مجله ترویج و توسعه آبخیزداری
پیاپی 18 (پاییز 1396)

Roughness 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 roughness coefficients which are mostly based on experimental tests. In river hydraulic, flow resistance or roughness 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. Gol-Gol River of Ilam dam 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. The HEC-RAS software used to determine the water level in different cross-sections for various discharges and roughness coefficients. Results showed that among various methods, results of Chow method was closer to the observed data, and this method had the lowest mean relative error, so it recommended as the best method to estimate the manning roughness coefficient of this river.

Monitoring system is a prerequisite for drought-response schemes, which time has a crucial role to play in its functionality and performance. One of the important issues in drought studies and monitoring is using of indicators which they can assess the severity, duration and magnitude of drought in one region. In this study, information of eight synoptic stations of Tehran province in order to monitor drought status during 18 years period (1996-2014) is used. In this regard, by using meteorological drought methods such as percent of normal precipitation (PNPI), standardized method index (Z), deciles index (DI) and SIAP indicator was analyzed. Also minimum amount of precipitation method was used to select appropriate indicators. Results revealed that most stations except Firoozkooh, at the same time that other stations fitted to minimum amount of rainfall, drought and severe drought was under normal condition too. The most severe drought in the months of June, July, August and September occurred and in most cases can not be used to determine the unique identifier. Most Z (wet 1.54) was for Abali station in March and the most severe drought (-1.62) has been allocated to Firoozkooh station in September. Zoning also showed the severity of the drought in southern regions is more than other regions.

The sub watershed prioritization of flood generation and flood hazard zoning are a great help to identify and management of vulnerable flood area. Since the urban area of the city of Ramsar located at the end of watershed outlet, control and identify the areas of the flood generator has special importance. The purpose of this study is to determine the potential flood generation of different areas of watershed and map development of flood hazard zoning for each sub-watershed. To achieve this objective, the watershed area was divided into seven hydrologic units and then lithological units have been identified in this watershed. The slope of approximately 97% of the watershed is greater than 15% percent. About 62.23%of the watershed has more than 45% vegetation. After determining the value of quantitative factors, flood potential were investigated with using Index-Overlay method in Geographic Information System (GIS) environment. Finally, Prioritization of Sub-basins was done with Lithological units, slope, land use and the percentage of vegetation cover. The results of this study showed that about 26.36 percentage of watershed area located in high potential flood generation and about 13.74 % located in very high potential flood generation area. The results of potential flood generation prioritization of sub-watershed showed that the Lot-Mohaleh’s sub-watershed with 5.41 % and the Javaherdeh’s sub-watershed with 80.39 % located in high and very high hazard zonal where they have the most and the least potential of flood generation in the Safarood watershed.

The purpose of this descriptive-correlation study was to investigate socio-economic and environmental impacts of the watershed management projects in Mahabad’s dam catchment. The research instrument was structural questionnaire with close-ended questions which its validity and reliability was confirmed. The target population of this study consisted of all householders who lived in Mahabad’s dam catchment (N=2458) out of which, according to Cochran’s formula, a number of 175 people were selected using cluster sampling in a simple randomization method (n=175). The descriptive results indicated the status of environmental, economic, and social impacts of watershed management in Mahabad’s dam catchment were at nearly high, nearly appropriate, nearly and low levels, respectively. These results also showed the main economic, environmental, and social impacts of watershed management were changing dry farming into irrigated farming, controlling flood, and attracting rural people’s participation, respectively. The results of Friedman test indicated environmental and social impacts were the most and the least amount of impacts of watershed management in Mahabad’s dam catchment, respectively. The results of correlation coefficient showed that there was the significantly positive relationship between land under cultivation and number of respondents’ household individual who participated in agricultural activities with impacts of watershed management in Mahabad’s dam catchment.

Identifying areas with high potentials for groundwater is a major factor for the management of groundwater resources. In this study, we tried to identify areas with the potentials for groundwater in Dehloran and Mosian-Abdanan plains, Ilam, by using frequency ratio and statistical index models. Conditioning Factors used in this study include: Groundwater levels, Lithology, geomorphology, slope, slope aspect, drainage density, land use, elevation, topographic wetness index, curvature, and texture of the soil. In the frequency ratio and statistical index models, at first wells with a discharge rate of 10 cubic meters per hour were extracted in the region; then, 70 percent Training wells (253 pcs) and 30% of the wells for validation (108 pcs) were randomly selected and divided and based on the frequency ratio, necessary analyses were conducted in classes and maps and maps were overlapped and, finally, the groundwater resources map for each of the models were produced. ROC curve method was used to evaluate the performance of models. The results showed that the frequency ratio and statistical index models 99 and 93 percent respectively have excellent efficiency in finding potential sources of groundwater in the plains of Ilam province, Dehloran, and Musian_Abdanan. Based on the model results, Frequency Ratio model functions better than Statistical Index. Based on this, the percentage of the area achieved in the Frequency model ratio are as follows 36% of the areas were Very weak; 15% Weak; 12% Average; 19% Good, and 18% Very good. It is suggested that respected Managers use Frequency Ratio model in their own programs

Flood water spreading (FWS) is one of the water resources management strategies in arid and semi-arid regions aiming at water harvesting, artificial aquifer recharge and optimum utilizing of floodwater. There are three kinds of drops (gates); vertical and inclined (type 1 and 2), as the main structure of a floodwater spreading system which is susceptible to collapse due to flooding damages. In this research, one of the independent systems of FWS was selected in Kowsar research station in Gareh Bygone, Iran in order for evaluation of technical and economic analysis of drops’ collapse. The study is performed by direct observation and fieldwork. Results show that the main causes of collapses are erosion of embankment, piping of drop and instability collapse of side walls. Contrary to even of flood discharge of Bisheh Zard1, at flood events in 2003, the results show that the amount of destruction in an inclined drop is more than the vertical drop. Inclined drop 1 and vertical drops are the less and the most expensive, respectively. Therefore, inclined drop 1 might be recommended for being widely used due to maximum stability and minimum costs (the ration of 0.6 between the costs of inclined 1/vertical drops).

A Groundwater resource is one of the most important sources that provide agriculture, domestic and industrial demand. The aim of this study is trend analysis of quantity – quantity groundwater fluctuations in the Minab plain from Hormozgan province. In order to assessment quantity and quality fluctuations was used Groundwater Resource Index (GRI) in the time period 1968- 2015 and EC, pH, SAR, TH in the time period 2008-2015, respectively. IDW method was used to map zoning of quality characteristics in ArcMap software. Mann- Kendal trend test used to analyze groundwater level oscillation. Result showed that groundwater level have decreasingly trend in the seasonal and annual time scale. As, Mann- Kendal Statistic is strong in the East and Southern plain. Iso- hyetal groundwater quality map showed that much of area (0.63%) has suitable water quality and the central of plain (0.37%) has unsuitable water quality.