مجله مدیریت آب و آبیاری
سال دهم شماره 3 (زمستان 1399)

One of the problems in coastal aquifers is seawater intrusion into fresh-water aquifers. Therefore, comprehensive knowledge and management of groundwater resources in such aquifers is very important for sustainable development. In this regard, the present study has been prepared with the aim of providing a framework for ranking management alternatives and selecting the best alternative for controlling the seawater intrusion in the Tajan coastal aquifer. Initially, the considered criteria including technical, economic, social and environmental criteria were weighted using SWARA method and their importance was determined. The results of SWARA method showed that the environmental criterion with a weight of 0.28 is more important than other criteria. Then, The COPRAS method was used to rank and select the top management alternatives. Based on the results of the COPRAS method, the alternatives of 5% reduction in pumping, 10% reduction in pumping and artificial recharge were ranked first to third. To evaluate the effect of the best alternative on salinity movement using SEAWAT model, first groundwater level changes and salinity concentration were simulated with MODFLOW and MT3DMS models, respectively. The results of the implementation of the best alternative using the SEAWAT model showed a decrease in salinity wedge movement.

Evaluating the performance of pressurized irrigation systems is one of the important strategies for managing farm water consumption. In this study, 5 sprinkler irrigation systems, 5 drip irrigation systems and 2 tape drip irrigation systems were selected for technical and hydraulic evaluation in agricultural lands of Hamedan. Evaluations were based on the Merriam and Keller method. Measured indices for sprinkler irrigation systems included Christiansen uniformity coefficient (CU), distribution uniformity (DU), potential application efficiency of low quarter (PELQ) and application efficiency of low quarter (AELQ). Also, Indicators measured for drip irrigation systems included uniformity factor (EU), efficiency reduction factor (ERF), potential application efficiency of low quarter and application efficiency of low quarter. The values of CU, DU, PELQ and AELQ for sprinkler irrigation systems were 65.6-80.1, 53.1-65.4, 31.1-55.7 and 28.3-52.5 percent, respectively. Also, the values of EU, ERF, PELQ and AELQ for drip irrigation systems were obtained in the range of 43.4 to 65.7, 0.8 to 1.3, 39.1 to 59.1 and 34.0 to 73.0 percent respectively. The results showed that in all systems the efficiencies under study were lower than expected, which can be attributed to improper design, the difference between the implemented system and the designed system, the impact of climatic factors such as high wind speed, operational problems such as the lack of adjust pressure by farmers, the use of inappropriate equipment and the lack of periodic reviews due to low levels of awareness, the lack of education and economic failures.

The use of modern irrigation methods, deficit irrigation, the use of cultivars more resistant to drought stress, are ways to increase water use efficiency in agriculture. To study the effect irrigation level and type of maize cultivar on water use efficiency in forage and grain maize production, this research was conducted at the research farm of Agricultural and Natural Resources College of University of Tehran (Karaj) in 2017. The main treatments included two levels of irrigation (100 and 80% of maize water requirement) in subsurface drip irrigation system; sub-treatments included three maize cultivars KSC704, KSC600, KSC400. Experimental design was based on split plots based on randomized complete blocks. The studied traits were forage yield, biomass, grain, water use efficiency in forage, biomass and grain production, 1000-grain weight and harvest index. The results showed that the effect of irrigation level on the measured traits was insignificant and the effect of cultivar on them was significant at both irrigation levels. The highest amount of water use efficiency in biomass production was 4.37 kg / m3 in KSC600 cultivar and the highest water use efficiency in grain production was 2.43 kg / m3 in KSC704 cultivar (with KSC400 cultivar in a Statistical group) obtained at the irrigation level of 80%. Also, KSC400 cultivar, being in the common statistical group with KSC704 cultivar, had the highest 1000-grain weight of 537.3 grams. Deficit irrigation up to 80% of water requirement using subsurface irrigation system had not any significant effect on the yield of maize cultivars.

The inverse transport problem is very difficult and challenging to solve due to some special characteristics, including the lack of solution, non-uniqueness and instability. Regarding to these complexities, usually some simplifications are made in solution process, which ultimately leads to identification methods that cannot be extended for real-world applications. This study aims to develop a practical method for pollution source identification in rivers under realistic conditions, which considers irregular cross-sections, unsteady flow and both physical and chemical transport processes. The stochastic framework of proposed method provides the possibility of estimation of source characteristics in greater time instances than available observation data as well as consideration of uncertainty due to error in those data. Considering that direct solution is also required in the solution of inverse transport problem, at first flow and transport equations is solved by finite difference numerical scheme. Then, inverse transport equation is solved to identify active pollution sources using the geostatistical method. Results of application of the method to three hypothetical examples and two sets of real data indicated the great accuracy and numerical stability of proposed method in reconstruction of source characteristics even in complicated real-world condition and using sparse and erroneous observation data. Furthermore, the identification uncertainty was considered through 95 percent confidence interval.

Estimation of Bed load transport in steep channels and mountain rivers, is important due to the complexity probabilistic processes of sediment transport and drawback of research in steep slopes. Most of bed load equations are developed for mild slope channels. Bed load transport in steep channels in additions to the effects of random properties of turbulent flow, and random distribution of grains in bed, also is affected by the steep slope. The probability of incipient motion in these channels is different form mild slope channels, and the conditional entrainment probability of them is less addressed. Therefore, in this study, a probabilistic based approach is used to develop the probability equations of the triple incipient motion thresholds of rolling, sliding and saltation on steep slopes and a probabilistic analytical model for estimating the bed load in steep slope rivers is presented based on the normal probability distribution of velocity fluctuations. Verification of the model results based on 564 experiments in slopes of one up to 20 percent, declares that the motion probability is a weighted summation of rolling, sliding and saltation probabilities. Comparing the bed load estimation in model with observed values indicates that the model with R2=0.92 and RMSE=3.52, have accurate estimation in steep slopes. The comparisons with six bed load equations in previous studies its superiority is confirmed. The main contribution of the study developed an analytical model for bed load transport in steep slopes that can used for bed load estimation in Mountain Rivers.

Estimating the exact value of reference evapotranspiration is very important in irrigation planning and determining the irrigation frequency. There are different methods for estimating the reference crop evapotranspiration. The aim of this study was to find the best combined method for estimating the reference evapotranspiration in arid, semi-arid, semi-humid and humid climates of Iran. In this study, based on different necessary data from first order weather stations in the period of 1995 to 2014, the reference evapotranspiration was calculated by some combined methods and compared with FAO 56 Penman Monteith method. The results showed that all methods except Businger and Van bavel method have a good correlation with FAO 56 Penman Monteith (R^2 > 0.96). The accuracy of Businger and Van bavel methods in all regions were low with RMSE and MAE values greater than 0.9 and 0.55 mm per day, respectively. In arid, humid and semi-humid regions of Iran, Penman 1948 and Penman Wright 1972 methods with RMSE and MAE values less than 0.39 mm per day and in semi- arid regions of Iran Penman Wright 1972 methods and Penman 1948 with RMSE and MAE values less than 0.35 mm per day had the highest accuracy.