The Evaluation of the Development of Karstic Aquifers in Relation to the Geomorphology of Dolines and Hydrodynamic Characteristic (Case Study: Shahu Karstic Terrain)

Shahu karstic aquifers are the main sources of drinking and agricultural water in Paveh, Javanrood and Ravansar cities. Therefore, according to the important role of karst aquifers in supplying water to local communities in Kermanshah Province, recognizing their hydrodynamic characteristics for qualitative and quantitative management plays an important role in water policy planning in the province. The aim of this study was to identify and analyze the characteristics of karstic Dolines in the Shahu area and its relationship to the hydrodynamic characteristics of the water resources of the region. The identification of the sinkholes and their dispersion along with the morphometric analysis of these forms in the study area can be used in discussions on morphological characteristics and environmental hazards assessment and provide usable data for environmental planning.

The purpose of this study was to evaluate the hydrogeological characteristics of Kavat and Holi springs in connection with the development of Karst geomorphology, which is based on library, field, and applied research. To this end, CCL, elongation index, sinusoidal index, D/H ratio, the analysis of the nearest neighbor in order to analyze the Dolin characteristics of the region and time series analysis methods were used. In addition, automatic correlation and spectral density were used in order to study the hydrodynamic characteristics of aquifers in the study area. The data on discharge and precipitation of hydrometric stations and rain stations of the Ministry of Energy were also used during the period of 2003-2014. The sinkholes identified in the Karst Shahu area were derived from 10-meter digital elevation model. Extensive field activities were carried out to check identified forms. A descriptive table including location, geology and morphometric characteristics for each doline were calculated. The doline morphometric characteristics were recorded. Then the data were analyzed by statistical methods in SPSS software. In this study, parameters including density, area, diameter, depth, slope and distance from faults were analyzed. The analysis of the hydrograph subsidence curve was used to evaluate the type of flow system in the karstic aquifers of the study. Finally, to evaluate the results obtained from the time series analysis, the results of the hydrograph curve analysis and karst geomorphological features in Shahu area were considered and the hydrodynamic features in the study aquifer was determined.

According to CCL method, 104 dolins were identified in the shahu area. These dolines covered 11km2. The majority of the dolines were located in the central and northwestern parts of the study area. The mean depth of dolines in Shahu was 15m. The morphometry of the hollows generally tended to be elliptical or stretched. In the Shahu area, elliptical dolines were predominant forms. This indicated the significant role of rock mass in the evolution of the dolines. Semi-circular hollows were the lowest type of hollows in the study area. These types of dolines represented the initial forms of the dolines and were in a young stage. The number of dolines associated with distance from fault showed that the farthest doline was located in 3400 km, while more than 60 percent of Dolines were located within 0 to 500 m of faults in the region. Dolin density was related to the area of Karsts and the number of dolin in the study area. Dolin density in the study  area reached over 1.5 per km2. The results of the analysis of the nearest neighbor showed that the mean of the nearest neighbor for Dolines in the study area was 0.86, which indicated the cluster distribution of Dolin. The cluster distribution of the Dolines indicated the evolution of the karstic system of the Shahu area. Correlogram of Kavat Spring had three distinct sections. In the first section, there was a quick drop in flow and within 10 days. This represented a quick flow in the karstic conduit. In the second part, the fluctuation was in the upper range of 2%.  It is indicative of a semi-fast current in large fractures. In the third section, the fluctuation was mainly in the range between -2 and 2 and had a roughly uniform shape indicating a basic flow and a low inertia and low dynamic reserve in the aquifer. The Holy Spring Correlogram also showed almost the same situation and consisted of three distinct sections. Consequently, the aquifers showed the behavior of a developed karst. The spectral density function of both studied fountains provided a broad spectral band at frequencies below 17% and less than 15%. Ravansar spring at frequencies above 17% had a good filtering effect. And this value for a holly spring was higher than 15%. Indeed, distinct peaks at different frequencies over a period of time led to the identification of periodic events and, thus, to the recognition of the characteristics of the karstic system. The spectral density function indicated low inertia of studied aquifers, poor filtering, rapid flow and expansion of karstic channel networks in this aquifer.

The comparative evaluation of the karst geomorphology in relation to the hydrodynamic properties of aquifers in the study area suggested the development of the karst system in Shahu area. The results showed that relatively large parts of the shahu karst area were covered with dolines. The Dolin morphmetery features helped to recognize Dolines origin. More than 90 % of the Dolin area was elliptical doline which had a dissolution origin. The high dolin density in this region indicated the development of karst system. Differences in the Dolin morphometric characteristics indicated that the Dolin type was different from the origin of formation, the conditions and the time of formation. The analysis of the hydrodynamic characteristics of the Kavat and Holi springs also indicated the development of Shah's karstic system. The analysis of the hydrograph of the studied springs suggested a high degree of karstfication  and the presence of a quick flow and the presence of karst coundit in Shahu area. The automatic correlation function of the springs confirmed the multiplicity of the behavior of the karstic system, the rapid response to precipitation, and the small volume of dynamic reservoir of aquifers. Accordingly, the existence of the developed karst forms, the multiplicity of elliptical dolin, their high density, the presence of joints, the abundant fracture in karstic masses, the presence of large karst conduit in the Shahu area indicated the development of the karst system and was confirmed by hydrodynamic surveys. [1]- Professor, Factualy of Geography, University of Tehran, Tehran, Iran. [2]- Associate Professor, Factualy of Geography, University of Tehran, Tehran, Iran.