h. faghih

Climate change and low water use efficiency are the main reasons for reducing the water entering the Urmia Lake. Therefore, water use management via irrigation scheduling can be an effective strategy to restore this lake. This research was conducted to investigate the effect of climatic variables on water requirements, identify water-sensitive growth stages, and prepare irrigation scheduling guidelines for wheat, which is one of the main crops in the studied region. For this purpose, crop Evapotranspiration (ETc) and Net Irrigation Requirement (NIR) of wheat growth stages were estimated by computing the daily soil water balance of the root zone for a period of 32 years (1985-1986 to 2016-2017). Dividing wheat growth period into nine phenological stages was performed using Growing Degree Days (GDDs) and Zadoks scale. These stages included intervals of [Sowing-Emergence (StE)], [Emergence-Trifoliate (EtT)], [Trifoliate-Double ridge (TtD)], [Double ridge-Jointing (DtJ)], [Jointing-Booting (JtB)], [Booting-Heading (BtH)], [Heading-Anthesis (HtA)], [Anthesis-Maturity (AtM)] and [Maturity-Harvesting (MtHa)], whose mean ETc was estimated to be 2.30, 1.33, 1.03, 3.63, 4.69, 5.13, 6.53, 7.09 and 1.35 mm d-1, respectively. The mean ETc, Effective Precipitation (Eff. P) and NIR of wheat during its growth period were estimated to be 774, 349, and 425 mm, respectively. Results showed that wheat sensitivity to water stress is high from booting to maturity, is low from sowing to double ridge and from maturity to harvesting, and is moderate in other stages. Therefore, increasing the irrigation interval in the first three stages of growth and eliminating the end-stage irrigation are recommended for water saving.

Overtopping is one of the main factors responsible for dam failure. To avoid overtopping, dam is equipped with one or some spillways to release the water impounded in the reservoir. The number and size of these spillways are determined on the basis of design flood. Determination of design flood of dam spillway can be formulated as a multiobjective risk problem. This problem can be solved by Quantitative Risk Analysis Methods. Here, four economical design methods which are based on risk analysis including, United States National Research Council (NRC), US Civil Engineering, Unit Curve and Partitioned Multiobjective Risk (PMR) were studied. In order to compare these methods, Risk Analysis was performed for re-determining design flood of Pishin Dam Spillway. This Dam has been constructed on the Sarbaz River. Owing to the fact that the integrals of the expected damage relations in the two methods, i.e., Civil Engineering, and Partitioned Multiobjective Risk are analytically unsolvable, Romberg numerical integration technique and Excel software were utilized for the related calculations and drawing graphs. Also, in order to select suitable distribution, the flood analysis was done using Smada software. The findings of the study indicated that design flood determined by the three methods, i.e., Civil Engineering, National Research Council and Unit Curve was almost the same, and that the amount of flood was less than the 10,000-year-old flood while design flood determined by Partitioned Multiobjective Risk Method, was larger than the 10,000- year-old flood.