Pregled bibliografske jedinice broj: 882806
Catchment (recharge area) in karst !?
Catchment (recharge area) in karst !? // Man and karst 2017 / Krklec, Kristina (ur.).
Zadar: Univeristy of Zadar, 2017. str. 6-7 (pozvano predavanje, sažetak, ostalo)
Catchment (recharge area) in karst !?
Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, ostalo
Man and karst 2017 / Krklec, Kristina - Zadar : Univeristy of Zadar, 2017, 6-7
Man and karst 2017
Mjesto i datum
Zadar, Hrvatska, 26-29.06.2017.
Karst hydrology and hydrogeology, catchment, turbulent flow, diffuse flow
Catchment area, drainage area or drainage basin can be defined as: (1) the area of land bounded by watersheds draining into a river basin, spring or reservoir ; (2) the entire geographical area drained by a river and its tributaries, and by spring ; (3) an area characterized by all runoff being conveyed to the same outlet. The determination of the catchment boundaries and the catchment area is the starting point in all hydrological analyses and one of the essential data which serve as a basis for water resources protection, management, understanding and modelling of water circulation through karst massif. A catchment in karst represents a complex system composed of numerous (generally unknown) and extremely different surface and underground karst formations. Due to its heterogeneity and anisotropy, unexpected water circulation may occur in such a space. An additional problem regarding catchment boundaries and area definition is the fact that connections between surface water and groundwater can change very fast in time and space as a result of both natural processes and anthropogenic interventions. These changes can be either occasional or permanent. Discovery and quantification of these connections is in many cases impossible, which present the main reason why the definition of exact catchment in karst is an extremely complex task, very often unsolvable. For a karst aquifer, the traditional concept of the term “ground-water basin” is somewhat of a misnomer in that it minimizes the highly interconnected nature of surface and subsurface waters and the role of concentrated storm water runoff as a significant source of recharge. For water circulation in karst, the classical, and relatively simple hydrological problem (determination of catchment area) represents extremely complex, sometimes unsolvable task. The differences between the topographic and hydrological catchments in karst terrain are so large that data about the topographic catchment are useless. Very often the position of the karst catchment boundaries depends upon the groundwater levels which strongly and sharply change in time and space. In some situations at very high groundwater levels (caused by heavy rainfall and during karst flash floods) generally fossil and inactive underground karst conduits are activated, causing the redistribution of the catchment areas, i.e. overflow from one to other catchment. A wide range of closed surface depressions, a well-developed underground drainage system, and strong interaction between circulation of surface water and groundwater typify karst. Due to very high infiltration rates, especially in bare karst, overland and surface flow is rare in comparison with non-karst terrains. Conditions for water circulation and storage in karstified medium are strongly dependent on space and time scales being considered, especially in the deep and morphologically complex vadose zone. This zone and underlying phreatic karst aquifer are two- component system in which the major part of storage is in the form of true groundwater in narrow fissures and matrix, where diffuse or laminar flow prevails. The majority of the water is transmitted through the karst underground by quick or turbulent flow in solutionally enlarged conduits. The interaction between these two types of flow is significant and permanent, and strongly depends of prevailing hydrological situations (wet or dry periods, low, medium or high waters). The main objective of this presentation is to demonstrate, discuss and explain some theoretical as well as practical aspects of catchment area determination in karst.