture which includes so heavy losses in the kind of water seems essential. Water shortage caused by population growth, climate change, industrial development and human conflicts has become a serious crisis, especially in arid and semi-arid regions. According to the Falcon Mark index and the United Nations, Iran is in a state of water stress and a severe water crisis, and this crisis can disrupt food security, economic development, public health, and the country's national security. Estimates of water consumption indicate that more than 92% of water consumption is in the agricultural sector. Therefore, efficient use of water is of high significance in this sector and the experts are constantly looking for offering solutions to reduce water losses caused by irrigation systems, particularly surface irrigation systems in agricultural sector. To this end, investigation on surface irrigation efficiency to provide appropriate solutions can reduce the loss of irrigation and increase furrow irrigation efficiency.

Materials and Methods

For this purpose, SIRMOD model was applied due to its ability to simulate hydraulic surface irrigation in order to obtain the indicator of CR (the ratio of time of cut off to advance time) then some diagrams on the basis of soil texture, inflow, farm length, and CR indicator were attained so that they can be deployed to help improve and facilitate the design of furrow irrigation systems, and also to increase the efficiency of water use in irrigation. Afterwards, in order to ensure the exactness of simulation operation and the obtained outcomes, SIRMOD model was validated; thereupon, the optimal CR indicators using SIRMOD model for furrow irrigation system with the four various lengths and soils with sandy-loam textures were achieved. After selecting a suitable field under the row irrigation system, determining the soil texture and testing double cylinders, in order to evaluate the irrigation system, field operations such as determining the forward and backward stations, smoothing the water path in the furrow to prevent water from leaving the furrow, The pipe at the end of the groove was used to determine the output runoff by volumetric method, standard and healthy siphons were selected to meet the input flow rate, and the input flow rate was determined by volumetric method. After the siphons were turned on by the farm worker, the advance time of the water to each station was noted, and after the completion of irrigation, the retreat times were also recorded Also, during the irrigation period, the amount of instantaneous runoff at the end of the furrow was estimated. This operation was done for the input flow of (0.5), (0.8) and (1.15) liters per second and three repetitions for each input flow rate.

Results and Discussion

The advanc time in the first furrow was 44.22 minutes, in the second groove 45 minutes and in the third furrow 42.88 minutes, and the water ressison times in the three furrow were equal to 293.1, 290.73 and 292.7, respectively. . Considering the relatively high speed of water in soils with a light texture and the water regression time values in all three furrows within a maximum period of 15 minutes, we realize the light texture of the farm soil and the correctness of the test results of the farm soil texture. Also, the results obtained from the measurement of the flow rate entering the furrow and the flow rate leaving the furrow during irrigation for a flow rate of 0.5 L/ According to the objective observations in the field, it took about 1 to 3 minutes for the siphon flow rate to stabilize, and after the flow rate stabilization during the irrigation period (from minute 2 to minute 279), according to the measurements, it was found that half of the water volume entered It has penetrated into the furrow along the length of the furrow and the other half of its volume has left the field as runoff. It should be noted that the input and output flows were measured by volumetric method.. the results of their simulation for inflow rate of 0.5 liter per second containing the CR, 8.37 for the length of 100 meters, 6.99 for the length of 120 meters, 5.41 for the length of 150 meters, and 3.31 for the length of 200 meters. As for the inflow rate of 0.8 liter per second, the optimal CR indicators equaled to 8.0 for the length of 100 meters, 7.25 for the length of 120 meters, 6.19 for length of 150 meters, and 4.63 for the length of 200 meters. Also, in the inflow rate of 1.15 liters per second, the optimal CR indicators were estimated for the length of 100, 120, 150, and 200 meters to be 7.42, 6.53, 6.11, and 5.06, respectively

Conclusion

The best water application efficiency in the farm, 83%, was associated with the inflow rate of 0.5 liter per second and the length of 200 meters and the CR equaled to 3.31.