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Human activities and the climate change affects the river flow therefore monitoring flow rate of river for an extended period can reveal the detail of involved mechanisms in these changes. The previous studies show impact of human activities and climate change on river temporal variations varies in different locations. Water scarce is one of most problem in this area therefore finding affected parameters in water accessibility is important for water management in Middle East. This study aimed to investigate the trend of annual and monthly flow changes in the Dez River branches in southwestern Iran by several nonparametric methods. A structural equation model was used to assess the effects of land use and climate changes on river discharge. The study results showed that the annual precipitation at all stations has no significant trend, but temperature and evaporation at most stations increased significantly. Additionally, more than 30% of the study area's rangeland and forestlands have been converted into agricultural and residential lands. The results showed that land use and climate can determine 43.2% of discharge changes. Also, land use changes are more effective than climate change on river discharge changes.

Flood is one of the most dangerous and destructive phenomena which endangers people’s lives and properties all around the world. According to statistics of a 30-year period (1974-2003), about 2162 major floods have occurred which constitute 34% of the world's disasters (Tajbakhsh and Khodashenas, 2012). Floods are frequent and ruinous in Iran due to severe weather condition. Several factors intensify the risk of flood in urban areas including urbanization, land use changes, inappropriate drainage systems, and impermeable area development (Sabeti, 2011). Likak has faced numerous floods due to high rain density, high rate of urban development, unsafe and unproductive urban development, ignoring safety criteria in developing urban areas, road watering issues, inefficient drainage systems, and inefficacious water channels. Water channels and drainage issues have never been evaluated in this town. Applying an effective runoff management plan is the ultimate solution for the problem of flood in Likak. Storm Water Management Model (SWMM) is one of the most reliable and prevailing models for evaluating and managing the urban runoff issue. SWMM is a dynamic rainfall-runoff simulator which can be used for simulating the quantity and quality of the run-off for a single raining event or continuous long-term rains (Gironas et al, 2010). Yu et al. (2014) adapted and calibrated SWMM to Jinan, a typical piedmont city in China. Fourteen storms were used for model calibration and validation, finally verifying large-scale applicability of the model to piedmont cities. Results of this study verified that SWMM is applicable to large-scale cities.

Modeling of the rainfall-runoff process is important. The Results of the rainfall-runoff models have been used directly on issues such as water resource management, flood control and design of hydraulic structures. According to variety of accessible rainfall runoff models, selecting an appropriate model for a basin is important in terms of productivity and water resources management. In this study the performance of two rainfall–runoff models, IHACRES and GR2M in simulation of monthly flow were evaluated in Darhe Tkaht basin between 2000 and 2013 time. The models in the study region were calibrated and validated. The error between observed and simulated flow values was estimated based on the criteria Nash, root mean square error and the total flow volume error. Simulations is indicative satisfactory performance of two models in monthly flow simulation. In addition, the results show that the HACRES model simulate monthly flow with The Nash coefficient 0.7 and RMSE 0.56, better than the GR2M model.