دبی

Temporal analysis of discharge gives information for water resources management. Meteorological variables change like precipitation has important effects on water resources. Management of pollutions has significant influences on water quality of the region.

Temporal trend of discharge and water quality of Kor river, for a 46 year, in Chamriz and Pol Khan stations, analysed, using Man Kendall and Sen slope trend analysis. Statistical distributions fitted to the data, then the parameters forecasted for different return periods, and compared in the stations. Water quality parameters compared with standard values of different uses.

Results showed that Pol Khan monthly average discharge is greater than Chamriz, which could be resulted from the entry of other rivers such Sivand. For 2-, 5- and 10-year return periods, the forecasted discharge of Pol Khan is greater than Chamriz, but for 20 and 50 years Chamriz discharge is more, which could result from River water control in Doroudzan Dam. In Chamriz all of the parameter’s average are in standard limits. In Pol Khan the TDS and EC values are higher than domestic use standards, but other parameters are in the limits. Except for EC, other parameters are in the limits of livestock and poultry, and irrigation standards. All of the parameter in Pol Khan are higher than Chamriz except PH. Trend analysis showed decreasing of discharge in the both stations. In Chamriz Na and SAR showed no trend, SO4 and PH had a decreasing and others had increasing. In Pol Khan, PH showed decreasing, and the others increasing. Except PH, all of the forecasted values, for all return periods, in Pol Khan are higher than Chamriz. Reduction of agricultural pollution, prevention of wastewater entry and treatments could be effective for improvement of water quality.

One of the solutions for flood management is flood zoning in different return periods, which can be an essential tool in determining development strategies and reducing flood damage. Calculating flood damage in existing uses provides useful information for various organizations such as insurance to be aware of the amount of damage in different uses in the event of a flood.

The study area is located in Rudak basin. In this regard, first maps, required hydrological data and DEM of the study area were prepared. Then, according to the flow data, the maximum annual moments in Rudak hydrometric station were fitted with normal log distribution (as the best distribution) and the flow rate was obtained in four return periods. Then, a single hydrograph was obtained by SCS method for different return periods. Then, using the HEC-RAS2D model, the flood zone with the mentioned return period is obtained and finally, based on the global damage-depth functions, the amount of damage in the return period is based on different uses, including residential, commercial, agricultural, roads was calculated.

By comparing the results of flood zoning and damage maps, which with increasing flood return period, the amount of damage and the area of ​​high-risk zone increases. The amount of flood zone in the return periods of 5, 25, 50 and 100 years is equal to 17.9, 18.9, 19.4, 19.9 hectares, respectively. Most of the damage is related to agricultural lands and then lands with commercial use. The rate of increase in damage to the area between floods 5 and 25 return period is about 47%, between floods 25 and 50 return period is about 6%, and between floods 50 and 100 years is about 15%. Therefore, a 50-year flood can be proposed to determine the flood protection plans of the region.

Trend analysis of stream flow provides practical information for better management of water resources on the eve of climate change. Therefore, the present study investigated river flow variations during three decades as well as projections of future discharge in the Gorganrood watershed. The Man-Kendall method has been used to detect the trend and methods of Pettitt, SNHT, and Buishand to identify points of a sudden change in discharge time series in 8 stations of Aq Qala, Galikesh, Gonbad, Haji Ghoshan, Nodeh, Ramyan, Sadgorgan, and Tamar. The Mann-Kendall trend test showed the existence of a significant negative trend (flow reduction) on a daily and annual scale in all stations. Monthly, the strongest negative trend in Aq Qala, Galikesh, Gonbad, Haji Ghoshan, and Ramyan stations was related to July, but in Nodeh and Tamar stations, it was related to August and February, respectively. A decreasing trend was observed in all stations on a seasonal scale, but this trend was not significant in some seasons. The results of the analysis of change points in discharge showed that the change points in the data used in this study are more of a decreasing and in some cases incremental type and some stations, no change points have been identified at all. Therefore, the number of decreasing changes in the studied hydrometric stations is significantly higher than the incremental changes and is more visible from 1993 to 1997 and 2005-2007 in three and four stations, respectively. Also, the most incremental changes among the stations are related to the Aq Qala station in 2017 with a flow rate of 234 cubic meters per second. Investigation of the flow of the basin in the past decades showed significant monotonic and abrupt changes which are mostly toward decreasing the basin’s discharge. The downward trend in discharge values at different time scales for all hydrometric stations of the Gorganrood watershed, which will be more severe in the future due to global climate change, and increasing the region's water needs for various future use due to population growth and the expansion of industries can also be considered as a serious warning for policymakers, planners, and local managers to prevent a possible water crisis in the region in the future with proper planning.

The main problem downstream of hydraulic structures, such as weirs, is scouring and movement of bed materials.  The piano key weirs (PKW) is one the types of weirs. Due to the fact that the geometric shape of the weir affects the condition of the downstream scour, therefore in this study, the downstream scouring of the piano key weirs with a trapezoidal geometric shape is studied. In this paper, the scour profile and the rate of change were compared with the change in the lateral wall angle of the weir.

For this purpose, four experimental models of this type of weirs were made and these models were tested in a laboratory flume at different flow rates. Also, to investigate the effect of tail water depth on scour profiles, one of the models was investigated at three different tail water depths.

The results of scouring characteristics showed that in trapezoidal piano key weirs, the maximum depth of the hole is created under the output key and by increasing the discharge and decreasing the tail water depth, the geometric dimensions of the scour hole increase in trapezoidal models. Also, in trapezoidal piano key weirs, by increasing the side wall angle of the weir, the geometric dimensions of the scour hole are reduced. In all flows, by increasing every 3 degrees of the side wall angle of the piano key weir, maximum scour hole depth on average, 5%, Spatial position distance, maximum scour hole depth and scour hole span length, respectively, and it decreases by 8% and 3% on average. Also, when Frd>65% is, this difference becomes insignificant and there is not a significant difference in the shape of the scour hole for PKW models.

The objective of the present research was to investigate the flow properties through the bottom outlet of the Nesa dam based on numerical and experimental studies. 22 piezometers were employed to measure the static pressure through the experimental model. The bottom outlet section was divided into three blocks to measure the endangered region. The graph of cavitation numbers was plotted for different flow discharge and cavitation damage levels to compare with a safe zone to find out the areas with a high risk of cavitation. The results illustrate that block No. 1 cavitation index is located at the “possible cavitation” damage. The studies showed that the cavitation index is the dependent parameter with the height of the water at the upstream reservoir. Furthermore, for block No. 2, the level of cavitation ranged from x/L = 0.44 to 0.90 and the cavitation level is related to the velocity, and by increasing the velocity to 16 m/s, the threat of the cavitation and its consequences is raised, dramatically. Regarding block No.2 and 3, the cavitation through this block depends on the negative pressure since the negative values of the cavitation index is related to the negative static pressure and it is assumed that the negative pressure can reach the threat of major damage. Also, a comparison between different numerical turbulence models illustrates that the k-ε RNG with fine mesh showed less error with experimental values which causing the numerical model with this condition to reach an appropriate agreement between numerical and experimental simulations.

In recent years, the outflows from the Karun Basin, especially in the interior of Khuzestan province, have decreased significantly. This study aimed to investigate the effect of climatic factors and drought on the inflow and outflow of the Karun basin in two parts (basin area inside Khuzestan plain and basin area outside Khuzestan plain).  The results indicate the onset of adverse climate change during the last two decades. During this period, especially in the last ten years, the study has witnessed a large decrease in rainfall compared to the previous decade in the Karun Basin. Changes in average, minimum, and maximum temperatures, evaporation and drought have also increased during the last two decades. Also, the results related to the effect of climatic parameters on the output discharge of the Karun basin showed that in Khuzestan province 83% of the output discharge changes were affected by climatic parameters (including rainfall, drought, and maximum temperature, respectively) and outside Khuzestan, 82% of discharge changes are due to climatic parameters (including rainfall, maximum temperature, and drought, respectively). Meanwhile, the surface currents of the basin during the last decade have been more critical than other decades and the output discharge outside Khuzestan (input to the province) has decreased by about 27%, and inside the province and the output of the basin has decreased by 44%, which due to the almost identical effect of climate on both areas, these changes can be attributed to the existence of other factors, including land management and human factors.

Due to the increasing number of small crops, the system of irrigation without a pump can be an economical way. Therefore, in this research, the effects of the type of droplet and the height of water supply system utilization on the characteristics of water distribution (discharge, dispersion uniformity coefficient (CU) and coefficients of variation of discharge) were investigated. In this research, the pressure functions of 1, 2, 3 and 4 meters and three irrigation repeats were investigated; also, the discharge characteristics of jet pots of 2 and 8 nozzles, easy dripper and netafim were addressed. The results indicated that at 1 m pressure, drippers of pots of 2 and 8 nozzles with the uniformity coefficients of distribution were equal to 89.39 and 99.30%, and the discharge rate was 3.60 and 3.62 liters per hour at a pressure of 2 m. An easy-drain drip with a discharge rate of 3.85 L / h and a uniform distribution of 99.44%, at a height of 3 and 4 m, the droplets of the netafim with an outlet discharge were 3.87 and 3.97 liters per hour and the uniformity coefficients of 99.32 and 99.47 percent had the best broadcast conditions. According to these significant differences (P <0.05), it can be concluded that at pressures less than 2 m of jar droplets and at more than 3 m, netafim and Easy Dipper types could  have better leakage due to pressure regulators. In general, each of the four types of emitters produced a uniform dispersion and the optimum discharge at different pressures.

The Lake Urmia basin in North West of Iran is one of the important basins of this country due to its climatological, economical, ecological and environmental condition. In this study in order to discover the likely causes of the lake shrinkage, trends of the two effective factors on its inflows (precipitation and rivers discharge), were investigated. For this purpose, rain gauges and hydrometric stations data at seasonal and annual scale across the basin were collected. Long time-series of variables were prepared and their trends were analyzed using the Mann-Kendall and seasonal Kendall test. According to the results although annual precipitation indicated decreasing or increasing trends at some stations, but most of them were not significant at 0.05 probability level. Despite lack of significant, decreasing trend for annual precipitation across the basin, the majority of hydrometric stations showed significant decreasing trend in the annual stream flow data at 0.05 probability level. Therefore, from statistical point of view, the significant decline at annual discharge of the streams draining into the lake and the shrinkage of the lake cannot be attributed to decline at annual precipitation. Therefore, some other causes such as increase in evapotranspiration due to atmospheric warm-up. Over-extraction of aquifers, extensive landuse changes, impoundment of water behind numerous dams and decline at the lake inflows might be effective on the Lake Urmia shrinkage.

Prediction of the flow discharge accurately is a key point in the optimum planning and management of water resources. The Ghorghanrood watershed is one of the watersheds in the north of Iran that it is located in Gholestan Province. The impact of drought and rain on basic fluctuations and overall flow of the river plays a major role in planning of implementation of watershed resources. In this research, the KNN model and M5 decision tree were used as one of the methods of data-mining for estimating the flow discharge of Ghorghanrood River that it is located in Sarmo Station. In this regard, the raining and flow discharge data of Sarmo Station (in Mohammadabad) under five various scenarios by applying transfer functions on the data. The results showed that M5 decision tree has mostly superiority over KNN model and reaches more accurate prediction. Also, in the defined scenarios, the b and c models which respectively include all data and daily raining data, last day raining and two days before raining, result the most accurate estimation. These two scenarios are under the transfer function, the five-day moving mean and have R2 standard of 0.999 and MAE and RMSE standards of 0.001.

Advance time is one of the most important factors, especially for determining irrigation timing. This project has been conducted for determining and evaluation of furrow advance time in two irrigation management including conventional and alternative furrow irrigation. Four different inflow rates within two periods of Maize growth stages for two furrow irrigation management were considered. Results showed, the water advance time in conventional furrow irrigation in two growth stages with inflow rate as 0.15, 0.28, 0.35 and 0.46 l/s were 1.8, 2.4, 1.6 and 1.6 times respectively comparative to alternative furrow irrigation. Also results in end of season revealed that with increasing inflow rate the advance time in conventional furrow irrigation were 1.3, 1.6, 1.4 and 1.5 times as comparatives to a conventional furrow irrigation. Soil surface moisture variation showed that the soil moisture content in alternative furrow irrigation decreased about 28% in comparison with the conventional furrow irrigation. With increasing furrow inflow rate the coefficients of advance power function (r & p) increased about 4 and 56% for conventional and 12 and 26% respectively alternative furrow irrigation.