فصلنامه مهندسی منابع آب
پیاپی 27 (زمستان 1394)

Evaluation of changes in groundwater quality and sustainable management of water resources is of crucial importance in plains. In this regard, the importance of information about the quality of groundwater for various uses is time-consuming and expensive involving data collection. The survey of conventional estimators to find the best parameters, through which other parameters can be derived at lower costs, is essential. In this study, the data collected from 94 production wells in the Dezful Plain, namely: SAR, Na, Ca, TDS, Ec and TH, are used to check the status of the groundwater quality of the plain and select the best procedure for estimating the parameters studied by geostatistial methods. The results indicated that the Cokriging method with the Gaussian variogram and cross variogram models were the best geostatistical based on the highest R2 and lowest NMAE and NRMSE. These parameters were then employed to prepare a map showing the water quality in the specified zone. The results of the zoning maps indicate that the quality of groundwater resources in parts of the southeastern and eastern regions of the plain is not satisfactory for drinking and irrigation.

A critical groundwater (GW) shortage in the Mahvalat Plain (MP) is alarming. As GW is the sole source of freshwater in the area, the objectives of this study are to survey and asses its current status, and to set a strategy for balancing the recharge and withdrawals to achieve the sustainable management of the most precious resource. The mean annual withdrawal and recharge of 48 production wells and 3 strings of aqueducts (Qanats) during the 1665-2008 period were 254 million m3 (Mm3) and 157 Mm3, respectively. This 97 Mm3 annual deficit resulted in the mean annual decline of the water table by 1.35 m during the same period. Chemical analyses of water samples from 48 wells and 3 strings of aqueducts indicate that the electrical conductivity (EC) increased from 0.17 s/m to more than1.5 s/m form the northeastern part of the MP towards its margins. Moreover, salinity, SAR and Sodium percentage of most samples made them unsuitable for irrigation. To achieve a sustainable management of the most precious resource, i.e., water, the solutions include: Restriction of the pumping hours according to the directives of the local water authorities to decrease the mean annual of 121Mm3, Reduction of the irrigated fields by 2/3 of the current practice, Installation of sprinkler and drip irrigation systems, Practicing advanced surface irrigation methods, Amortization of the wells with an EC of more than 0.75s/m of their water by the Government and closing them completely, and installation of smart water meters on the remaining productions wells and their continuous monitoring.

Severe freshwater scarcity in Iran has raised interest in utilizing abundant brackish and grey water resources. The presence of vast resources of such water in the province of Esfahan (PE) and tremendous volume of municipal and industrial nutritious grey water in that area dictates that those unconventional resources should replace freshwater for irrigation of salt tolerant crops, i.e., barley. Therefore, an experiment was conducted in the Borkhar District of PE using brackish groundwater, grey water, and mixture of both with an electrical conductivity (EC) of 7.0, 1.4, and 4.0 ds/m, respectively. There were 3 replications pretreatment. Effects of water conductivity on barley yield and its components were significant at the 5% level except for the plant height. Irrigation with the grey water produces the highest yield, larger 1000 kernel weight, seed dry weight, spike length, and leaf area. The mixture of ground and grey water took the second position. As the repeated irrigation with grey water may adversely affect the soil, its consequences should be monitored periodically.

Spur dikes and triangular-shaped vanes are structures that control the erosion of a river’s outer bend by the diversion of flow from there to its center. In this study, the erosion and sedimentation patterns around a spur dike and a triangular-shaped vane was investigated using an experimental model with a 90-degree mild bend. The triangular-shaped vane and spur dike with an effective length of one-fifth of the width of the canal (14 cm) and under different hydraulic conditions (Froude numbers 0.194, 0.214, 0.233 and 0.253) were tested. In all tests, a single triangular-shaped vane with an angle of 30 degree to the upstream direction, and a spur dike with an angle of 90 degree were installed in the outer bank of a flume in a 72° position, where the maximum scour depth usually occurs. For all tests, flow depth was kept constant equal to 13 cm. Bed topography was measured at the end of each experiment and the geometry of scour hole and point bar were determined. The results show that the maximum scour depth of the spur dike structure was more than that of the triangular-shaped vane. The average of maximum scour depth of the triangular-shaped vane and spur dike were 0.55 and 1.0 times that of the structure effective length, respectively. In addition, the maximum scour depth distance from the outer bank with a triangular-shaped vane was more than of the spur dike. The average distance of the maximum scour depth of spur dike and triangular-shaped vane structures from the outer bank were1.0 and 1.4 times the effective length of the structure, respectively. The point bar distance from the outer bank the spur dike structure was more for the triangular-shaped vane. The average point bar distance from the outer bank for spur dike and triangular-shaped vane were 0.34 and 0.1 times of effective length of the structure, respectively.

Karst aquifers are one of the most important water resources on the global scale. Vulnerability assessment and hazard zonation mapping approach is important in the management of those resources. Sometimes, where thin soils cover the recharge conduits, the scattered and occasional vugs, the aquifers are vulnerable to contamination. The purpose of this study is to map the vulnerability of the Baji, Neishabour karst aquifer to surface contamination using the COP and PaPRIKa methods as management tools to preserve these resources. Appropriate parameters for both methods were developed, introduced into the GIS software, and the required map was drawn. According to the results obtained though employing the PaPRlka method, the region was delineated into very high, high and medium vulnerability classes; these classes covered 8.9, 63.8, and 27.2 percentages of the research domain. The results further indicate that the COP index for the study area ranged from 0.5 to 12. Based on the COP index, there are 4 vulnerability classes: high, medium, low, and very low, which covered 4.8, 50.0, 25.6, and 14.6 percentage of the area, respectively.

The Mont Carlo simulation is widely used for data generation based on specified distribution. However, generation of correlated data is only possible for specific distributions (bivariate normal), while it is required to deal with non-normal distributions, e.g. in regional frequency analysis. To tackle the problem, an innovative approach was proposed by using the genetic algorithm. Since it is possible only to change the order of numbers in an array, our problem is not completely in agreement with the classic genetic algorithm. Therefore, we reordered the algorithm; the internal of each chromosome was changed instead of crossing two different ones. The proposed method was applied for one random variable, and it was shown that the genetic algorithm produces multi-solutions, while unique solution is obtained using the Mont Carlo simulation procedure. We presented an appropriate objective function to include any bivariate distribution and showed its hither versatility as compared with the Mont Carlo simulation (only for the bivariate normal distribution). The multi-solutions in our proposed methodology is due to the fact that any array can be reordered in different possible combinations, each of which having a unique correlation coefficient with another fixed array. It was shown that these different combinations increase as the correlation coefficient decreases.

Due to the lack of a dense network of hydrometric stations in most basins in Iran, developing methods is necessary to estimate the daily stream flow that lead to improvement information required for water resources management. These methods usually use precipitation as the input data in most hydrological models. In order to measure precipitation as the key variable in stream flow estimation, one can employ satellite algorithms with high spatial and temporal resolutions. Among the several hydrological models suggested to simulate stream flow, IHACRES is a simple one that uses only rainfall and temperature data to achieve this objective. Daily stream flow of the Sarough-Chai River of the Zarinehrood basin was simulated using the IHACRES model with the daily rainfall gauge, temperature, and discharge data from 1988 to 2008. Then, the model was validated and calibrated using two different periods. Moreover, in order to evaluate the performance of the satellite rainfall algorithms in stream flow simulation that was the aim of this research, the daily data of PERSIANN, TMPA-3B42V7 and CMORPH products from the 2003 to 2008 period were employed as an input into the calibrated IHACRES model. Considering the indices of CC, RMSE, MAE, and RBias, the results of this research indicate that TMPA-3B42V7 performs a better in simulation of stream flow than PERSIANN and CMORPH in the study area.

Density current is produced because of a density contrast with the ambient fluid. This density difference can result from dissolved solids, suspended materials, temperature, etc. Density jumps significantly influence the quality characteristics of the gravity currents and the ambient fluid (e.g., lakes and reservoirs). In this research, using dimensional analysis and incomplete self-similarity method, these jumps were studied and a new equation was obtained for calculating the sequent depth ratio. This equation was validated using experimental results. Therefore, these experiments were carried out on both smooth and rough beds. The results indicate that the new relationship is more accurate than the classical equation; it was shown that the effects of both the entrainment ratio and the bed roughness are not negligible, even for their small amount.