Journal of Watershed Management Research

Sustaining environmental flows to preserve biodiversity of aquatic plant and animal species, as well as constancy of water for human communities, is essential in many river ecosystems. On the other hand, hydrological changes caused by the dam and its related environmental problems have provoked many concerns for hydrologists, ecologists and policymakers. Therefore, the main aim of this research was to study the rate of change in the Environmental Flow Components (EFCs) caused by the construction of Sabalan Dam in the Qarehsou River of Ardebil at stations of Arbabkandi and Dostbeiglou (before and after Dam) using IHA Software7.1 during the time period of 2005-2014. For this purpose, the values of 34 environmental flow parameters were estimated at each hydrometric station. Consequently, changes in the parameters of the environmental flow discharge were investigated in four groups of Extreme Low Flows, Low Flows (Base flow), High Flow pulses, and Floods events. The diagram below shows the parameters of minimum flow, peak flow and small flood. Based on the results, the frequency of Extreme Low Flows at the Dostbeiglou station had a 59% increase with respect to Arbabkandi station. On the other hand, the peak flow component showed more balanced nature in Dostbeiglou station after the dam, which can be related to the regulating effect of dam on high flow and balancing outflow in downstream reaches. The Peak flow, Duration, Timing and Frequency of small flood events had decreased in Dostbeiglu Station compared to the Arbabkandi with amount of 27, 78, 68 and 17 percent, respectively. Also, the peak and frequency of large floods had decreased at Dostbeiglu station with amount of 26 and 50%, compared with the observed flood events at the Arbabkandi station which located before the Sabalan dam.
 

Extended Abstract
Introduction and Objective: Intensification of natural disasters make it important to know the time variations of rainfall for wet and dry spell management and adaptation strategies. Measuring and predicting of precipitation anomalies using statistical methods is an important tool for climate studies. Seasonal changes determine the distribution of precipitation occurrence over a year period.
Material and Methods: The purpose of the present study was to investigate the seasonality variations of monthly rainfall data using circular statistics method at 28 rain gauge stations in a 30-years period. According to the results, the seasonality index of monthly rainfall, standard deviations and standard deviations were calculated in the monthly time scale. In the circular statistics method, the time of occurrence of the event is determined based on the angle on the scale of the studied event interval.
Results: According to the results, the value of the seasonality index (r) in the 8 rain gauge stations are greater than unity, which includes Pol Almas, Kousetopragi, Nir, Lay, Sarein, Siyahpoosh, Neur and Yamchi, meaning that the occurrence of precipitation in these stations occur completely with seasonal natureAccording to the results, there is no correlation between the mean amount of rainfall and the values of the seasonality index (r). The highest Seasonal index (r) is calculated for the Lay station with a value of 1.53 and the minimum value of the seasonality index (r) is assigned to the time series of Totoonsin station with zero SI value. At most of the studied stations, it is observed that the value of the SI value (r) is close to 1 which indicate the seasonal nature of the precipitation occurrence.
Conclusion: Based on the values of the seasonality index, wet periods and the time distribution of rainfall in different months of the year can be determined. Also, the seasonality index can be used to determine the duration of droughts. The numerical calculation of the index over a long period of time can provide a more comprehensive understanding of precipitation distribution. Most of the rain gauges with seasonal rainfall pattern located in the east and west part of the Ardebil province. In conclusion, determining the distribution of precipitation in the study area showed that the precipitation occurrence in the Ardabil province occurs seasonal with distribution of precipitation in two to three months of the year.

Extended Abstract
Introduction and Objective: The severity and frequency of floods, depends on watershed characteristics, including shape, slope, drainage density and terrain parameters. Also, hydrological characteristics such as rainfall, storage, interception, infiltration, and anthropogenic activities can intensify or reduce the flood losses. Determining flood-prone and flood-prone areas is a prerequisite for flood management planning and damage.
Material and Methods: This study was conducted to assess the flood susceptibility of Khiavachai sub-watersheds located in the west of Ardabil province with an area of 12,680 hectares using frequency ratio method. Parameters of elevation, slope, land curvature, topographic wetness index, distance from rivers, direction, drainage density, hydrological soil group, geology and land use were used to assess flood sensitivity and prioritize

sub-watersheds. The spatial map of selected parameters was prepared in raster format. Then, according to the historical flood events, the spatial location of 107 flood points in the area was determined. The observed flood event points were randomly divided into groups consisting of 74 points (70%) for calibration and 33 points (30%) for validation. Then, by comparative analysis between the occurrence of previous floods and environmental parameters affecting the occurrence of floods, the impact weight of each class of parameters was obtained. Finally, a flood probability map of the study area was obtained.
Results: According to the flood potential map, flood susceptibility of Khiavachai watershed was shown as five classes with very high, high, medium, low and very low levels. The results showed that the sub-watersheds (1 and 2) adjacent to the outlet of the basin have the highest flood sensitivity. In other words, flooding of sub-watersheds located downstream of Khiavachai watershed is due to runoff accumulation and high flood prone due to the impact of other variables of slope and rainfed agricultural land use.
Conclusion: Protecting the river and carrying out various watershed management operations to convey the flow in these areas can reduce the potential damage caused by floods. The proposed flood sensitivity map can be the basis for prioritizing flood areas as well as control measures for flood management. Therefore, watershed management measures to control floods in this area are more important.