Classification of karst springs for flash-flood-prone areas in western Turkey

Abstract

Abstract. Flash floods are caused by heavy rainfall that has become more frequent. They are more prominent in lowstorage karst regions, although karst terrain often acts as a natural flood control particularly when it is bare and dominated by conduits. A study using a hydrogeochemical approach and assessing data from several springs in different carbonate rock in western Turkey has made it possible to classify karst aquifers based on their response to heavy rainfall events. According to this aim, physico-chemical measurements in wet and dry seasons and discharge rates in springs are compared in order to explain aquifer characteristics. Groundwater samples have a pH ranging from 6.3 to 8.9, temperature (T ) varying from 7 to 35 • C and electrical conductivity (EC) ranging from 140 to 998 µs cm −1 . Groundwater samples with high EC, high T and low dissolved oxygen (DO) represent the deep circulating water, while low EC, low T and high DO are linked to the shallow circulating water. Lower variability between wet and dry seasons reveals that fracture permeability is predominantly controlled by diffuse groundwater flow with low or high storage, and conduit permeability with high storage. However, variability of the physico-chemical characteristics is higher in a conduit permeability with low storage. These types of aquifers with high transfer capability, predominantly controlled by turbulent groundwater flow, affect flash floods.

Hydrochemical and Isotopic Difference of Spring Water Depending on Flow Type in a Stratigraphically Complex Karst Area of South Korea

“…Type Ⅱ seemed to discharge both the flow component through the epikarst zone and the baseflow from the lower reservoir, as defined by Tritz et al (2011) who used two reservoirs (i.e., the upper epikarst/soil zone and the lower vadose and saturated zone) to simulate the behavior of a karst system catchment and assumed a fast flow through the epikarst and slow baseflow from the lower reservoir. The deep groundwater rising at springs was also observed by other researchers including Moore et al (2009), Bicalho et al (2012), Demiroglu (2016), Gil-Márquez et al (2019, Lorette et al (2018), andZhu et al (2020). Some implied fast transfer through conduits unlike Tritz et al (2011).…”

“…The low storage seemed to cause the discharge quickly responding to rainfall not only during the typhoon event in 2000, but also in the small precipitation events in 1999 (Figure 2), and the rainfall accounting for 87% of the discharge at peak flow and continuing to flow out and contributing more than half of the discharge after the heavy rainfall stopped at S46 (Figure 11; Table 3). Similarly, Demiroglu (2016) reported that developed karst sinkholes allow fast percolation of heavy rainfall into an aquifer up to 80%, and explained that the very low storage combined with the high transmissivity means that most of the recharge will not be retained by the karst system, but will rapidly flow out to springs, rivers, lakes, or seas. In contrast, the delayed response to the storm and quick recovery to the baseflow condition after it stopped raining at S41 and S45 (Figure 11; Table 3) were probably due to the storage effect of the vadose zone, given that all three springs had flow characteristics through permeable conduits.…”

“…Karst aquifers differ from unconsolidated granular aquifers regarding subsurface flow behavior because of various types of porosity, e.g., matrix, fractures, and conduits (Ghasemizadeh et al, 2012;Hartmann et al, 2014;Demiroglu, 2016). In addition, the epikarst plays a significant role in karst recharge and storage (Aquilina et al, 2005;Aquilina et al, 2006;Doctor et al, 2006;Chang et al, 2019).…”

“…Therefore, we conducted hydrochemical, environmental isotopic, and hydrograph separation studies to assess the subsurface flow in a stratigraphically complex karst area with thrusts where both low discharge and high discharge springs occurred (Figure 1). It was assumed that the low discharge and high discharge come through diffuse and conduit pathways, respectively, because the flow in karst aquifers is turbulent in conduits such as caves and sinkholes, while diffusive through the fissured matrix or intergranular unfractured bedrock (Demiroglu, 2016;Chang et al, 2019). Specifically, springs were divided into Type Ⅰ and Ⅱ when sampled based on the manner by which the discharge occurred (i.e., low and high, respectively) as in Mocior et al (2015) who surveyed the spatial distribution of springs in mountains and categorized them by discharge.…”

Application of an improved distributed Xinanjiang hydrological model for flood prediction in a karst catchment in South‐Western China

“…At the same time, karst aquifer systems have weak water holding capacity and water storage capacity. When the cumulative rainfall of a rainfall event is greater than the capacity of the karst conduits and fissures in aquifer systems (Gázquez, Calaforra, & Fernández‐Cortés, 2016), it is easy to trigger karst flash floods (Demiroglu, 2016; Martinotti et al, 2017). With the increasing risk of extreme weather events worldwide, the probability of sudden floods in karst watersheds has increased significantly (Gázquez et al, 2016); therefore, it is of great practical significance to study flood prevention countermeasures in karst basins.…”