فهرست مطالب behnaz khatar

Evaluating the response of rivers to natural changes and man-made manipulations are of great importance in managing river water quality. The main purpose of this study is to evaluate the negative effects of quantitative management without qualitative management of river flow. In this regard, by simulating water quality in river exploitation scenarios based on environmental policies, including minimum flow allocation, reduction of flow quality from aquaculture standards, taking into account the quality factors and pollution caused by the development of marginal urban communities, will be discussed.

The present study, which should be omitted was conducted on the Azadrud River in the Sarvabad region of Kurdistan Province. In this regard, by measuring quantitative and qualitative parameters in two monthly periods, the QUAL2KW quality model was calibrated and validated. In the first part of the study, the quality of the river along 22 km was simulated by changing the flow rate based on flow allocation scenarios in the Tenant method, and in the second part, the values of qualitative parameters in different flow management scenarios were compared with the accepted standard values for aquaculture (fish).

Based on the results, while the minimum environmental discharge according to the Tenant method for the studied river is 1.1 m3/sec, the critical quality discharge for March and April were estimated at 7.7 and 10 m3/sec, respectively. The study showed that the poor tenant scenario is not suitable for allocating the minimum environmental flow to meet the quality requirements of the river at all. 

The results showed that the conventional flow allocation method, i.e., without considering the quality conditions of the river, is not suitable and can cause serious damage to the environmental conditions of the river. This study showed that ignoring the quality conditions at the time of flow allocation causes the ecological health of the stream to be lost and the river to not meet the required standard for aquaculture.

This study aims at evaluating and modifying the Texas method for allocating environmental flow. This hydrologic method, while using the minimum amount of data, is a rival for the Tenant method and has the capability of introducing an amount of discharge to maintain the ecological regime of rivers. In this paper, after distinguishing the worthiness of the Texas method and observing some differences between the results of the method and the historical regime in the case study, the method was modified in such a way that while preserving the basic principal of the original method, could propose a flow regime which was laid between the observed long-term minimum and mean monthly discharges. The new method is called the Modified Texas method. For evaluating the Texas and Modified Texas methods concerning the allocated annual volume, the equivalent scenario from the Tennant method was employed. The allocated volumes by the Modified Texas, Texas, and Tenant methods were 50%, 47%, and 40-60%, respectively. This paper, concerning the achieved results for the case study, shows that employing the Texas and Modified Texas methods instead of the Tenant method and enhancing the method to the level of a native method provides reasonable results comparable with those of the habitat simulation or holistic methods.

Summary: One of the most important steps to make use of any renewable energy is to perform an accurate estimation of solar energy. Incoming shortwave (300-4000 nm) solar radiation is an important component in evaluating environmental factors. In addition to local solar radiation، a detailed spatial and temporal information of Global Solar Radiation (GSR) is required in urban design and regional plans. Further، beside the atmospheric parameters، the variability of the elevation، the surface orientation and the obstructions due to elevations are a source of great local differences affecting the incoming solar radiation. For this reason، several models based on GIS techniques have been recently proposed and developed، which consider the local topography for retrieving global solar radiation on the Earth’s surface. Actual irradiation which is received at any time and location depends on many factors such as solar zenith angle، solar declination angle، atmospheric transmissivity (i. e. cloud amount، aerosol optical depth)، diffused radiation، slope orientation and local topography. The commonly used radiation models (e. g. Angstrom- Prescott model) do not consider diffused radiation، atmospheric transmissivity (turbidity) and topography of the study sites; as they are not usualy available for model estimation. Using the Arc GIS tool، Batless et al. (2008) estimated the global solar radiation on a monthly basis. They showed that summer month estimations are more accurate than winter times. For a region with a different topography، Martinez et al. (2009) employed satellite images (Meteosat) and Digital Terrain Model for estimation of GSR. Their results showed reasonable performance for the model estimates. Bosch et al. (2010) addressed the same problem. To evaluate the potential of solar energy for Oman، Gastli and Charabi (2010) used Arc GIS method in their work. They found that Oman had ahigh potential of solar energy which could be used as a sustainable source of renewable energy. Iran is located in an unique part of the world، which experiences significant variation in altitude and latitude. The altitude of the country، which has a complex totography، varies from -40 to 5670 m above sea level. These geographical factors cause a wide range of climate types and different amounts of solar irradiance at the surface. The majority of the radiation modeling in Iran has relied on straightforward and simple radiation models such as Angstrom and Angstrom-Prescott. The main constraint of these models was the regional estimates of GSR which were not easily possible from the local estimates. As the first attempt in Iran، this work aimed to consider the effect of complex topography and altitude on surface GSR. In this study، global solar radiation was produced for four central provinces of Iran using the Solar Analyst model implemented on Arc GIS 9. 3. The Solar Analyst uses input parameters such as the diffuse fraction (k) and the atmospheric transmissivity. These parameters are not usually available in radiation networks. In this work، the aforesaid parameters were obtained with use of global solar radiation data (as measured in radiation sites) and extraterrestrial radiation (determined by astronomical models). Monthly localsolar irradiation in the year 2007 was calculated from a digital terrain model (DTM) with spatial resolution of 300 m، diffuse fraction (k) and atmospheric transmissivity (τ) for the study sites. Results were accordingly compared against the measured GSR values. Evaluation of the annual regional global solar radiation showed that the southern and northern slopes received the maximum and minimum incoming solar radiation، respectively. It was found that the elevation differences have less effect on the incoming global solar radiation than other topographic variables such as slope، surface orientation and the obstructions.