نشریه مهندسی آب
سال هشتم شماره 3 (پاییز 1399)

Rainfall erosivity is the ability of rain to separate soil particles and has a high correlation with soil erosion. The aim of this study was to investigate the temporal spatial variations of rainfall erosivity using the EI30 index. In this study, EI30 index was calculated for different months and seasons in 9 recording rain gauge stations in Khouzestan province. Then, using regression relationships between EI30 index and other easily accessible rainfall specifications and indices in rain gauge stations, the values of EI30 index for 65 rainfall stations were estimated. In order to prepare the monthly and seasonal rainfall erosivity map, the point data of EI30 index in 74 recording raingauge and non-recording raingauge stations were interpolated using Cockriging geostatistical method. According to the prepared maps, the highest amounts of monthly and seasonal rainfall erosivity are in the east and north of Khouzestan and the lowest amounts of rainfall erosivity are in the south and west of Khouzestan province. On average, the highest monthly rainfall erosivity index occurs in December with a value of 292 Mj.mm.ha-1.h-1 and the highest seasonal erosion index occurs in winter with a value of 576 Mj.mm.ha-1.h-1 and the value of this index is zero for summer.

Drought is one of the natural disasters that cause great damage to human life and natural ecosystems and is different from other natural disasters. The main differences in the gradual impact of drought over a relatively long period are the impossibility of determining the exact time of onset and end and the geographical extent of its impact. On the other hand, the lack of an accurate and acceptable global definition of drought has added to the complexity and confusion of this phenomenon. And the severity of droughts was determined and described based on drought indices ZSI, PNPI, SPI. These indicators are consistent with each other so that based on the above indicators. the results show that in Shahid Abbaspour Dam in the wet years (2007-2008) the most severe drought occurred in the statistical period. SPI index of drought periods Shows more, so it is a more sensitive index than ZSI and PNPI and has a higher sensitivity and more complete classification in the study of dry periods.

Although dams have the potential to achieve macro and national goals, they sometimes also provide the necessary ground for threats to occur. One of these threats is the risk of flooding due to the possible failure of dams for settlements located near them. In this study, the failure of Gheshlagh Dam, a dam located 12 km north of Sanandaj, the capital of Kurdistan Province, has been investigated. The failure of this dam has been analyzed using the HEC-RAS program and the results confirm that after the start of the failure of the dam, in the early stages of the river, the water level rises sharply and submerges the heights on both sides of the river. But the downstream topography of the dam is such that although much of the land around the river is submerged, urban areas are less vulnerable to flood risk. However, given the risk to life on the riverbank, the use of a flood warning system is suggested as an effective solution.

In order to determine the strengths and weaknesses of the management of operation and maintenance of irrigation and drainage networks of Daryun 1 and 2, the mentioned network was examined using the classical evaluation method. For evaluation in the model, the indicators were divided into five windows: technical, service-management, environmental, social and economic. 66 required indicators of the model were identified. To weigh the indicators, a specialized questionnaire of pairwise comparisons of the index was designed and provided to the experts.According to the results of the questionnaires, 11 matrices were prepared for each section and then a matrix was prepared for each group. The internal numbers of the mentioned matrix were obtained from the geometric weight average of each 11 matrices.Finally, the weight of window indicator indices was calculated by special vector calculation method by Maple software, then the numerical value of different window indices was calculated using SAW model.Based on the results obtained from the model calculations, the environmental window with a score of 0.956 is in the first place and its evaluation is good. The evaluation of the network in social, service-managerial, technical fields with scores of 0.864, 0.853, 0.827 in the next categories, respectively It is located and evaluated as average and the network has the lowest rank in economic fields with a score of 0.768. In general, it can be said that the performance of Dariun irrigation and drainage network with a score of 0.853 is generally average.

Design of the rain gauge network to increase accuracy and cost decrease in precipitation prediction value needs to find optimum location of the rain gauge station. Most precipitation prediction errors is due to location of the rain gage station that optimum design of the rain gauge stations can reduce precipitation prediction error. In this study used geostatistic methods named Kriging and cokriging to optimization of the Khuzestan rain gauge station network. 49 rain gauges used for 6 daily rainfall. After determination of the best model of semivariograms and the best geostatistic method, in the first step, the rain gauge which precipitation prediction in them has appropriate accuracy determined with the help of other rain gauge network. Result showed that kriging had more accuracy and most daily rainfalls was fitted with gaussian model. In the next step, using assessment of network prediction error value which remain from first step, the points that needs new rain gage determined. Finally7 unnecessary rain gage stations determined and 5 new rain gages added to the network.

Assessing and monitoring groundwater quality is always an important challenge that is associated with specific problems. In order to use groundwater for drinking, its quality must be examined. In this study, the quality of groundwater used in drinking water in Baghmalek plain was investigated. For this purpose, the groundwater of this area was initially classified according to eight important parameters that have a decisive role in the quality of groundwater. These 8 parameters are: Cl (Cl), Sodium (Na), Water hardness (TH), Bicarbonate (HCO3), Sulfate (SO4), Total dissolved solids (TDS), Magnesium (Mg) and Calcium (Ca). , Then the weight of each of the main factors was determined by AHP hierarchical method and the different information layers were merged based on the resulting weights and finally a raster map was obtained using GIS software and layers integration. In the hierarchical analysis, according to the experts, the TDS parameter had the highest weight. The results of qualitative evaluation indicate that about 88% of the study area is in good and acceptable range and about 12% is inappropriate and very inappropriate.

The purpose of this study was survey on 2,4-D concentration in Ahvaz drinking water in 2018-2019. A descriptive cross-sectional study was based on 10- month sampling program (from December 2018 to September 2019) in six points of distribution networks were conducted. All measured concentrations were less than the maximum allowable concentrations recommended by the National Standards Organization of Iran (1053) and WHO guidelines. In this study, the total THMs determined in autumn, winter and spring ranged from <0.004-2.98μg/L, 0.02-2.41μg/L and 0.01-0.04μg/L, and in summer less than the LOD, respectively. Different studies have shown that pesticides residue concentration in water samples have a relationship with the amount of pesticides used in an area, physical and chemical refractory properties of pesticides and environmental conditions. Thus, using resistant pollutants such as pesticides will be a serious threat to health of water consumers if they are not properly controlled.