Mahsa Tashakori; Mehdi Hayatzadeh; Ali Fathzadeh; Javad Chezgi; Akram Bemani Kharanagh
Abstract
Introduction The most important problem in the development and construction of underground dams is the complexity of determining suitable areas for dam construction. This problem arises from the fact that many criteria and factors including social, economic, geological and hydrological criteria are involved ...
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Introduction The most important problem in the development and construction of underground dams is the complexity of determining suitable areas for dam construction. This problem arises from the fact that many criteria and factors including social, economic, geological and hydrological criteria are involved in its proper location. Therefore, it is important to use methods that can determine suitable places for the construction of underground dams with high accuracy and with the least amount of time and cost. The construction of an underground dam is recommended as one of the solutions for water supply in arid areas where there is no access to usual sources, such as wells and permanent rivers, or they have few water resources. For this purpose, in the present study, the location of the prone areas for the construction of such dams has been investigated. The studied area is the Rodan Watershed in Hormozgan Province, which has a good potential for the construction of an underground dam due to its dry climate and special geological conditions.Materials and methodsIn this study, the number of eight initial locations were identified as potential points for construction underground dam by combining digital elevation model, topographic features, geological and hydrological features in GIS. In the following, after forming the decision matrix using Vicor model, ranking, determining the index and selecting the smallest index as the best option were done. Finally, the options were sorted based on the values of desirability index, dissatisfaction index and Vicor index. Then, the best option that has the smallest Vicor index was selected.Results and discussionAccording to the obtained results, the value of Vikor index (Q) was 0.0158 and 0.097 for sites 5 and 2, respectively, and that way, based on Vikor index, the first rank belonged to the site 5 and the second rank belonged to the site 2. Therefore, out of the initial eight locations, only two places were suitable spots and other suitable sites were rejected due to the distance from the centers of population concentration and agriculture. Rank one, located in the east of Ziarat Ali, is one of the best places to build an underground dam due to the hydrological and topographical conditions, including the fact that the slope in this site is less than five percent. The second priority, located in the north of Brentin district, was considered as a suitable option for the construction of an underground dam due to its location in the vicinity of a sparsely populated village where drinking water is supplied through a well. Among the criteria used in the present research, the criteria of water need, distance from the village, pH and EC parameters, and water quantity were the most important in the sites that have been assigned the first and second priority.Conclusion Examining the results of the reservoir surface factor in this research showed that the larger the reservoir surface, the higher the priority in locating this structure. In underground dams, unlike surface dams where the large reservoir surface is considered a disadvantage due to losses by evaporation, regardless of other factors, the best place to build an underground dam in a river is the canyons that have the maximum area of the reservoir in upstream. Looking at the axes selected in the current research, it can be seen that the highest priorities and the most valuable axes are selected in the quaternary formations, which can indicate the accuracy of the structure's positioning. Since the peak of water consumption in the region is in the spring and summer seasons, therefore, by constructing an underground dam in the proposed sites, part of the water shortage and crisis in the hot seasons can be compensated.
Vahid Moosavi; Mehdi Hayatzadeh
Abstract
Groundwater recharge or deep drainage or deep percolation is a hydrologic process where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. Groundwater recharge depends ...
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Groundwater recharge or deep drainage or deep percolation is a hydrologic process where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. Groundwater recharge depends on several factors such as infiltration capacity, stochastic characteristics of rainfall, and climate factors. Groundwater recharge is of great importance especially in semiarid regions. In arid and semi-arid regions of the world, groundwater serves as an essential alternative to surface water resources for water supply purposes. It plays a significant role in meeting the water demands of man and the ecosystem and is perceived as the panacea to the looming water scarcity scare. Determination of recharge quantity provides worthy help for managers in water resources management. Ground water recharge includes recharge as a natural part of the hydrologic cycle and human-induced recharge, either directly through spreading basins or injection wells, or as a consequence of human activities such as irrigation and waste disposal. The Soil and Water Assessment Tool (SWAT) is a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds. SWAT is a public domain hydrology model with the following components: weather, surface runoff, return flow, percolation, evapotranspiration, transmission losses, pond and reservoir storage, crop growth and irrigation, groundwater flow, reach routing, nutrient and pesticide loading, and water transfer. SWAT is a continuous time model that operates on a daily time step at basin scale. Its objective is to predict the long-term impacts of management and of the timing of agricultural practices within a year (i.e., crop rotations, planting and harvest dates, irrigation, fertilizer, and pesticide application rates and timing). It can be used to simulate at the basin scale water and nutrients cycle in landscapes whose dominant land use is agriculture. It can also help in assessing the environmental efficiency of best management practices and alternative management policies. In this study, the hydrologic process of the Marvast basin was simulated using SWAT Model in order to determine the amount of groundwater recharge in Marvast plain. In this way, firstly, the required maps i.e. slope, soil and land use maps were produced. In order to produce land use maps, panchromatic and multi-spectral imagery were fused to enhance the spectral and spatial resolution of Landsat imagery. In the next step, the fused imagery was used to produce land use maps using pixel based and object oriented image processing techniques. The slope map was produced using digital elevation model. The soil map was also produced using soil profiles in the regions. The requisite climatic data were also imported to the model with a daily scale. According to the importance of irrigation and its effect on evapotranspiration and groundwater recharge, irrigation amounts were also considered importing irrigation plan in SWAT Model. Afterwards, the model was calibrated using SWAT CUP software and the SUFI-2 algorithm. Finally, the verification showed that the model with Nash-Sutcliff of 0.59, coefficient of determination of 0.83 and the root mean square error of 0.05 has a relatively good performance. The results showed that object oriented image processing technique outperformed pixel based technique. It was shown that the amount of groundwater recharge was 27082602 cubic meters and the irrigation water return coefficient is 34%. It was confirmed that SWAT Model has a relatively good performance for groundwater recharge modeling. Improving the cropping pattern, preventing development of unauthorized wells and excessive groundwater withdrawals, as well as proper irrigation systems, can be effective in reducing the groundwater storage deficiency and preventing an increase in water resource crisis. This study showed that this model is not efficient for short term runs, however, its performance is better for long term runs. It is suggested that the SWAT and MODFLOW Model be used together to study both surface and underground currents. Also, lysimeters or SWAP Model can be used to better determine the amount of return flow and groundwater recharge.