علی باقری

In this paper, river regime equations through developing of unit stream power equation and based on data of babolrood River were derived. For this purpose, with the review of previous research, the principles and concepts of regime and hydraulic geometry of the river is mentioned. then, methods and out-comes of former researchers are classified. On the next step, based on dimensional analysis, unit stream power as a function of river flow parameters including suspended sediment load and specific gravity of particles is developed. Using the unit stream power equation and babolrood River' data, regime equations are derived for these rivers. Finally, the results derived from regime equations are compared with the field data and regime equations of the other researchers. A good agreement was observed between field data and values resulted from developed regime equations in this research.

Manning's coefficient is one of the main factors that lead to energy loss in channels and rivers which have a very important role in water level in cross-sections of rivers. There are several methods that suggested by various researchers for estimating Manning's coefficients which are mostly based on experimental tests. In river hydraulic, flow resistance or Manning's coefficient is changing because of bed mobility. In this case, a flow resistance formula cannot be used directly without any information about changes of flow resistance coefficient, in different situations of flow and sediment processes. Babolroud- River of mazandaran selected for this study. So, results of various empirical methods obtained to find out this coefficient using field survey and characterization of rivers such as cross-sections, soil materials of river bed and banks, then results compared with observed and simulated data of river flow. According to the obtained results, koven's method, which has the lowest relative error percentages of 6.17% and 3.46%, and also the lowest root mean square error of 2.7 and 3.2, respectively, in Pashakola and Quran Talar hydrometric stations, is suggested as the best method for estimating Manning's coefficient in this river. After kowen's method, Jarrett's method with relative error percentage of 10.11% and 5.41%, and also the root mean square error of 4.5 and 4.5, respectively, is chosen as the second method for determining Manning's coefficient in Pashakola and Quran Talar hydrometric stations.

Stage -discharge rating curve is mainly developed from measured data in any hydrometry station. Measured data usually obtain in low to medium flow discharge, because in most cases it is very difficult to measure the flow discharge during flood. Therefore, the stage-discharge is extrapolated beyond the measured data to compute the flood which may estimate low or higher value. This is because during the high flow, the bed form is developed which causes the flow resistance to change. In order to establish a better stage - discharge rating curve, it is important to apply methods which consider the bed form resistance. In this research, Einstein-Barbarossa, Shen, White, Engelund and Brownlie methods were used to complete the final part of the Stage- discharge rating curve obtained from the measurement at the Ablo hydrometry station located on the nekarud river or to construct the Stage – discharge rating curve at the mentioned station. After collecting the required data including river cross section, discharge and related stage and bed material gradation in this station and calculating the corresponding Stage – discharge using the mentioned methods in the water year 2021-2022, various statistical comparisons were made between calculated and measured discharges. The results showed that the Einstein-Barbarossa method has the lowest absolute mean error of 6.9 and minimum root mean square error of 2.7 compared to other methods.

Unfortunately, at some meteorological stations, there are no facilities for measurement of some weather parameters, so, they should be estimated. Therefore, determining the correctness of the reference evapotranspiration (ETo) method by using the estimated data is very important. Based on this, the objective of the present study was to evaluate the performance of the Penman-Monteith method for estimating ETo in Mazandaran Province, Iran, when solar radiation (Rs), vapor pressure (ed) and relative humidity (RH) data are not available. Data of Sari, Qarakheil, and Amol synoptic stations were used to compare the estimated ETo by the Penman-Monteith method for the complete and limited data sets. The results showed that when RH and ed data were missing, the Penman-Monteith method was still a very good option for estimating ETo in Sari, Ghaemshahr and Amol station, with RMSE values smaller than 0.3 mm day-1. However, when Rs was missing, the Penman-Monteith method was not good enough for estimating ETo, and RMSE increased to more than 1 mm day-1. The results also showed that solar radiation was the most effective parameter on ETo estimation and both vapor pressure and relative humidity had the same effect on ETo estimation.

Because of limited water resources in Iran, decrease the water seepages and increase the water are necessary. Water productivity and the management conditions of irrigation and drainage systems shows that more attention should be paid to this subject. This research was conducted in 2019 in tajan irrigation network in mazandaran province. The losses and efficiencies of water conveyance and distribution in the water conveyance network of tajan were estimated using field measurements. Initially, 16 intervals were selected to indicate the state of the network. Field measurements were made using the inflow outflow method for each interval. All measurements on selected ranges of the channels to minimize evaporation were carried out in the early morning using a flow velocity meter with three repetitions. Then the discharge of each part of the cross section was calculated and finally the discharge of the whole section was obtained. The results show that the canals conveyance efficiencies vary between 88.2% and 99.5% and on average about 95.8% was estimated. Also, the distribution efficiency of the network has changed between 68% and 96% and on average about 77.25% was estimated. To prevent water losses in irrigation water conveyance and distribution channels, things like the growth of weeds in the channels, the accumulation of sediment in the channels, the accumulation of garbage in the channels, the cracking of the channel lining, the crushing or displacement of concrete parts in the channels, the destruction caused by poor quality of materials used, the destruction caused by executive issues, It should be controlled and fixed.

At this day and age continuous flood irrigation during the crop growth period in the paddy fields of northern Iran has caused high water consumption (WC). Due to the lack of water resources in Iran, proper irrigation management is necessary to reduce WC in different rice cultivars. Therefore, the present study was conducted to investigate the effect of irrigation management on yield and yield components of four rice genotypes.

The experiment was conducted as split plot in a randomized complete block design with three iterations at the research farm of the Iranian Rice Research Institute, Mazandaran Deputy (Amol). In this experiment, rice genotypes at four levels (G1: Toloo, G2: Tarom, G3: Tisa and G4: Shiroudi) as main factor and irrigation at six levels (I1: continuous flooding (CF) from transplanting to 20 days after 50% flowering and then cutting irrigation, I2: CF from transplanting to 15 days after 50% flowering and then cutting irrigation, I3: CF from transplanting to 10 days after 50% flowering and then cutting irrigation, I4: CF from transplanting to 5 days after 50% flowering and then cutting irrigation, I5: CF from transplanting to flowering stage and then cutting irrigation and I6: Intermittent irrigation from transplanting to 10 days before harvest and then cutting irrigation) were considered as sub-factors. At physiological maturity, the yield and yield components such as plant height, panicle length, total number of tillers per hill, number of filled grains per panicle and 1000-grain weight were measured.

The results showed that the highest and lowest grain yield were 6765 and 4255 kg.ha-1 from Toloo and Tarom cultivars, respectively. Application of I1 resulted in maximum grain yield (6291.8 kg.ha-1), while with the application of I5, yield decreased by 17.4%. Application of I6 while producing optimal grain yield (5911 kg.ha-1), can have a good ability to reduce WC in paddy fields, so it was selected as the best irrigation management option in case of water shortage for irrigation.

According to the results, intermittent irrigation from transplanting to 10 days before harvest and then cutting irrigation in rice plant in the study area will have acceptable yield in water deficit conditions and to achieve maximum yield, Toloo cultivar as a suitable genotype is suggested.

Due to the importance of rice cultivation, especially in Mazandaran Province, it is necessary to plan carefully for the optimal use of water resources in the province in the agricultural sector, especially rice, to reduce water demand for rice production. For this purpose, an experiment was conducted in the form of a complete block-design with three replications and four treatments using Tarom Hashemi cultivar, during the 2021 crop year in the Rice Research Institute of Iran-Amol. Treatments included conventional planting with flood irrigation (T1) and drip irrigation (T2), transplanting in un-puddled bed with drip irrigation (T3) and direct seed cultivation in dry bed with drip irrigation (T4). The results showed that the cultivation method was effective on yield, plant height, water consumption and irrigation water, water productivity and water use efficiency and was statistically significant at 1% and 5% level of probablity. The highest and lowest yields belonged to T1 and T4 treatments with 4079 and 2876 kg/ha, respectively, and T2 had the highest water productivity with 0.61 kg/m3, which had no significant difference with T1. The lowest water productivity belonged to T4 with 0.45 kg/m3. The highest and lowest irrigation water productivity belonged to T2 and T1 with 0.67 and 0.52 kg/m3, respectively Based on the results, conventional planting with drip irrigation did not have a significant reduction in yield compared to conventional planting with flood irrigation and increased water productivity by saving water consumption Therefore, the conventional planting method with drip irrigation was recognized as the best treatment in this study.