Water-energy nexus: A systematic analysis and evaluation of a center-pivot irrigation system

Water-energy nexus plays a crucial role in addressing the issue of water wasting as well as planning, developing, and optimization of the agricultural product irrigation demands. The objective of this paper is to improve the water and energy use in value crops irrigated by center pivot systems under conventional irrigation planning in southern Algeria. This study is based on the field evaluation of the real water and electrical energy consumption, in two types of center pivot systems, large pivots and traditional Mini-Center Pivot Systems in two different areas (Ouargla and El Oued). Over two years, irrigation campaigns on six pivots systems with six different crops were analyzed to evaluate and characterize their water and electrical energy use. The CROPWAT model was used to determine the crop water requirements and compared with the water volumes currently applied by conventional irrigation planning. The results showed that there was over-consumption of water followed by high electrical energy use due to the poor planning of irrigation, which was generally excessive. In addition, the amount of water applied by conventional irrigation planning and that estimated by CROPWAT do not coincide during the most stages of crop growth. Closer inspection of the results shows that the irrigation water use efficiency for different crops was low and ranged between 0.25 and 3.27 kg/m(3) due to the Over-irrigation. Furthermore, the modern pivots presented the most efficient equipment in terms of Energy Use Indicators with 1.1 kW ha(-1) while the average of the traditional mini pivots was four times more (4.15 kWh(-1)). No significant difference was evident between the present specific consumption Es (in the average of 0.274 kWh m(-3)) and those reported in the literature due to high power installed in the pumping station for Mini-Center Pivot Systems. Therefore, the study findings are expected to draw the attention of decision-makers to the extent of wasting water and energy. Also, these findings reveal the harmful effects of farmers' incorrect irrigation practices and motivate them to take strong measures toward sustainable agriculture.