JWSS - Journal of Water and Soil Science

The irrigation and drainage network of Zarrinehroud with an area of 65,000 hectares is the most important network of Lake Urmia basin, with the direct link to the lake. With the current crisis in the lake, an assessment of the existing network's performance is essential in the Urmia Lake Rescue Program. The purpose of this study was, therefore, to evaluate the transmission, distribution, and utilization efficiency and irrigation efficiency at the surface of the network. Three products were selected from the cultivar with the highest crop area (10% beet, 22% and 22%, and 38% wheat). The dominant method of irrigation was surface irrigation. At the network level, soil moisture in the field before and after irrigation, soil physical and hydraulic properties and water use volume for irrigation were measured. The results showed  that the average transmission efficiency in canals with the concrete coating of the network was about 79%, which was  in the range of 33% (in the  smaller channels) to 100% (in the  larger channels). The water distribution efficiency in the network was, on average, 76%, varying from 50% to 100%. Water use efficiency in the fields based on soil moisture balance analysis varied from 41% in the sandy loam soils to 66% for the clay texture. Based on the analysis of the data on the amount of harvest, production costs and product sales price, the water use efficiency (in kilograms of product per cubic meter of water used) varied from 0.4 for the  elderly hay to 5.1 for the  sugar beet. The amount of water used in this network (in Rials per cubic meter of water consumption) was between 2740 for alfalfa aged over 10 years and 6900 for wheat. It can be concluded that in the case of water constraints, wheat, sugar beet and alfalfa could be the most economic cultivar, respectively.

Integrated simulation of water resources systems is an efficient tool to evaluate and adopt various options in macro-policies and decision-making procedures that are in line with the sustainable development of drainage basins. One of the drainage basin management policies is to enhance the efficiency of agricultural land use. Considering the complicated function of the drainage basin elements and their interaction with each other due to water discharge fluctuations caused by various factors such as climate change, the evaluation of these policies is of great importance. Given the low irrigation efficiency in Iran, the present study was aimed to evaluate the effects of management scenarios (including long-term irrigation efficiency increased up to 20% with 5% intervals) and discharge fluctuation scenarios (including 5% and 10% decrease in the average basin inflows) on the reliability and vulnerability of water resources system in Dez Basin. The integrated scenarios were simulated in the WEAP model. The scenarios were separately simulated for the Dez irrigation network and all farmlands across Dez Basin. According to the results, reliability was decreased by 5.69 and 18.89% in the scenarios with 5% and 10% decrease in the average basin inflows, respectively. Furthermore, the irrigation efficiency of 20% in the scenario considering the current inflows ended up with the reliability of 73.58%. Moreover, in the scenario involving 5% decrease in the average basin inflows, the reliability was increased by 3.8% with an increasing efficiency of 20%; with 3.8% and 5.7%, there was an increasing efficiency of 15% and 20% in all farmlands, respectively. In the scenario consisting of 10% decrease in average basin inflows, the reliability was increased by 1.91%, 3.8%, and 5.7% with the increasing efficiency of 10%, 15%, and 20%; on the other hand, with, these were 3.8% 9.46%, and 13.2% with increasing efficiency in all farmlands, respectively. In all scenarios, the vulnerability was found to fluctuate between 25% and 31%, which was systematically analyzed.