IRANIAN JOURNAL OF WATERSHED MANAGEMENT SCIENCE AND ENGINEERING
Year:2017 | Volume:11 | Issue:37 |Papers Count:9

Climate change in addition to the direct impact on climate parameter indirectly will affect on the economy, society, agriculture and so on and will cause consequences such as floods, drought, migration, and poverty. Thus, it is necessary to determine the mechanism and proper planning to reduce the negative consequences of climate change phenomenon. Because of the importance of the climate change phenomenon on water resources in rivers, scrutiny of river behavior and especially river discharge in the future periods which is affected by climate change is essential to water resource management and finding solutions for adaptation and mitigation to climate change. Goal of this research is investigation of climate change impact on watershed runoff of Tuyserkan River and appropriate solutions to reduce the impact of these changes. For this purpose, hydrometric and meteorological data and soil characteristics and topography of the area were collected. The soil moisture accounting algorithm was implemented to continuous rainfall-runoff model for sub-basin of Tuyserkan plain. Then, by applying 15 general circulation models and LARS-WG model with the beta distribution function were simulated rainfall under A1B and B1 scenarios. Rainfall-runoff model was run using future rainfall and volume of runoff in each of sub-basin for the future period of 2011-2030. Finally, with 10% increase in rainfall by cloud seeding technique river runoff was estimated. The results showed that the decrease in rainfall due to climate change will reduce runoff volume of each sub-basin. As of 40. 5 million cubic meters in base period will be 34. 9 and 35. 8 million cubic meters under scenarios A1B and B1. The results showed that the 10% increase in precipitation from clouds seeding, about 2 million cubic meters of runoff volume declined due to climate change will be compensated.

The first step in the study of landslide susceptibility and hazard is to produce a landslide inventory map. The usual methods of landslide mapping include field investigations, combined with visual interpretation of aerial photographs. Modern and newfangled remote sensing techniques, using satellite images, causes in facilitating of landslide mapping and reduce the required time. In this study, a semi-automatic model based on object oriented analysis was developed in eCognition software to identify landslides at the central part of the Albourz Mountains in Vazroud watershed. A total of 105 landslide events were detected within the study area using documentation from previous research, interpretation of aerial photographs and visual inspection of the Google Earth images. 70% (74 points) of detected landslides were randomly selected for training, and the remaining 30% (31 points) cases were used for test. The model was developed based on spatial, spectral and geometry characteristics of training landslides as well as thematic maps of the study area. Results showed the model accuracy of 74. 19% in the detection of test landslides. Also the accuracy of 41. 28% was achieved in detection of the extent of landslides which in the condition of using high-resolution images, would be improved.

Soil erosion in the watersheds is a function of some factors such as climatology, topography, soil type and land use. Within these factors, the importance of precipitation because of its high variation and land use because of the role of humans on community development is very clear. In this research, the precipitation, discharge and sediment data in a statistical period from 1967 to 2009 were used. Drought situation was calculated by standard precipitation index with 3 months’ time scale. Land use maps were prepared in three periods based on satellite images, and the changes of land use between these periods were compared. Results showed that the area of rangelands and farms from initial to final section of study period varied from 14% and 21% to 41% and 11%, respectively. Significant difference in sedimentation rate is visible between initial and final sections of study period. Percentage of drought occurrence increased to triple from initial to final period. The result of Mann-Kendall test showed a negative trend for watershed discharge at 95% significant confidence level. Therefore, it seems that increasing drought occurrences and therefore decreasing runoff and change of farms to rangeland, caused to the decreasing suspended sediment load in Senobar watershed.

Precipitation, Temperature, runoff and floods are some of important parameters among climatic and hydrological parameters for forecasting and determination of their behavior in water resources management. In this research, for investigation of change in hydrological regime of Gorganrood River in Tamar gaging station, the 44 years of hydrological data during 1969-2012 were used to model by GIS, ILWIS 2. 1 and SMADA. Then, physical characteristics of watershed, temperature, precipitation, runoff trends, floods and discharge hydrograph were evaluated. The results show that the climate of the region will change to dried climate based on increase in temperature and reduction in precipitation, an increase in rainfall intensity and an increase in peak flow. On the other hand, the average monthly and annual discharge show the small increase which is in accordance to world climate change in Northern hemisphere and 30 degree latitude. Based on floods in Tamar gaging station, the biggest floods are in month of November, March, April and May during the period of 10 years with frequency of 14, 12, 12, and 12, respectively. Based on several recorded flood in Tamar gaging station, unit hydrograph of watershed was determined. Flood hydrographs with return period of 2 to 2000 years were determined based on time of concentration and time distribution pattern of rainfall.

Climate change is one of the most important problems in the present century. So, assessing and prediction of future changes is important to mitigate climate change impacts on water resources is very important for economics and socio-economic affairs. The purpose of this research is to predict the temperature and precipitation changes under Scenario A1B, A2 and B1 HadCM3 general circulation models during 2011 to 2030 using LARS-WG downscaling model in the Urmia Lake Basin synoptic stations. The results of the analysis were evaluated in three synoptic stations including Saghez, Tabriz and Urmia in the base period (1990-1961) and in 2010-2030 (2020s) for three variables including minimum temperature, maximum temperature and precipitation. During assessing process, LARS-WG model is evaluated via measures of MSE, RMSE, MAE and the coefficients of determination and correlation. The results showed the model is able to predict the above mentioned parameters accurately, but has less accuracy in the simulation of precipitation. Also, the results indicate a decrease in precipitation in Urmia and Tabriz stations for the next 20 years compared with the base line period. Maximum and minimum temperatures show an increase in all the three stations. It is estimated there would be an increase equal to 1. 5 degrees Celsius for the whole basin. Maximum temperature would rise in Tabriz and Urmia stations. An increase in minimum temperature and the maximum amount of rainfall would occur in the Urmia station. It would be equal to 1. 6 ° C and 2. 26 mm, respectively.

Human being as one of the main factors affecting water resources has important and decisive role in water resources stability. Relation between human as stakeholder with natural ecosystem should be an important issue in policy and integrated water resource management. Accordingly, for successful water resources management, there is a need for shift toward collaborative management. One of the important social theories in relation to the management of natural resources, especially water resources, is social capital. Important aspect of this issue, trust and collaboration are the most important factors in social networks. Other issue that will be discussed in this research is social cohesion, which is related to a group or community relations together. The goal of this study is to analyze the structure of social relations between local beneficiaries of water resources within ecological boundaries of Valiabad village, with an emphasis on trust and collaboration and macro-level indicators of social networks. According to results of this research, based on network density, the cohesion and social capital in local stakeholder network of water resources in the village, based on trust component is average and based on collaboration is weak, and this represents a challenge for water resources policies in the region that should increase cohesion and social capital with strengthening trust and especially collaboration to be successful in water resources co-management.

The Vortex Settling Basins is one of the sediment separation methods used by researchers. In the previous researches, the geometric and hydraulic conditions of basin have been considered to maximize the efficiency. In this study, the trap efficiency of two series connected settling basins is investigated. The effect of the system inflow and the central orifice outlet discharge of basin on the removing efficiency and trapping efficiency-or efficiency-are investigated in this research. The results showed: 1) in comparing with one basin, the use of two series connected settling basins increased the removing efficiency and trapping efficiency about 12% and 15%, respectively; 2) the maximum efficiency was increased from 75% to 90%; 3) the removing efficiency of basins is directly related with the inflow discharge and the washout flow rate (outlet discharge of basin central orifice); 4) the basin efficiency increases with increase of washout flow rate and decreases with increase of inflow discharge.

Erosion, sediment transport, sedimentation and water quality are considered as very important controversial issues in watershed management. Since many watersheds in countries including Iran don’ t have any sediment gauging station, using statistical techniques to analyze erosion/sediment process is one of the important strategies for evaluating the trend of sediment yield. According the purpose of this study was to statistically evaluate the trend of suspended sediment load by using time series analysis in the Bar watershed, Neyshabur. In this work, the sediment load statistical records of the Bar hydrometric station during the period 1967-2012 were analyzed through the Mann-Kendall and Pettit tests. Results showed that the gradual change of sediment load was decreasing and significant at the level of 5%. Abrupt change of sediment load time series was also significant at the level of 5%. The change point was matched with the year 2003 in which the average sediment load of 317. 62 tonnes per day declined by 17. 25 tonnes per day after that. The statistical trend analysis of daily rainfall at the representative stations “ Karkhane Ghand” , “ Marusk” and “ Bar” and water discharge time series at the Bar hydrometric station for the period 1967-2012 showed no significant trend at the level of 0. 05. As a result, it can be stated that at least in the last three decades, there was no marked changes in rainfall and water yield and consequently meteorological and hydrological drought in the watershed. Therefore, we cannot attribute the decreasing trend of sediment load of the Bar watershed to metorological drought conditions in the period leading up to the change point. Investigations revealed that watershed management operations in the Bar basin started in 2005 (corresponding with the change point in time series of suspended sediment load) and officially continued until 2010. Therefore, the downward trend in the time series of suspended sediment load can be associated with structural operations (Gabion, rock and soil chack dams) from the late 90's until now which trap a considerable part of sediments.

In regional flood frequency analysis, instead of using the data from a single station, it considers the data and characteristics of a group of similar stations. This study was carried out in Qazvin province and is based on linear momentum that Hosking and Wallis are provided this method as a new approach to flood frequency analysis. The results of factor analysis showed that perimeter, equivalent diameter, time of concentration, length of main waterway and area were the main variables affected flood magnitude. Based on cluster analysis and using the factors affected flood peak, the remaining 15 stations, were divided into two homogenous regions. Homogeneity of these two regions was confirmed using homogeneity test of L-moments. Based on the best-fit criteria of Zdist, GNO distribution is the best fit for the entire region but for one and two homogeneous regions, GLO and GPA distributions were the best fit, respectively. Parameter values for each of the selected distributions were calculated using linear moments and discharges with different return periods were estimated using the best regional distribution for all stations. Finally, after drawing of growth curves, the regression relation between average discharges and watershed areas were obtained at each region. Based on these relationships, at un-gauged locations, peak discharges can be estimated using index flood method for different recurrence interval.