Evaluation of Eco-geomorphology and anthropogenic factors role on Karun River water quality (between Gotvand dam to Ahwaz)

The knowledge of eco-geomorphology is adapted from both ecology and geomorphology that investigates the living organisms and their locations due to the effects of habitat geo morphological features (moghimi, 1391). Anthropogenic impacts or Human Effects on the environment include impacts on the biophysical environment, biodiversity and other resources (Shaney& et al., 2010). These variables (often based on some factors such as geological formations and geomorphology of basin, river discharge regime, waste water from human activities and etc,) are used in order to evaluate the water resources status as well as development projects of utilization and allocation of water to different uses. Also, studies on eco-geomorphology and anthropogenic factors in river basin show the natural and unnatural effects on these resources. Arian et al. (2015), using multi-variety statistical techniques on water quality of the Bano River in Pakistan, showed that the water in some regions of this area was not suitable for drinking and irrigation, due to increased alkalinity. The main aim of this study was evaluating the role of eco-geomorphology and anthropogenic factors on water quality of the Karun River and management options, from Gotvand to Abadan. The research method was analytical. The data were collected from library and field methods. In this study, at first, indicators of water quality were analyzed by using the Excel and Chemistry software. Then, ARC GIS10.2 and Expert choice11 software was specially used to analyze the role of effective factors in the Karun River water quality and finally vulnerable areas were assessed. Then, the effect of eco-geomorphology and anthropogenic factors on the physical and chemical properties of the river water was investigated and results were analyzed. The next step for determining the vulnerable areas of the Karun River, affected from eco-geomorphology and anthropogenic factors, was performed by using Fuzzy-AHP model. After filling of Gotvand dam reservoir and increasing the contact of surface water with layers of water-soluble salts, especially in Gachsaran formation, million tons of salt dissolved in the reservoir. Due to the increasing density, saltier water placed in the bottom levelsand the water of the better quality in the upper layers.Eventually, the layer formation stated due to the quality of in the reservoir . So, in lower levels, water salinity is 3 to 4 times more than the seawater, while in the high levels, the water quality is suitable and salinity degree is less than allowed limit for variety of purposes including drinking water. In terms of geomorphology, sedimentation and any factor that exacerbates the issue should be considered for sensitively in this area. The increase in agricultural land has been associated with increased use of chemical fertilizers and pesticides that are transported to the river by drainage and cause the undesirable water of Karun River. Modern irrigation networks of Dez and Gotvand damscontain irrigated lands in Karun and Dez basins, mainly located in the southern region of Dezful and between Gotvand and the south of Shushtar. This area enters annually 152 million cubic meters of drainage water into the river. Also opening some units of sugarcane development project such as Imam Khomeini unit (Shoeybyeh) and part of the projects in Ahvaz, the amount of agricultural water withdrawals was increased significantly. Therefore, the waste water of these lands, which is generally saline with high Ec (Electrical Conductivity), increased sharply in this region and caused reducing the quantity and quality of the Karun River. Other factors such as sewage and urban wastes, dam construction and withdrawals of sand from the riverbed, themselves have caused pollution and changes in water quality. Finally, according to the investigations of eco-geomorphology and anthropogenic functions on the quality of Karun, the rate of these effects in different parts were zoned and then analyzed, that indicated the rate of the effects on the quality of water is very high at the confluence of Dez River, Gargar and Shoteyt to the down part of Ahwaz. The impact of these factors is relatively low in the upstream areas, comparing to the downstream; in other parts also, as the distance to Karun increases, the rate of impact of those factors lessens. According to taken investigations, maps and field observations, the causes of the unpleasant Karun water from Gotvand dam to Shushtar are as the following: The entrance of salty river to Aghili plain; drainage of extensive fish ponds (17,000 hectares) into the Gargar River; and the sewage from Shushtar town and surrounding villages. Also, in a branch of Shoteyt, part of the wastewater from Shushtar town entering the river as well as about 30 percent of wastewater from the sugarcane industry has increased 600 EC in the Karun River at the interval of regulatory dam of Gotvand to Bandeghir, on Shoteyt branch. Increase of EC of the Karun river from the junction of the Gargar and Shoteyt to the downstream is due to the surrounding villages, factories and industries near the river, agricultural areas and entrance of the Dez River (which contains sewage of surrounding towns, and drainage of sugarcane agro-industry of Imam Khomeini, Haft-tappeh, Mianab, and 70% of Karun agro-industry). Moreover, the eco-geomorphological and anthropogenic effects on water quality of the Karun River were assessed very high, from the junction of Dez- Gargar -Shoteyt down to Ahwaz. But, at the upstream areas, the impact of the factors is less.