Flood protection and water utilization of karst poljes: example of Gatačko Polje, Eastern Herzegovina

Abstract

Eastern Herzegovina is highly karstified area, with porosity of karstified rock mass between 0.8 and 2%. It is an area with high precipitation (average annual values in wet year are around 2450 mm), but its distribution is uneven, with 70% of annual precipitation occurring during the wet season (late fall to early spring). The outflow coefficients are very high, between 0.7 and 0.8. The ratio between flow in the low water period (Q95%) and in the period of high water flow (Q1%) is 1:4000(5000). Due to such hydrological conditions, with limited dewatering capacity of karst channels and ponors, floods of karst poljes occur frequently. This article presents, in very general terms, the properties of the natural water regime of the Gatacko Polje, highest polje in Eastern Herzegovina, including some hydrological and hydrogeological specificity. Special attention is referred to floods and possible ways to mitigate such events, as there are coal mine and coal power plant “Gacko” situated in the polje. Several possible measures are presented in the paper, such as passive protection measures, active flood protection by proper reservoirs management, as well as spatial planning measures. Also, the possibility of transferring part of the water from the Gatacko Polje watershed to the multipurpose hydrosystem Trebisnjica for usage in hydropower production, irrigation, water supply and other secondary benefits is considered.