Investigating the Potential of Groundwater Resources in Hard Formations as a Way to Manage Water Crisis (Case Study: Kalat Naderi Basin)

1. Introduction Water shortage problem has gained new complicated dimensions in a variety of countries located in arid regions of our planet including Iran which has forced the researchers to think of the solutions for this problem. Water resources in the depth of hard formations are considered as one of the most significant resources of fresh waters. On the other hand, there are a wide range of these types of formations in Iran which have attracted a huge amount of studies. Therefore, there is a necessity in studying the baseline of the springs originating from hard formations in optimum managing and exploiting underground waters. Land morphological features are commonly used for preparing underground potential existence maps. Additionally, in aquifers located in hard cracked formations, a variety of parameters including surface topography, lithology, cracking density, ground water feeding rates, land uses, slope classes, drainage patterns, atmospheric status or a group of them are used in order to map moving underground waters.
In a comprehensive GIS–RS and logistic regression model based research run in Maxent software package environment, this paper determined the maximum amount of parameters which affect spring flooding patterns in hard formations located in Kalat Naderi region through which simulated spring's distribution patterns using GIS, Maxnet software based on logistic regression and measurement in a comprehensive.
Kalat Naderi watershed is located in Khorasan Razavi province, northeast of Iran between 18'63¬°58 " to "35'79¬°60 of eastern longitude and 09'53¬°37 to "25'32°36 of northern latitude. Geologically, the study area is located in Bojnurd – Shirvan lithology sheets mostly in Koppedagh zone. Stratigraphical history of Kalat Naderi watershed dates back to Ordovician period in Paleozoic and quaternary eras. The studied watershed is 8565 square kilometers of area with 236 and 3069 meters from seed level in lowest and highest points, respectively.
2. Material and Methods We used 13 parameters (fault density, distance from faults, distance from rivers, land use, profile curvature, tangent curvature, total curvature, surface ratio, mean rainfall, elevation, lithology, geographical aspects and slope degrees) in order to analytically prepare springs existence map layers and verify the maps in the field. Indeed, all of the aforementioned parameters have influence on groundwater infiltration, feeding or harvesting amount. A report of 895 springs located in the study area was gained from Iranian Water Resources Management Office (IWRMO) and regression model in Maxent software environment was used in order to verify the data. Fifity replications and 895 random points were used to model the gathered data. Also, 75% of the selected points were used as the learning points and 25% of the remaining points were utilized to plot the model. It is worth mentioning that lithology, land use and geographical maps were classified based on surface infiltration potentials and spring outcrop entered to the model.
The other maps were entered to the model in a continuous rasterized format. Jackknife resampling method was used in order to define the importance of each variable on species distribution patterns. Furthermore, ROC curve was utilized to define model's accuracy and efficiency.
3. Results and Discussion Sensitivity analysis for morphometric factors, jackknife analysis and the logistic regression in Maxent software environment for defining the chance of existence of springs showed that precipitation related variables and lithological characteristics are the most significant factors which directly influence the chance of springs to exist so that the more their frequency are, the more the chance of springs existence. In addition, the results revealed that more porosity of the lithological sheets show a higher chance for the springs to exist. Forests and westward- northward aspects showed higher chance for the springs to exist. A negative relationship was seen among distances from faults and distances from rivers with the chance of springs existence. Also, there is a positive relationship among springs distribution patterns and elevation from see level up to 2800 meters.
Results showed a decreased chance of springs existence with increased slope degrees due to less infiltration amount. A positive relationship was seen between fault density and the chance of springs to exist.
Finally, the groundwater potential quality map was classified into four (very low, low, medium and high) classes with 33.03, 14.07, 4.01 and 48.9 percent of the total area. ROC curve showed a high accuracy of 92.3 % for the model.
Finally, it is concluded that, due to its accordance with the existing data, the model is considered as a suitable method for tracking groundwater tables especially in hard formations which result in a high efficient management for water resources.