The correct and accurate estimation of river flow can play an important role in reducing the effects of flood damage. In this research, Gene Expression Programming (GEP) model and Bayesian Network (BN) were used to predict daily flow of Mahabad River in Urmia Lake Basin. Accordingly, four input models with a delay of one to four days used to estimate daily flow at time t+1 over a 23-years period and 75% of data was used to train the models and 25% of the remaining data was used for the test stage. Results showed that the best model in both methods was the input pattern with three-time lags. Also, based on the correlation coefficient (R), Root Mean Square Error (RMSE) and Nash-Sutcliffe (E) coefficient in the test stage of the GEP method with R=0.902, RMSE=2.71(m3s-1) and E=0.812 compared to the BN method with R=0.905, RMSE=2.679(m3s-1( and E=0.817 is more accurate. In general, both methods have acceptable accuracy and are they relatively similar, but because of the simpler modeling, Bayesian Network method can be used as an efficient method for predicting river flow.

The subject of the study is to analysis nrtttap of Mahabad Riverchannel. This area is located on the south of Uromia Lake. Rapidchanging of its channels nrtttap is an important characteristic whichthe evaluation of these characteristics is necessary to anyimplementation of development projects. For this purpose, themorphological changes of river channel were recognized by the arealphotographices and satellite imageduring different times periods. Therelationship between effective variables on the channel pattern suchas, discharge, slope, stream power, stream bank clay content andwidth of bed, and observed pattern changes were analyses. The resultsshowed that formation of braising channels could be the result ofaccumulation of bank coarse materials and increasing of width todepth ratio. The nrtttap of the river changed to sinuosity at thedownside of braiding channel. The increased discharge and more riverbank resistance due to high clay content caused to river patternchanged from breading to sinocity. In the distance between Mahabaddam at the upstream and diversion dam at the downstream, the rivernrtttap was changed to Anabaranching. Assessment and comparisonof Arial photographs before and after of Mahabad dam constructionrevealed that these types of channels were developed recently. Reduction of peak flows and sediment deposition in the channel as theresult of dam construction, prepared the essenssial conditions to formAjjjjfjjnabrancing

Background and Objectives: Regards of water scarcity, inappropriate distribution of precipitation, implementation and development of projects in water resource fields such as dam construction and inter-basin water convenience is unavoidable. For prevention of long-term negative environmental impacts of such projects and for water allocation acts, it is necessary to study hydrological and ecological demands of river as an "environmental water demand". The "environmental water demand" usually is defined as a set of discharges which are determined by the magnitudes, frequencies, occurrences and given flows, but the employed methods in this research calculate environmental flows in the form of mean annual runoff (MAR). These flows which provide appropriate conditions for conservation of aquatic life and ecosystem processes for sustainability goal, are called "environmental flows". This article aimed to study the "environmental demand" estimation for Mahabad-Chai River. Materials and Methods: Mahabad-Chai sub basin is located on southwest of Lake Urmia; and considering its extent, it is the fourth largest sub-basin of Lake Urmia Watershed. Its geographic area ranges from 44˚ 45΄ E to 45˚ 56΄ E and 36˚ 22΄ N to 37˚ 10΄ N and is composed of two main branches “ BYTAS & KOTER” . The ecological river demand was estimated and compared with four hydrological methods (Tenant, Tessman, FDC-shifting and DRM), then suitable method was introduced. Results: The ecological demand of Mahabad-Chai river is estimated and compared by four hydrological methods, FDC-shifting method biological class C, because of considering ecological specifications of the river, was chosen and the environmental demand of Mahabad-Chai River was estimated to 0. 35 cms in BYTAS station and 1. 17 cms in KOTER station. The annually average flow was 1. 73 and 6. 17 cms in BYTAS and KOTER hydrometric station respectively. Conclusion: Based on the results, the suggested flow of FDC-shifting method at C class is recommended as minimum environmental flow for Mahabad-Chai River, because this method needs the less data, doing early and rapid assessment in data and simulating current hydrological conditions by considering desirable ecological conditions, whereas other methods can’ t do this action. Moderated class C (relatively modified) consider about %20 MAR to %30 MAR as environmental flow, that in this condition basic function of ecosystem has not changed and more species is survived. Also moderated class C has good match with regime of flow at several months and is acceptable in area in terms of managerial, agricultural uses, drinking and etc. The suggested method in this research is not the ultimate solution for environmental problems of Mahabad-Chai River. Lack of comprehensive required ecological information at river’ s ecosystem studies, cause to estimating eco-hydrology by less coefficient of confidence.

Mahabad River is located in south part of Urmia Lake. The River is deformed to Anabranching in the region between the upstream of Mahabad dam and downstream of detour dam. The aim of this research is evaluation of the factors that affects the formation of this kind of channel. For this purpose, multiple physical variables including wide bed, stream power, channel slope and the amount of the bank clays were studied. The form of channel were assessed at two different times before and after build of the dam based on 1346 and 1382 aerial photographs. The aerial photographs scanned and processed in Geographic Information System, in order to extract of the wide channel. Finally, the effect of the dam on river and changes after the construction of the dam were determined. The results showed that increasing recent period’s runoff potential and basin erosion were provided the necessary potential for Anabranching formation in this area. But, the most important factor for construction the Anabranching was the dam building causes decreasing peak flow and increasing bedmaterial deposing rate. The river adjusted by deformation in response to deposition of bed-materials as a result of decreasing stream power. On the other hand, decreasing island length and nonoccurrence of Anabranching channel to Nanson and Knighton model was the result of the presence of the detour dam on downstream.

The river morphometric has been reviewed by using topographic maps, digital model and field data for determining the role of lithology and tectonic changing resistance on longitudinal profile of Mahabad river catchment area in south part of Urmia Lake. For this purpose, the basin was divided in to 5 (five) parts. Streams were ranked based on Astraler method. In order to determine the fractures, the longitudinal profile of each class was adjusted with geology and tectonic formations from 1: 100000 geology maps. The obtained results showed that in Daras and Agri limits, changing from one resistant lithology to a nonresistant lithology has caused a clear and distinguished fracture in longitudinal profile and the breaks can only be seen in the formation borders which indicate the high effect of lithology on longitudinal profile. In Kootar and Bytas areas, the fractures can be seen inside the lithology and there in no fracture at the formation border. Based on geo tectonic index, Kootar and Bytas limits has more tectonic activities in comparing with the other areas, so that it is understood that the relationship between the afflux due to tectonic and the effect of bed rock on the longitudinal profile is reversed. Therefore tectonic afflux reduces the effect of bed rock on longitudinal profile.

Background and Objective: In water resources management and operation, especially for dam reservoirs, supplying the minimum water demand for protecting the life of the different plant and aquatic species is essential. Allocating the environmental flow for Mahabad River, as one of the most important rivers in the Urmia Lake basin, is very crucial. Therefore, the purpose of this study was to estimate the minimum environmental flow for Mahabad River using Eco-Hydrology methods. Method: In this study, the environmental flow for Mahabad River was estimated by five methods, namely Tenant, Tessman, Flow Duration Curve (FDC) Shifting, Desktop Reserve Model (DRM), and Flow Duration Curve Analysis (FDCA). Findings: According to the results obtained in this study, to protect Mahabad River in the acceptable minimum environmental condition, the FDC shifting model considering class B (35. 1% MAR (mean annual runoff), equivalent to 2. 75 m³ /s) and DRM considering class B/C (27. 24% MAR, equal to 2. 13 m³ /s) led to approximately similar and acceptable results. Discussion and Conclusion: Generally, the FDC shifting model and DRM that consider different hydrological classes are preferable to other methods, and these methods can be used to determine the environmental flow for Mahabad River.

Surface and groundwater dynamically interact at different spatial or temporal scales within a plain. Accurate estimation of water balance components is an important simulation of such interactions. Despite the rapid expansion of numerical models over the past two decades, there is still room for improvement for comprehensive and integrated assessment as well as management of surface and groundwater resources. In particular, the use of coupled surface and groundwater models is important to connect both surface and groundwater, and for proper representation of the water balance in the unsaturated root zone. The results of various studies suggest that the combination of SWAT and MODFLOW models can satisfactorily simulate the interaction between surface and groundwater at different spatial and temporal dimensions (Sophocleous and Perkins, 2000; Sun and Cornish, 2005; Bejranonda et al., 2007). Indeed, if both models are used simultaneously, not only the limitations of the two individual models can be improved, but also the temporal-spatial properties of the target area can be adequately reflected (Kim et al., 2008; Park and Bailey, 2017; Wei et al., 2018). Specifically in the Urmia Lake Basin, which has been severely affected by indiscriminate exploitation of water resources, these models can be used to maximize the supply of Urmia Lake based on the pattern of supplying irrigation needs from integrated water sources. This requires the interaction of surface and groundwater resources in different locations of plains and aquifers to be simulated and predicted based on different shares of agricultural water supply from integrated water sources.The main purpose of this study was to evaluate the interaction between ground and surface water in Mahabad plain using the coupled SWAT-MODFLOW-NWT model as a comprehensive and integrated model. The main challenge in this study is the interaction and monitoring of water table adjacent to the surface water bodies.

The Mahabad River Watershed has been exposed to severe erosion as a result of landuse change. The aim of this study is to quantify the amount of sediment yield and the relationship between land use change and slope. Different sources such as geologic and topographic maps, satellite images, hydrometric as well as meteorological data were used to extract and gather the information needed for this research. Six factors including altitude, slope, precipitation, rock erodibility, time of concentration and land use were specified as the most effective factors. The overlapping of the six factors maps resulted in the preparation of sediment delivery potential map. The distribution maps prepared on each of these parameters and their overlaps have shown that areas with more severe slopes are categorized as highly susceptible to erosion. However, in areas with resistant rocks, change of land use has been the determining factor. Comparison of water and sediment discharge data of 1996-97 with 2001-02 (similar annual water volume) showed that the sediment yield has increased. Studying land use map prepared using satellite imagery of 1987 and 1998 showed that land use of the area has severely changed from pasture to dryland farming. This factor has also caused the intensification of mass movement recently occurred in the area. Landuse is the only parameter modified by human, and it is the only one which can be quickly and effectively changed. Hence, it seems that the upstream areas in the south and southwest of the basin with low concentration time, steep slope, high erodibility, high amount of precipitation, and the landuse of forest and pasture mixture as well as alluvial terraces with fine and granular sediments are the most sensitive areas which need protecting and control measures.

To select a statistical distribution to describe a set of data, there are several criteria that can be used. Rather than the selection of a criterion according to traditional methods, the combination of two or more criteria may be used to achieve the best choice. But when more than two criteria are applied to find out the best model, selection becomes more difficult. In these cases, the use of multi-criteria decision making (MCDM) is essential. This study compares eleven commonly used distributions in hydrology based on five selection criteria. These selection criteria are: The Kolmogorov-Smirnov test, the errors in skewness and kurtosis, the errors in cumulative distribution function, the errors in probability distribution function and the root mean square error. Three MCDM methods, namely, simple additive weighting, weighted product method and fuzzy majority approach, are employed. In the present study, we examine the sensitivity of the results of MCDM by changing the weights and number of criteria. The methods are applied to a case study of Mahabad River, a major river flowing into Lake Urmia in northwestern of Iran. Results of this study have shown that three-parameter Weibull, three-parameter Weibull and generalized extreme value distributions have the best fit for peak flow, volume and duration of Mahabad River flood data, respectively. The result of this study can be used to improve the flood frequency analysis.