Geological and hydrogeological controls on possible transboundary groundwater flow between Bulgaria and Greece

Abstract

A major issue in groundwater and surface water management and monitoring is transboundary groundwater flow between neighbouring countries. The subject of our study is the assessment of the groundwater flow across the state border between Bulgaria and Greece, which is characterized by complex natural features. We present a study on the factors that control the groundwater flow and formation, such as lithological composition, geological structure, topographic features, surface water network, etc. It was determined that, in most sections along the state border, the probability of transboundary groundwater flow is rather small, due to the position of the surface and groundwater divides. In the areas where the state border follows a ridge with fissured groundwater system, there are no prerequisites for transboundary flow. Groundwater flow is likely to occur only in the marble-dominated karst areas, as well as in the Quaternary or Neogene–Quaternary aquifers in river valleys that host porous groundwater bodies. The probability of transboundary groundwater flow could increase in response to certain human activities.

Spatial and temporal variations of groundwater contribution to streamflow in the Mesta River Basin

“…In recent years, hydrogeological descriptions of the study area have been made in view of the formation of the chemical composition of shallow groundwater (Vasileva and Toteva, 2019;Vasileva, 2020;Vasileva and Sholev, 2021;Mihaylova et al, 2022Mihaylova et al, , 2023. The hydrogeological conditions in the border areas of Bulgaria and Greece, along with assessment of the probability of transboundary transfer of groundwater, are presented in Spasov et al (2017). Mihaylova et al (2023) considered geological conditions as a prerequisite for groundwater formation.…”

“…They are cracked, locally tectonically fractured, and highly karstified. This region represents a transboundary karst massif between Bulgaria and Greece (Spasov et al, 2017). The associated groundwater feeds springs in the basins of the Mesta and Struma rivers in southwestern Bulgaria, as well as on the territory of Greece.…”

Geological factors for the formation of the chemical composition of groundwater in the catchment area of the Mesta river

“…Изготвен е ГИС слой, в който след анализ на хидрогеоложките особеностите на всяка геоложка формация са отделени съответните водоносни хоризонти, комплекси и водоупори. След това, на основата на досегашни хидрогеоложки изследвания (Хидрогеоложка карта на България, М 1:200000 2 ; Antonov, Danchev, 1980;Spasov et al, 2017;Gerginov, 2021) те са обобщени в групи, всяка от тях се характеризира със специфични условия за формиране и движение на подземните води, както следва:…”

“…(Boyadzhiev, 1964;Antonov, Danchev, 1980;Mihaylova et al, 2022), всеки от които представлява самостоятелна хидрогеоложка единица. С най-висока водообилност не само от тях, но и в целия водосбор на р. Места са Разложкият и Гоцеделчевският, като последният продължава и на територията на Гърция, както и във водосбора на р. Струма (Spasov et al, 2017). Тези басейни се характеризират с типичен алпийски При регионалната оценка за влиянието на химичния, минераложки и петрографски състав на скалите по класификацията на Кехайов във водосбора на р. Места от 11 групи са установени само 7 (фиг.…”