Journal of Irrigation and Water Engineering
Year:2017 | Volume:7 | Issue:28 |Papers Count:12

Nowadays piano key weirs (PKW) are widely used in many projects, because, in comparison to linier weirs, they have high discharge capacity and more storage volume of dam reservoir. The piano key weirs performance reduce in high discharges, so this research investigate the various combinations of interrupted non-sloped and sloped parapet walls on the piano key weirs performance. It is used an experimental flume to do research. By using analytical integration method, the results show that they improve the weir performance about 35 percent, when the 4.5-centimeter-hight non-sloped parapet walls were on the weir's side crest, while setting non-sloped parapet walls on the whole of the weir crest increase it about 14.8 percent. In addition the sloped parapet walls improve the weir performance. According to this method, the results show that the discontinued parapet walls improve the weir performance. Finally, by SPSS software, two equations were developed for the piano key weirs discharge coefficient with sloped and non-sloped parapet walls. For non-sloped models, these equations have respectively regression coefficients, measuring error index, RMSE, and MAE about 0.783, 0.048 and 0.03, but for sloped models, they are about 0.941, 0.03, and 0.025.

In this paper, the Nearest Neighbor Algorithm has been applied to predict cavitation damage on dam spillways. In this research, based on flow velocity and cavitation index, five different damage levels from 'no cavitation damage' to 'major cavitation damage' have been determined.The hydraulic characteristics of flow over the Shahid Abbaspour dam spillway were calculated for different flow rates. Then, the Nearest Neighbor Algorithm has been applied to predict cavitation damage levels and locations on this dam spillway for different flow rates.Comparison of the model results with the observed damages occurred during past floods on this spillway structure, shows that this algorithm predict damage levels and locations appropriately.Finally, the efficiency and precision of the model results have been evaluated by some statistical coefficients. Appropriate values of the correlation coefficient (r=0.896), the Mean Absolute Error (MAE=0.101), the Root Mean Square Error (RMSE=0.108) and Efficiency of model (EF=0.813) confirm that the present model can be suitable and efficient.

Stilling basins are the most common structures for energy dissipation downstream of spillways. A properly designed stilling basin can ensure 60-70% dissipation of energy in the basin. The purpose of this study is to evaluate the performance of perforated end sill and effect of the sill on characteristics of hydraulic jump. The perforated sills with different heights and four ratios of opening 12, 25, 50 and 75% were tested for three tail water depths. Results of experiments confirmed significant effect of the perforated sill on dissipation of energy, reduction of the basin length and reducing dependence of jump location on tail water depth. Based on experimental observation, in a constant Froude number, decreasing of the tail water depth causes the hydraulic jump to move forward toward the end of the basin. In this case, to control the jump and to avoid the hydraulic jump being swept out of the basin, sill distance is decreased. Also, observation showed the sill height needs to be increased as inflow Froude number increases and tail water decreases. In the other words, relative sill height increases up to 30% as tail water depth ratio decreases from 1 to 0.8. Furthermore, the results showed that sills with the 50% opening in comparison with other openings have most effective in energy dissipation and reduction of the hydraulic jump length. The comparison of stilling basin with perforated sill and free jump indicated that the sill with perforation ratio of 50% dissipated 60-90% of water energy in inflow Froude number range of 4.5-12. Moreover, once Froude number increases from 4.5 to 12, stilling basin length increases about 19% for this perforated sill in the tail water depth ratio of 1.

The Beerkan single ring infiltration experiment is a simple and inexpensive method for estimating soil hydraulic properties and is gaining scientist's attention in recent years. The purpose of present study was to compare the performance of modified forms of CL (cumulative linearization) and DL (derivative linearization) methods with the main Beerkan algorithm (i.e. BEST slope) in estimating saturated hydraulic conductivity (Ks) and the value of a (i.e. the ratio of gravity force to the capillary force) in the modified forms of CL and DL. For this purpose a number of 113 Beerkan infiltration experiments were carried out in Sistan Dam' research field.The negative values of Ks estimated by the BEST slope algorithm were eliminated and the 101 remaining experiments were selected for final analysis. According to the results, Ks values estimated by DL and CL were negative in most Beerkan experiments while the modified DL and CL methods resulted in positive values in all cases. The results were compared using a weighted coefficient of determination (wr2). According to the results, the Ks values estimated by the modified DL were more similar to those obtained by BEST slope algorithm (wr2=0.8135) when compared to those obtained by the CL method (wr2=0.7506). Besides, the difference between Ks values estimated by BEST slope algorithm and the modified DL or CL methods decreased as the percentage of clay increased. The calculated value of a in modified DL (a=0.019) was more similar to that reported previous studies (in similar soil texture, i.e. loam and sandy loam) than that obtained in CL model (a=0.023).

Rainwater harvesting is an effective method for the utilization of surface water resources in different regions. Since the impervious surfaces have noticeable potential of rainwater harvesting, designing and planning in order to collecting of rainwater is a suitable solution for adapting of water shortage in many places. In this research, the possibility of rainwater harvesting for supplementary irrigation of wheat and barley in their cultivation periods from third decade of November to second decade of June in the Rigcheshmeh village, south of Sari city, Mazandaran Province has been investigated. The average of required annual water for wheat and barley has been calculated 271 and 230 mm, respectively, by NETWAT software.For calculating of the precipitation average, 35-year precipitation of the Rigcheshmeh rain gauge station has been used. The cumulative amount average of 10-days precipitation with cumulative evapotranspiration of wheat and barley were compared in the same period during the 35-year period calculated and sprinkle irrigation system gross irrigation requirement was obtained. The amount of runoff from a 250 m2 roof covered with tar paper has been estimated and a reservoir with dimension of 2.5*5*8 m has been considered. The results showed in this place for supplementary irrigation of wheat and barley due to the average 35-year precipitation and with 80% confidence level, could be at least 15 percent of the farm area to be considered as impervious surface for collect rainwater.

Flood management needs to identify and prioritize of watershed flood source area. The most studies in the field of flood management are based on the application of the integrated-conceptual models. These models have not appropriate precision to identify watershed-wide flood source area and moreover they have restriction to investigate the spatial distribution of effective components in runoff generation. The main aim of this study is to determine the severity of flooding and priority determination of flood generation potential area based on unit response approach using Mod-Clark distributed (spatial) hydrological model for Qaranqu watershed. In this study, digital elevation model (DEM) with a cell size of 30 m was prepared in the GIS using the topographic maps. Furthermore the watershed gridded file, based on the Standard Hydrologic Grid (SHG), was created using HEC-GeoHMS as input data for the HECHMS model. In order to choose the suitable grid scale, two different resolutions of 1*1 and 2*2 kilometers were utilized. Although the results revealed that the 1*1 km grid scale could more accurately specifies the boundaries of flood area source, there is no significant difference between results in comparison to 2*2 km grid. Outcomes of the current study suggest 1*1 km resolution for priority determination of the flood source area. By iterative execution of Mod-Clark model for different scenarios, flooding severity index of the basin was spatially determined. Based on the flooding severity index the Almalochai sub-watershed was recognized as the most flood source areas from point of flood peak flow generation view.

Drought is one of the most important climatic phenomena which occures in all climate conditions and regions of the earth. Drought forecasting, therefore plays an important role in designing and management of natural resources and water resources systems, assessing plant evapo-transpiration. For this purpose, in this study, data from four meteorological stations nourabad, borujerd, aleshtar and doroud in Lorestan province, on time scales of 6 and 12 months were used to analyze drought by using standardized precipitation index SPI. Then, droughts were evaluated using neural network model estimation. The results showed, Boroujerd and Doroud stations have the longest drought period, and severe drought is recorded in Nourabad station. The results of the survey showed that Boroujerd Station had maximum amount of drought months occurred during the drought period. The results of using wavelet neural network model showed best estimation of SPI for Doroud station than others in both time scales. In conclusion, the results showed more accuracy of wavelet neural network model in estimation of long-term drought, and the use of wavelet neural network model can estimate the drought effectively, Which in return facilitates the development and implementation of management strategies to avoid drought.

One of the crucial mechanisms in order to achieve a sustainable agriculture and water consumption management in the field is to continuously monitor the performance of pressurized irrigation systems. In the present study, the wind velocity effect on the performance of semi-portable sprinkling irrigation systems in Zanjan province was evaluated. Therefore, the experimental tests were performed on 13 agricultural fields in two climatic conditions include high and low-intensity wind velocity. Spray losses, Christiansen uniformity coefficient, distribution uniformity of low quarter, actual application efficiency of lower quarter and the changes in the system's pressure were determined. The results indicated that, the lowest and highest value of spray losses were determined 7.3 and 51.8%, respectively, and the general average values of spray losses in low- and high-intensity wind conditions were determined 13.0 and 31.7%, respectively. The minimum and maximum values of distribution uniformity of low quarter in low-intensity wind velocity condition were obtained 47.3 and 74.5% and in high-intensity wind speeds were obtained 27.4 and 65.5%, respectively. The average values of those indices in the low- and high-intensity wind conditions were obtained as equal to 62.9 and 42.3% respectively. The actual application efficiency of low quarter was measured 41.5 to 61.8% and 17.3 to 46.4% in low and high wind velocity condition, respectively. Intensifying the wind velocity led to a reduction of 21.4% in actual application efficiency of low quarter and 20% in water distribution uniformity. Finally, the results indicate that, wind velocity has had a significant effect on reducing the water distribution uniformity and application efficiency.Application of high irrigation water depth and pressure changes in sprinkle irrigation systems were identified as other factors affecting on reducing technical performance of semi-portable sprinkling irrigation system.

Yaghuti grape is an important grape variety mostly found in subtropical regions of Iran. Studies have shown that many of Yaghuti grape orchards are over irrigated which in addition to having a negative impact on groundwater resources; also reduce the quantity and/or the quality of the fruit. Up to now, little work has been done to determine water requirement of this variety. To do so, a study was conducted in a Yaghuti grape orchard in Qir-karzin region in Fars Province, Iran for a period of 2 years. Different amounts of irrigation water based on 60, 80, 100 and 120 percent of crop water requirement estimated by the Penman-Montieth method were applied to the experimental treatments in four replications. An irrigation treatment managed by the farmer was also considered as control. Results showed that different amounts of irrigation water given to Yaghuti grape did not affect the quality or quantity of the fruit. Comparison of soil moisture and canopy temperature measured before irrigations with the corresponding critical limits also indicated that none of the treatments had faced water stress. However, the treatment irrigated with 60 percent of crop water requirement was approximately the starting point of water stress. Therefore, it is concluded that the best irrigation amount could be based on 60 percent of crop water requirement estimated by the Penman-Montieth method equivalent to irrigation volume of 3800 cubic meter per hectare.

Maize cultivation is considered as one of the main crops in the Khuzestan province. Mostly, in planning water requirement is calculated as a point, while irrigation is preformed locally. Therefore, this data must be converted from the spot to the region. In this research, in order to determination irrigation scheduling in Khuzestan province were planted spring Maize in lysimeter at the Faculty of Water Sciences Engineering of Shahid Chamran University of Ahvaz. The aim of this cultivation were compared between the current methods of determination of water requirement and lysimeteric method and determine the appropriate equation. The results showed that the Blaney-Criddle equation is the best method to estimation evapotranspiration in case study area. After determining the appropriate equation of water requirement, mention equation and meteorological data were used for zoning Maize water requirement with geostatistical methods. The zoning was performed using ARC GIS 10.3. First, the data were normalized. Then, according to the lowest RMSE were selected the best semi variogram and zoning model. The results show that simple kriging with circular semi-circular model in all months is considered optimal model. RMSE value of this model was calculated, the amount of it was 0.08, 0.17, 0.46 and 0.48 for March, April, May and June. The result of water requirement zoning showed that this parameter in south is more than north of Khuzestan province. Also, the amount of water requirement in last months is more than first months.During the study period (from March to June), water requirement was 1.98, 5.52, 11.78 and 11.97 (mm/day) monthly. Small amounts of RMSE was indicated the optimum of water requirement zoning.

Identification of factors affecting hydrological processes plays an important role in water resources management. In this study, the effects of hydrological parameter variations such as rainfall, temperature and runoff time series are prioritized on the groundwater level fluctuations for the Silakhor plain using cross and coherence wavelet transforms. Cross wavelet transform and coherence wavelet transform estimate the interaction and time lag between two time series relatively. These transformations indicate that two time series have depended on period and phase lag. For this purpose, the time series of groundwater level- runoff, groundwater level-rainfall and groundwater level-temperature have entered into the cross wavelet transform and coherence wavelet transform algorithm mutually to determine the effects and interaction between these time series. The results show that runoff time series as the human activity factors with the mean wavelet correlation coefficient estimated as 0.83 is more effective than rainfall and temperature time series whereas the climate change factors are with the mean wavelet correlation coefficients of 0.52 and 0.58, respectively concerning groundwater level decline of the Silakhor plain. Thus, the human activity factors are more effective than the climate factors in declining the groundwater level in this plain.

Overland flow is one of the main causes of erosion and decrease of soil fertility, sedimentation in reservoirs and decrease of water quality of rivers. Therefore, accurate prediction of catchment's response to rainfall events is an important issue. Hydrologic models are simplified representation of a real hydrological system which helps us study the catchments reaction towards different inputs and better understand hydrological processes. Besides, the increase of greenhouse gases in future periods, and consequently, the aggravation of changes in climate parameters may have many negative effects on different systems, such as water resources, environment, industry, hygiene, agriculture, and all systems which are interacted with climate system. Considering simultaneous changes of fluctuations and average values of climate variables which influence runoff, will lead to more realisticresults. This study aims to consider the effect of climate change on overland flow in Mohammad-Abad Catchment, located in Golestan Province, during 2011-2040 periods. In this study, HBV-light model was calibrated for understudy region. Then, based on the output of HadCM3 model under A1B, A2 and B1 emission scenarios, temperature and precipitation data for 2011-2040 period were downscaled using LARS-WG model and used as input for HBV-light model to simulate surface runoff. The results in addition to verify the efficiency of LARS-WG model, showed that the temperature in the period of 2010-2040, will increase in comparison to the observation period (1982-2010), and also precipitation will increase in some months and will decreased in others in future in comparison to the observed period.