Irrigation
A. Vaezihir; M. Khalkhali; M. Tabarmayeh
Abstract
Introduction Groundwater is an important resource for domestic, agricultural, and industrial purposes (Andualem and Demeke, 2019). However, the growing population and advanced irrigation technologies have significantly led to increased groundwater exploitation resulting in aquifer depletion. Exploitation ...
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Introduction Groundwater is an important resource for domestic, agricultural, and industrial purposes (Andualem and Demeke, 2019). However, the growing population and advanced irrigation technologies have significantly led to increased groundwater exploitation resulting in aquifer depletion. Exploitation of groundwater from fractured rock aquifers using wells to supply drinking water is more sustainable than the utilization of springs with low and variable discharge. In the case of drought and periods of critical condition of water usage, springs of fractured rock aquifers may dry up or decrease making them unreliable water resources to supply drinking water. Over recent decades, the use of fractured rock and karstic units as a remarkable water resource is known as a valuable source of freshwater worldwide. However, these aquifers are extremely vulnerable to contamination due to their unique hydrogeological characteristics and require more protection (Zarvash & Vaezi, 2014). These resources contribute to providing more than 70% of the rural population and around 50% of the urban population with drinking and household demand needs. Since the degree of development of karst landforms varies substantially from region to region, exploring groundwater potential zones in karstic or fractured rock domains across the world is important, which is mostly achieved using evaluating affecting factors in creating the groundwater occurrence. This evaluation is done by incorporating weighted factors such as Weighted Overlay, Weighted Sum, and Fuzzy Overlay and utilizing geographic information systems (GIS) or other remote sensing techniques, which is addressed frequently in literature summarized by Vaezihir and Tabarmayeh (2016); Seif and Kargar (2011); and Amiri et al. (2021). Considering the importance of such issue, this research aims to investigate the potential of karstic or fractured rock resources in West Azerbaijan to gain more insight into this valuable resource of groundwater. Materials and MethodsWest Azerbaijan province, with an area of 43,660 km² including Lake Urmia, is equivalent to 2.65% of the total area of Iran and located in the Alborz-Azerbaijan structural zone with a mean annual precipitation of about 370 mm. The maximum temperature of this province, dominated by a semi-arid and Mediterranean climate, is recorded in Shahin Dezh and Miandoab, and the minimum is measured in Chaldoran, and Tekab Metrological Stations, respectively. About 78% of the total area of West Azerbaijan province is formed by karstic units with more spatial distribution in the southern area. This karstic area encompasses 71% of the total province springs with 59% of the total discharge. In the current research, lithology unit types, fracture density, elevation, slope, aspect, drainage density, and vegetation coverage, along with the precipitation, area, and humidity index as the main factors were regarded as governing factors in the development of karst aquifers, have been considered to evaluate the potential groundwater resources. After the preparation of all affected layers using various data resources including available geological maps digital elevation map of West Azerbaijan Province obtained from the Geological Survey and Mineral Exploration of Iran, Landsat satellite data, the Fuzzy logistic and SUM and Weighted overlay technique has been used to prepared groundwater potential zone. Results and DiscussionThe groundwater potential zone were determined through combining 9 affected layers in developing the groundwater resource. The results obtained based on employing both weighted overlay and SUM were classified into 5 classes including low, very low, medium, high and very high potential zones. The index value in SUM methods estimated to be 16.24, 26.24, 24.24, 20.95, 12.13%, while it changes to 22.82, 24.13, 22.14, 16.23, and 14.67 respectively. Overlaying the location of springs as an indicators of groundwater resource on hardrock and karstic domain on generated maps showed that 30.9 and 33.08 percentage of springs fall in area with the high and very high potential zone, respectively. A significant differences on maps generated based on two mentioned technique, particularly in area classified as low potential zone with 24.13 and 16.24 percent in weighted overlay and SUM. ConclusionInvestigation of the groundwater potential zone by integrating the layer provided by Fuzzy logic technique through two SUM and weighted overlay methods indicated the province of Azerbaijan Arabi has a moderate level of classification. However, in some areas, there were significantly higher or lower potentials.
Irrigation
Abdorreza Vaezihir; Vahede Aghaie; Mehri Tabarmayeh
Abstract
IntroductionDetermining the capture zone of water resources is a strategic approach proposed at the national level of water resources management in Iran. One of the important actions for this purpose is protection of karst water resources, which are considered one of the vital sources for supplying water ...
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IntroductionDetermining the capture zone of water resources is a strategic approach proposed at the national level of water resources management in Iran. One of the important actions for this purpose is protection of karst water resources, which are considered one of the vital sources for supplying water due to the widespread karst formations in this country and the limitation of groundwater resources in alluvial aquifers. Generally, water flows out through the springs in the karst system. The land area where the water contributes to the spring is called the spring's capture zone. The study and analysis of the recession curve of the springs, the area extending from a discharge peak to the base of the next rise, along with the other physical characteristics of springs such as electrical conductivity is a useful indicator for getting knowledge about the condition of the catchment area and other properties of the heterogeneous karst terrain. In estimating the water budget, unlike the non-karst areas where the surface runoff or the outflow is considered the main factor in the estimated water budget, the recharge component is an important factor in the karst domain. The difference between hydrogeological and hydrological (topographic) catchments is one of the obvious features in karst landscapes. The identification of these basins or their boundaries is possible by combining geology and topography information. Soufiyan Cement Company in the vicinity of Chelleh Khanehe Olya spring located in Moro Mountain is associated with the creating social problems due to the expansion of mining activities and the negative impact on spring water in this area. Therefore, this study aims to determine the catchment area and the capture zone of the Chelleh Khanehe Olya spring by determining the protective boundary for the extraction of limes by the Soufiyan cement factory to prevent the negative impact of this factory on the spring.Materials and MethodsIn this research, the hydrograph of the recession curve related to a rainfall event has been analyzed by taking into account the mean monthly discharge rate of spring to determine the sub-regimes of diffuse and conduit flow by employing the following equation:Qt=Q0e-αt (1)Where Qt is the discharge rate at time t, Qo reveals the discharge at the initial time, and α is a recession coefficient.In addition, The Qmax/Qmin ratio has been calculated to estimate the flow type and the degree of karstification in the catchment area.In the next step, to determine the Chelleh Khanehe Olya spring catchment area and its capture zone, spring hydrogeological boundaries were determined and investigated using the SCS method and estimating the area's water budget. Due to the lack of sufficient rainfall and groundwater discharge information in this region, the water budget for a given period (2019-2020) has been computed indirectly by measuring the monthly discharge rate from the selected stations. After collecting the required data, the following equation developed by Milanovich (1989) has been used to estimate the water budget as follows:P=E+R+I (2)Where P, E, R, and I denote precipitation (P), evaporation at the basin level (E), runoff (R), and recharge to the aquifers (I). All the parameters are in mm units.Results and DiscussionAnalyzing the variation of electrical conductivity along with the discharge rate indicates that by decreasing the discharge rate from 2.5 l/s to 8.1 l/s, the electrical conductivity increase from 463 µs/cm to 500 µs/cm, reflecting an increase in the volume of the reservoir, the dilution of the aquifer. The hydrograph recession curve during 2019-2020 indicated two laminar and turbulent sub-regimes. Micro regimes α1 (01.002) and α2 (0.013) represented that the dominant system of karst development in the region is diffuse. The high density of fractures and the lack of purity of lime are the main reasons for the weak development of the karst fracture in the region, which the Chelekhaneh Alia spring recession curve analysis, maximum to minimum ratio of discharge, and karstification coefficient confirmed this issue. Determining the catchment basin using geological, hydrogeological information, and water budget showed that the hydrological and hydrogeological boundary of the spring is different. The protected zone of Chelekhane Alia spring, which includes the total hydrogeological basin and the Cretaceous limestone area below the level of the spring, was estimated to be about 184,000 square meters (18 hectares). According to the findings of this research, Sufian Cement Factory does not have the right to enter the hydrogeological boundary to extract limes, and on the other hand, to prevent the water level from decreasing due to the excessive extraction of lime as a result of the excavation depth reaching the level of the water table, it suggests to extract from the unsaturated part of the aquifer (unsaturated limes) to prevent the flow rate of Chele Khana spring from decreasing and even drying it up.ConclusionAnalyzing the discharge rate, electrical conductivity, hydrograph recession curve, and its recession coefficient(α=0.002), revealed that the dominant flow in the system is diffuse, which results from the high density of fractures and region lithology consisting of impure cretaceous limestone. Since the result revealed the inconsistency between hydrological and hydrogeological boundaries, the geological profile of the site was prepared and the spring of the catchment was estimated. Based on the findings of this research, the Chelle Khanehe Olya capture zone consists of the hydrogeological area, obtained from the groundwater budget estimation, and the protective boundary for the limestone below Cheleh Khaneh Olya spring (the unsaturated zone of the area's limestones), which covers an area of about 18 hectares.
