Groundwater and connected ecosystems: an overview of groundwater body status assessment in Croatia

Background Croatia, as a Member State of the European Union, has to shape its water policy in accordance with the European Union Water Framework Directive. One of the tasks is to determine whether groundwater are susceptible to anthropogenic changes that would result in a significant surface water status reduction as well as terrestrial and aquatic ecosystems that directly depend on the groundwater. Methods Quality and quantity data on groundwater and surface water, as well as ecosystems data were collected from multiple sources. Data were analyzed for the selection groundwater associated aquatic and groundwater-dependent ecosystems. Chemical time series data were analyzed and compared with the national guideline limits set by the Croatian water quality standard. The impact of the groundwater abstraction on the groundwater-dependent ecosystem was considered by analyzing the aquifer hydrogeological characteristics, as well as location of the pumping site in relation of the ecosystem, the pumping rate and groundwater level or discharge. Results In karst areas of Croatia, groundwater-dependent aquatic ecosystems are predominant; while in the Pannonian area of Croatia, typically, there are groundwater-dependent terrestrial ecosystems. The status of groundwater bodies was defined as good. The analyzed chemical parameters are at acceptable concentration levels. Groundwater abstraction does not adversely affect most ecosystems. However, many springs that are captured for the water supply dry up in the summer. Given that this is also a common phenomenon at springs not captured, it has to be expected that such environments will be inhabited by organisms that have already adjusted to these conditions. Many different bioindicators have been found to indicate a good chemical and quantitative state of groundwater. Conclusions To increase the degree of reliability, research monitoring has been proposed. The monitoring should reduce knowledge gaps including an increase of knowledge of the status of the ecosystems, the definition boundary conditions and threshold values of a good quantitative and qualitative status for individual ecosystems. In future prospects, unavoidable focus has to be climate change that may compromise the availability of groundwater resources.