Print ISSN: 1813-0526

Online ISSN: 2220-1270

Main Subjects : Irrigation


Effect of Nozzle Angel & Cyclic Pressure Head Variation on Water Distribution Uniformity for Stationary Sprinkler Systems

Esraa Ali Younis; Haqqi Ismail Yasin

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 93-104
DOI: 10.33899/rengj.2020.127209.1040

The present  research included studying the effect of the sprinkler nozzle angle and cyclic variation of the operating pressure head on the uniformity of water distribution for many sprinkler heads spacing with rectangular  and triangular sprinkler heads arrangement for different sprinkler heads. The research conducted 40 tests to measure a single sprinkler water distribution pattern under similar climatic operating conditions by adopting the water distribution pattern along a beam that represents the radius of the wetting circle which its center is a sprinkler head for different sprinkler nozzle angles (Ɵ + 5 °, Ɵ + 3.5 °, Ɵ, Ɵ -3.5 °, Ɵ -5 °) and the constant-cyclic operating pressure head conditions for different sprinkler heads. 320 patterns were found for field water distribution pattern and uniformity coefficient for four different spacing  with  a rectangular and triangular sprinkler heads arrangement for   the sprinkler heads and  the measured water distribution patterns.
The research revealed that 70% of the uniformity coefficients in the rectangular arrangement are greater or equal to its value in a triangular arrangement. The increase in the nozzle angle results in increasing the uniformity coefficient of 1.4% for each degree, an increase in the nozzle angle, and can reach 2.4% for each degree for a specific spacing, arrangement, and sprinkler head. Also, the difference between the two water distribution patterns in the case of operating with constant pressure head  and variable pressure head is slight, but it shows in the values of the uniformity coefficient, where the maximum difference reaches 10%, and in general, the best in the values of the uniformity coefficient requires determining the nozzle angle, the spacing and the arrangement of sprinkler head as well as the case of operating pressure head constant or variable.

Modelling of Wetting Front Advance and Discharge Change of Subsurface Line Source

Abdulghani Kh. Mohammed; Entesar M. Ghazal

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 84-92
DOI: 10.33899/rengj.2020.127221.1042

Sub-drip irrigation is one of the most important and the latest high-performance irrigation systems that are characterized by a high ability to reduce losses of deep percolation and evaporation from the soil surface. Twelve laboratory experiments were carried out to study the effect of soil texture, dripper depth and initial water content on the wetting pattern, dripper discharge. Further, non-linear regression approach was applied to predict empirical relationships for estimation the wetting pattern dimensions and actual dripper discharge. The results showed a significant match between the observed and estimated values ​​of the wetting front advance and the dripper discharge change. At a specific volume of water application, the size of wetting soil increased (8-20%) with the initial water content increase and (2.5-6.25%) with dripper depth increase and this size decreased (4.5-36%) with the clay content increase. The rate of vertical upward advance decreased with increasing the initial water content. The dripper discharge gradually decreased with the continuation of water application due to positive pressure increase at the dripper opening, and this decrease increased with increasing dripper depth, clay content and the initial water content of the soil.

Water Management under Deficit Irrigation

Haqqi Ismail Yasin; Entesar M. Ghazal

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 1, Pages 32-40
DOI: 10.33899/rengj.2020.126551.1011

Depending on the production function, irrigation water cost function and the sale price of yield, previously, lengthy mathematical expressions have been developed to estimate the optimal levels of water used in deficit irrigation, that would maximize yield (Wm), under water limiting (Ww), and under land limiting (Wl) and the amount of water that leads to income equal to income of Wm when land is limited (Wel), and that leads to farm income equal to farm income of Wm when water is limited Wew . Therefore, in this paper, firstly the previous lengthy expressions for (Wel) and (Wew) were simplified. Secondly, simple expressions for both (Wel) and (Wew) were derived under presence of rainfall. Thirdly, very simple mathematical relations between (Wm & Wl) and (Wm & Ww) were derived in order to determine much easier expressions than those previously derived for Wel, and Wew respectively, with and without rainfall.